Exact Decking

[pmcnamara]

Got a question.. I have a stock 86 Tall Block.

Using Stock 2.5 crank and stock 2.5 rods.

And Flat Top 2.2 Pistons with a 1.574" COMPRESSION DISTANCE.

I'm trying to calculate the exact amount of material to deck of the block to create the perfect fit.

I'm not sure what the deck deck height of the tall block 2.5 is, but lets say it was 9 inches. And Let's say the stroke of the crank is 3 inches (another variable I can't find the answer too).

9 inches minus half the stroke of 3inches (1.5inches) gives us a rod and piston compression distance of 7.5inches. If the compression distance of this piston is 1.574, the center to center on the rod has to be 5.926inches long.

Once the stroke is determined and deck height is determined, the rod length(s) are determined, we get something that comes the closest combination to the top of the deck of the block, shave the rest to get it as close to the top as possible.

Sooo.. Does anyone know the variables so we can do the math ?

[pmcnamara]

So.. Tall deck deck height = 249.9mm (9.839in); Non-Common Block Crank = 104 mm (4.094); 2.5 long rod = 157mm (6.181in); 2.2 TBI piston CH = 39.2mm (1.574in)

9.839 - 2.047 = 7.791 rod/piston compression distance
8.028 - 1.574 = 6.217 center to center distance
6.217 - 6.181 = 0.036 amount to be decked ??

[4Daytonas]

Thought you said 2.5 crank-you're using figures for 2.2 crank

[pmcnamara]

My bad.. edit made.

[4Daytonas]

Quote:

Originally Posted by pmcnamara So.. Tall deck deck height = 249.9mm (9.839in); Non-Common Block Crank = 104 mm (4.094); 2.5 long rod = 157mm (6.181in); 2.2 TBI piston CH = 39.2mm (1.574in) 9.839 - 2.047 = 7.791 rod/piston compression distance 8.028 - 1.574 = 6.217 center to center distance 6.217 - 6.181 = 0.036 amount to be decked ??

While that would make a zero deck engine ,is that what you want? It's okay to raise compression on carb or TBI engine ,but if it's a turbo you want to leave it alone.Less compression means you can run more boost because of greater swept volume.

[pmcnamara]

Not a turbo.

[kermit]

Double check your math with a dial indicator...