Increased compression ratio and octane rating
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Given the flow ratio of intake to exhaust on those heads I would not install a split duration cam. I'd go with a 270/270 or similar on a 110 not overdo the overlap and keep the cylinder pressures up for TQ. Also it looks like the flow really starts happening @ .500 and higher. Given that a 1.6 rr to get the lift up may be a good idea. Stopping @ .4something is limiting to the heads potential.
Maybe something like this https://www.summitracing.com/parts/c...rolet#overview
has 50* overlap and .470 lift. put in 1.6 rr and you get .500 lift.
That 1102 has 59* of overlap and the 1103 has 69* both of those are giving up a lot of bottom end torque.
I'd also pour the intake track on those. I suspect that it is more than 180cc given the flow numbers. This will slow down your intake velocity. At least you'll know what you have.
If you add up split duration on a 112 giving more overlap than required, with larger than advertised intake track, and larger than advertised combustion chamber you end up giving up quite a bit of bottom end torque and torque below peak torque RPM. I'd focus on keeping those items as good as you can. You can't really control the volumes other than limiting material removal, but the cam specs can be tailored a bit to optimize it.
What is going to help is the 700r4 trans. Geared much lower in 1st gear, But big jump to second, so you're still gonna want that bottom end torque. That converter stall will probably work just fine with the trans. Higher is better for sure with 3.08 but it's better than stock on a th350 L-48.
Maybe something like this https://www.summitracing.com/parts/c...rolet#overview
has 50* overlap and .470 lift. put in 1.6 rr and you get .500 lift.
That 1102 has 59* of overlap and the 1103 has 69* both of those are giving up a lot of bottom end torque.
I'd also pour the intake track on those. I suspect that it is more than 180cc given the flow numbers. This will slow down your intake velocity. At least you'll know what you have.
If you add up split duration on a 112 giving more overlap than required, with larger than advertised intake track, and larger than advertised combustion chamber you end up giving up quite a bit of bottom end torque and torque below peak torque RPM. I'd focus on keeping those items as good as you can. You can't really control the volumes other than limiting material removal, but the cam specs can be tailored a bit to optimize it.
What is going to help is the 700r4 trans. Geared much lower in 1st gear, But big jump to second, so you're still gonna want that bottom end torque. That converter stall will probably work just fine with the trans. Higher is better for sure with 3.08 but it's better than stock on a th350 L-48.
272/272 advertised duration @ .004",
216/216 @ .050",
.454"/.454" lift,
110 LSA,
5 degrees of advance ground in.
Operating range 1600-5400 rpm.
According to the cam card, it has 52 degrees of overlap, but that's at .004". Measured at .006" lift, that might be a little closer to 50 degrees, maybe?
It sounds an awful lot like the cam specs you recommend, doesn't it? Crane measured their advertised duration @ .004" instead of .006", like everybody else, for some reason, but that's a pretty small increment. I think this cam works out to be a teensy, weensy bit smaller than the good ole Comp Cams 268H High Energy grind. Anyway, I'm thinking now that maybe I should just stick to the original plan. I'l break the cam in using new, stock valve springs, and switch them out for Z-28 springs once it's broken in.
I'm still waiting for intake valves, so once they're back in stock and I can get my hands on 'em, I'll measure the intake port volume when I measure the combustion chambers, and I'll let you guys know how that comes out.
It's been a while since I looked at the flow numbers, but I seem to remember the intake port pretty much shutting down at .500". I figured the flow stops increasing somewhere between .400" and .500" and I compromised with the .454" lift camshaft. 1.6:1 rockers would increase that lift to .484", so that might be worth doing down the road aways. We'll see. The heads in question come assembled with a valve spring installed height of 1.800" with a .100" longer valve stem and a maximum valve lift of .550". I bought them bare and am using stock sized components (Valves, valve springs, etc.) so I may be cutting it kinda close even at .454" of valve lift using a valve spring installed height of 1.700" or even 1.720". The devil's in the details, as they say, right? My grand-dad used to say, "Measure twice, cut once."
Thanks for dealing with my wishy-washyness and self-doubt for the last few days, I think I'm back on track now. I still may decide to split the job up into 2 parts, though, we'll see. Probably not.
Scotty
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
my understanding of the vette waterpump is it has the same clearance behind it as any other water pump in fact im sure of it.. retro roller cam doesnt need any special timing chain cover either that im aware of, I used a cheap ebay aluminum cover and a nylon cam button. its really not hard. just have to make sure the right amount of endplay is present after the cam button is installed which is why I went with the nylon button so I could file or grind it which I did.
Scotty
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Yes I think that cam you have will work ok for what you want. 272* @ .004 may be 275* @.006 or so. So about 55* of overlap if that is close to correct.
Consider that although the flow of the heads pretty much flattens out at .500 that the time it takes to get from .454" to .500 or more is more time and square area for air to flow into the cylinder. And if you lift it to .500 it goes past .454" twice in that movement rather than just stopping there and reversing once. This may become particularly important if you find that your 180cc heads pour at 187cc's.
More lift = more better IMO.
It seems that the problems with flat tappet cam break ins may be more related to the lifters than the cams as of late. so some extra effort in researching the best lifters may be worth the time and probably additional expense those lifters will cost.
Consider that although the flow of the heads pretty much flattens out at .500 that the time it takes to get from .454" to .500 or more is more time and square area for air to flow into the cylinder. And if you lift it to .500 it goes past .454" twice in that movement rather than just stopping there and reversing once. This may become particularly important if you find that your 180cc heads pour at 187cc's.
More lift = more better IMO.
It seems that the problems with flat tappet cam break ins may be more related to the lifters than the cams as of late. so some extra effort in researching the best lifters may be worth the time and probably additional expense those lifters will cost.
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
So many good comments from the folks you normally expect to see them from here.
Things I think are worth repeating:
The L48 compression ratio needs all the help it can get. The Felpro shim gasket helps, but yea... The non D-dish pistons don't help the quench velocity as much as they could. If using the shim gasket: you DO need a perfectly flat deck surface so check it with a straight edge; my deck was NOT perfectly flat, and it had to be made flat first. That gasket requires a pretty smooth surface finish on the deck surface, so, IMHO, copper coat is cheap insurance to deal with any minor deck imperfections if using that 1094 gasket.
-Although Quench IS very beneficial and a "free" octane equivalent with every tank fill up, so is cold air, and to a lesser degree, reasonable engine coolant temps. The David Vizard quote is that every 7 deg Fahrenheit drop in intake air temps is equivalent to 0.5 octane worth of detonation resistance... -If your engine bay is 42F warmer than your outside air, that's like getting 90 octane when you're only actually putting 87 octane in the tank! (If you're not a Vizard fan, Gale Banks just calls people flat out stupid for not ensuring they feed their performance engine with cold air; lol!)
If you DO get some pinging in high heat, you can always add a good octane booster like Boostane at a measured quantity OR get that distributor recurved to pull a couple of degrees around the torque peak / where it ping or remember to down shift a gear when going up a hill instead of laboring up hill in OD.
Modern heads are not like the old GM factory heads, those heads see HUGE jumps in airflow from .300" (174 CFM) to .400" (207 CFM) and a decent jump from .400" to .500" (233 CFM) of lift. Those heads want a more modern cam with a more aggressive ramp to get the valve open further for longer. (And they probably already come with springs that will support such a cam, too.)
Someone mentioned Comp XE flat tappet and Voodoo cam lobes and the issue of longevity with cam lobes that are too aggressive; Ed Iskenderian used to have a rule he called the "47.5% rule" that said "If you take 1.5 rocker on an SBC and take the .050" duration and divide by the max valve lift, the resulting number should exceed 47.5% to avoid longevity issues (for a flat tappet SBC cam)" -> The Comp XE lobes technically "break" the 47.5% rule and have pretty high velocity at the close which gives them their sewing machine (valve train destroying) sound... (I'd SWEAR I came across a Harold Brookshire post where he stated that the close rate on the XE lobes was too fast and he slowed down the close rate on the Voodoo line, and I've been trying to find it again for 3 or 4 years to no avail, so maybe I made it all up...)
Personally, I think time moves on and materials and technology improves, but the most aggressive flat tappet grinds DO technically come in below the Isky 47.5% rule, but not by much... (Higher %s are less aggressive)
Comp XE262H: 218 deg duration @ 0.050" / 462 thousandths lift = 47.2%
Lunati Voodoo: 262/268 cam: 219 deg dur @ 0.050" / 468 thou lift = 46.8%
-The intensity may vary within the supposed lobe family, too; I feel like I remember two different lobe intensities all branded under Comp XE flat tappet SBC cams in the Master Catalog...
On the cam button end play, timing covers and the Corvette water pumps: I think there ARE combinations that could be problematic. I was worried about this too and Gary from NY helped me with this: a standard double-roller Cloyes chain set, Comp cams roller button, the cheap yet attractive AllStar Performance aluminum timing cover, FelPro paper "blue stripe" gasket, and a proper Corvette-style water pump with flat-headed bolts on the rear cover fit 100% perfect and snug with zero extra clearance. -He said it's a combination he uses all the time and it fits perfect and he was NOT stretching the truth one bit.
The aluminum covers ARE thicker, so I think having a thin paper gasket and having the flat headed screws on the back of the Corvette water pump are important. There's no way the water pump with rounded-head screws would've fit on mine, anyway. -I'm not sure whether the Corvette style water pumps are shorter / closer to the block on the rear or not, but I do have a note that says that the distance between the block surface to the water pump hub IS different between a standard short-style SBC water pump (5 5/8") vs. the Corvette water pump with a distance of 5 13/16" from the block to the hub.(So it's not just the pilot shaft size and roller bearing that's the diff between the standard short and Corvette pumps, anyway; there is at least one other dimensional difference.)
I think I've added almost nothing new to the thread except maybe the Isky rule; I'm mostly just repeating what I think are the good ideas people have already stated and one combination of retrofit roller cam parts, timing covers, and water pump rear cover bolts that definitely work without issue.
Adam
Things I think are worth repeating:
The L48 compression ratio needs all the help it can get. The Felpro shim gasket helps, but yea... The non D-dish pistons don't help the quench velocity as much as they could. If using the shim gasket: you DO need a perfectly flat deck surface so check it with a straight edge; my deck was NOT perfectly flat, and it had to be made flat first. That gasket requires a pretty smooth surface finish on the deck surface, so, IMHO, copper coat is cheap insurance to deal with any minor deck imperfections if using that 1094 gasket.
-Although Quench IS very beneficial and a "free" octane equivalent with every tank fill up, so is cold air, and to a lesser degree, reasonable engine coolant temps. The David Vizard quote is that every 7 deg Fahrenheit drop in intake air temps is equivalent to 0.5 octane worth of detonation resistance... -If your engine bay is 42F warmer than your outside air, that's like getting 90 octane when you're only actually putting 87 octane in the tank! (If you're not a Vizard fan, Gale Banks just calls people flat out stupid for not ensuring they feed their performance engine with cold air; lol!)
If you DO get some pinging in high heat, you can always add a good octane booster like Boostane at a measured quantity OR get that distributor recurved to pull a couple of degrees around the torque peak / where it ping or remember to down shift a gear when going up a hill instead of laboring up hill in OD.
Modern heads are not like the old GM factory heads, those heads see HUGE jumps in airflow from .300" (174 CFM) to .400" (207 CFM) and a decent jump from .400" to .500" (233 CFM) of lift. Those heads want a more modern cam with a more aggressive ramp to get the valve open further for longer. (And they probably already come with springs that will support such a cam, too.)
Someone mentioned Comp XE flat tappet and Voodoo cam lobes and the issue of longevity with cam lobes that are too aggressive; Ed Iskenderian used to have a rule he called the "47.5% rule" that said "If you take 1.5 rocker on an SBC and take the .050" duration and divide by the max valve lift, the resulting number should exceed 47.5% to avoid longevity issues (for a flat tappet SBC cam)" -> The Comp XE lobes technically "break" the 47.5% rule and have pretty high velocity at the close which gives them their sewing machine (valve train destroying) sound... (I'd SWEAR I came across a Harold Brookshire post where he stated that the close rate on the XE lobes was too fast and he slowed down the close rate on the Voodoo line, and I've been trying to find it again for 3 or 4 years to no avail, so maybe I made it all up...)
Personally, I think time moves on and materials and technology improves, but the most aggressive flat tappet grinds DO technically come in below the Isky 47.5% rule, but not by much... (Higher %s are less aggressive)
Comp XE262H: 218 deg duration @ 0.050" / 462 thousandths lift = 47.2%
Lunati Voodoo: 262/268 cam: 219 deg dur @ 0.050" / 468 thou lift = 46.8%
-The intensity may vary within the supposed lobe family, too; I feel like I remember two different lobe intensities all branded under Comp XE flat tappet SBC cams in the Master Catalog...
On the cam button end play, timing covers and the Corvette water pumps: I think there ARE combinations that could be problematic. I was worried about this too and Gary from NY helped me with this: a standard double-roller Cloyes chain set, Comp cams roller button, the cheap yet attractive AllStar Performance aluminum timing cover, FelPro paper "blue stripe" gasket, and a proper Corvette-style water pump with flat-headed bolts on the rear cover fit 100% perfect and snug with zero extra clearance. -He said it's a combination he uses all the time and it fits perfect and he was NOT stretching the truth one bit.
The aluminum covers ARE thicker, so I think having a thin paper gasket and having the flat headed screws on the back of the Corvette water pump are important. There's no way the water pump with rounded-head screws would've fit on mine, anyway. -I'm not sure whether the Corvette style water pumps are shorter / closer to the block on the rear or not, but I do have a note that says that the distance between the block surface to the water pump hub IS different between a standard short-style SBC water pump (5 5/8") vs. the Corvette water pump with a distance of 5 13/16" from the block to the hub.(So it's not just the pilot shaft size and roller bearing that's the diff between the standard short and Corvette pumps, anyway; there is at least one other dimensional difference.)
I think I've added almost nothing new to the thread except maybe the Isky rule; I'm mostly just repeating what I think are the good ideas people have already stated and one combination of retrofit roller cam parts, timing covers, and water pump rear cover bolts that definitely work without issue.
Adam
Last edited by NewbVetteGuy; May 16, 2022 at 06:35 PM.
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
If going with a stamped steel stock style cover, I think just a slightly more substantial gasket would make up the extra thickness of an aluminum cover and it would fit essentially the same.
I've heard people say that they needed to use 2 sets of water pump gaskets to get more clearance between the timing cover and the water pump; I'm not sure whether that's because they're using a standard short water pump and it fits closer to the block, or if they're using a water pump with rounded bolts on the rear cover, or why they have that problem...
Adam
Last edited by NewbVetteGuy; May 17, 2022 at 12:54 PM.
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Yes I think that cam you have will work ok for what you want. 272* @ .004 may be 275* @.006 or so. So about 55* of overlap if that is close to correct.
Consider that although the flow of the heads pretty much flattens out at .500 that the time it takes to get from .454" to .500 or more is more time and square area for air to flow into the cylinder. And if you lift it to .500 it goes past .454" twice in that movement rather than just stopping there and reversing once. This may become particularly important if you find that your 180cc heads pour at 187cc's.
More lift = more better IMO.
It seems that the problems with flat tappet cam break ins may be more related to the lifters than the cams as of late. so some extra effort in researching the best lifters may be worth the time and probably additional expense those lifters will cost.
Consider that although the flow of the heads pretty much flattens out at .500 that the time it takes to get from .454" to .500 or more is more time and square area for air to flow into the cylinder. And if you lift it to .500 it goes past .454" twice in that movement rather than just stopping there and reversing once. This may become particularly important if you find that your 180cc heads pour at 187cc's.
More lift = more better IMO.
It seems that the problems with flat tappet cam break ins may be more related to the lifters than the cams as of late. so some extra effort in researching the best lifters may be worth the time and probably additional expense those lifters will cost.
Scotty
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Gale Banks just calls people flat out stupid for not ensuring they feed their performance engine with cold air; lol!)
Ahhh, yes.....the less lift the duration is measured at, the longer the duration. That makes sense. I was thinking it was the other way around comparing .004" and .006". I feel a little foolish, now. Thanks for straightening that out.
I type plenty of stuff only half focusing on what I'm typing and look uninformed at times too. This isn't my job, nothing is riding on what I put down here.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Use the Allstar 90010 steel timing cover, short cam button and a Fel-Pro timing cover gasket will give you .010 endplay for a roller cam in most situations….if not, you can tweak the cover to get what you need…..I have setup over 20 small blocks with this setup and it is as close to bolt on endplay as you will get….
Jebby
Jebby
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Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
I can't wait until I'm old enough to just play the part of the old guy who's "lost his filter".
Seriously I think I like late 70s early 80s aged Gale Banks the best!
His rants against Diesel guys who "roll smoke" and try to say that equates to a good tune that makes good power are even more brutal and hilarious.
Adam
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
I just want to point out the overdrive in the 700r4 with 3.08 gears is going to lug the engine a bit when locked up and if your going to get pinging I would think this might be when it will occur.. I still dont think you have to worry based on my 3.08 gears and compression but I realize its not quite the same quench wise.
Scotty
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I'm kinda worried about lugging the engine on the highway, too. Somebody must make some gizmo that unlocks the converter when manifold vacuum dips below a certain threshold, allowing the tranny to downshift or even just get a few hundred more rpm from the converter slip. I normally do about 80 on the highway anyway, but it's New England.....fairly hilly around here.
Scotty
Scotty
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
According to an online calculator, my engine rpm at 70 m.p.h. should nominally be 1872 rpm, which would probably induce some slippage, meaning extra heat.
I have a toggle switch that I will be installing in the dash that will turn off the TC lock up, but I plan on using it more as a way of "arming" the lock up feature when I want it to work, like on the highway, and turn it off when I'm putting around town. I might just leave the tranny in third gear until I pull onto the highway, and bump the shifter up into overdrive when I get up to speed. I think the TC only locks up in overdrive. I would rather not do that, though. I'd prefer it to just work like the more modern daily driver cars I've been driving for the last few decades.
Scotty
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Yes and no to the slippage below stall.
I have a 3000 stall converter in my th350. I often am below 3000 rpm and as long as the load on the engine is not great like pulling a hill at low speed the slippage is minimal, not noticeable and the heat generated is not excessive.
The slippage is load dependent I guess is what I’m saying. Cruising at 70 just below stall rpm the load is minimal and so is the slippage. If you accelerate suddenly then the load increases and so does the slippage, which is what we want.
I have a 3000 stall converter in my th350. I often am below 3000 rpm and as long as the load on the engine is not great like pulling a hill at low speed the slippage is minimal, not noticeable and the heat generated is not excessive.
The slippage is load dependent I guess is what I’m saying. Cruising at 70 just below stall rpm the load is minimal and so is the slippage. If you accelerate suddenly then the load increases and so does the slippage, which is what we want.
Le Mans Master
Joined: May 2007
Posts: 5,029
Likes: 1,120
From: North tonawanda NY
So many good comments from the folks you normally expect to see them from here.
Things I think are worth repeating:
The L48 compression ratio needs all the help it can get. The Felpro shim gasket helps, but yea... The non D-dish pistons don't help the quench velocity as much as they could. If using the shim gasket: you DO need a perfectly flat deck surface so check it with a straight edge; my deck was NOT perfectly flat, and it had to be made flat first. That gasket requires a pretty smooth surface finish on the deck surface, so, IMHO, copper coat is cheap insurance to deal with any minor deck imperfections if using that 1094 gasket.
-Although Quench IS very beneficial and a "free" octane equivalent with every tank fill up, so is cold air, and to a lesser degree, reasonable engine coolant temps. The David Vizard quote is that every 7 deg Fahrenheit drop in intake air temps is equivalent to 0.5 octane worth of detonation resistance... -If your engine bay is 42F warmer than your outside air, that's like getting 90 octane when you're only actually putting 87 octane in the tank! (If you're not a Vizard fan, Gale Banks just calls people flat out stupid for not ensuring they feed their performance engine with cold air; lol!)
If you DO get some pinging in high heat, you can always add a good octane booster like Boostane at a measured quantity OR get that distributor recurved to pull a couple of degrees around the torque peak / where it ping or remember to down shift a gear when going up a hill instead of laboring up hill in OD.
Modern heads are not like the old GM factory heads, those heads see HUGE jumps in airflow from .300" (174 CFM) to .400" (207 CFM) and a decent jump from .400" to .500" (233 CFM) of lift. Those heads want a more modern cam with a more aggressive ramp to get the valve open further for longer. (And they probably already come with springs that will support such a cam, too.)
Someone mentioned Comp XE flat tappet and Voodoo cam lobes and the issue of longevity with cam lobes that are too aggressive; Ed Iskenderian used to have a rule he called the "47.5% rule" that said "If you take 1.5 rocker on an SBC and take the .050" duration and divide by the max valve lift, the resulting number should exceed 47.5% to avoid longevity issues (for a flat tappet SBC cam)" -> The Comp XE lobes technically "break" the 47.5% rule and have pretty high velocity at the close which gives them their sewing machine (valve train destroying) sound... (I'd SWEAR I came across a Harold Brookshire post where he stated that the close rate on the XE lobes was too fast and he slowed down the close rate on the Voodoo line, and I've been trying to find it again for 3 or 4 years to no avail, so maybe I made it all up...)
Personally, I think time moves on and materials and technology improves, but the most aggressive flat tappet grinds DO technically come in below the Isky 47.5% rule, but not by much... (Higher %s are less aggressive)
Comp XE262H: 218 deg duration @ 0.050" / 462 thousandths lift = 47.2%
Lunati Voodoo: 262/268 cam: 219 deg dur @ 0.050" / 468 thou lift = 46.8%
-The intensity may vary within the supposed lobe family, too; I feel like I remember two different lobe intensities all branded under Comp XE flat tappet SBC cams in the Master Catalog...
On the cam button end play, timing covers and the Corvette water pumps: I think there ARE combinations that could be problematic. I was worried about this too and Gary from NY helped me with this: a standard double-roller Cloyes chain set, Comp cams roller button, the cheap yet attractive AllStar Performance aluminum timing cover, FelPro paper "blue stripe" gasket, and a proper Corvette-style water pump with flat-headed bolts on the rear cover fit 100% perfect and snug with zero extra clearance. -He said it's a combination he uses all the time and it fits perfect and he was NOT stretching the truth one bit.
The aluminum covers ARE thicker, so I think having a thin paper gasket and having the flat headed screws on the back of the Corvette water pump are important. There's no way the water pump with rounded-head screws would've fit on mine, anyway. -I'm not sure whether the Corvette style water pumps are shorter / closer to the block on the rear or not, but I do have a note that says that the distance between the block surface to the water pump hub IS different between a standard short-style SBC water pump (5 5/8") vs. the Corvette water pump with a distance of 5 13/16" from the block to the hub.(So it's not just the pilot shaft size and roller bearing that's the diff between the standard short and Corvette pumps, anyway; there is at least one other dimensional difference.)
I think I've added almost nothing new to the thread except maybe the Isky rule; I'm mostly just repeating what I think are the good ideas people have already stated and one combination of retrofit roller cam parts, timing covers, and water pump rear cover bolts that definitely work without issue.
Adam
Things I think are worth repeating:
The L48 compression ratio needs all the help it can get. The Felpro shim gasket helps, but yea... The non D-dish pistons don't help the quench velocity as much as they could. If using the shim gasket: you DO need a perfectly flat deck surface so check it with a straight edge; my deck was NOT perfectly flat, and it had to be made flat first. That gasket requires a pretty smooth surface finish on the deck surface, so, IMHO, copper coat is cheap insurance to deal with any minor deck imperfections if using that 1094 gasket.
-Although Quench IS very beneficial and a "free" octane equivalent with every tank fill up, so is cold air, and to a lesser degree, reasonable engine coolant temps. The David Vizard quote is that every 7 deg Fahrenheit drop in intake air temps is equivalent to 0.5 octane worth of detonation resistance... -If your engine bay is 42F warmer than your outside air, that's like getting 90 octane when you're only actually putting 87 octane in the tank! (If you're not a Vizard fan, Gale Banks just calls people flat out stupid for not ensuring they feed their performance engine with cold air; lol!)
If you DO get some pinging in high heat, you can always add a good octane booster like Boostane at a measured quantity OR get that distributor recurved to pull a couple of degrees around the torque peak / where it ping or remember to down shift a gear when going up a hill instead of laboring up hill in OD.
Modern heads are not like the old GM factory heads, those heads see HUGE jumps in airflow from .300" (174 CFM) to .400" (207 CFM) and a decent jump from .400" to .500" (233 CFM) of lift. Those heads want a more modern cam with a more aggressive ramp to get the valve open further for longer. (And they probably already come with springs that will support such a cam, too.)
Someone mentioned Comp XE flat tappet and Voodoo cam lobes and the issue of longevity with cam lobes that are too aggressive; Ed Iskenderian used to have a rule he called the "47.5% rule" that said "If you take 1.5 rocker on an SBC and take the .050" duration and divide by the max valve lift, the resulting number should exceed 47.5% to avoid longevity issues (for a flat tappet SBC cam)" -> The Comp XE lobes technically "break" the 47.5% rule and have pretty high velocity at the close which gives them their sewing machine (valve train destroying) sound... (I'd SWEAR I came across a Harold Brookshire post where he stated that the close rate on the XE lobes was too fast and he slowed down the close rate on the Voodoo line, and I've been trying to find it again for 3 or 4 years to no avail, so maybe I made it all up...)
Personally, I think time moves on and materials and technology improves, but the most aggressive flat tappet grinds DO technically come in below the Isky 47.5% rule, but not by much... (Higher %s are less aggressive)
Comp XE262H: 218 deg duration @ 0.050" / 462 thousandths lift = 47.2%
Lunati Voodoo: 262/268 cam: 219 deg dur @ 0.050" / 468 thou lift = 46.8%
-The intensity may vary within the supposed lobe family, too; I feel like I remember two different lobe intensities all branded under Comp XE flat tappet SBC cams in the Master Catalog...
On the cam button end play, timing covers and the Corvette water pumps: I think there ARE combinations that could be problematic. I was worried about this too and Gary from NY helped me with this: a standard double-roller Cloyes chain set, Comp cams roller button, the cheap yet attractive AllStar Performance aluminum timing cover, FelPro paper "blue stripe" gasket, and a proper Corvette-style water pump with flat-headed bolts on the rear cover fit 100% perfect and snug with zero extra clearance. -He said it's a combination he uses all the time and it fits perfect and he was NOT stretching the truth one bit.
The aluminum covers ARE thicker, so I think having a thin paper gasket and having the flat headed screws on the back of the Corvette water pump are important. There's no way the water pump with rounded-head screws would've fit on mine, anyway. -I'm not sure whether the Corvette style water pumps are shorter / closer to the block on the rear or not, but I do have a note that says that the distance between the block surface to the water pump hub IS different between a standard short-style SBC water pump (5 5/8") vs. the Corvette water pump with a distance of 5 13/16" from the block to the hub.(So it's not just the pilot shaft size and roller bearing that's the diff between the standard short and Corvette pumps, anyway; there is at least one other dimensional difference.)
I think I've added almost nothing new to the thread except maybe the Isky rule; I'm mostly just repeating what I think are the good ideas people have already stated and one combination of retrofit roller cam parts, timing covers, and water pump rear cover bolts that definitely work without issue.
Adam
As far as the timing chain cover I think if experimenting or guesswork isnt wanted, sticking with jebbys recommendation is wise, I used a polished aluminum water pump sold by Skip white https://www.ebay.com/itm/33438277145...AAAOSwGAhbeGXP and this timing chain cover. https://www.ebay.com/itm/18531573874...8AAOSwkp9iGmi3 the timing cover barely clears the pump with thick gaskets but it does...
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Yes and no to the slippage below stall.
I have a 3000 stall converter in my th350. I often am below 3000 rpm and as long as the load on the engine is not great like pulling a hill at low speed the slippage is minimal, not noticeable and the heat generated is not excessive.
The slippage is load dependent I guess is what I’m saying. Cruising at 70 just below stall rpm the load is minimal and so is the slippage. If you accelerate suddenly then the load increases and so does the slippage, which is what we want.
I have a 3000 stall converter in my th350. I often am below 3000 rpm and as long as the load on the engine is not great like pulling a hill at low speed the slippage is minimal, not noticeable and the heat generated is not excessive.
The slippage is load dependent I guess is what I’m saying. Cruising at 70 just below stall rpm the load is minimal and so is the slippage. If you accelerate suddenly then the load increases and so does the slippage, which is what we want.
Scotty
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
The torque converter is not really part of the transmission. It is a fluid coupling between the engine and the transmission.
It does share the fluid with the transmission and thereby the heat generated from the torque converter. So in that regard I guess you could say it is part of the transmission system.
I just would not confuse the clutches in the transmission and how they are driven or driving various outputs with the fluid coupling of the converter. No clutches in the converter just vanes that pump fluid and vanes that receive fluid under pressure.
One set of turbine blades drives another set. A "free" coupling if you will. Where the flow of fluid forces vanes to turn much in the same way a fan will turn if you blast compressed air at it.
So regardless of the transmission involved the torque converter uses the same principle of operation.
It does share the fluid with the transmission and thereby the heat generated from the torque converter. So in that regard I guess you could say it is part of the transmission system.
I just would not confuse the clutches in the transmission and how they are driven or driving various outputs with the fluid coupling of the converter. No clutches in the converter just vanes that pump fluid and vanes that receive fluid under pressure.
One set of turbine blades drives another set. A "free" coupling if you will. Where the flow of fluid forces vanes to turn much in the same way a fan will turn if you blast compressed air at it.
So regardless of the transmission involved the torque converter uses the same principle of operation.
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
The torque converter is not really part of the transmission. It is a fluid coupling between the engine and the transmission.
It does share the fluid with the transmission and thereby the heat generated from the torque converter. So in that regard I guess you could say it is part of the transmission system.
I just would not confuse the clutches in the transmission and how they are driven or driving various outputs with the fluid coupling of the converter. No clutches in the converter just vanes that pump fluid and vanes that receive fluid under pressure.
One set of turbine blades drives another set. A "free" coupling if you will. Where the flow of fluid forces vanes to turn much in the same way a fan will turn if you blast compressed air at it.
So regardless of the transmission involved the torque converter uses the same principle of operation.
It does share the fluid with the transmission and thereby the heat generated from the torque converter. So in that regard I guess you could say it is part of the transmission system.
I just would not confuse the clutches in the transmission and how they are driven or driving various outputs with the fluid coupling of the converter. No clutches in the converter just vanes that pump fluid and vanes that receive fluid under pressure.
One set of turbine blades drives another set. A "free" coupling if you will. Where the flow of fluid forces vanes to turn much in the same way a fan will turn if you blast compressed air at it.
So regardless of the transmission involved the torque converter uses the same principle of operation.
Scotty
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
https://www.monstertransmission.com/...l#.YoZFkIpMGhA
such converters do exist. I don’t think you risk damaging the trans at al, but I’m no expert on the 700r4. Just be sure to have an additional cooler to manage the additional heat.
I run my fluid through the radiator then through an additional cooler and back to the trans. Some guys bypass the radiator all together and just use an auxiliary cooler.
if you want lower stall than 2400 without lockup that is likely doable too. Just have to talk to someone to get that.
https://www.rampfesthudson.com/can-y...ithout-lockup/
here is another discussion on the subject,
https://www.thirdgen.org/forums/tran...-question.html
such converters do exist. I don’t think you risk damaging the trans at al, but I’m no expert on the 700r4. Just be sure to have an additional cooler to manage the additional heat.
I run my fluid through the radiator then through an additional cooler and back to the trans. Some guys bypass the radiator all together and just use an auxiliary cooler.
if you want lower stall than 2400 without lockup that is likely doable too. Just have to talk to someone to get that.
https://www.rampfesthudson.com/can-y...ithout-lockup/
here is another discussion on the subject,
https://www.thirdgen.org/forums/tran...-question.html
Last edited by REELAV8R; May 19, 2022 at 09:46 AM.
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
I actually linked a thread about the 47% rule a few days ago in another thread discussing the XE and voodoo cams I mistakenly thought I mentioned it in this one too but yeah I also read in another forum (OLD thread I think in yellow bullet) where Harold claimed the older XE line of cams he designed were inferior to the voodoo cams which he thought were safer. I also read about the crappy lifters being an issue a year ago in a thread here where I shared some you tube videos from a guy who had been installing them for years and recently started experiencing failures.
As far as the timing chain cover I think if experimenting or guesswork isnt wanted, sticking with jebbys recommendation is wise, I used a polished aluminum water pump sold by Skip white https://www.ebay.com/itm/33438277145...AAAOSwGAhbeGXP and this timing chain cover. https://www.ebay.com/itm/18531573874...8AAOSwkp9iGmi3 the timing cover barely clears the pump with thick gaskets but it does...
As far as the timing chain cover I think if experimenting or guesswork isnt wanted, sticking with jebbys recommendation is wise, I used a polished aluminum water pump sold by Skip white https://www.ebay.com/itm/33438277145...AAAOSwGAhbeGXP and this timing chain cover. https://www.ebay.com/itm/18531573874...8AAOSwkp9iGmi3 the timing cover barely clears the pump with thick gaskets but it does...
I used a blemish polished aluminum PRW Corvette water pump I got from their eBay store and it worked perfectly too. The only blemish I could find was that the neck around the inlet wasn’t finely polished and looked like someone had sanded it with 80 grit. I couldn’t believe they’d offer a blemish discount for that especially as it would be under the hose and impossible to see.
Adam
Melting Slicks
Joined: Jun 2016
Posts: 2,979
Likes: 332
From: Woodinville WA
The thing about automatic transmissions is that if you run them at an engine rpm that is below the stall speed of the converter for a considerable length of time, they generate a lot of heat from the slippage. I believe this is the real reason for the torque converter lock up in the first place.
According to an online calculator, my engine rpm at 70 m.p.h. should nominally be 1872 rpm, which would probably induce some slippage, meaning extra heat.
I have a toggle switch that I will be installing in the dash that will turn off the TC lock up, but I plan on using it more as a way of "arming" the lock up feature when I want it to work, like on the highway, and turn it off when I'm putting around town. I might just leave the tranny in third gear until I pull onto the highway, and bump the shifter up into overdrive when I get up to speed. I think the TC only locks up in overdrive. I would rather not do that, though. I'd prefer it to just work like the more modern daily driver cars I've been driving for the last few decades.
Scotty
According to an online calculator, my engine rpm at 70 m.p.h. should nominally be 1872 rpm, which would probably induce some slippage, meaning extra heat.
I have a toggle switch that I will be installing in the dash that will turn off the TC lock up, but I plan on using it more as a way of "arming" the lock up feature when I want it to work, like on the highway, and turn it off when I'm putting around town. I might just leave the tranny in third gear until I pull onto the highway, and bump the shifter up into overdrive when I get up to speed. I think the TC only locks up in overdrive. I would rather not do that, though. I'd prefer it to just work like the more modern daily driver cars I've been driving for the last few decades.
Scotty
My setup just causes the TC to lockup when I’ve flipped that switch to on. I think I actually paid extra to get the TC with lockup switches because I like the reduced RPM and heat.
There’s definitely better and more advanced controllers that give you more control over tc lockup and shifts out there for the 4l60e and 80es, though. I can’t recommend the tci controller.