So my buddy currently has a stock-block '96 EFI 460 running ~7 PSI of boost. Years back, he had grand plans to build the internals of the engine to handle something like 20 PSI of boost. We had put together a whole list of components - Scat h-beam rods, Probe forged dished pistons, etc.. Well the build got put on the back burner for ~3-4 years, and now that he's getting back into the swing of things, he's been looking to start buying parts.
The issue is, the probe pistons we originally priced out appear to no longer be available, and now I'm having a hard time finding a suitable piston. All of the pistons with the correct compression height (1.77" for the late EFI engines like this one) are flat-top or very slightly dished (3cc or so), which according to my calculations will push the compression into the 9.5-9.7:1 range, which seems a bit too high for a turbocharged engine?
I can get pistons with a lower compression height which would pull the compression down into the 9:1 range, which I'd be more comfortable with, but the problem with that, is that it pulls the piston down into the bore and makes quench much worse.
With 0.040" head-gaskets and 1.77" compression height and 3 cc dish piston, I'd be looking at a quench of around 0.055"-0.060" and a compression of ~9.7:1. With the same gaskets and a 1.756" CH 3cc dished piston, we're looking at ~9:1 compression, but quench is now around 0.074".
Is the extra quench that big of a deal? Should I maybe look into different pistons in different bore sizes than the standard 0.030" over (maybe .040" over 4.400" pistons?)
Also, we're debating on whether or not to keep the stock '96 truck cam. We're going for a "high-torque low RPM" type of build, so higher boost at low RPM. Expected RPM range is basically from idle to ~4500 RPM. Hoping to push enough boost for 500-600 HP. Any suggestions for a cam, or is the stock unit good enough? The cam must idle smooth and have good low-end power.
The issue is, the probe pistons we originally priced out appear to no longer be available, and now I'm having a hard time finding a suitable piston. All of the pistons with the correct compression height (1.77" for the late EFI engines like this one) are flat-top or very slightly dished (3cc or so), which according to my calculations will push the compression into the 9.5-9.7:1 range, which seems a bit too high for a turbocharged engine?
I can get pistons with a lower compression height which would pull the compression down into the 9:1 range, which I'd be more comfortable with, but the problem with that, is that it pulls the piston down into the bore and makes quench much worse.
With 0.040" head-gaskets and 1.77" compression height and 3 cc dish piston, I'd be looking at a quench of around 0.055"-0.060" and a compression of ~9.7:1. With the same gaskets and a 1.756" CH 3cc dished piston, we're looking at ~9:1 compression, but quench is now around 0.074".
Is the extra quench that big of a deal? Should I maybe look into different pistons in different bore sizes than the standard 0.030" over (maybe .040" over 4.400" pistons?)
Also, we're debating on whether or not to keep the stock '96 truck cam. We're going for a "high-torque low RPM" type of build, so higher boost at low RPM. Expected RPM range is basically from idle to ~4500 RPM. Hoping to push enough boost for 500-600 HP. Any suggestions for a cam, or is the stock unit good enough? The cam must idle smooth and have good low-end power.