Head Bolts Size 7/16 or 1/2

Fred · #1 (**permalink**) 08-25-2003, 11:27 AM

I am building a new motor for the Cobra. I have had head gasket problems and was going to increase from 7/16 to 1/2 bolts or studs.

What is the process to do this? If I place the block on my bench and tap the block for 1/2 bolts, the original diameter of the 7/16 threads is greater than the minor diameter for a 1/2 threads. The major and minor diameters do not work out. The thread depth will not be what it should be.

Am I to concerned about this?

Fred

Excaliber · #2 (**permalink**) 08-25-2003, 11:41 AM

http://www.clubcobra.com/forums/show...632#post380632

This thread makes a comment about this very thing!

Ernie

EarlsflyinCobra · #3 (**permalink**) 08-25-2003, 11:42 AM

Fred,
Here is a post another member put on a thread I started, I am wondering the same thing you are? Hope someone gives us the right answer......Earl

Hi,
I ran an '87 LX coupe with a TO4B 15 years ago now.
The worst thing is the wimpy 7/16" head bolts, you'll blow head gaskets. While you have the engine at the machine shop to get bored, get them to drill and tap the head bolt holes for 1/2" 351 head bolts. You can torque the heads down to 95 lbs instead of the 70 for a 302. Small port heads are fine for a turbo as it will blow air right through any restriction.
Perry.