Is the tread bolt a 1/2 x 12 British size and not the 12 x 13 US size. I tried to get new Head bolts and I could not find the right thread. I think I found a site that says it is the 1/2 x 12 British thread. Is that correct?
Yes the 4 cylinder engines used 1/2-12 threads for the head bolts.
Whenever someone mentions replacing them, my suggestion is to replace ALL of them as a set.
Another VCCA member (John Thorpe - a Certified Caterpillar Mechanic) told me that it was a policy at Caterpillar to replace all bolts (during an engine rebuild) that could stretch from previous use. Since a used bolt is of unknown quality, they play it safe and replace them all.
The Filling Station and other places sell new 1/2-12 head bolts.
Cheers, Dean
Dean "Rustoholic" Meltz
San Leandro, CA
3511 posts on vccachat.org
1927 LM one ton truck - tinyurl.com/Lurch-VCCACHAT-Gallery
1928 AB Canopy Express (1/2 ton truck) - tinyurl.com/Justin-Stovebolt-Gallery
Thanks Dean