78 402 Is this the correct piston?

[fordv840]

Hi all,
I am rebuilding a 78 402. I had the cylinders bored .015" over and ordered new pistons. The new pistons (sierra part# 18-4152) have a big hole machined in the side of them, my stock pistons do not. Can I still use these pistons or are they the wrong ones? Besides the hole they are identical.
Thanks,
Jason

 

[MortenH]

Re: 78 402 Is this the correct piston?

Hello

If the pistons are identical, and the Sierra part# matches your serial, I guess these pistons are OK. The big hole in the side are made to fit the, I think it is called "power port" - it matches a cutout in the cylinder wall to allow more fuel / air mixture to the cylinder to get more power.

-M-