Brattons pistons

[Chuck Sea/Tac]

Anyone use brattons pistons, and do the listed .002”/.003” clearances work. The machine shop has a tight .002, and I’m nervous. Anyone know who makes them?

[George Miller]

Originally Posted by Chuck Sea/Tac

Anyone use brattons pistons, and do the listed .002”/.003” clearances work. The machine shop has a tight .002, and I’m nervous. Anyone know who makes them?

.002 is to tight on 3 and 4. They will score and might seize in the cylinder. The old .001 per inch rule works well. Model A's do not have a water jacket all the way to the bottom of the cylinder. 3 and 4 do not get as much water movement as 1 and 2.

I would hone them to at least .0035

[Synchro909]

Right on, George.

[d.]

call Brattons, they are helpful people.

[700rpm]

.003 is too tight. My engine shop bored my cylinders to piston factory specs, which were .003. The engine seized up whenever it got warm. I pulled it apart and had it honed to .0045. No more seizing.

[Chuck Sea/Tac]

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Ray, where did the pistons come from?

[glenn in camino]

I've always used Brattons pistons. I order one size larger if I'm having the block bored, and get the rings too

[Chuck Sea/Tac]

Originally Posted by glenn in camino

I've always used Brattons pistons. I order one size larger if I'm having the block bored, and get the rings too

But what is your piston to cylinder clearance?
The weird thing is I know a guy with 75 engines with brattons pistons with .002” clearance, and no problems. Yet others have seizures. There has to be something that’s different.

[briphaeton]

Some newer pistons are---- Hypereutectic pistons are made of an aluminum alloy which has much more silicon present than is soluble in aluminum at the operating temperature. Hypereutectic aluminum has a lower coefficient of thermal expansion, which allows engine designers to specify much tighter tolerances.

[George Miller]

It maters how you check the clearance. Piston size and bore size will not give you a true reading. You need to have final check with feeler gauge, on the piston skirt.

[briphaeton]

Using inside a micrometer and double checking the measurement with a outside micrometer works good enough for engine rebuilders. Outside micrometer are checked against a standard. I like my Intrimik mics for checking the bore but you can't use them while boring the cylinder.

[Jim Brierley]

I agree with George, use a feeler ga. I bore to .003, then hone another .0005, much more on a racing engine.

[1930-Pickup]

A good machinist will bore the cylinders to fit the new pistons...this will solve any issues of piston manufacturing tolerance variations. My machinist even makes sure to mark which piston goes to which cylinder.

If the clearance is too small on your motor after rebuilding it, it sounds like the machinist didn't do a good job.

[George Miller]

Originally Posted by 1930-Pickup

A good machinist will bore the cylinders to fit the new pistons...this will solve any issues of piston manufacturing tolerance variations. My machinist even makes sure to mark which piston goes to which cylinder.

If the clearance is too small on your motor after rebuilding it, it sounds like the machinist didn't do a good job.

I do the same, but you still need to do a final check with a feeler gauge.

[[email protected]]

The problem may not be the clearance. It may be the pistons.
A couple years ago I took some new pistons and a block to a machine shop for fitting. The machinist looked at the pistons and noticed the skirt of the piston was rather thin. He measured the piston, held it hot tap water for a few minutes and measured the piston again. The piston skirt had expanded over two thousands of an inch under hot tap water. He refused to use them. I bought some Silver-o-lite pistons, bored the cylinders 3 thousands over and have not had a problem.

[700rpm]

Originally Posted by Chuck Sea/Tac

Ray, where did the pistons come from?

Snyder's. BTW, George gave me the good advice about honing out to .0045. Thanks again, George!