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1996 LT4, going to build the engine, need opinions please!


Jul 2, 2016
Las Vegas
1996 Polo Green LT4 6 Speed
Ok, so unfortunately my 50k mile clean 96 LT-4 has what sounds like a wrist pin or piston skirt issue, so we are going to be pulling the motor. As far as im aware, this is the original all stock motor but we wont know for sure until tear down obviously.

The plan is too make this a pretty nasty build. Since the car is a weekend toy, mileage and drivability is very low on the list. Everything about the car is for gear head enjoyment so loud, lumpy cammed and obnoxious is high on the list.

Talking to Lingenfelter, they still offer CNC porting of the OEM LT-4 heads and intake, but are willing to hand port match a more modern intake to their heads (I was looking at the Edelbrock Air Gap as one option). I like the stealthy idea of OEM appearing heads/intake vs AFR or DART, etc. But with a big nasty cam, small nitrous plate system and long tubes with no cats, this wont likely be "stealthy" in any other way, so im more concerned with performance numbers. They emailed me a data sheet on their CNC numbers:

.600 valve lift 92% on 300 scale: 276 cfm intake
.600 valve lift 67.5% on 316 scale: 213 cfm exhaust
.650 valve lift 93.5% on 300 scale: 280.5 cfm intake
.650 valve lift 68.5% on 316 scale 216.4 cfm exhaust
202 cc intake runners

Anyone here have personal experience with their setup? Im balancing the time/effort and cost with just buying a complete set of heads from the competition (DART, AFR, Edelbrock, etc.) who offer even larger CC's, but im not sure the limit on the ported stock/Edelbrock/Miniram intakes? No point in putting huge heads/cam in if I dont have a reasonable intake option to feed it.

Second part, the bottom end. Id love to put a bigger 4340 (383 ish or more) crank and some long H-beam rods, but on the last build I did on an 88 TPI motor, I had to do some serious block and rod bolt clearancing and id rather pass on that this time around. This was mostly due to a "core shift" issue on that block, but how common is this on the LT series motors? This will be my first time inside these. I hate to bore out perfectly good cylinders to add displacement, much prefer doing it via stroke, but these motors also make power much higher in the RPM's than was reasonable on the TPI motors.

Since this is a 6 speed car, we will be re-gearing the diff (and adding a friggn drain plug, I want to CHOKE GM for that stupid decision) while the motor and trans is out of the car (likely 4.11 or higher). The plan is for bias ply's for the track but im running C6 Vette OEM 18/19" rims for the street. Anyone gone as high a 4.56's?

It looks like the trans needs to come out before the motor can, due to input shaft length. What is your guys preferred method? I dont have a high enough garage roof to pull the motor inside, so we will have to roll the car into the drive way to pull the motor. So it will be tricky to lift the car to take out the trans first. Im hoping there is a trick that im not ware of???

That Dual Mass flywheel is going in the trash as well so flywheel/clutch recommendations would be very helpful. Ive been out of the hobby for a while so im out of date and stuck with reading tons of many years old forum posts! =)
Don't trash that dual-mass if it's in good condtion. Sell it. Dual-mass wheels are hard to find. When I had a C4, I sold the dual-mass for a pretty song and went to a McLeod aluminum wheel and a McLeod clutch. Worked great. Had that set-up for 15-years or so and it was in the car when I sold it.

A 4.10 axle is the way to go, but you need wide sticky wires to keep from blowing the tires away all the time.

You're going to hate the idle and low-speed drivablility unless you have a really good tuner working for you.
I just built my l98 up to a 383. As far as I know these 5.7 liter blocks need to have the lower cylinders notched in order for the rotating assembly to move freely. I ran the eagle I-beam connecting rods with no issues with clearance.
I just built my l98 up to a 383. As far as I know these 5.7 liter blocks need to have the lower cylinders notched in order for the rotating assembly to move freely. I ran the eagle I-beam connecting rods with no issues with clearance.

Yeah I had to do that and the cam lobes hit the rod bolts so i have to do a lot of clearancing for that. It was a nightmare!

I do need to work out how to go about the tune. When I did the L98 I got a Moates ZIF adapter and used a laptop. But that was an OBDI not this one of a kind OBDII. =(

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