I have a LSX block that I have now owned since the first year they went on sale. I cant decide on a good combo to build using a supercharger. I always run into so many conflicting stories about 4" stroke isnt good for for the street, and various other stories.

I would like you guys opinion on a combo that will be streetable, but still perform at the track every now and then.

I currently Have:

LSX Block
Callies Compstar Rods 6.125"
Vortech S-trim 700hp rating (will be upgrading to bigger SC)

Any suggestions? I was leaning toward 427-440 cid, but could never decide how I should go about this project. Thanks fellas!

 

Oh forgot to mention, that my final goal is 1,000-1200hp once I upgade the supercharger.

As far as heads, I will be going with the LSX/LS7 heads fromm GMPP
The intake, I have my mind set on the LS style Victor JR with the carb setup.

Any info on what direction I should take would be helpful, or anyone of you sponsors care to help with this build would be awesome (dreaming)!

 

Arent the longer strokes bad only if its due to the sleeve length being to short for some 4.100 and 4.125 cranks, and also because you then begin thinning the piston to accommodate the larger cranks thus reducing the amount of boost you can run.

I'd say forged 427 4.125x4. You can always re bore it out to a 440 4.155x4 if something should happen (gotta love iron)

don't forget a custom cam or at least one spec'd for blowers

 

I know what you mean. Had thought about future needs of rebuilding, I guess 427cid would be a good starting point. well at least I dont have to get custom pistons.

 

I would stick with the 4" stroke, not longer. The problem is having enough compression height on the piston for a decent ring pack, and/or poor rod ratio. If you go with a longer stroke, the piston gets too short and/or you have to push the top ring too high or the rod ratio goes to heck.

Here's what I used on mine:

4.125 x 4
6.125 rods
9.250 deck height
That gives a compression height of 1.125, which leaves enough room to have the top ring .25 down. With a 14cc dish, 73cc relieved LS7 chambers, and an .051 LSX gasket, compression came out to 9.8:1, which was right on target. Rod ratio is 1.531 which is not far from the stock LS7.

We kept the 4.125 bore both for gasket seal and to be able to still have gasket seal after an overbore, if and when. This is for a street FI application, and yes, I'm very conservative. The way I look at it is, for a street car, what's a few HP here or there? Go bigger on heads or cam or FI if that's what you need to do to hit your goals. Then leave yourself some considerable margin on all the parts. Don't push things to the limit. But that's just my opinion.

 

Thanks for the details Gannet, very helpful!
But if I start out with a 4.130 bore that also leaves me good room for future rebuilds also right?
What pistons did you use? I would like to keep compression at no more that 8.5:1 but I am considering running E85 so I could run higher compression along with FI.

 

I wouldnt suggest running the static compresison that low unless you are planning on a turbocharger with a high boost level.

 

So what compression should I shoot for? Is the sweet spot 9.5:1.. I would like to be able to Tom 15lbs of boost even go up to 20 in the future, if it's possible with 9.5:1.