Hey everyone,

I have been researching LS swaps like crazy for my 96 Impala SS and I had a plan that I was hoping to start working on in a few weeks.

My goal is to build a 96 Impala SS that could hang with whatever modded late model my friends have. I'm looking to make enough power to push my 4200lb boat into the low 10's, maybe high 9's (traction willing) while still fulfilling its primary duty as my every-nice-day cruiser and long distance road trip car.

My plan was to go with an LSX B15 and a 3.3 or 4.0 whipple, whichever I could fit once I mock it up. It was a toss-up between that and a TSP 408, but I felt the LSX had more significant advantages for the same price including the block and the 6 bolt heads that flow better than the TSP base head package. The rods/pistons are a weak spot, but seem to hold up to 1000hp and the block/heads leave me with a lot of room to grow when the first rebuild comes around.


I'm so close to ordering the parts I need to begin the swap, but the LT4 just keeps catching me eye. The swap would cost me about the same, granted the B15/whipple will make a lot more than a stock LT4.

What I am really interested in is the power potential of an LT4 versus a modified LS motor like the LSX B15, without getting into internal engine mods for either motor.

Here's what I am looking at-----


Block---I would think the LSX block would be a great deal stronger, but the block probably isn't the weakest link for either engine.

Crank---Both engines have forged cranks, but again, I don't think either would be considered the weakest link seeing how far GM forged cranks have been pushed.

Rods/Pistons---Both engines have forged powdered metal rods and forged pistons. The LSA rods seem to be the weak spot of the LSX B15. Does anyone know if there is any significant design advantage of the LT4 rods (and/or pistons) vs the LSA rods? I can't find too much info on this.

Heads- Also can't find too much info on head specs. I believe the LSX-LS3 head used in the B15 flow 332cfm's at .600. Haven't found flow numbers for the LT4 head. I would assume the two are very close.


I am seeing a hand full of LT4 cars making over 700WHP without internal engine mods, and bottom ends supporting 1000rwhp with cam/heads. I believe it was Chevy Hardcore made 1100 crank HP with a B15 and a cam swap. Of course dyno numbers alone say nothing about the longevity of the short block at those power levels.

Unless I am missing something in the piston/rod design or head flow numbers, it seems to be that improved TQ and efficiency of the direct injection is the only advantage of the LT4 I can see.


What do you guys think? Without digging into the engine, maybe the most internal work being a cam swap, will the LT4 reliably produce more power than a B15 LSX topped with a large whipple? Do you think any one bottom end has any big advantage over the other, as a whole, when attempting to hit the 1000 crank HP mark?

 

 

LSX with the priority main oiling, 6 bolt heads, and overall block strength is WAY more durable than the LT4

both will likely meet your goals. What is the budget and the desired HP? 1000 hp and turbos can be had pretty cheap now

LT4 crate engine is about 13,500 or so and the B15 is 8500 but lacks manifolds and lots of parts.

either won't be cheap. I use the little 4.8 blocks and make all the power you can handle.

much cheaper too. that old imp will shake like a rag doll with 1000 hp though, gonna cage it? What tranny and rear?

I have a 480LE that would work well for it and can take the HP.