Destroked LS1 Questions.....
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Teching In
Joined: Aug 2004
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Destroked LS1 Questions..... Well hello forum. I am buying an LS1 to eventually be dropped into an FD RX7 after it is built. But i had a few Q's about the engine.
Since this is going to be a turbo application i would like to be able to rev the engine upwards of 8K maybe even 9K. the reason being making the most out of pump gas that i can (93 oct) with 16-19 lbs of boost. more overall useable power ON THE TRACK. barely on the street.....if at all. plenty of gear.
i understand this engine does not have an overhead cam(s) so rotating weight will be a factor. but i am not very familiar with this engine so if somebody could tell me what would be the LOWEST possible displacement fromt he 5.7L i could get..just curious.
Thank you
Drew
Since this is going to be a turbo application i would like to be able to rev the engine upwards of 8K maybe even 9K. the reason being making the most out of pump gas that i can (93 oct) with 16-19 lbs of boost. more overall useable power ON THE TRACK. barely on the street.....if at all. plenty of gear.
i understand this engine does not have an overhead cam(s) so rotating weight will be a factor. but i am not very familiar with this engine so if somebody could tell me what would be the LOWEST possible displacement fromt he 5.7L i could get..just curious.
Thank you
Drew
Last edited by AM2; Sep 1, 2004 at 11:51 AM.
You should be able to use the crank from a gen3 4.8 liter engine. The stroke of the 4.8 is 3.27", stock stroke is 3.622". With this crank and stock bore you would come out with somewhere around a 312. The 5.3L engine uses the same crank as ls1.
If u found a 3.200 stroke you can get a 306CiD LS1 with the stock Bore of 3.622. Going to 8K or even 9K in a V8 will require a stout top end too. U might want to get forged pistons and rods too. I never heard of anyone taking their LS1 to 8k yet. If you are going to turbocharge the LS1 then u dont need to take it that high since u will have full boost around 3K RPM with a T76. U can take the 346CID to 7200RPM or so with no problems, but again u will need to change pushrods, springs, ti retainers, and valves to do so safely. Also the choice of the Cam will be really important to hold the power you want to redline. Good luck.
Originally Posted by Lostpatrolman
ls1power. Stock stroke is 3.622, stock bore is almost 3.9. Where would you find a 3.2" stroke crank? Can you use cranks from the old SB chevys?
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Thread Starter
Teching In
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man you guys respond QUICK! thanks
302ci would be doable.
turbo yeah i know it would be full boost at 3K but holding 16 lbs to 8K is what i am after. not holding 16lbs to 6K...you get me? i would have a much broader flat curve with more usable power up top. say 4-8K is 600+hp flat...thats what im after. i will most likely be running far less boost than that but that is MAX.
im sure a stock bore/stroke LS1 can be made to spin that high...but for how long?
most of the time the engine will be at the top of its powerband whatever that may be. i would just pfrefer to have a longer powerband than 4-6K i would rather have 4-8K and i know i will have no probs making any amount of power i want with either setup. hehe....i was actually hoping you guys would tell me 4.8 or maybe just maybe even a 4.5 but that is impossible with the ls1 right?
thanks everybody!
Drew
302ci would be doable.
turbo yeah i know it would be full boost at 3K but holding 16 lbs to 8K is what i am after. not holding 16lbs to 6K...you get me? i would have a much broader flat curve with more usable power up top. say 4-8K is 600+hp flat...thats what im after. i will most likely be running far less boost than that but that is MAX.
im sure a stock bore/stroke LS1 can be made to spin that high...but for how long?
most of the time the engine will be at the top of its powerband whatever that may be. i would just pfrefer to have a longer powerband than 4-6K i would rather have 4-8K and i know i will have no probs making any amount of power i want with either setup. hehe....i was actually hoping you guys would tell me 4.8 or maybe just maybe even a 4.5 but that is impossible with the ls1 right?
thanks everybody!
Drew
Last edited by AM2; Sep 1, 2004 at 01:29 PM.
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Originally Posted by AM2
i was actually hoping you guys would tell me 4.8 or maybe just maybe even a 4.5 but that is impossible with the ls1 right?
thanks everybody!
Drew
thanks everybody!
Drew
The 4.8 crank will work with the LS1 engine, but that would put u around 312-314CID. I think its the cheapest route to go to because u dont have to look for a 3.165 stroke. Good luck.
If you can use the old SB chevy cranks then you can go with some crazy small strokes, Im just not sure if you can. I know the bore spacing is the same. Just wait, Im sure someone will be on soon that can help you out more.
I dont really see how p/v would be too much of an issue as long as it isnt high compression. Since the motor is going to be built for a turho, compression should be down low anyways.
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From: Central, MA
Originally Posted by Lostpatrolman
I dont really see how p/v would be too much of an issue as long as it isnt high compression. Since the motor is going to be built for a turho, compression should be down low anyways.
I'm thinking the pistons won't "get out of the way" quick enough, when they won't be up as high to begin with.
Thread Starter
Teching In
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just fyi.... the engine is going to be a completly forged rotating assembly, i dont know what heads yet...and compression......maybe (just throwing out numbers) 8 or 8.5:1 of course this is just speculation.
all i know is will be Forged.
all i know is will be Forged.
You cannot use the old school SB cranks in the LS1. If you want a crazy small stroke your best bet would be to use a 4.8 and have it welded up and re ground to whatever stroke you want.
The chevy 302 of old had a 4" bore and a 3" stroke. Which was made out of a small journal 350/327 block and 283 crank.
The chevy 302 of old had a 4" bore and a 3" stroke. Which was made out of a small journal 350/327 block and 283 crank.
Staging Lane
Joined: Dec 2002
Posts: 90
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From: Houston - Clear Lake
Read this thread
https://ls1tech.com/forums/showthrea...t=piston+speed
This was posted recently. It has a lot of good information. There are a lot of very knowledgeable people in it who have done a lot of R&D.
https://ls1tech.com/forums/showthrea...t=piston+speed
This was posted recently. It has a lot of good information. There are a lot of very knowledgeable people in it who have done a lot of R&D.
Launching!
Joined: Jul 2004
Posts: 200
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From: Gainesville, Florida
I don't get it 
If you decrease the displacement, you will hurt spool and therefore your powerband will shift upwards. Also, forces on the rotating assembly rise with the square of RPM. These forces are almost always greater than the forces from combustion. So if you cut the stroke in half, no way can you double the RPMs, it would be more like you could rev 41% higher.
I just can't think of any good reason why anyone would want to do this?? Its not like the rod/stroke ratio on a stock LS1 is that bad, I think its 1.68:1.
Some people like to say that RPM stands for Ruins Peoples Motors. Without any detonation more boost and less RPM is usually better for the bottom end than less boost and more RPM. Of course the stock LS1 rings and head don't work too well with high cylinder pressures from high boost, but thats another story...
Then you've got more valvetrain wear to worry about at 8000 rpm.
If you decrease the displacement, you will hurt spool and therefore your powerband will shift upwards. Also, forces on the rotating assembly rise with the square of RPM. These forces are almost always greater than the forces from combustion. So if you cut the stroke in half, no way can you double the RPMs, it would be more like you could rev 41% higher.
I just can't think of any good reason why anyone would want to do this?? Its not like the rod/stroke ratio on a stock LS1 is that bad, I think its 1.68:1.
Some people like to say that RPM stands for Ruins Peoples Motors. Without any detonation more boost and less RPM is usually better for the bottom end than less boost and more RPM. Of course the stock LS1 rings and head don't work too well with high cylinder pressures from high boost, but thats another story...
Then you've got more valvetrain wear to worry about at 8000 rpm.
Last edited by Grant B; Sep 1, 2004 at 05:31 PM.