68Bronco

Was wondering if anyone knows the dia. of the headbolt holes in a 351W head? Also, if anyone knows the bolt spacing pattern for the head. Can't seem to find this info on the net anywhere.


Thanks!

Ford1158

They're 1/2" - not sure about hole spacing off hand (could check). Same as 302 but 302 head bolts are 7/16"

68Bronco

Thanks, but maybe I should have phrased my question a little different. How much would you have to open up the holes in a 302 head to use on a windsor?

I mic'd the 351W ARP bolts that I have and they where 0.499which isn't going to fit in a 1/2" hole... Typical machine design practice would have a 1/32" clearance on the OD. So the hole would be 0.531 (17/32). Was wondering what Ford deemed acceptable for clearance.If it was a 32nd, a 16th, etc.

If noone knowsI suppose I could measure the holes in my 302 heads and figure out how much clearance they provided for the 7/16" bolt

Thanks!

dudeboy

I drilled my 302 heads with a .500" drill bit.
No problems with installation...


If you know about 'Typical machine design practice'
... do you really need to ask?

These holes aren'tthat critical on diameter

68Bronco

Found this on another site today.

"3. Since I was using 289 heads, I had to drill out the head bolt holes for use with the larger bolts. 1/2" seemed a bit tight for the ARP bolts, so I went back to Travers and purchased a 33/64" bit to loosen them up a bit. a 17/32" would have worked as well, and could have been purchased locally. You MUST use a drill press that can keep the head level and straight for this step."

Guess it isn't all that critical. Thanks for the replys though. Suppose I'll go with the 17/32"and it on the millto get it fairly accurate. Which brings up the second question. Anyone know the spacing between the holes? Figure I can square up the head to the table and use the digital readout to speed up the process.

Thanks again,

Ford1158

I see - I misunderstood your question.

I went 17/32" on my GT-40P's. I didn't want to go larger and risk the heads walking at high revs with high compression or boost. Don't know if that's a real concern but I've seen a lot stranger things happen.