Can anyone tell me how to tell the difference of a 1131 when it's in the engine? Silv-o-lite showa 4 different types of 1131's. I want to know if the engine builder put the correct one in.

Robert P.

 

news to me, i have those pistons, they are 1.76 comp height, and i believe 8cc from 4 dishes. The 1131's are one piston that fits various applications, maybe i am wrong though.

 

Apparently they are split into two different categories, Hypereutectic and non-Hypereutectic.
The 10.1 comp. ratio is intended for the 390 and the 8.2 comp. ratio is intended for the 360.
With that being said, how would one tell which one they have will the are in the block with the heads bolted down?
I am referring to the 10.1 or 8.2 ratio not hyper or not.
Or, as fordever is referring to; is it one piston that can be installed into two differently stroked motors (i.e. 390 vs. 360) making the difference in comp. ratio?

Robert P.

 

See here:

http://www.kb-silvolite.com/spistons...iv=Ford&ci=390

And they're not really a 10.1 compression piston. Try more like 9.3. That's when used with the common Fel-Pro head gasket and 73cc chambers. KB-Silvolite uses the most optimistic methods for their stated compression.

 

http://beckracing.com/slvpg51.htm

 

OK, mine shows a 1131 for a 360. Try this.
Now back to my question.

Robert P.

 

I bought my Fairlane with a rebuilt 390, the guy said he put in Silvolite 1131's. What I did was borrow a bore scope from work and put it down the spark plug hole and determine the valve recess shape or dish size according to the previous chart from Beck Racing. Later I wound up taking the engine out and verified the pistons with the Silvolite logo and 1131 part number on the bottom side of the piston.

 

The 360 pistons used in a 390 bump the compression up to what the higher HP car motors ran hence the dual application(as opposed to the dished out low compression truck 390 pistons). Hyper vs Non-Hyper is a component of the metals used, can't tell that from looking through the holes...

--Mike

 

So it is one in the same piston? If the 1131 is put into a 360 it has 8.2 comp. ratio? And if the 1131 is put in a 390 it is 10.0 comp. ratio?

I am assuming that the difference here is because of the difference in the crank stoke from the 390 and the 360?

Robert P.

 

You are correct.
P.S. If a bunch of other posts show up it is the server.

 

like i was saying, one piston with a couple of applications


1.76 compression height
8cc from 4 valve reliefs
cast piston
5/64
3/32
3/16
rings lands

 

Thank you guys for straightening that up for me. I can finally get some sleep knowing I have 10.1 instead of 8.2 comp. pistons in my engine.

I having been letting this unknown bother me since it's rebuild two years ago.

time for beddy bye.

Robert P.

 

well not quite 10 to 1, but its mid 9's.