I measured the cylinders and they are good, but, the pistons have just a little too much wear on them, under 3.950, so I'm going to get new pistons for it, but witch ones?
It's an '87 block converted to carb and the pistons now aren't the D shape top yet that's what I see most of. pics later
Are all the pistons the same as far as measurements, comp. ht. and pin?

 

Any 300 stock configured hypereutectic piston will work.

Pistons - L6 Engine Type - SummitRacing.com

 

This is what I mean about which piston to use.


This piston top or,



I'm planning on using a 240 head with the ports cleaned up a little, the top piston were in the '87 block and the bottom from a '82.

 

Where did you measure the bores? You need to measure top and bottom and check for taper. There is generally more wear at the bottom of the piston travel. Why bother with new pistons if you aren't going to bore the block?

 

Precision. What I'm really wanting to know is what c/r might be with either type piston with use of the 240 head. I did check the taper and it's all good, what I don't want is possible piston slap, the pistons are just on the edge of too much wear. Knowing the hone job won't take much at all off, but, precision.
My first motor re-build was a 1969 Chevy 396, it needed bored but I was strapped for cash and just honed it, wrong decision, it busted the ring s and landing in no time because of the ridge it had. I learned from there.

 

What are the numbers? How much taper and how much piston wear? Just curious because your terms seem a little vague. Are you planning on using used pistons from a different engine?
Also you can knurl piston skirts to tighten them up a little. It's not practiced much anymore though.
What you did to that 396 was not a rebuild.
Precision is good.

 

The EFI piston with the 240 head should give you roughly the same compression as the stock EFI 300.

A carbed 300 piston with the 240 head should give you roughly a .5 bump in your compression ratio.

But there are a lot of variances in the different components. So to make sure you have to check/measure all your components and figure out your compression ratio yourself.

 

careful with knurling the skirts...its basically a band aid for your issue brother. do it right the first time, or don't bother. just my .02