4.3 LT1 crank
10-06-2008, 09:21 AM
#1
Registered User
Thread Starter
Join Date: Jan 2007
Location: Flower Mound, Tx
Posts: 298
4.3 LT1 crank
I was reading about a project that GM did and we are thinking about duplicating, if we have it figured out. I just need to know if the 4.3 LT1 crank will bolt in to a 5.7 LT1 block. As in if main caps are the same. Thanks.
Last edited by texas97z; 10-06-2008 at 01:09 PM.
10-06-2008, 03:07 PM
#4
Registered User
Thread Starter
Join Date: Jan 2007
Location: Flower Mound, Tx
Posts: 298
I was reading in Hot Rod about a 97 LT1 that GM built that was a 302 cid. I did some math and a standard bore LT1 block with the 3" stroke of the L99 would put CID at 301.5 or at 10 over it would be 303.(something), basically a 302 cid. This had to be how they built it cause I doubt GM would use the resources need to build a reverse cooled 327 block to make a traditional 302. I think this would be a cool engine package to put together, just more of a road course engine probably because of the high revs that the 302 is known for and likes to stay at. But we are going to dyno/strip time test it, as well as run it around the track and see how it behaves. Wasn't going to say anything untill it was completed because of the time and money it will take to test it out. But that is the project.
What do you think?
What do you think?
Last edited by texas97z; 10-06-2008 at 03:35 PM.
10-06-2008, 04:15 PM
#6
Registered User
Join Date: May 2006
Location: Ohio
Posts: 1,856
I was reading in Hot Rod about a 97 LT1 that GM built that was a 302 cid. I did some math and a standard bore LT1 block with the 3" stroke of the L99 would put CID at 301.5 or at 10 over it would be 303.(something), basically a 302 cid. This had to be how they built it cause I doubt GM would use the resources need to build a reverse cooled 327 block to make a traditional 302. I think this would be a cool engine package to put together, just more of a road course engine probably because of the high revs that the 302 is known for and likes to stay at. But we are going to dyno/strip time test it, as well as run it around the track and see how it behaves. Wasn't going to say anything untill it was completed because of the time and money it will take to test it out. But that is the project.
What do you think?
What do you think?
10-06-2008, 05:35 PM
#7
Registered User
Join Date: Feb 2004
Posts: 4,800
Been done, use the L99 rods with stock LT1 pistons even. Ends up torqueless.
The L99 rod is 5.940, if you do the math on that the shorter stroke coupled with the longer rod makes the stock LT1 piston the right height.
I gave my old L99 crank and rods to a guy who tried just this.
The L99 rod is 5.940, if you do the math on that the shorter stroke coupled with the longer rod makes the stock LT1 piston the right height.
I gave my old L99 crank and rods to a guy who tried just this.
10-06-2008, 07:18 PM
#9
Registered User
Join Date: Aug 2007
Location: Bennett N.C.
Posts: 746
just remember the parts it takes to turn say 7500, and survive, with a 302, can be done with a 350
in the late 80s I built a 302 and loved it
got the crank from a guy that raced at Caroway speedway
5.7 rods and 12.to1 pistons huge solid cam and 292 turbo heads victor junior intake,, 8500 instantly
didn't do to well in my 69 camaro with 5.13 gears and 14x42 Firestones, tried 6.14 gears and gained 1 tenth
bought a dirt track car and it made 5 races before one of the pistons went through the block
circle track parts and drag racing sometimes dont mix
all this was before I got married
in the late 80s I built a 302 and loved it
got the crank from a guy that raced at Caroway speedway
5.7 rods and 12.to1 pistons huge solid cam and 292 turbo heads victor junior intake,, 8500 instantly
didn't do to well in my 69 camaro with 5.13 gears and 14x42 Firestones, tried 6.14 gears and gained 1 tenth
bought a dirt track car and it made 5 races before one of the pistons went through the block
circle track parts and drag racing sometimes dont mix
all this was before I got married
10-07-2008, 01:25 PM
#11
Registered User
Thread Starter
Join Date: Jan 2007
Location: Flower Mound, Tx
Posts: 298
I wasn't going to use the 5.94 rods. Not that it makes that much of a difference but H-beam 6inch was in the budget as was forged pistons. Sad to hear it was torque less, what RPM did you take it to? Heads and cam? Just curious.
This engine is more aimed as a good fun engine combo for less than a stroker and a unique CID to brag about. I priced a refurbished crank with all bearings at $250 shipped. Do some ebay shopping and you can find forged 6" h's and some forged flat tops for $700 or less with shipping. Total in bottom in $950, seeing the confused look on their face when you tell them it is a 302, priceless.
Now I do agree that it is POINTLESS if it doesn't make atleast as much power as a 350 would. But I would emagine with a good set of heads and a good cam selection, it should make as much as a 350 and be a great road course/street engine. It might even do better in the upper RPM's due to the short stroke. Only time will tell.
Now 96caprice, if you are telling me you did it with heads and cam and it made less power then I would def like to know. Also curious if this was in an F-Body or heavy chevy. Probably wouldn't do well in a heavy car as it doesn't have the low end torque needed to get it moving.
Thanks to all for the opinions though. OH and mdacton, I have a 383 in here and no plans on changing down to 302. This would be a fun project for a different car, just to see. I have a friend in to roadcourse and he brought up the idea. I am just doing the digging.
This engine is more aimed as a good fun engine combo for less than a stroker and a unique CID to brag about. I priced a refurbished crank with all bearings at $250 shipped. Do some ebay shopping and you can find forged 6" h's and some forged flat tops for $700 or less with shipping. Total in bottom in $950, seeing the confused look on their face when you tell them it is a 302, priceless.
Now I do agree that it is POINTLESS if it doesn't make atleast as much power as a 350 would. But I would emagine with a good set of heads and a good cam selection, it should make as much as a 350 and be a great road course/street engine. It might even do better in the upper RPM's due to the short stroke. Only time will tell.
Now 96caprice, if you are telling me you did it with heads and cam and it made less power then I would def like to know. Also curious if this was in an F-Body or heavy chevy. Probably wouldn't do well in a heavy car as it doesn't have the low end torque needed to get it moving.
Thanks to all for the opinions though. OH and mdacton, I have a 383 in here and no plans on changing down to 302. This would be a fun project for a different car, just to see. I have a friend in to roadcourse and he brought up the idea. I am just doing the digging.
Last edited by texas97z; 10-07-2008 at 03:58 PM.
10-07-2008, 02:24 PM
#12
Registered User
Join Date: Oct 2001
Location: Engineerland
Posts: 1,517
There is nothing to see, it will be a dog with lt1 parts/efi.... period.
You cant make as much hp as a 350 would. In order to match the volume of air a 350 can move at 7000rpm you would need to turn about 8100. You cannot rev that high with an lt1 pcm no way no how, and if you did the opti rotor would go BANG.
Besides that, in racing when on a budget you build a low rev easy running combo. Big high rpm is great if you want to be a hero but it will put your *** in the poor house every time unless you pack a real big wallet. Engine life (or any machine) is about the number of cycles at a given stress level. You are going to be pushing the valvetrain of a 302 every bit as hard as its bigger counterpart.
Not trying to get down on you, just throwing out some food for thought. Your idea is one of novelty not going fast. Put the same money into good pistons and rods and do a 355... tell them its a 302. Unless you race superman nobody will know.
You cant make as much hp as a 350 would. In order to match the volume of air a 350 can move at 7000rpm you would need to turn about 8100. You cannot rev that high with an lt1 pcm no way no how, and if you did the opti rotor would go BANG.
Besides that, in racing when on a budget you build a low rev easy running combo. Big high rpm is great if you want to be a hero but it will put your *** in the poor house every time unless you pack a real big wallet. Engine life (or any machine) is about the number of cycles at a given stress level. You are going to be pushing the valvetrain of a 302 every bit as hard as its bigger counterpart.
Not trying to get down on you, just throwing out some food for thought. Your idea is one of novelty not going fast. Put the same money into good pistons and rods and do a 355... tell them its a 302. Unless you race superman nobody will know.
10-07-2008, 02:42 PM
#13
Registered User
Join Date: Jul 2007
Posts: 321
High rpm standard SBCs destroked to 302s then turbo'd were fairly popular, but it takes a LOT of cash to do it right...and like already stated the LT1 is not a good platform for it. If you go to rear mount dist to ditch the opti, and run an aftermarket ECU setup it could be done...but that just adds more and more to the cost. Not to mention the crazy expensive and lightweight parts needed to hold that kind of rpms and power.
There is something impressive about a turbo'd V8 spinning to 8 grand, but even if I had that kind of cash for all top of the line parts I would not choose an LT1 as the platform to work off of.
There is something impressive about a turbo'd V8 spinning to 8 grand, but even if I had that kind of cash for all top of the line parts I would not choose an LT1 as the platform to work off of.
10-07-2008, 03:53 PM
#14
Registered User
Thread Starter
Join Date: Jan 2007
Location: Flower Mound, Tx
Posts: 298
I am not feeling beaten up so no need to apologize. You are absolutley right that it is a novelty based idea. That having been said if it doesn't make since,well....there you go.
We had thought about going boosted but turned it down due to added cost involved. The opti problem had occured but we weren't planning on revving past 7k. The original 302 was rated at about 350fwhp I think at 5500 rpm but it was stated at the time that it would make 425fwhp at 6700. So we figured about the same for this set up. Maybe a little less because of not wanting to shift higher than 7k because of factory computer limitations. We also thought with advances in cylinder head porting and camshaft design that we may get more out of it. I consider that decent power, about 370 rwhp thru a 6 speed with 12% loss.
I guess what I am not seeing is why this LT1 would have to be rev'd even higher than the original one was. I have seen guys on here shifting pretty close to what I am talking about going for stock bottom end biggest power so I know the ECU can handle it if it is working for them. I would think EFI would operate better than a carb would with providing the right fuel at the right point so I don't think that is it.
?
We had thought about going boosted but turned it down due to added cost involved. The opti problem had occured but we weren't planning on revving past 7k. The original 302 was rated at about 350fwhp I think at 5500 rpm but it was stated at the time that it would make 425fwhp at 6700. So we figured about the same for this set up. Maybe a little less because of not wanting to shift higher than 7k because of factory computer limitations. We also thought with advances in cylinder head porting and camshaft design that we may get more out of it. I consider that decent power, about 370 rwhp thru a 6 speed with 12% loss.
I guess what I am not seeing is why this LT1 would have to be rev'd even higher than the original one was. I have seen guys on here shifting pretty close to what I am talking about going for stock bottom end biggest power so I know the ECU can handle it if it is working for them. I would think EFI would operate better than a carb would with providing the right fuel at the right point so I don't think that is it.
?
10-07-2008, 05:42 PM
#15
Registered User
Join Date: Feb 2004
Posts: 4,800
The guy I gave my parts to was aiming for a better fuel economy setup in a Caprice and it ended up cycling the converter so much he gave up on it. He took it down the track once with sad results too.
As said the 350 crank will spin beyond what the pcm can handle so there is no real point here.
I understand the will to try something different, but this has been tried and deemed a failure already.
I am not a blind believer in displacement the way most here are, on the otherhand I would not go trying to make the engine smaller when held to such low rpm limits, and if you give it adequate rpm to make it work the GM crank is the wrong place to start.
As said the 350 crank will spin beyond what the pcm can handle so there is no real point here.
I understand the will to try something different, but this has been tried and deemed a failure already.
I am not a blind believer in displacement the way most here are, on the otherhand I would not go trying to make the engine smaller when held to such low rpm limits, and if you give it adequate rpm to make it work the GM crank is the wrong place to start.