I'm not stroking the motor but wanting to go to the 4.125 bore with the 2.100 rod journals. But when doing the math (with the online calculators) with the available choices in compression height for forged pistons (albeit through Summit) to get around the desired compression ratio (8 to 8.5) using 77cc heads I had to look at 400 pistons for a 5.7 stroke but using a 6.200 rod. The idea that I am off on something along the lines is quite possible though.

Olds pistons are usually in the 1.6ish range om a 6.000 rod for compression height yes?

The math I used was:

Deck Height = 9.330
Bore = 4.125
Stroke = 3.385

So:

6.000 rod length
(0.5 x Stroke) 1.6925
1.6375 = Compression height

6.200 Rod length
1.4375 = Compression height

I'm working with a builder but this is all for me to learn.

BTW, this forum needs stickie/permanent threads with info at the top bad. A basic tech one, common build one, etc. I'm surprised there isn't any.

J

 

Good ideal on sticky but someone has to carry the ball to the moderator and changes can get done. Guys in the know would have to furnish info.Then it would benefit those who don't.JMO

 

Look for a piston with a dish around 12cc and a cd of 1.425. That'll give you about 8.3 with a 77cc head and a little deck clearance.
Even with just a little boost I'd deck the block to clean it up though.
And you'll need to pay close attention to the alignment on the small end of the rod going up into the piston. Olds rods are centered, Chrvy rods are offset.
By the way, your builder should've known all of this.

 

Thanks.

I'm sure he does but this was really for my benefit, not his. I can have just told him what I was looking for and he could do it but I don't like to just have someone do everything for me and be entirely oblivious to the process.

It was also to help me know on a simple parts basis where to look from some manufacturers.

J

 

Here's a couple photos of the car in case anyone was curious.





Before and after.

 

You'd never get everyone to agree to the same parameters of the permanent threads

 

Update:

As with many projects, this one has been shelved for a bit as other ones got in the way.

Short block is finished though and I went with a set of 8 heads and had them opened up some, new valves (with 3-angle valve job), springs, and combustion chambers polished for a bit of extra CC's and reduction in detonation. Dick miller main caps and girdle installed on the bottom end and ARP everything. Should be just under 8-1 static compression.

Schneider custom ground hydraulic roller cam set up and lifters.

282-RH HYDRAULIC ROLLER CAMSHAFT

282 DURATION
230 @ .050" LIFT
.576" LIFT WITH 1.6 ROCKER RATIO
114 LOBE CENTER

Got a Hampton 6-71 unpolished set up for the supercharger. Intake will be port matched to the heads. Still need to have the crank broached and 2nd key way installed and dampener machined for the 2nd key way as well (don't want to risk shearing!)

J

 

Cool, what pistons were used?

 

Single pattern cam?