Head bolts

[dcotant]

Just a heads up on head bolts. There have been recommendations on the Pioneer head bolts ( PIO-PG-362-25 ) from Summit Racing. People should be aware that the bolts no longer match the picture on their web site, in particular, instead of 11/16 inch hex heads they have gone to 1/2 inch hex heads which to my thinking and aesthetic is wrong. Here is a picture of my existing head bolt along side a new Pioneer head bolt. I will be going to DCM or someone else I guess. 

 

I was also worried that the thread portion was shorter but it appears after penetrating the head and gasket the threads are all that show.

 

[kencombs]

No pic showing for me.

[dcotant]

Trying attachment method

[Los_Control]

Someone please correct me if I'm wrong ... (again 🙄)

 

I(IRC, head bolts are not the same threads as a standard bolt ... I thought they had a unusual pitch to them to make them work better for a specific job.

 

Just my personal opinion, the newer bolts do not look correct with the smaller head .... I would bet someone else's dollar they are actually stronger then the original bolt.

Just with better modern technology ... it is possible to build better with less.

Could be a offshore metal compound and actually worse .... why I'm betting someone else's $$ and not mine.

 

Seems I read somewhere that the Chevrolet SBC 283 shared the same head bolts as our engines. .... they may be more plentiful in the aftermarket world.

 

Either way, unless building a show car .... could replace all the head bolts together and nobody would know ... except a judge at a car show.

With only 90 pounds PSI torque .... they really are light duty for the way they are constructed.

 

If you want to restore a show car ... then snatch up some good original bolts from a parts engine .... otherwise there are other options.

[Plymouthy Adams]

the head bolts are not same diameter shank from thread to beneath the head of the bolt, the are undercut so to prevent rust and seizing.  

Edited Friday at 08:51 PM by Plymouthy Adams

[Veemoney]

I believe the undercut on head bolts and other type bolts does aid in the removal when seizing and rust can be present. The primary reason for undercutting of the shanks as I understood it was to allow the bolt to stretch evenly across the shank rather than the threaded portion and at the head when torqued and during heating and cooling. 

 

Thread size and pitch of 7/16-14 which would be a standard thread size though the class of the thread fit may be other than standard call out as well as the strength of the bolt when considering differences.