Block/Cam/Head Combos for 25hour Enduro Racing
04-24-2005, 11:01 PM
#1
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Block/Cam/Head Combos for 25hour Enduro Racing 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
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, 01:28 AM
#3
No problem Steve, good to see someone doing this type of racing with an LS1. Ineresting project you have as well. There are a small number of people around here (on LS1Tech) that do ORR (Open Road Racing such as Silver State Classic,) they would be the best ones to answer your questions. Much different than a a 11 second run down the drag strip. I do a little LSR (Land Speed Racing) and plan to start ORR at some point, so I'm interested in the same things. Maybe NataSS Inc will jump in here, he has some experiance with this, or you could page him.
In my limited experiance with max power long runs, I've toasted two cats and one tire, but haven't had any other problems. I suspect you will want upgraded cooling and oiling, but other than that the LSx engines are very durable at the power level you are talking about. A dry sump oiling system would be a good idea. I'd run ARP head studs and 2002 MLS metal head gaskets as well. And be sure to keep an eye on your oil level, these engines tend to go through oil when at max output with their light tension rings.
The cam I used could easily achieve 460 hp with higher than stock compression, a more agressive spark curve, and good ported heads. This cam has a .600 lift. I'm using minimal effort, home ported heads. You should go with Comp 918 springs, titanium retainers, and LS6 sodium filled valves to keep your valve train light.
In my limited experiance with max power long runs, I've toasted two cats and one tire, but haven't had any other problems. I suspect you will want upgraded cooling and oiling, but other than that the LSx engines are very durable at the power level you are talking about. A dry sump oiling system would be a good idea. I'd run ARP head studs and 2002 MLS metal head gaskets as well. And be sure to keep an eye on your oil level, these engines tend to go through oil when at max output with their light tension rings.
The cam I used could easily achieve 460 hp with higher than stock compression, a more agressive spark curve, and good ported heads. This cam has a .600 lift. I'm using minimal effort, home ported heads. You should go with Comp 918 springs, titanium retainers, and LS6 sodium filled valves to keep your valve train light.
Last edited by Cal; 04-25-2005 at 01:40 AM.
04-25-2005, 01:42 AM
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Originally Posted by Cal
No problem Steve, good to see someone doing this type of racing with an LS1. Ineresting project you have as well. There are a small number of people around here (on LS1Tech) that do ORR (Open Road Racing such as Silver State Classic,) they would be the best ones to answer your questions. Much different than a a 11 second run down the drag strip. I do a little LSR (Land Speed Racing) and plan to start ORR at some point, so I'm interested in the same things. Maybe NataSS Inc will jump in here, he has some experiance with this, or you could page him. In my limited experiance with max power long runs, I've toasted two cats and one tire, but haven't had any other problems. I suspect you will want upgraded cooling and oiling, but other than that the LSx engines are very durable at the power level you are talking about. A dry sump oiling system would be a good idea. I'd run ARP head studs and 2002 MLS metal head gaskets as well. And be sure to keep an eye on your oil level, these engines tend to go through oil when at max output with their light tension rings.
04-25-2005, 02:46 AM
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I am not doing any endurance racing, but I am also looking into ways to make my engine last at the track.
Here are two sources for LS1 dry sump systems:
http://www.daileyengineering.com
http://www.drysump.com
In road racing, the engine will see high rpms for long times. That means that you can't build the engine like the drag racers do. It's probably best to stick with a short stroke, which reduces all the forces on the internals, and also makes the engine spin more easily. Notice that the new C6R has a very short stroke.
The cam also needs less agressive lobes. The ASA-cam works in road racing, but may not quite give you the power you are looking for. A custom road racing cam would (hopefully) help your engine survive, but will give you much less power than the agressive cams sold by most tuners, and due to the overlap a pretty bad idle.
I would also try to get the best lifters you can get. (Morel?)
I don't know which rockers would be best. If the lifters can take the extra stress, maybe 1.8:1 rockers with a very low lift cam would be best. The pushrods and lifters would have to move less.
The lighter the valves, the less stress on your valve train. AFR offers lighter valves as an option.
Tuning the car, I would make sure that the mixture at full throttle, high rpm is not too lean. This may cost you some power (and gas), but will help the engine run cooler.
Maybe there are exhaust valves that last, are light, and also very heat resistent (Any ideas?). Then you could go with a leaner mixture.
Also, try to get your headers coated. It works very well. If it isn't enough, you can still wrap them.
Till
Here are two sources for LS1 dry sump systems:
http://www.daileyengineering.com
http://www.drysump.com
In road racing, the engine will see high rpms for long times. That means that you can't build the engine like the drag racers do. It's probably best to stick with a short stroke, which reduces all the forces on the internals, and also makes the engine spin more easily. Notice that the new C6R has a very short stroke.
The cam also needs less agressive lobes. The ASA-cam works in road racing, but may not quite give you the power you are looking for. A custom road racing cam would (hopefully) help your engine survive, but will give you much less power than the agressive cams sold by most tuners, and due to the overlap a pretty bad idle.
I would also try to get the best lifters you can get. (Morel?)
I don't know which rockers would be best. If the lifters can take the extra stress, maybe 1.8:1 rockers with a very low lift cam would be best. The pushrods and lifters would have to move less.
The lighter the valves, the less stress on your valve train. AFR offers lighter valves as an option.
Tuning the car, I would make sure that the mixture at full throttle, high rpm is not too lean. This may cost you some power (and gas), but will help the engine run cooler.
Maybe there are exhaust valves that last, are light, and also very heat resistent (Any ideas?). Then you could go with a leaner mixture.
Also, try to get your headers coated. It works very well. If it isn't enough, you can still wrap them.
Till
04-25-2005, 07:28 AM
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How about a big bore (LS2 block maybe) and a 4.8 crank. What about a cam with very low overlap. Wouldn't that bring the powerband down some, make torque sooner, and not have to rev the crap out of it?
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04-26-2005, 09:20 AM
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Thanks guys for all the help.
Clearly, from your experience and once thinking about it, by focussing on minimizing the internal movements of the engine, it will add to its reliability. I will absolutely set-up an oil cooler and most likely dry dump before attempting this.
I would really like to go for as much displacement as possible, as then it seems that I would be able to build for durability, leaving peak power on the table, and still have enough power to achieve our goals. If the rumors are true that the LS7 block will be out by year's end, then I may hold out to see what that will run me price wise, as I believe that it's already got the dry sump system.
Until the LS7 becomes available for checking out, I may simply put all my energy to lightening and the chassis/suspension, so less power is needed. My plan is to run the lightened chassis with the stock LS1 in spring races (20-40 minutes), to see just how far off pace I/the car is from similar cars to the one that won the 25 Hour race last year (Porsche 911 GT3 Cup Car).
Thanks again for the tips!
Steve
Clearly, from your experience and once thinking about it, by focussing on minimizing the internal movements of the engine, it will add to its reliability. I will absolutely set-up an oil cooler and most likely dry dump before attempting this.
I would really like to go for as much displacement as possible, as then it seems that I would be able to build for durability, leaving peak power on the table, and still have enough power to achieve our goals. If the rumors are true that the LS7 block will be out by year's end, then I may hold out to see what that will run me price wise, as I believe that it's already got the dry sump system.
Until the LS7 becomes available for checking out, I may simply put all my energy to lightening and the chassis/suspension, so less power is needed. My plan is to run the lightened chassis with the stock LS1 in spring races (20-40 minutes), to see just how far off pace I/the car is from similar cars to the one that won the 25 Hour race last year (Porsche 911 GT3 Cup Car).
Thanks again for the tips!
Steve