destroked motor?
Launching!
Joined: Jun 2003
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From: Kansas City
My Dad's got an original '69 Z/28 with a 302 that he bought new his senior year in highschool. The original motor was pulled and put in the back of the shop in 1973. He then bought a replacment 302(back when you could) and had it balenced and blue-printed. That car is WICKED FUN. I've had it to 8k before with nary a wimper from the motor. But, being able to wrap it up that high isn't where the fun is. Take it out on the twisty streets or coned off parking lot, "side-step" the clutch, and take a hard corner. The only aftermarket suspension parts it has are different shocks, but other than that... this car straight PULLS out of the corners. Now I know that a '69 302 and a Gen 3 design are 2 completely different things, but I'd think that it would be the same out come in the end. High RPM pulling. And if you were wanting to fart around on a street with some good turns I'd say go for it. Plus... how cool would it be to put "302" badges on a 4th gen Z/28.
I think he is trying to build a bonneville motor. Not a street racer extreme motor. The only reason the little ricers turn that high of an rpm is to make enough power to not get bumped by a Mus-stank. I asked the same thing early last year, or around this time, and a received a pm inreference to it.
The guy had a 302 LS1, said it was fun to "drive around", not friendly on street, but revved nicely, Xpensive, and made in the area of 550rwhp if I remember correctly. Thats nice, but when you have to turn 7800+ to get it, no thanks, if I am not at bonneville then the time I hit 8000+ every cop in the district will know where I am.
If this makes you happy then build it. Look at all the people that said the ASA is too much for a street LS1, and before you know it they are in A4 LS1's, almost in mine, but anyway you could find some new ways to improve it and be superhero status, or lay back with a 9k rom spinning cop caller and trying not to hear all the "I told you so's"....your call.
Charlie
The guy had a 302 LS1, said it was fun to "drive around", not friendly on street, but revved nicely, Xpensive, and made in the area of 550rwhp if I remember correctly. Thats nice, but when you have to turn 7800+ to get it, no thanks, if I am not at bonneville then the time I hit 8000+ every cop in the district will know where I am.
If this makes you happy then build it. Look at all the people that said the ASA is too much for a street LS1, and before you know it they are in A4 LS1's, almost in mine, but anyway you could find some new ways to improve it and be superhero status, or lay back with a 9k rom spinning cop caller and trying not to hear all the "I told you so's"....your call.
Charlie
Well having an original 302 in my 69, i can say that it is a different beast to drive. You don't realize your turning the rpms because with that short of a crank it wraps up FAST. 
I've been playing with this idea of destroking an ls1 and have had the ideas that it could be a dead ringer to make 500 rwhp 
....however the price you will pay is torque. With that short of a stroke you make a shitload of hp but not as much torque....so you make up for it with Gears At this point in the process finding the valve train to support 8k rpm is hard and very expensive. Rods you can come by...pistons too, even the crank if you have a couple of grand to blow, but the springs and lifters for the ls1 are hard to find that would support it, not to mention the lift on the cam. After all whats a hot rod without a nice lopey cam
I've been playing with this idea of destroking an ls1 and have had the ideas that it could be a dead ringer to make 500 rwhp ....however the price you will pay is torque. With that short of a stroke you make a shitload of hp but not as much torque....so you make up for it with Gears At this point in the process finding the valve train to support 8k rpm is hard and very expensive. Rods you can come by...pistons too, even the crank if you have a couple of grand to blow, but the springs and lifters for the ls1 are hard to find that would support it, not to mention the lift on the cam. After all whats a hot rod without a nice lopey cam 
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breathing motors over 90 hp per liter in many cases.
hp/liter is not a serious way to compare motors. It unfairly favors small motors.
Take for instance, the new S2000. It makes 120 hp/liter, compared to an LS1's ~55 hp/liter.
Now consider:
The s2000 is ~600 lbs lighter, almost a second slower in the 1/4, and is epa rated to get worse gas mileage.
But it makes twice as much hp/liter!
Piston speed is a concern
Why not a 302ci that spins to 8k rpms and a nice turbo setup?
Benefits of that over a nicely setup 346 with a turbo setup?
Benefits of that over a nicely setup 346 with a turbo setup?
Do you see F1 superbikes running smaller engines to turn more rpm or F1 cars?
Of course, if they could they'd go bigger, but probably only in bore as much as practical!
Anyways...
...
There is no logical reason related to power to destroke an LS1. Increasing the stroke isn't always the best way to increase power, especially with FI, but a shorter stroke isn't going to give you any more useable power anywhere in the RPM range. You'd have to spin well past 8000 RPM to start worrying about piston speed with a stock stroke.
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From: Texas, it's like your state, but better.
Rich,
it's the area under te curve man. if you've got identical CI motors, and one makes 450 ftlbs @2800 then it drops to 290's at 5800, and the other makes 450 ft lbs @ 2800 to 5800 which motor will make a faster car? duhh.. the latter.
i'd change the setup to a 388, and use C5R heads, solid roller, ect ect.. but thats just me
a motor with a rod/stroke combo like this would make SICK flat torque, all the way to 8k rpms w/ the right parts. now, with the gear and tire choices, everyone knows that more gear and taller tires = more MPH. w/ 28's and 5.57's something like this would mph freak nasty.
i just like the idea for a light car, w/ a glide and some stuipd gears. like another datsun LS1 project. that'd be a ball.
it's the area under te curve man. if you've got identical CI motors, and one makes 450 ftlbs @2800 then it drops to 290's at 5800, and the other makes 450 ft lbs @ 2800 to 5800 which motor will make a faster car? duhh.. the latter.
i'd change the setup to a 388, and use C5R heads, solid roller, ect ect.. but thats just me
a motor with a rod/stroke combo like this would make SICK flat torque, all the way to 8k rpms w/ the right parts. now, with the gear and tire choices, everyone knows that more gear and taller tires = more MPH. w/ 28's and 5.57's something like this would mph freak nasty.
i just like the idea for a light car, w/ a glide and some stuipd gears. like another datsun LS1 project.
that'd be a ball. LS1 Tech Stories
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The F1 cars run the least stroke possible, because they make all their power at high rpms with a turbo.
Of course, if they could they'd go bigger, but probably only in bore as much as practical!
Anyways...
...
There is no logical reason related to power to destroke an LS1. Increasing the stroke isn't always the best way to increase power, especially with FI, but a shorter stroke isn't going to give you any more useable power anywhere in the RPM range. You'd have to spin well past 8000 RPM to start worrying about piston speed with a stock stroke.
Of course, if they could they'd go bigger, but probably only in bore as much as practical!
Anyways...
...
There is no logical reason related to power to destroke an LS1. Increasing the stroke isn't always the best way to increase power, especially with FI, but a shorter stroke isn't going to give you any more useable power anywhere in the RPM range. You'd have to spin well past 8000 RPM to start worrying about piston speed with a stock stroke.
For a given displacement the faster they spin it the greater HP.
joel
It really is only for cube limited classes.
The Trans Am series is 311 CID max Displacement. they use anywhere from a 2.9-3.1 stroke, and the accomodating bore. Big bore, short stroke, 8200 series limited redline.
The same cars can step up to the Grand Am series, but the CID rule is now 377. Funny, no one runs a 311 CID engine any more
The Trans Am series is 311 CID max Displacement. they use anywhere from a 2.9-3.1 stroke, and the accomodating bore. Big bore, short stroke, 8200 series limited redline.
The same cars can step up to the Grand Am series, but the CID rule is now 377. Funny, no one runs a 311 CID engine any more
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From: Troy, AL
I think a destroked LS1 engine with C5R heads turning 9500 with a 7500 stall and some 5.13 gears would be pretty cool in a stock CI class...especially one that doesn't have in place a 300 lb penalty for C5R heads. Hmmm... 
TECH Senior Member
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From: Troy, AL
...But for street cars or classes that allow more cubic inches, go with the CIs over RPMs any day of the week.
BTW, who says you can't have a 400ci+ engine that turns over 8000 RPM? Mine does. And it'll turn at least 8500 before I'm done with it. IMO, a 4.125 bore with a 3.7-3.8" bore would be perfect for turning 9000 RPM. This would make for a 396-406ci engine. You'de still have the CI to make some serious power and you would have a descent enough rod to stroke ratio to get there before the point of deminishing returns, IMO (I'd study further into this to dial the final idea in.)
"u can have a high displacement engine making 1000 ft pounds and it redlines at 4k rpm, but if u have a motor making 600ft pounds and it revs to say...8500 rpm, the torque monster has no advantage in power at all. more usable RPMs are always good."
You're not going to make anywhere near 1000 ft lbs of TQ NA with an LS1 based engine but in a little fantasy world, let's just say you did...
1000 ft/lbs EVEN IF it were made at the 4000 RPM redline (and of course peak TQ is made well before the redline) would be only 761 HP. 600 ft/lbs at 8500 RPM would be 971 HP! Well of course 971 HP is going to beat 761 HP. But...gimme 1000 ft/lbs at just 5500 RPM instead and let's see what happens. That would be 1047 HP at that TQ and RPM (reminding once again that I'm just talking about HP at the TQ peak, NOT peak HP which would be well after the TQ peak...just for an example.) I'll take that engine over the 8500 RPM 971 HP engine any day of the week.
BTW, who says you can't have a 400ci+ engine that turns over 8000 RPM? Mine does. And it'll turn at least 8500 before I'm done with it. IMO, a 4.125 bore with a 3.7-3.8" bore would be perfect for turning 9000 RPM. This would make for a 396-406ci engine. You'de still have the CI to make some serious power and you would have a descent enough rod to stroke ratio to get there before the point of deminishing returns, IMO (I'd study further into this to dial the final idea in.)
"u can have a high displacement engine making 1000 ft pounds and it redlines at 4k rpm, but if u have a motor making 600ft pounds and it revs to say...8500 rpm, the torque monster has no advantage in power at all. more usable RPMs are always good."
You're not going to make anywhere near 1000 ft lbs of TQ NA with an LS1 based engine but in a little fantasy world, let's just say you did...
1000 ft/lbs EVEN IF it were made at the 4000 RPM redline (and of course peak TQ is made well before the redline) would be only 761 HP. 600 ft/lbs at 8500 RPM would be 971 HP! Well of course 971 HP is going to beat 761 HP. But...gimme 1000 ft/lbs at just 5500 RPM instead and let's see what happens. That would be 1047 HP at that TQ and RPM (reminding once again that I'm just talking about HP at the TQ peak, NOT peak HP which would be well after the TQ peak...just for an example.) I'll take that engine over the 8500 RPM 971 HP engine any day of the week.
