383 build for C2
01-20-2018, 04:30 PM
#41
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Forget about top end power. Guys obsess over this, but how often are you going to rev it over 5000. Properly configured a 383 will produce massive low end torque, which means big power and terrific throttle response in the low to mid range, where you spend 99+ percent of driving time compared to a similarly configured 327.
Whatever cam you choose top end power is going to be more of a function of head flow than the cam, so massage OE heads or buy aftermarket heads with inlet port volume of no more than 180cc that flow at least 220/170 CFM at 0.5" valve lift, 28" H2O depression.
The L-46/82 cam would be a good choice. It will make better than 80 percent peak torque at 2000 and useable power to 5500-6000 depending on head flow. If you want more low end torque the McCagh Special cam will make about 90 percent peak torque at 2000. Massaged heads are REQUIRED for this config., and it will make nearly the same top end power as the L-46/82 cam and easily pull a 3.08 or 2.73 axle with a manual or automatic for easy highway cruising.
I do know of one 383 with massaged heads and the McCagh Special cam. It's in a Shark with an original base 350/300 HP engine and TH400/3.08 axle. I haven't been able to talk the owner into a chassis dyno test, but he says it's a beast compared to the original base engine config. Other than the cam and head work it's all OE, looks completely original, and has idle behavior identical to the original 350/300.
Simulations indicate around 250-260 maximum SAE corrected RWHP in the 5000-5500 range depending on head flow, inlet and exhaust system configuration (for comparison a decent base 300 HP engine is about 195), but in the low to mid range it makes 10-30 percent more power than an identically configured 327, and the lower the RPM, the greater the increase in power - right where it's most usable for a high performance road engine.
Duke
Whatever cam you choose top end power is going to be more of a function of head flow than the cam, so massage OE heads or buy aftermarket heads with inlet port volume of no more than 180cc that flow at least 220/170 CFM at 0.5" valve lift, 28" H2O depression.
The L-46/82 cam would be a good choice. It will make better than 80 percent peak torque at 2000 and useable power to 5500-6000 depending on head flow. If you want more low end torque the McCagh Special cam will make about 90 percent peak torque at 2000. Massaged heads are REQUIRED for this config., and it will make nearly the same top end power as the L-46/82 cam and easily pull a 3.08 or 2.73 axle with a manual or automatic for easy highway cruising.
I do know of one 383 with massaged heads and the McCagh Special cam. It's in a Shark with an original base 350/300 HP engine and TH400/3.08 axle. I haven't been able to talk the owner into a chassis dyno test, but he says it's a beast compared to the original base engine config. Other than the cam and head work it's all OE, looks completely original, and has idle behavior identical to the original 350/300.
Simulations indicate around 250-260 maximum SAE corrected RWHP in the 5000-5500 range depending on head flow, inlet and exhaust system configuration (for comparison a decent base 300 HP engine is about 195), but in the low to mid range it makes 10-30 percent more power than an identically configured 327, and the lower the RPM, the greater the increase in power - right where it's most usable for a high performance road engine.
Duke
with you comments above EXCEPT for the 5000 rpm comment. I would jump that up to around 6000 rpms. People that spend the money for a 383 build ARE looking for more power than their stock small blocks. I built MY 383 specificly in mind to have that kind of power but to also have a good, dependable, high mileage engine but not hurt it by driving it the way I wanted to. My cam is designed to be all done at 5800 rpms which I feel gets all of the power out of MY build and gives me a safe top rpm for the engine.
01-20-2018, 11:09 PM
#42
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Forget about top end power. Guys obsess over this, but how often are you going to rev it over 5000. Properly configured a 383 will produce massive low end torque, which means big power and terrific throttle response in the low to mid range, where you spend 99+ percent of driving time compared to a similarly configured 327.
Whatever cam you choose top end power is going to be more of a function of head flow than the cam, so massage OE heads or buy aftermarket heads with inlet port volume of no more than 180cc that flow at least 220/170 CFM at 0.5" valve lift, 28" H2O depression.
The L-46/82 cam would be a good choice. It will make better than 80 percent peak torque at 2000 and useable power to 5500-6000 depending on head flow. If you want more low end torque the McCagh Special cam will make about 90 percent peak torque at 2000. Massaged heads are REQUIRED for this config., and it will make nearly the same top end power as the L-46/82 cam and easily pull a 3.08 or 2.73 axle with a manual or automatic for easy highway cruising.
I do know of one 383 with massaged heads and the McCagh Special cam. It's in a Shark with an original base 350/300 HP engine and TH400/3.08 axle. I haven't been able to talk the owner into a chassis dyno test, but he says it's a beast compared to the original base engine config. Other than the cam and head work it's all OE, looks completely original, and has idle behavior identical to the original 350/300.
Simulations indicate around 250-260 maximum SAE corrected RWHP in the 5000-5500 range depending on head flow, inlet and exhaust system configuration (for comparison a decent base 300 HP engine is about 195), but in the low to mid range it makes 10-30 percent more power than an identically configured 327, and the lower the RPM, the greater the increase in power - right where it's most usable for a high performance road engine.
Duke
Whatever cam you choose top end power is going to be more of a function of head flow than the cam, so massage OE heads or buy aftermarket heads with inlet port volume of no more than 180cc that flow at least 220/170 CFM at 0.5" valve lift, 28" H2O depression.
The L-46/82 cam would be a good choice. It will make better than 80 percent peak torque at 2000 and useable power to 5500-6000 depending on head flow. If you want more low end torque the McCagh Special cam will make about 90 percent peak torque at 2000. Massaged heads are REQUIRED for this config., and it will make nearly the same top end power as the L-46/82 cam and easily pull a 3.08 or 2.73 axle with a manual or automatic for easy highway cruising.
I do know of one 383 with massaged heads and the McCagh Special cam. It's in a Shark with an original base 350/300 HP engine and TH400/3.08 axle. I haven't been able to talk the owner into a chassis dyno test, but he says it's a beast compared to the original base engine config. Other than the cam and head work it's all OE, looks completely original, and has idle behavior identical to the original 350/300.
Simulations indicate around 250-260 maximum SAE corrected RWHP in the 5000-5500 range depending on head flow, inlet and exhaust system configuration (for comparison a decent base 300 HP engine is about 195), but in the low to mid range it makes 10-30 percent more power than an identically configured 327, and the lower the RPM, the greater the increase in power - right where it's most usable for a high performance road engine.
Duke
Thanks,
Mike
01-21-2018, 06:30 AM
#43
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Unless technology has changed from my drag racing days (way back when), with hydraulic lifters I would expect to get valve lifter float just below that 6000 RPM level.
In any case, even my solid lifter fuelies rarely get wound to 6000 RPM today. So I'd say my goal would be generally to keep it under that 5000-5200 range.
In any case, even my solid lifter fuelies rarely get wound to 6000 RPM today. So I'd say my goal would be generally to keep it under that 5000-5200 range.
01-21-2018, 10:57 AM
#45
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The SB400 with moderately massaged 462 2.02/1.6 stainless valves, Comp Cams 1.52 roller tip rockers and a flat tappet hyd cam has occasionally been spun to 6600 (and it will do it at will if I so desire). NO, I READILY ADMIT, this is less than desirable rpm for a SB400, but my simple point is that it will do it.
Will it do 7000? I have no clue, I've never asked it to do that---------------------6600 makes me nervous!
A 383 and a SB400 are the same thing and built the same way, except the 383 just has a slightly smaller bore (.095in smaller).
Will it do 7000? I have no clue, I've never asked it to do that---------------------6600 makes me nervous!
A 383 and a SB400 are the same thing and built the same way, except the 383 just has a slightly smaller bore (.095in smaller).
Last edited by DZAUTO; 01-21-2018 at 11:00 AM.
01-21-2018, 11:19 AM
#46
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With careful setup of the OE 3911068 valve springs - installed height set to allow .090-.100" coil bind clearance, the valve train limiting speed is about 6700-6800 before pumpup with these OE lobes. (The McCagh Special uses OE lobes "tuned" to the flow characterisitcs of massaged OE heads and maintains the smooth idle behavior of base engines, which is the target application for those who want to maintain base engine characteristics such as the smooth idle and stump pulling low end torque while producing SHP type top end power and useable revs.)
Taylor's Rule states that two identically configured engines other than stroke will produce about the same top end power at the same mean piston speed, so increasing stroke alone will not increase top end power, but it will increase average power through the useable rev range due to the greater average torque from the increased displacement. The way to increase top end power is with better head flow.
I designed the McCagh Special camshaft at Mike's request and decided to name it after him given his long membership and service to NCRS. The entire story including dyno tests is documented in the "Tale of Two Camshafts" article that was published in The Corvette Restorer circa 2008, and a pdf of the article in on this site in a thread started by me, so it's an easy search; and if you know Mike, I'm sure he will be willing to give you his honest opinions of that infamous '57 283/250HP FI "cheater motor" that earned a Duntov Award.
Funny story - given the substantial torque/power increase of that engine across the rev range over the OE configuration I suggested he only use 3/4 throttle for the WOT to 90 percent of redline that is part of the PV test. Otherwise the judge would probably know that the engine had considerable invisible internal massaging. Of course, Mike is a very experienced PV judge, and his response to me was that when he PVs one of his cars, his objective is to scare the sh...t out of the judge!
BTW both versions of the TF fully assembled heads have valve springs that are WAAAAAY higher than necessary for OE cam lobes, which increases the probability of lobe/lifter problems. My recommendation is to buy the bare heads and install you own valves/springs/seals. This way you can trim both the valve seat and valve areas to .040/.060"seat widths with additional cuts on the seats and valve to angle back unused seat area (basically a three-angle valve job). You don't need SS inlet valves. The Federal Mogul OE replacement alloy steel inlet valves are more than adequate, but "upgrading" to 21-2N SS exhaust valves should guarantee very long valve life.
Duke
Last edited by SWCDuke; 01-21-2018 at 12:02 PM.
01-25-2018, 09:51 PM
#48
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Note that I said above 5000, which is well within the 10 percent peak power bandwidth. Both cams I mentioned should peak in the 5000-5500 range on a 383 (10 percent peak power bandwidth from about 4500 to close to 6000), assuming properly massaged OE heads or the Trick Flows out the box, which flow about the same up to about 0.4" valve lift (about the peak lift of both cams with OE rockers). Both the torque and power curves with either cam and OE exhaust manifolds are very "flat" - very broad 80/90 percent peak torque bandwidth and 10 percent peak power bandwidth, which is what makes them such great road engines. The pull hard and linearly from off idle to peak revs.
With careful setup of the OE 3911068 valve springs - installed height set to allow .090-.100" coil bind clearance, the valve train limiting speed is about 6700-6800 before pumpup with these OE lobes. (The McCagh Special uses OE lobes "tuned" to the flow characterisitcs of massaged OE heads and maintains the smooth idle behavior of base engines, which is the target application for those who want to maintain base engine characteristics such as the smooth idle and stump pulling low end torque while producing SHP type top end power and useable revs.)
Taylor's Rule states that two identically configured engines other than stroke will produce about the same top end power at the same mean piston speed, so increasing stroke alone will not increase top end power, but it will increase average power through the useable rev range due to the greater average torque from the increased displacement. The way to increase top end power is with better head flow.
I designed the McCagh Special camshaft at Mike's request and decided to name it after him given his long membership and service to NCRS. The entire story including dyno tests is documented in the "Tale of Two Camshafts" article that was published in The Corvette Restorer circa 2008, and a pdf of the article in on this site in a thread started by me, so it's an easy search; and if you know Mike, I'm sure he will be willing to give you his honest opinions of that infamous '57 283/250HP FI "cheater motor" that earned a Duntov Award.
Funny story - given the substantial torque/power increase of that engine across the rev range over the OE configuration I suggested he only use 3/4 throttle for the WOT to 90 percent of redline that is part of the PV test. Otherwise the judge would probably know that the engine had considerable invisible internal massaging. Of course, Mike is a very experienced PV judge, and his response to me was that when he PVs one of his cars, his objective is to scare the sh...t out of the judge!
BTW both versions of the TF fully assembled heads have valve springs that are WAAAAAY higher than necessary for OE cam lobes, which increases the probability of lobe/lifter problems. My recommendation is to buy the bare heads and install you own valves/springs/seals. This way you can trim both the valve seat and valve areas to .040/.060"seat widths with additional cuts on the seats and valve to angle back unused seat area (basically a three-angle valve job). You don't need SS inlet valves. The Federal Mogul OE replacement alloy steel inlet valves are more than adequate, but "upgrading" to 21-2N SS exhaust valves should guarantee very long valve life.
Duke
With careful setup of the OE 3911068 valve springs - installed height set to allow .090-.100" coil bind clearance, the valve train limiting speed is about 6700-6800 before pumpup with these OE lobes. (The McCagh Special uses OE lobes "tuned" to the flow characterisitcs of massaged OE heads and maintains the smooth idle behavior of base engines, which is the target application for those who want to maintain base engine characteristics such as the smooth idle and stump pulling low end torque while producing SHP type top end power and useable revs.)
Taylor's Rule states that two identically configured engines other than stroke will produce about the same top end power at the same mean piston speed, so increasing stroke alone will not increase top end power, but it will increase average power through the useable rev range due to the greater average torque from the increased displacement. The way to increase top end power is with better head flow.
I designed the McCagh Special camshaft at Mike's request and decided to name it after him given his long membership and service to NCRS. The entire story including dyno tests is documented in the "Tale of Two Camshafts" article that was published in The Corvette Restorer circa 2008, and a pdf of the article in on this site in a thread started by me, so it's an easy search; and if you know Mike, I'm sure he will be willing to give you his honest opinions of that infamous '57 283/250HP FI "cheater motor" that earned a Duntov Award.
Funny story - given the substantial torque/power increase of that engine across the rev range over the OE configuration I suggested he only use 3/4 throttle for the WOT to 90 percent of redline that is part of the PV test. Otherwise the judge would probably know that the engine had considerable invisible internal massaging. Of course, Mike is a very experienced PV judge, and his response to me was that when he PVs one of his cars, his objective is to scare the sh...t out of the judge!
BTW both versions of the TF fully assembled heads have valve springs that are WAAAAAY higher than necessary for OE cam lobes, which increases the probability of lobe/lifter problems. My recommendation is to buy the bare heads and install you own valves/springs/seals. This way you can trim both the valve seat and valve areas to .040/.060"seat widths with additional cuts on the seats and valve to angle back unused seat area (basically a three-angle valve job). You don't need SS inlet valves. The Federal Mogul OE replacement alloy steel inlet valves are more than adequate, but "upgrading" to 21-2N SS exhaust valves should guarantee very long valve life.
Duke
Do you have a Crane part number for the McCagh Special?
Thanks,
Mike
01-26-2018, 06:04 AM
#49
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Now I get a message on the Crane Cams site that it may be hacked...
01-26-2018, 09:55 AM
#50
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Yes, Crane has a part number assigned, and I believe they have produced about half a dozen. Unfortunately due to computer problems I don't have access to the RFP file, but I'll look to see if I have a hard copy. Send me an email via the CF.
Also, contact Mike as he may have the RFP and cam card, and your point of contact is Jerry Clay, whose been with Crane a long time.
Also, understand that the McCagh Special is specifically designed for the flow characteristics of massaged OE heads, particularly the E/I flow ratio and will not provide good performance with production machined heads, but these new Trick Flow "double hump" aluminum heads have about the same E/I flow ratio as massaged OE heads, so they would be a good choice.
Duke
Also, contact Mike as he may have the RFP and cam card, and your point of contact is Jerry Clay, whose been with Crane a long time.
Also, understand that the McCagh Special is specifically designed for the flow characteristics of massaged OE heads, particularly the E/I flow ratio and will not provide good performance with production machined heads, but these new Trick Flow "double hump" aluminum heads have about the same E/I flow ratio as massaged OE heads, so they would be a good choice.
Duke
Last edited by SWCDuke; 01-26-2018 at 10:04 AM.
01-27-2018, 10:23 PM
#51
Drifting
Thanks, I am going with the Trick Flow aluminum heads.
I read up on the stroking, GearheadJoe wrote a great article in the Corvette Restorer on that. Gonna get in touch this week with Scat about a crank, rods, and pistons, so I can get started with clearancing the block.
Be a while before I get to the cam. My intent now is to go hydraulic, with 327-350 type characteristics, but revised for the increase in cubes. Not sure who to use for that, but the fuel injection system is from Comp Cams, so maybe they're the right choice.
Gotta learn more about bearings, any suggestions for a resource would be great.
Thanks,
Mike
I read up on the stroking, GearheadJoe wrote a great article in the Corvette Restorer on that. Gonna get in touch this week with Scat about a crank, rods, and pistons, so I can get started with clearancing the block.
Be a while before I get to the cam. My intent now is to go hydraulic, with 327-350 type characteristics, but revised for the increase in cubes. Not sure who to use for that, but the fuel injection system is from Comp Cams, so maybe they're the right choice.
Gotta learn more about bearings, any suggestions for a resource would be great.
Thanks,
Mike
Glad you liked my first NCRS Restorer article about stoking an original '657 block to 383. I wrote a "Part 2" article in the Summer 2017 Restorer that described the rest of the build, including dyno results.
The second article touches on several of the key issues/decisions you will have to deal with as you plan your build.
Send me a PM with your email address and I will send you a copy of the Part 2 article.
I think the new Trick Flow heads are a great way to go if you want to retain a stock appearance. You should have no trouble at all achieving your 425 HP goal, and the engine will be well behaved for normal street driving too.
Note that there are other rods with more block clearance than the ones I used in my build. Currently my favorites are the Manley Sportsmaster and the Scat Pro Stock. I hope to have more information on this topic in a couple months.
BTW, if the '657 block you have was machined at the factory for large-journal mains, it was intended for a 1967 Camaro SS 350 (GM's very first 350). If your block came from an actual production Camaro SS 350, and has the correct stampings on the pad, it is a very rare and valuable block. You could probably finance half of your 383 build by selling that block to a Camaro person. For your purposes, any '657 block (except some early ones) would be fine.
01-28-2018, 12:25 AM
#52
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Hi Mike:
Glad you liked my first NCRS Restorer article about stoking an original '657 block to 383. I wrote a "Part 2" article in the Summer 2017 Restorer that described the rest of the build, including dyno results.
The second article touches on several of the key issues/decisions you will have to deal with as you plan your build.
Send me a PM with your email address and I will send you a copy of the Part 2 article.
I think the new Trick Flow heads are a great way to go if you want to retain a stock appearance. You should have no trouble at all achieving your 425 HP goal, and the engine will be well behaved for normal street driving too.
Note that there are other rods with more block clearance than the ones I used in my build. Currently my favorites are the Manley Sportsmaster and the Scat Pro Stock. I hope to have more information on this topic in a couple months.
BTW, if the '657 block you have was machined at the factory for large-journal mains, it was intended for a 1967 Camaro SS 350 (GM's very first 350). If your block came from an actual production Camaro SS 350, and has the correct stampings on the pad, it is a very rare and valuable block. You could probably finance half of your 383 build by selling that block to a Camaro person. For your purposes, any '657 block (except some early ones) would be fine.
Glad you liked my first NCRS Restorer article about stoking an original '657 block to 383. I wrote a "Part 2" article in the Summer 2017 Restorer that described the rest of the build, including dyno results.
The second article touches on several of the key issues/decisions you will have to deal with as you plan your build.
Send me a PM with your email address and I will send you a copy of the Part 2 article.
I think the new Trick Flow heads are a great way to go if you want to retain a stock appearance. You should have no trouble at all achieving your 425 HP goal, and the engine will be well behaved for normal street driving too.
Note that there are other rods with more block clearance than the ones I used in my build. Currently my favorites are the Manley Sportsmaster and the Scat Pro Stock. I hope to have more information on this topic in a couple months.
BTW, if the '657 block you have was machined at the factory for large-journal mains, it was intended for a 1967 Camaro SS 350 (GM's very first 350). If your block came from an actual production Camaro SS 350, and has the correct stampings on the pad, it is a very rare and valuable block. You could probably finance half of your 383 build by selling that block to a Camaro person. For your purposes, any '657 block (except some early ones) would be fine.
At this point, it looks like the Trick Flow heads and a rotating assembly from Scat, with a forged stroker crank and the Pro stock rods. Don't know on the pistons, yet, but forged aluminum flat top may be my choice.
After I read duke's "tale of Two cams" article, I also like the idea of using the "McCagh Special" cam that Duke mentions.
I'll read your part 2 and see what else I learn
Mike
01-28-2018, 09:55 AM
#53
Safety Car
Be careful and think through your build. Flat tops with those heads are going to be around 12.8:1 compression. I would stay at 10.5:1 or less. The Scat assembly is your best bet. I'm not sure what they offer but if they offer it in small journal rods and their small journal rods are actually smaller than large journal that's your best route. Even with their normal rods they should clear the cam but you'll be much better off not running a small base circle cam and not having to grind the rods for clearance. I like Michigan P bearings for stock engines and H bearings for performance. But they are about double the price. Moly rings absolute must. Good luck!
I'll just add looking at your block. It reminds me of many years ago a friend of mine built a motor. It smoked like a freight train from the get go. He took it apart and when I looked at it , it had never been honed. He didn't know any better and thought when he had it bored .030" over he was good. The only time I've ever seen it but just throwing it out there.
I'll just add looking at your block. It reminds me of many years ago a friend of mine built a motor. It smoked like a freight train from the get go. He took it apart and when I looked at it , it had never been honed. He didn't know any better and thought when he had it bored .030" over he was good. The only time I've ever seen it but just throwing it out there.
01-28-2018, 12:58 PM
#54
Drifting
Be careful and think through your build. Flat tops with those heads are going to be around 12.8:1 compression. I would stay at 10.5:1 or less. The Scat assembly is your best bet. I'm not sure what they offer but if they offer it in small journal rods and their small journal rods are actually smaller than large journal that's your best route. Even with their normal rods they should clear the cam but you'll be much better off not running a small base circle cam and not having to grind the rods for clearance.
I agree with your comment that small journal (2.0") rods could be expected to offer more block clearance and cam clearance than large journal (2.1") rods of the same type.
I think that if the crank is a forged crank with large journal mains, reducing the rod journals to 2.0" would not create any significant weakening of the crank.
As you noted, it can't be assumed that the small journal version of a rod will have smaller external dimensions than the large journal version of the same rod. Some rod manufacturers use the same raw forging for both small journal rods and large journal rods. With these rods there is no advantage to using the small journal version. An example of such a rod is the Scat Pro Stock rod.
However, both the Eagle SIR and the Manley Sportsmaster do have a smaller big end on the small journal version than on the large journal version. The clearance improvement is in the range of .035" to .050". I expect to have more accurate measurements in a month or so.
01-28-2018, 01:22 PM
#55
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I compared the L-46 cam installed at the as designed/manufactured IPOML of 114 deg. ATDC with the McCagh Special at the as designed/manufactured 116 deg. ATDC IPOML.
The McCagh Special is a real "torque monster" with up of 20 percent more torque at the bottom of the useable rev range. The torque/power graphs cross at about 4700 RPM with the L-46 providing a bit more peak power and a slower rolloff with maximum useable revs of about 6500. The McCagh Special has a useable limit of about 6000.
Then I retarded the McCagh Special four degrees to an IPOML of 120 deg. ATDC. The crossover point increased slightly to 4800, and about halved the difference above that at an miniscule loss below 4800, so I know what I'd do, and you can decide when we talk on the phone and I can refine the simulations.
Duke
01-28-2018, 01:27 PM
#56
Safety Car
And one other thing above all else make absolutely certain you get every piece of shot where they shot peened the block out of the oil galleys. One piece could lead to disaster. Chase threaded holes check corners nooks and crannies that stuff will hide everywhere.
01-28-2018, 01:57 PM
#57
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Yesterday I configured a 383 to your specs including the Trick Flow aluminum double hump heads, but I still need some details on your induction/exhaust systems and gearing.
I compared the L-46 cam installed at the as designed/manufactured IPOML of 114 deg. ATDC with the McCagh Special at the as designed/manufactured 116 deg. ATDC IPOML.
The McCagh Special is a real "torque monster" with up of 20 percent more torque at the bottom of the useable rev range. The torque/power graphs cross at about 4700 RPM with the L-46 providing a bit more peak power and a slower rolloff with maximum useable revs of about 6500. The McCagh Special has a useable limit of about 6000.
Then I retarded the McCagh Special four degrees to an IPOML of 120 deg. ATDC. The crossover point increased slightly to 4800, and about halved the difference above that at an miniscule loss below 4800, so I know what I'd do, and you can decide when we talk on the phone and I can refine the simulations.
Duke
I compared the L-46 cam installed at the as designed/manufactured IPOML of 114 deg. ATDC with the McCagh Special at the as designed/manufactured 116 deg. ATDC IPOML.
The McCagh Special is a real "torque monster" with up of 20 percent more torque at the bottom of the useable rev range. The torque/power graphs cross at about 4700 RPM with the L-46 providing a bit more peak power and a slower rolloff with maximum useable revs of about 6500. The McCagh Special has a useable limit of about 6000.
Then I retarded the McCagh Special four degrees to an IPOML of 120 deg. ATDC. The crossover point increased slightly to 4800, and about halved the difference above that at an miniscule loss below 4800, so I know what I'd do, and you can decide when we talk on the phone and I can refine the simulations.
Duke
The gearing is as follows: current rear end 3.08:1, likely changing to 3.5:1 The trans is a Tremec TKO 600 with the following ratios:
2.87
1.89
1.28
1.00
.64 O/D
I'll give you a call later.
The block has been tanked and checked for cracks, but is going in for cylinder work. The bores measure 4.015-4.020 with no apparent issues. I plan on having them opened up to 4.030, by an engine builder.
Robert, I'm going to call Scat on Monday to discuss journal options for their cranks. I am not fixed on the flat-top pistons, I will calculate the CR on the combination before I place the actual order for the rotating assembly. My intent had been to shoot for about 10:1.
Thanks for all the advice.
Mike
01-28-2018, 03:17 PM
#58
Le Mans Master
You might want to look at the Icon FHR 4032 alloy pistons, they offer a nice 18cc dished piston in both 5.7 and 6" rod length that would result in approx 9.6 CR. A call to CNC Motorsports might be worthwhile, they offer Scat as well as Icon pistons among others and can balance all your parts.
Last edited by Scott Marzahl; 01-28-2018 at 03:20 PM.
01-28-2018, 03:35 PM
#59
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Location: Redondo Beach USA
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I like the first four, but would prefer something like 0.80 fifth to keep the gap narrow.
With OE diameter tires and the 3.08 axle fifth gear revs will be about 1500 at 60, but the McCagh Special will work well at that low engine speed, and with a well tuned EFI it should get low to mid 20s MPG at legal freeway speeds.
The 2.87 first with a 3.08 axle is about the same overall as a CR four-speed and 4.11. A shorter rear gear will make first virtually useless. A 3.55 would be the equivalent of a CR with a 4.63 axle. Given the low end torque of the McCagh Special I don't think you could use WOT in first gear without wheel spin at any speed unless you have real sticky tires, but if you like to do burnouts it should be a champion.
Unless you're going to beat on it real hard, KB hypereutectic pistons would be a good choice and are much less expensive than forged. I recommend a CR in the range of 10-10.25 and KB probably has an off-the-shelf piston that should get in that range depending on deck clearance and gasket thickness.
Given the tall fifth gear it would probably be best to keep closer to 10:1, so you can run as aggressive a spark advance map as possible. The most efficient operating condition of any engine is high load at low revs, but you have to be able to run a lot of spark advance and the lower the engine speed the greater the detonation tendency, so it's a tradeoff. Also, low overlap cams will operate much more efficiently at low revs than high overlap cams, and the McCagh Special has the same effective overlap as the base engine cam, which also means it will idle very smooth in neutral at 450-500 at about 18" manifold vacuum.
Duke
Duke
With OE diameter tires and the 3.08 axle fifth gear revs will be about 1500 at 60, but the McCagh Special will work well at that low engine speed, and with a well tuned EFI it should get low to mid 20s MPG at legal freeway speeds.
The 2.87 first with a 3.08 axle is about the same overall as a CR four-speed and 4.11. A shorter rear gear will make first virtually useless. A 3.55 would be the equivalent of a CR with a 4.63 axle. Given the low end torque of the McCagh Special I don't think you could use WOT in first gear without wheel spin at any speed unless you have real sticky tires, but if you like to do burnouts it should be a champion.
Unless you're going to beat on it real hard, KB hypereutectic pistons would be a good choice and are much less expensive than forged. I recommend a CR in the range of 10-10.25 and KB probably has an off-the-shelf piston that should get in that range depending on deck clearance and gasket thickness.
Given the tall fifth gear it would probably be best to keep closer to 10:1, so you can run as aggressive a spark advance map as possible. The most efficient operating condition of any engine is high load at low revs, but you have to be able to run a lot of spark advance and the lower the engine speed the greater the detonation tendency, so it's a tradeoff. Also, low overlap cams will operate much more efficiently at low revs than high overlap cams, and the McCagh Special has the same effective overlap as the base engine cam, which also means it will idle very smooth in neutral at 450-500 at about 18" manifold vacuum.
Duke
Duke
Last edited by SWCDuke; 01-28-2018 at 03:41 PM.
02-04-2018, 10:53 AM
#60
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I went ahead and configured the engine and ran it through EA 3.0.
Basic specs are
383 CID
new Trick Flow al. double humps heads
10.25:1 CR
OE Rochester FI or OE FI manifold converted to EFI
Clutch fan and alternator
OE exhaust manifolds and under-the car exhaust
The two data sets represent the L-46 and McCagh Special camshaft (retarded four degrees from the as designed/ground IPOML of 116 deg. ATC), everything else equal.
Output is SAE net at the flywheel as installed in the vehicle.
You can estimate SAE gross by multiplying the data by 1.14 and SAE corrected RWHP by multiplying by 0.85.
So which camshaft is which, and what do you think is the best configuration for typical vintage car use - a fun cruiser with occasional road trips - no racing. Be sure to consider the gear spacing and top fifth gear revs @ 60 in your choice.
BTW, my experience with EA 3.0 and these two cams is that top end power prediction is within a couple of percent of test results, but rolloff past the peak is slower.
Peak predicted torque is a few percent high, but low end predicted torque is up to 20 percent low, however, the percent difference is about the same because the error washes out when comparing. That's why simulations should be based on comparisons to a known baseline if at all possible.
Duke
Basic specs are
383 CID
new Trick Flow al. double humps heads
10.25:1 CR
OE Rochester FI or OE FI manifold converted to EFI
Clutch fan and alternator
OE exhaust manifolds and under-the car exhaust
The two data sets represent the L-46 and McCagh Special camshaft (retarded four degrees from the as designed/ground IPOML of 116 deg. ATC), everything else equal.
Output is SAE net at the flywheel as installed in the vehicle.
You can estimate SAE gross by multiplying the data by 1.14 and SAE corrected RWHP by multiplying by 0.85.
So which camshaft is which, and what do you think is the best configuration for typical vintage car use - a fun cruiser with occasional road trips - no racing. Be sure to consider the gear spacing and top fifth gear revs @ 60 in your choice.
BTW, my experience with EA 3.0 and these two cams is that top end power prediction is within a couple of percent of test results, but rolloff past the peak is slower.
Peak predicted torque is a few percent high, but low end predicted torque is up to 20 percent low, however, the percent difference is about the same because the error washes out when comparing. That's why simulations should be based on comparisons to a known baseline if at all possible.
Duke