Gen 2 Busa Engine Build for Drag Racing

[Racing4Real]

I'm currently in the process of gathering the required parts for my new build. Currently I have 85mm custom pistons from RC Performance with the wrist pins moved up .100 using Gen 1 rods, 72mm marine billet crank and cylinder head ported by RC as well with 445/415 cams. I've been trying to figure out the exact base spacer and head gasket to use. Doing some math for what I found online I would need to get a .040 base spacer and run the stock .030 head gasket. Is this correct?

 

[Dennis]

Pins moved up 0.100" (2.5 mm) from Gen1 or Gen2 pistons? This is how I would calculate it.

From Gen2 pistons, (72-65)/2-2.5=1 mm spacer
From Gen1 pistons, (72-63)/2-2.5=2 mm spacer

In the end most builders measure how far down the piston is in the hole and adjust from there, maybe an extra base gasket or something if needed.

What was the reason for custom pistons? You could have run an off the shelf piston and thicker spacers. Head gasket will be for an 85 mm bore, not stock.

 

[Racing4Real]

They are custom pistons designed for stroker motors by RCPerformance. It makes it so that you dont need as much of a base spacer if you kept the wrist pins in the original location or to not have to go to a shorter rod. Plus some other goodies he designed into the piston. I did order a 85mm bore .030 head gasket already. Im just trying to figure out the base spacer.

 

[Racing4Real]

Pins moved up 0.100" (2.5 mm) from Gen1 or Gen2 pistons? This is how I would calculate it.

From Gen2 pistons, (72-65)/2-2.5=1 mm spacer
From Gen1 pistons, (72-63)/2-2.5=2 mm spacer

In the end most builders measure how far down the piston is in the hole and adjust from there, maybe an extra base gasket or something if needed.

What was the reason for custom pistons? You could have run an off the shelf piston and thicker spacers. Head gasket will be for an 85 mm bore, not stock.

G20mm wristpins so Im guessing their Gen 1 pistons and Gen 1 rods

 

[Dennis]

Gen 1 and Gen 2 pistons use different pin heights, so if you aren't sure which they are you would want to measure them. It would probably be a fair question for RC since you bought the stuff from them. I think my math is right, but you need to know what the parts are.