I am rebuilding a 400, just got the block back from the machine shop and would like to double check the tollerance they keep (trying a new shop).

The pistons (new .060) seem a little sloppy to me, I have never had to check before.

How do I do it and what should it be?

Thanks
Curt

 

Measure the bore and measure the piston and subtract. The piston MFG may specify a specific place on the piston to measure. Lacking the inside micrometer... (like me) I push one of the new rings down the bore and measure the end-gap in several places. GL

 

The thing I have seen lately from machine shops that bothers me is taper in the cylinder. Just got a gague that measures it down to the 1/10,000. Surprising what you see.

 

OK, I checked some things.
Piston, 4.035 top, 4.058 at the bottom of the skirt(sp).
Cylinder, 4.058-4.060. I just measured the top of the cylinder.

I thought I asked a simple question but I am not sure what the measurement should be.
Its an internal combustion engine like every other one.

What should the measurement be? Is it that much different than anything else.

Sorry for sounding like a D*CK, I am just frustrated with alot of things right now (son just broke a timing chain on his '70, long weekend.)

 

All I am looking for is a ballpark figure on what the clearance should be.
I can measure all the pistons and match them to the cylinders that best fit the size.

I just need someone to give me a clue, .002-.010-.050? I just need a small clue.

Thanks a lot guys, I cant tell you how much help I have gotten over the last couple of years. Thanks again!

Curt

 

Sorry, missed the last half of the question. It is somewhat dependent on the material the piston is made from. Here is a link that discusses hypereutectic, scroll down to piston clearence section. Asking the MFG is prob the safest route. Sorry I can't be more specific.
http://www.speedomotive.com/Building%20Tips.htm
EDIT: Yes, I can. Chilton's publishes .0014-.0022 all years

 

Thanks Ecuri, thats all I needed.

 

everyone needs to realize that when a machine shop bores an engine, they use a torque plate, they bolt this plate down where the head would be, it simulates how the block changes shape as the heads are torqued down. To measure acurately bolts your heads down to the proper specs, flip the engine over and measeure from the bottom. thus is much more accurate.

 

Something to keep in mind is that most pistons are not round. They are finished slightly out-of-round when cold, and will expand when hot to a round shape. Measure your piston across the pin and then again in the same direction of the piston pin. You'll see the difference. ...Terry

 

My cylinder wall clearances are .025" in my 400.This is what the piston manufactor recommended.If you need any more clearances I can give you all of them for my motor.

 

What kind of pistons are you putting in? Forged pistons expand more than cast or hypereutectic, and need more clearance. I agree with what has been said, contact the piston mfg.

When I had my block bored (FE, but applies to any motor) I brought the pistons along to the machine shop and they fitted the pistons to the bore, so they could verify the clearance.