Block/Cam/Head Combos for 25hour Enduro Racing
04-24-2005, 11:02 PM
#1
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Block/Cam/Head Combos for 25hour Enduro Racing (copy of thread from LS1 Engine forum, as possibly the road racers might not frequent it much, and I'm very very interested in your actual experiences road racing with these engines!)
Thanks Cal for your help on my Cam thread.
Race-car basics:
"Best Bang for the Buck Competetive Race-car"
1987 Porsche944 turbo chassis
LS1 powered
projected race weight - 2100-2300lbs.
projected wheels - 18x12's all around w/wide rubber
exhaust - currently 3" straight back w/o muffler
intake - K&N cone filter in nose of car (outside engine bay)
CA 91 octane pump gas
Goal - be competetive at 25 Hours of Thunderhill (this year or next)
Plan - combine chevy reliability and incredible bang for the buck power with the 944's light weight and exceptional handling to become a contender.
Questions:
1) While of course the C5R blocks are legendary in their proven success at the 24 Hours of Le Mans, what's your experience with how reliable the LS1 or LS2 could be for a 24 hour race? (no $25+k budget for an engine right now :-)
2) What block, head, cam combinations might you suggest that will achieve, say, 450-500rwhp, while maintaining reliability for an enduro.
3) Add good fuel economy as a goal for #2 combinations (better fuel economy means fewer pit stops for us)
4) Best bang for the buck to achieve these goals?
I'm thinking that if done in a good "bang for the buck" way, if an engine had more than enough power to outrun the competitors in speed, then we could short shift and run it at lower rpms, which would then give better reliability over 24 hours, plus better fuel economy.
Coming from the Porsche community in which running a GT3 cup car will cost in the neighborhood of $35k each engine rebuild, I am so stoked on the LS1!! I really want to see what we can do with it, so I appreciate your help with your vast experiences.
Thanks,
Steve
Thanks Cal for your help on my Cam thread.
Race-car basics:
"Best Bang for the Buck Competetive Race-car"
1987 Porsche944 turbo chassis
LS1 powered
projected race weight - 2100-2300lbs.
projected wheels - 18x12's all around w/wide rubber
exhaust - currently 3" straight back w/o muffler
intake - K&N cone filter in nose of car (outside engine bay)
CA 91 octane pump gas
Goal - be competetive at 25 Hours of Thunderhill (this year or next)
Plan - combine chevy reliability and incredible bang for the buck power with the 944's light weight and exceptional handling to become a contender.
Questions:
1) While of course the C5R blocks are legendary in their proven success at the 24 Hours of Le Mans, what's your experience with how reliable the LS1 or LS2 could be for a 24 hour race? (no $25+k budget for an engine right now :-)
2) What block, head, cam combinations might you suggest that will achieve, say, 450-500rwhp, while maintaining reliability for an enduro.
3) Add good fuel economy as a goal for #2 combinations (better fuel economy means fewer pit stops for us)
4) Best bang for the buck to achieve these goals?
I'm thinking that if done in a good "bang for the buck" way, if an engine had more than enough power to outrun the competitors in speed, then we could short shift and run it at lower rpms, which would then give better reliability over 24 hours, plus better fuel economy.
Coming from the Porsche community in which running a GT3 cup car will cost in the neighborhood of $35k each engine rebuild, I am so stoked on the LS1!! I really want to see what we can do with it, so I appreciate your help with your vast experiences.
Thanks,
Steve
04-25-2005, 01:41 AM
#2
Renegade Hybrids makes a kit to install the LS1 into a 924/944. Check out their race car.. it is around 2700lbs I believe and looks like it should rip. Hope the transaxle holds up!
Have you looked at building an LS1 powered RX-7 ('86-91 are a dime a dozen)? You can really get the weight down (some are 2600lbs stock '86-88 base model)... the T56 (Camaro) trans would be used and the Turbo 2 rear diff is very strong (4:10 gear with 8" ring gear, and clutch pack style LSD). Wide body kit allows 285's up front an 335's out back.
I think you will need more cubes and less lift to make 450rwhp+ on 91 octane and make it reliable for 25 hours WOT. A good set of cylinder heads are a must. Hope your valvesprings can take the abuse. A dry sump oiling sytem is a good idea! http://www.drysump.com/ An oil cooler is a must as well even if it is January and temps are super cold.
Budget buildup:
Stock LS1 block/crank, good forged rods/pistons, milled AFR 205cc heads, LS6 intake/ported stock TB or FAST 90mm intake/90mmTB, custom long tube headers, underdrive pulley, larger injectors, custom tuning, alum flywheel and you should be good to go for a budget buildup.
A custom cam is probably your best bet. There are a few custom cam grinders on this forum. Contact JRP about the custom cam guy he used for his road race setup. He is running around 12:1 compression and proposes to run 91 octane. His cam bleeds off a lot of compression which allows the lower octane.
Should be a pretty wild setup. 25hours of Thunderhill typically has rain.... With 2100-2300lbs you won't need to much power to kick *ss.
-Mark
Have you looked at building an LS1 powered RX-7 ('86-91 are a dime a dozen)? You can really get the weight down (some are 2600lbs stock '86-88 base model)... the T56 (Camaro) trans would be used and the Turbo 2 rear diff is very strong (4:10 gear with 8" ring gear, and clutch pack style LSD). Wide body kit allows 285's up front an 335's out back.
I think you will need more cubes and less lift to make 450rwhp+ on 91 octane and make it reliable for 25 hours WOT. A good set of cylinder heads are a must. Hope your valvesprings can take the abuse. A dry sump oiling sytem is a good idea! http://www.drysump.com/ An oil cooler is a must as well even if it is January and temps are super cold.
Budget buildup:
Stock LS1 block/crank, good forged rods/pistons, milled AFR 205cc heads, LS6 intake/ported stock TB or FAST 90mm intake/90mmTB, custom long tube headers, underdrive pulley, larger injectors, custom tuning, alum flywheel and you should be good to go for a budget buildup.
A custom cam is probably your best bet. There are a few custom cam grinders on this forum. Contact JRP about the custom cam guy he used for his road race setup. He is running around 12:1 compression and proposes to run 91 octane. His cam bleeds off a lot of compression which allows the lower octane.
Should be a pretty wild setup. 25hours of Thunderhill typically has rain.... With 2100-2300lbs you won't need to much power to kick *ss.
-Mark
04-26-2005, 09:40 AM
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Thanks Mark.
I checked out the dry sump site, and it looks good. I am tending to think the same as you, that more displacement may be in order, to make reliable 450+rwhp power for such a long race. Actually, the racecar on Renegade's site is my car. :-) Currently it's 2500lbs., yet I will be working with another shop on stripping the chassis of all unnecessary steel, and replacing some of the glass with lexan. Even with stock LS1 power this car should fly, but I will need to see just how competetive it is vs. the 911 GT3 cup cars, as that was what won last year's 25 hrs. of Thunderhill.
I think I will simply work on lightening as much as possible, and developing the chassis/handling until the LS7 block comes out. I'm curious to see just how much it's going for, and I believe that it's got the dry sump built in. Now while it sounds like an awesome block, once again, 25 hours of racing is a very different animal.
Who knows, maybe it's just not going to be worth it to take a non-C5R block up there, to try to endure the stresses of such racing. Heck Chevy did design it specifically for running and winning a 24 hours race!
Ah what fun!
Steve
I checked out the dry sump site, and it looks good. I am tending to think the same as you, that more displacement may be in order, to make reliable 450+rwhp power for such a long race. Actually, the racecar on Renegade's site is my car. :-) Currently it's 2500lbs., yet I will be working with another shop on stripping the chassis of all unnecessary steel, and replacing some of the glass with lexan. Even with stock LS1 power this car should fly, but I will need to see just how competetive it is vs. the 911 GT3 cup cars, as that was what won last year's 25 hrs. of Thunderhill.
I think I will simply work on lightening as much as possible, and developing the chassis/handling until the LS7 block comes out. I'm curious to see just how much it's going for, and I believe that it's got the dry sump built in. Now while it sounds like an awesome block, once again, 25 hours of racing is a very different animal.
Who knows, maybe it's just not going to be worth it to take a non-C5R block up there, to try to endure the stresses of such racing. Heck Chevy did design it specifically for running and winning a 24 hours race!
Ah what fun!
Steve
04-26-2005, 01:14 PM
#4
Steve,
I would focus on that transaxle first. Granted, the 951 trans is stronger than the NA cars, but under roadrace conditions, you'll be asking a lot from it with Chevy power. Since the 951 has an oil pump and cooler, I would suggest you maximize it for longevity. Motor doesn't matter if the trans breaks.
Andy1
I would focus on that transaxle first. Granted, the 951 trans is stronger than the NA cars, but under roadrace conditions, you'll be asking a lot from it with Chevy power. Since the 951 has an oil pump and cooler, I would suggest you maximize it for longevity. Motor doesn't matter if the trans breaks.
Andy1