Question piston to wall clearance.

When the spec is say.. .003 clearance, does that mean overall, or per side? So would it really be .0015 away on either side?

Just had a block machined. Machine shop is good, but I'm paranoid. The pistons seemed to go in pretty tight... not that I had to force them or anything, just seemed pretty close.

Maybe it's because I just put together an 01 Cobra motor with a bunch of stock parts and things were pretty loose?

Usually, you can push on the top and bottom of the piston and get "some" rock. This one moves just a little, but not nearly as much as the already driven stock 01 I just put together...

Thanks
Jeff

Yes it would be .0015per side. I would say if the Piston is going in tight that's a good thing. The reason is there is still stock available to remove and make larger. If it's loose you're screwed! Find out what the dimension is supposed to be and have someone check the inside diameter with telescoping gages! Oh, I forgot they better get the dimension from the telescoping gages with a set of good Micrometers! Do not use Calipers because they aren't accurate enough! They better know what they're doing with the gages to because you need some experience with them to get a good number! Plus check it multiple times to make sure the number is good! I don't know how to build engines or do electrical stuff with them but when it comes to numbers and machining that's my game!

What pistons are we using here???

Stockers?? If so the factory spec is quite tight for a 4032 forged piston.

If you look at what the different piston manufacturers recommend for their 4032 forgings you will find most run more clearance than Ford did with our Zolners.

But Ford had to pass emissions tests and also didn't want customer complaints about cold start piston knocking noises during the warranty period.

The horsepower level is going to play a role also. Unlike the Ford GT our blocks do NOT have piston crown oilers for cooling... we just have splash cooling and what little cooling the evaporating fuel does on the intake stroke.

The more power... the more heat... the more rapidly the pistons and rings will expand.

If you are running aftermarket forgings... run what they recommend for your power level and end usage type.

They know how much their pistons will expand.


...:thumbsup:

CP pistons.

Jfoster said:

CP pistons.

Click to expand...

Are they 4032 alloy or 2618???

Do not run factory piston to wall clearance!!!

Contact CP and run the clearance they tell you for those exact pistons!

They are an excellent piston... but even the 4032 version is going to grow quite a bit.

The 2618s are a race piston and need even more clearance.

Call em up..:thumbsup:


..

4032. When I talked to the machine shop, they sounded like they had looked it up and that the clearance was supposed to be .003. I hate to be the typical paranoid customer by bugging them, so maybe I'll take your suggestion and call CP today to verify. Hopefully it's correct because the shortblock is now assembled

Jfoster said:

4032. When I talked to the machine shop, they sounded like they had looked it up and that the clearance was supposed to be .003. I hate to be the typical paranoid customer by bugging them, so maybe I'll take your suggestion and call CP today to verify. Hopefully it's correct because the shortblock is now assembled

Click to expand...

Sounds about right,,,, @ .003"

Jfoster said:

4032. When I talked to the machine shop, they sounded like they had looked it up and that the clearance was supposed to be .003. I hate to be the typical paranoid customer by bugging them, so maybe I'll take your suggestion and call CP today to verify. Hopefully it's correct because the shortblock is now assembled

Click to expand...

that .003 is the difference between the inside diameter of the block's bore and the outside diameter of the piston.
hence:
you have a TOTAL tollerance of .003 compairing diameters or .0015 on the radius