Hi all

I’ve got a LS3 and I’m looking to get more power out of it while also improving reliability as much as possible. I plan to use the car for road course / track day circuit events (15-20 minute sessions, 4-5 sessions per event) as well as a small amount of street use.

I was thinking a N/A 415-416 build with high compression running E85 only would be ideal, however I spoke to a local engine builder who told me I should stick with the stock crank as a 4” crank creates too much piston speed and can quickly cause piston skirt wear during racing events.

Keen to get more opinions and thoughts on this and any advice on the best options for my build. Would love to make close to 750hp at the crank.

Cheers!

 

You should consider a 3.9 stroke crank. Im in the middle of doing one in a 4" ls2. Read Scott Cramer (Che70velle) recent thread 403" stroker. He knocked one out of the park.

 

The sleeve length for LS 3 also a little short for the 4 inch crank and can cause piston rock. The GM LS7 block which has the 4 inch crank the cylinder sleeve is like .250 longer. The Scott motor was resleeved motor I think with like 5.80 or 5.85 inch sleeves. I think LS3 are like 5.50 or 5.60 inches in length. They make special piston to account for this too.

 

Just asking the question. Would a person be better off sleeving a LS2 block from RED (Race Engine Development)? I did a LS2 and stroked it to 427 cubes. Ran great. I used a Manley stroker kit. IIRC RED uses longer ductile iron sleeves.

 

Scott's recent 403" was a stock oem ls3 block honed to 4.070 hence the 3.9" stroke instead of a 4" stroke.

 

750hp in a road course car is going to be a handful... My buddy has 640hp in his C6 vette track car and its a monster.

Im going the other way in my road course car precisely for the reason your engine builder told you dont go to a longer stroke... im de-stroking with a 4.8 crank to slow the pistons down a bit. I dont need the torque in a 2300lb car, so a bit less piston speed may help with longevity, making less heat, etc... and a bit less torque might help make the car driveable on track...

HP in a road course car isnt all its cracked up to be. Theres a local guy with a 2020 GT500 with 750+hp(whatever they have stock) and all the bells and whistles(carbon wheels and whatever) and his car isnt much faster around a track than a Spec Miata with 120hp... I "think" he's actually a decent driver, but he said the car is just a handful due to the power and however heavy it is.

 

Yes, that block was an OEM LS3 block that we simply CNC honed to 4.070…stock sleeves. Here’s a link for you @demuck https://ls1tech.com/forums/generatio...-n-buildo.html

 

Now fwiw, I’m about to start a build for Grubinski here on Tech. It’s a 4.155” bore build with a 3.75” arm that should be outrageous in his Miata on the track. It will have a very mild cam for the app that should make enough torque for all of us here. I wasn’t going to share this info until Mike did, and he let the cat of the bag recently…so it’s no secret anymore. Coming soon to another build thread near you.

 

Factory GM L8T crank.. 3.860" stroke , with some Brodix or CID LS7 heads

https://www.ebay.com.au/itm/314182992732

 

I was thinking of going this route but was discouraged when I was told these cranks usually require quite a bit of mallory to balance. I'll have to look but my 3.9" crank was only $800-900 from BTR and was told it comes from Callies.

 

Well C6 Z06s have a 4" stroke and they're used for track days all the time. So piston speed isn't the problem.

The sleeves for an LS3 might not be the optimal depth for it though.

 

You make a good point, maybe time for me to speak to a different engine builder

 

There is no reason to not do a 416 IMO. It is a race engine so after a season it probably needs a refresh anyway. At that point you can determine if you want to resleeve it. One thing is for sure... if you don't have some serious cylinder heads and intake on it... you will never get close to 750hp.... and big compression. If you have aero and on sticky tires you should factor in a real dry sump system as the factory style oil pump above about 7000rpm will cavitate and cause issues... plus you won't make 750hp without revving it higher unless you had major cubic inches (and dollars).

It is all power to weight. A 2600lb car doesn't really need a ton of power to have fun. A 3600lb car will not feel as wild given the same engine and also consumes tires at a faster rate as well as wheel bearings/suspension items, etc
Try to run a square tire setup if you can so you can in order to rotate the tires to really extend tire life and minimize the hit on your wallet!

Here is a little local to me LS3 Miata running a 430hp crate GM LS3 and dog box transmission... it has big aero and does very well at events. Next engine he is building has 250hp more hahahahaha

https://nasaspeed.news/cool-rides/fi...or-a-v8-miata/