Quench, CR question
03-17-2002, 04:06 PM
#1
Moderator
Thread Starter
Quench, CR question
Got my block at the machine shop. '73 350 4 bolt. It's going .030 over and I have the TRW L2256F30 (4 relief) forged pistons on order from Summit. Should be 9.72 CR according to the mag. I was hoping to be right at 10.1. I'm confused about decking or just resurfacing the block for a higher CR. Do all 350 (355 now) blocks have the same deck height? I'm guessing so and just what piston is used determins the 'quench' . Should I go with a thinner head gasket or just leave it alone and put it together? Oh, I'm using 64cc Sportsman II heads and the XE274H cam. Is the CR ok for this cam/head combo? Dang it, I should quit reading about 'Quench', just too much info for a back yard wrench-head!! :crazy: :lol: Need to know soon guys, I gotta tell the shop what to do. Thanks :cheers:
03-17-2002, 09:35 PM
#2
Racer
Member Since: Feb 2001
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
Re: Quench, CR question (MasterDave)
MasterDave;
I have the exact same questions as you! I've recently added a '69 SB to my already overloaded garage and will be building up the engine within the next month.
I don't know if you caught the thread in the Engine Mod Section but the quench issue was being addressed there. Don't give up! Quench is important.
From what I can gather, a zero deck clearance is preferred. Meaning that the top outer edge of the piston is level to the head gasket surface. You'd use a normal head gasket thickness, and work with the piston dome to achieve the desired CR.
Without decking the block, from what I can gather, the piston would sit .020" below the deck surface, which is detrimental to piston temps and aggrevates pinging.
So I asked the very same question you are now asking in the Mod Section, the only response I got was don't deck the block. Well if you don't deck the block, it's either custom pistons or rods! :confused:
If you need an answer quickly, IM 427HotRod. Mountainmotor is out of town for about another week or so. If you email me I can give you 427's work phone.
I personally am going to deck my block to zero. Just mill it. That's after the crank bearings have been bored/honed. Then mock-up the assy w/ pistons and rods installed and determine how much to cut from the deck. Measure in all 4 corners and you'll be able to determine if the crank sits true within the block. But you're going to need your pistons to do this measuring. An 010 block isn't worth that much anyway.
[Modified by kahuner, 8:49 PM 3/17/2002]
I have the exact same questions as you! I've recently added a '69 SB to my already overloaded garage and will be building up the engine within the next month.
I don't know if you caught the thread in the Engine Mod Section but the quench issue was being addressed there. Don't give up! Quench is important.
From what I can gather, a zero deck clearance is preferred. Meaning that the top outer edge of the piston is level to the head gasket surface. You'd use a normal head gasket thickness, and work with the piston dome to achieve the desired CR.
Without decking the block, from what I can gather, the piston would sit .020" below the deck surface, which is detrimental to piston temps and aggrevates pinging.
So I asked the very same question you are now asking in the Mod Section, the only response I got was don't deck the block. Well if you don't deck the block, it's either custom pistons or rods! :confused:
If you need an answer quickly, IM 427HotRod. Mountainmotor is out of town for about another week or so. If you email me I can give you 427's work phone.
I personally am going to deck my block to zero. Just mill it. That's after the crank bearings have been bored/honed. Then mock-up the assy w/ pistons and rods installed and determine how much to cut from the deck. Measure in all 4 corners and you'll be able to determine if the crank sits true within the block. But you're going to need your pistons to do this measuring. An 010 block isn't worth that much anyway.
[Modified by kahuner, 8:49 PM 3/17/2002]
03-18-2002, 12:24 AM
#3
Advanced
Re: Quench, CR question (MasterDave)
MasterDave,
Kahuner is on the money about running a zero deck, the engines run more efficiently with this setup. Chevrolet recommends a minimum .035" clearance between pistons and head for steel rods. If you run a zero deck, with a Fel-Pro composition gasket with a compressed thickness of .041", you should be in the ball park, but be sure to calculate your actual compression ratio. If I remember correctly, This combination yields a compression ratio over 10:1. Anything over 10:1 using iron heads , with pump gas is asking for trouble,so check carefully.
Cheers,
Bill
Kahuner is on the money about running a zero deck, the engines run more efficiently with this setup. Chevrolet recommends a minimum .035" clearance between pistons and head for steel rods. If you run a zero deck, with a Fel-Pro composition gasket with a compressed thickness of .041", you should be in the ball park, but be sure to calculate your actual compression ratio. If I remember correctly, This combination yields a compression ratio over 10:1. Anything over 10:1 using iron heads , with pump gas is asking for trouble,so check carefully.
Cheers,
Bill
03-18-2002, 02:51 AM
#4
Race Director
Member Since: May 2000
Location: Redondo Beach USA
Posts: 12,487
Received 1,973 Likes
on
1,188 Posts
Re: Quench, CR question (Bill T)
Chevrolet's minimum recommended quench zone clearance is .035 -.040". This dimension is a combination of your piston crown to deck clearance and the compressed thickness of the head gasket. Since most composition head gaskets are at least .040" a deck clearance of zero will get you in the ballpark.
The nominal blueprint crankshaft centerline to deck dimension for a SB is 9.025". The calculated piston crown deck clearance is the sum of the crank throw dimension, rod length, and piston compression height. A good machine shop should have the tools to measure the block deck height and verify that is is parallel to the crankshaft centerline.
One should always measure the deck clearance on teardown to get a ballpark number of where you're at. Then either the block and all parts should be carefully measured to determine what, if any, material should be taken off the deck, or, preferably, you assemble everything, measure all eight deck clearances, and them deck the block and machine the piston crowns as required to get the number you want. Of course, all this must be done AFTER the head gasket has been selected since its compressed thickness is part of the quench zone clearance calculation.
Composition head gaskets are more forgiving of a little surface warp than the thin shim type gaskets, but compositions will typically give you a much larger quench zone clearance if you just throw everything together out of the box without making careful measurements, so you will probably not get the CR you think you have.
Another thing to consider is that if the quench zone clearance is too great the engine may have more propensity to detonate, even though the CR is lower!
The way to do it right is to line up your ducks ahead of time, have a firm written plan, and MEASURE EVERYTHING!!!
One other thing is that if you have an original engine, I would NOT recommend decking the block as it will destroy the factory stamp pad and OEM broach pattern.
Duke
The nominal blueprint crankshaft centerline to deck dimension for a SB is 9.025". The calculated piston crown deck clearance is the sum of the crank throw dimension, rod length, and piston compression height. A good machine shop should have the tools to measure the block deck height and verify that is is parallel to the crankshaft centerline.
One should always measure the deck clearance on teardown to get a ballpark number of where you're at. Then either the block and all parts should be carefully measured to determine what, if any, material should be taken off the deck, or, preferably, you assemble everything, measure all eight deck clearances, and them deck the block and machine the piston crowns as required to get the number you want. Of course, all this must be done AFTER the head gasket has been selected since its compressed thickness is part of the quench zone clearance calculation.
Composition head gaskets are more forgiving of a little surface warp than the thin shim type gaskets, but compositions will typically give you a much larger quench zone clearance if you just throw everything together out of the box without making careful measurements, so you will probably not get the CR you think you have.
Another thing to consider is that if the quench zone clearance is too great the engine may have more propensity to detonate, even though the CR is lower!
The way to do it right is to line up your ducks ahead of time, have a firm written plan, and MEASURE EVERYTHING!!!
One other thing is that if you have an original engine, I would NOT recommend decking the block as it will destroy the factory stamp pad and OEM broach pattern.
Duke
03-18-2002, 04:40 AM
#5
Racer
Member Since: Feb 2001
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
Re: Quench, CR question (SWCDuke)
Duke;
I have a couple of questions.
First, regarding my SB. It's a correct block (casting number) but not original to the car, so the engine pad doesn't mean squat. If the piston sits at a
-.020" to the deck surface, decking the block is the most resonable option at about $150 in order to get the zero clearance right?
Second, I'm being told that 10.4:1 CR is about max for pump premium gas. True or false?
Lastly (and this is the one that has me stumped) how would you recommend getting to a zero deck clearance if you didn't want to deck the block in order to preserve the pad identification numbers, as is the case with my L72 engine?
I'm left with the impression that this whole subject of squish gap or quench, is something that has been discovered subsequent to the design of these engines. Possibly driven by the reduction of octane in today's fuels and Governmental regulations.
So I feel like I have 3 choices when it comes to preserving all of the performance that I possibly can in my L72. (1) Rebuild the engine stock, 11:1 CR and run Sunoco Turbo blue, (2) reduce the CR back to 9.5:1 and run pump grade premium which I think would be the least desireable option due to negative deck clearance, pinging and performance, or (3) 10:1 CR, zero deck.
Isn't achieving zero deck clearance with 10:1 CR the best option so that at least you could travel in the car w/o searching for racing fuel and maintain performance? It just kills me to think that if I put the engine back together with a 9.5:1 CR, that a good 383 stroker motor could out run me!
I have a couple of questions.
First, regarding my SB. It's a correct block (casting number) but not original to the car, so the engine pad doesn't mean squat. If the piston sits at a
-.020" to the deck surface, decking the block is the most resonable option at about $150 in order to get the zero clearance right?
Second, I'm being told that 10.4:1 CR is about max for pump premium gas. True or false?
Lastly (and this is the one that has me stumped) how would you recommend getting to a zero deck clearance if you didn't want to deck the block in order to preserve the pad identification numbers, as is the case with my L72 engine?
I'm left with the impression that this whole subject of squish gap or quench, is something that has been discovered subsequent to the design of these engines. Possibly driven by the reduction of octane in today's fuels and Governmental regulations.
So I feel like I have 3 choices when it comes to preserving all of the performance that I possibly can in my L72. (1) Rebuild the engine stock, 11:1 CR and run Sunoco Turbo blue, (2) reduce the CR back to 9.5:1 and run pump grade premium which I think would be the least desireable option due to negative deck clearance, pinging and performance, or (3) 10:1 CR, zero deck.
Isn't achieving zero deck clearance with 10:1 CR the best option so that at least you could travel in the car w/o searching for racing fuel and maintain performance? It just kills me to think that if I put the engine back together with a 9.5:1 CR, that a good 383 stroker motor could out run me!
03-18-2002, 01:03 PM
#6
Race Director
Member Since: May 2000
Location: Redondo Beach USA
Posts: 12,487
Received 1,973 Likes
on
1,188 Posts
Re: Quench, CR question (kahuner)
First, quit yaking about this "zero deck" business. Guys throw this "zero deck" vernacular around out of context i.e. with no reference to the head gasket thicksness, and you end up with another myth. You want to focus on QUENCH ZONE CLEARANCE, and this is a function of BOTH piston crown deck clearance and HEAD GASKET COMPRESSED THICKNESS. Not everyone runs a .040" composition head gasket, which would require the piston crowns to be level with the deck to .005" above the deck to be achieve the minimum quench zone clearance dimension. If you had zero piston crown to deck clearance with a .016" stainless steel shim gasket you would have too little quench zone clearance and likely too much compression for commercially available fuels.
Decking the block is the most convenient way to achieve the minimum quench zone clearance, but some piston crowns might have to be shaved to achieve the same dimension on all eight cylinders. It's probably okay to be within a few thou on all cylinders of your target number, but I like to keep variation to plus or minus half a thou. If you don't care about the pad numbers or the broach pattern, it's okay to shave the deck to get your crown/deck clearance, which can only be computed AFTER you have selected the head gasket and pistons and have accurate dimensions for them. Then you select a target CR and compute the deck clearance that you need to achieve this target with the specific head gasket and pistons you have selected. If the CR is too high with the quench zone clearance in the minimu range, then you have to increase the combustion chamber size by suitable machining of the pistons.
You need to do a this engineering up front, and I also prefer preassembling the short block before any deck/piston machining to measure the actual piston/deck clearance on each cylinder. It tells me a story of how accurately all the components are machined and how much tolerance stack up I have, if any. Then I know exactly how much to take off the deck and each piston to achieve my design quench zone clearance clearance, and like I said, I measure the crown/deck clearance on disassembly to see where I am starting, so I can get a ballpark number of how much will have to come off the deck and crowns with the new components that I have preselected.
The actual CR the engine can handle is dependent on the cam. A high overlap cam will handle more compression on a given fuel octane. In general, if you are running an OEM SHP cam, you should be able to run an HONEST 10:1 on pump premium. Detonation is primarily a low rev phenomenon, and high overlap cams kill low speed dynamic compression, which reduces detonation potential, but final tuning of the ignition curve, primarily the rate the centrifugal advance comes in will often be required to keep the engine out of signficant detonation.
The OHV quench combustion chamber was developed by GM in the late forties. By confining the combustion chamber to about half the bore, an engine can run higher compression. (Smaller combustion chambers have less propensity to detonate.) With optimum timing, peak cylinder pressure occurs about four degrees ATC and at this piston position the quench zone clearance is near minimum. The flame will not propagate into the quench zone because the relatively cool piston and cylinder head relative to the 4500 deg. F flame front literally "quenches" the flame - and any tendency for this furthest portion of the chamber mixture to detonate. The quench zone also increases turbulence, because as the pistons approaches TDC the mixture is forced away from the quench zone, and the greater the turbulence the faster the mixture is consumed, which reduces detonation potential. Also, the shorter the distance from the ignition source to the end of the combustion chamber, the more CR you can run on a give fuel octane quality, so forcing combustion to occur on one side of the cylinder further reduces detonation potential. The key to running the highest CR on a given fuel octane quality is to have a small, highly turbulence combustion chamber,
Detonation is a function of the amount of "clock time" the "end gas" or last of the unburned fuel-air mixture is exposed to high temperature and pressure. We want the mixture to be consumed by combustion as quickly as possible, so high turbulence, small chambers, and high revs minumize the time it takes for combustion to consume the fuel-air mixture. Minimizing the clock time to complete combustion also gets us closer to the thermodyamic ideal of "constant volume combustion", so a small turbulent combustion chamber will result in greater thermal efficiency, which means more power and lower BSFC.
The problem with the quench chamber is that it generates HC emissions because the unburned fuel in the quench zone becomes exhaust emissions, and this is why the BBs were redesigned with an "open" chamber in the late sixties. GM was able to control SB emissions without a total redesign of the combustion chamber.
I believe a L-72 can be run on pump gas with the OEM cam and a true 10:1 CR. One option you should look at is buying the Federal Mogul (TRW) OEM replacement pistons and then machining the dome off. The F-M Performance Parts Catalog lists piston compression heights and dome volumes - numbers you need along with head gasket compressed thickness to determine what options you have to simulataneously achieve both minimum quench zone clearance and your target CR.
If the CR is too high at minimum quench zone clearnance, you can further shave the crown, but only the half below the combustion chamber, until you achieve the desired combustion chamber volume to end up with your target CR.
The best way to really understand this is to sketch out a schematic of the a cylinder cross section showing the block, piston, head gasket and head combustion chamber. Pick some deck heights, gasket thicknessness and using the appropriate dimensions/volumes from the piston manufacturer, start computiing some CRs.
If you don't want to deck the block, you can probably achieve minimum quench zone clearance by using a steel shim gasket. The risk here is that they work best on freshly machined surfaces that are dead flat. A composition gasket will have a higher probabililty of sealing the OEM machined surfaces. Your quench zone clearance will probably be well above minimum, but that's not the end of the world. You can just accept whatever quench zone your components give you and then buy and off the shelf piston to achieve your target CR. If such is not available, you buy the closest you can get on the high side and suitably machine the piston crowns to achieve your target CR.
The problem that I have in establishing the maximum CRs that can be run on current premium unleaded is finding accurate data. Guys will say they are running "X" CR, and then when I ask them about deck height, gasket thickness, etc. they look at me like I'm from Mars. There are two issues here. First, most guys don't know how to compute the actual CR, and almost no one take any measurements. If you don't understand all the dimensions that are critical to actual CR you can't give the machine shop specific instructions, and if you don't measure anything on assembly you have no idea where you're at. The one thing I DO know is that "advertised" CRs are about a quarter to a half point more that what was actually achieved, and I believe most aftermarket pistons are about the same. You can buy a set of pistons that are advertised at "10:1", but this is with a specific deck height, compressed head gasket thickness, head chamber volume, and piston crown geometry. Without this data "10:1" is out of context, just like "zero deck" and is pretty much meaningless. I guess the best you can count on is that piston CRs are generally overstated, so if you buy an advertised "10:1" piston, the actual CR on a production machined engine will probably average about 9.5:1 and the variation for the max to min on eight cylinders is probaby at least a quarter point and maybe as much as a half point.
Duke
Decking the block is the most convenient way to achieve the minimum quench zone clearance, but some piston crowns might have to be shaved to achieve the same dimension on all eight cylinders. It's probably okay to be within a few thou on all cylinders of your target number, but I like to keep variation to plus or minus half a thou. If you don't care about the pad numbers or the broach pattern, it's okay to shave the deck to get your crown/deck clearance, which can only be computed AFTER you have selected the head gasket and pistons and have accurate dimensions for them. Then you select a target CR and compute the deck clearance that you need to achieve this target with the specific head gasket and pistons you have selected. If the CR is too high with the quench zone clearance in the minimu range, then you have to increase the combustion chamber size by suitable machining of the pistons.
You need to do a this engineering up front, and I also prefer preassembling the short block before any deck/piston machining to measure the actual piston/deck clearance on each cylinder. It tells me a story of how accurately all the components are machined and how much tolerance stack up I have, if any. Then I know exactly how much to take off the deck and each piston to achieve my design quench zone clearance clearance, and like I said, I measure the crown/deck clearance on disassembly to see where I am starting, so I can get a ballpark number of how much will have to come off the deck and crowns with the new components that I have preselected.
The actual CR the engine can handle is dependent on the cam. A high overlap cam will handle more compression on a given fuel octane. In general, if you are running an OEM SHP cam, you should be able to run an HONEST 10:1 on pump premium. Detonation is primarily a low rev phenomenon, and high overlap cams kill low speed dynamic compression, which reduces detonation potential, but final tuning of the ignition curve, primarily the rate the centrifugal advance comes in will often be required to keep the engine out of signficant detonation.
The OHV quench combustion chamber was developed by GM in the late forties. By confining the combustion chamber to about half the bore, an engine can run higher compression. (Smaller combustion chambers have less propensity to detonate.) With optimum timing, peak cylinder pressure occurs about four degrees ATC and at this piston position the quench zone clearance is near minimum. The flame will not propagate into the quench zone because the relatively cool piston and cylinder head relative to the 4500 deg. F flame front literally "quenches" the flame - and any tendency for this furthest portion of the chamber mixture to detonate. The quench zone also increases turbulence, because as the pistons approaches TDC the mixture is forced away from the quench zone, and the greater the turbulence the faster the mixture is consumed, which reduces detonation potential. Also, the shorter the distance from the ignition source to the end of the combustion chamber, the more CR you can run on a give fuel octane quality, so forcing combustion to occur on one side of the cylinder further reduces detonation potential. The key to running the highest CR on a given fuel octane quality is to have a small, highly turbulence combustion chamber,
Detonation is a function of the amount of "clock time" the "end gas" or last of the unburned fuel-air mixture is exposed to high temperature and pressure. We want the mixture to be consumed by combustion as quickly as possible, so high turbulence, small chambers, and high revs minumize the time it takes for combustion to consume the fuel-air mixture. Minimizing the clock time to complete combustion also gets us closer to the thermodyamic ideal of "constant volume combustion", so a small turbulent combustion chamber will result in greater thermal efficiency, which means more power and lower BSFC.
The problem with the quench chamber is that it generates HC emissions because the unburned fuel in the quench zone becomes exhaust emissions, and this is why the BBs were redesigned with an "open" chamber in the late sixties. GM was able to control SB emissions without a total redesign of the combustion chamber.
I believe a L-72 can be run on pump gas with the OEM cam and a true 10:1 CR. One option you should look at is buying the Federal Mogul (TRW) OEM replacement pistons and then machining the dome off. The F-M Performance Parts Catalog lists piston compression heights and dome volumes - numbers you need along with head gasket compressed thickness to determine what options you have to simulataneously achieve both minimum quench zone clearance and your target CR.
If the CR is too high at minimum quench zone clearnance, you can further shave the crown, but only the half below the combustion chamber, until you achieve the desired combustion chamber volume to end up with your target CR.
The best way to really understand this is to sketch out a schematic of the a cylinder cross section showing the block, piston, head gasket and head combustion chamber. Pick some deck heights, gasket thicknessness and using the appropriate dimensions/volumes from the piston manufacturer, start computiing some CRs.
If you don't want to deck the block, you can probably achieve minimum quench zone clearance by using a steel shim gasket. The risk here is that they work best on freshly machined surfaces that are dead flat. A composition gasket will have a higher probabililty of sealing the OEM machined surfaces. Your quench zone clearance will probably be well above minimum, but that's not the end of the world. You can just accept whatever quench zone your components give you and then buy and off the shelf piston to achieve your target CR. If such is not available, you buy the closest you can get on the high side and suitably machine the piston crowns to achieve your target CR.
The problem that I have in establishing the maximum CRs that can be run on current premium unleaded is finding accurate data. Guys will say they are running "X" CR, and then when I ask them about deck height, gasket thickness, etc. they look at me like I'm from Mars. There are two issues here. First, most guys don't know how to compute the actual CR, and almost no one take any measurements. If you don't understand all the dimensions that are critical to actual CR you can't give the machine shop specific instructions, and if you don't measure anything on assembly you have no idea where you're at. The one thing I DO know is that "advertised" CRs are about a quarter to a half point more that what was actually achieved, and I believe most aftermarket pistons are about the same. You can buy a set of pistons that are advertised at "10:1", but this is with a specific deck height, compressed head gasket thickness, head chamber volume, and piston crown geometry. Without this data "10:1" is out of context, just like "zero deck" and is pretty much meaningless. I guess the best you can count on is that piston CRs are generally overstated, so if you buy an advertised "10:1" piston, the actual CR on a production machined engine will probably average about 9.5:1 and the variation for the max to min on eight cylinders is probaby at least a quarter point and maybe as much as a half point.
Duke
03-18-2002, 02:05 PM
#7
Advanced
Re: Quench, CR question (MasterDave)
MasterDave,
The formula to roughly calculate your compression ratio for your 350, is as follows:
swept vol.+chamber vol.+gasket vol.+deck vol.+piston vol.,divided by chamber vol.+gasket vol.+deck vol.+piston vol.=compression ratio
To figure Swept vol. in cu. in =4.030" x4.030" x3.48" x .7854 = 44.389"
Chamber vol. in cu. in =64cc x .061 =3.904"
Gasket vol. in cu. in. for a Fel-Pro composition gasket=9.1cc x.061=.5551"
Deck vol. ( for a minus .020" deck height)= 4.030" x 4.030" x.020"x.7854=.255"
Piston vol.(valve relief+ crevice vol. ,estimated)=.250"
So,( 44.389"+3.904"+.5551"+.255"+.250")=49.35 1 Divided by:
(3.904"+.5551"+.255"+.250")=4.96
so, 49.351/4.96=9.94
c.r.=9.94:1(rough estimate),for a minus .020" deck height
c. r. =10.425:1 (rough estimate, for zero deck)
These estimates do not account for tolerance stack-up, or actual measured volumes of your motor.
Dave,IMHO, I would stick to the lower c.r. I have a 350,zero deck, 10.5:1 c.r. motor that I have previously run in a '68 camaro, and didn't have any detonation problems on pump gas, but that motor has Brownfield aluminum heads. I'm planning on putting that engine in my '64 coupe.Hope this helps. :cheers:
Bill
The formula to roughly calculate your compression ratio for your 350, is as follows:
swept vol.+chamber vol.+gasket vol.+deck vol.+piston vol.,divided by chamber vol.+gasket vol.+deck vol.+piston vol.=compression ratio
To figure Swept vol. in cu. in =4.030" x4.030" x3.48" x .7854 = 44.389"
Chamber vol. in cu. in =64cc x .061 =3.904"
Gasket vol. in cu. in. for a Fel-Pro composition gasket=9.1cc x.061=.5551"
Deck vol. ( for a minus .020" deck height)= 4.030" x 4.030" x.020"x.7854=.255"
Piston vol.(valve relief+ crevice vol. ,estimated)=.250"
So,( 44.389"+3.904"+.5551"+.255"+.250")=49.35 1 Divided by:
(3.904"+.5551"+.255"+.250")=4.96
so, 49.351/4.96=9.94
c.r.=9.94:1(rough estimate),for a minus .020" deck height
c. r. =10.425:1 (rough estimate, for zero deck)
These estimates do not account for tolerance stack-up, or actual measured volumes of your motor.
Dave,IMHO, I would stick to the lower c.r. I have a 350,zero deck, 10.5:1 c.r. motor that I have previously run in a '68 camaro, and didn't have any detonation problems on pump gas, but that motor has Brownfield aluminum heads. I'm planning on putting that engine in my '64 coupe.Hope this helps. :cheers:
Bill
03-18-2002, 02:53 PM
#8
Moderator
Thread Starter
Re: Quench, CR question (Bill T)
Wow Bill, it's obvious you spent some time doing this. I very much appreciate it, thank you. I'm gonna hafta print this so I can spend some time absorbing the info. :cool: For your .020 deck height you are considering the piston down in the hole at TDC and not above the deck, correct?
[Modified by MasterDave, 10:55 AM 3/18/2002]
[Modified by MasterDave, 10:55 AM 3/18/2002]
03-18-2002, 07:39 PM
#9
Instructor
Re: Quench, CR question (MasterDave)
I am building my 350 with the same pistons. The block has never been decked and there is about .020 between the top of the pistons and the deck. I'm using some old 3991492 angle plug heads which were advertised as 64CC but I CCed them closer to 67. I'll be somewhat less than the 9.72:1, but will be using a Crane h-278-2 cam and "fast bleed" lifters - should be good to go with the lower CR.
Be sure you inspect your pistons closely. Mine came from Summit with a few shipping dings. One interfered with the rings and had to fix it with some careful filing.
Be sure you inspect your pistons closely. Mine came from Summit with a few shipping dings. One interfered with the rings and had to fix it with some careful filing.
03-18-2002, 08:02 PM
#10
Moderator
Thread Starter
Re: Quench, CR question (jkmhb)
Gotcha (jkmhb), I will check the pistons for sure. I once ordered a set of Cragar wheels from them. They arrived in the original, not double boxed, thin cardboard boxes. Three of them were flat on 2 sides. Summit didn't send them bent, but if they would have packaged them right, UPS would have had a harder time screwing them up. Sent 'em back right away. Everything else I've ordered has always been boxed in way too many styrofoam peanuts. Stuff that don't matter, like shirts & catalogues 'n stuff. :crazy: Thanks for the heads up.... :cool:
