Piston swapping with out machining?

Joey7508

Member
Oct 23, 2005
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Kerrville TX
I bought a Fordracing short block. It was one of the explorer left over ones. So it is brand new standard bore block, crank rods, and hyper-u pistons. All new. I have maybe 5000 miles on it. I want to switch out the rods and pistons with a set off DSS lower compression forged piston and race prepped rod,they are basically stock rods with ARP bolts. A little better rings and some better head gaskets while I am there. They will make the pistons in standard bore no problem there, but the guy I spoke to over at DSS said I shold have the block looked at or even bored 30 over. I am trying to skip the machining and just swap out the pistons. What do you guys think?
Here is the over all plan. I am putting a single turbo set up on the car now. I want to run it on low boost until I get the money for the engine I want which would be a purpose built Boss block 331. I am running TF heads, intake, f cam on my stock block right now, and want to run the turbo on what I have now. I know I should buy the built engine first and turbo later, but where is the fun in that.
So do you see any problem with switching the pistons with out machining the block? I think it would just be like re-ringing an engine.
 
As long as your tune was remotely close (IE no wash down or detonation) and the engine wasn't defective from the factory, you should be fine with just honing the block a little, as 5k miles isn't anything.

Although I would have your rotating assembly rebalanced.
 
The advice is pretty solid in this thread and I have to agree.

There is just to many production tolerances between pistons. Just because both brand X and brand Y pistons have the same bore size, they can still vary within several thousandths.

It is those several thousandths that make or break engine longevity and reliability.

Then you would also like a nicely laid out cylinder wall, which will require some grit honing to get a proper ring seal for the new rings.

I have no doubt that many backyard guys have did the swap and did "okay" with it, but it is not something suggested by me.

Good Luck with it all.