Small washers under iron head bolts

[Ian G.]

Re: Small washers under iron head bolts

A possible alternative would be using antiseize on the bolt threads and head if you really want to avoid the points loss. This would make the bolts tighten more smoothly.

This is my plan for the outside exposed bolts. hardened washers for the ones concealed by the valve covers.

Someone correct me if I'm wrong.

[Jim L.]

Re: Small washers under iron head bolts

A possible alternative would be using antiseize on the bolt threads and head if you really want to avoid the points loss. This would make the bolts tighten more smoothly.

This is my plan for the outside exposed bolts. hardened washers for the ones concealed by the valve covers.

Someone correct me if I'm wrong.

The original torque specs were those needed for bolts with dry threads to reach a prescribed amount of stretch. Lubrication of any kind reduces the torque needed to stretch the bolt by the prescribed amount. The amount of torque reduction is a function of the nature of the lubricant and isn't something one can predict without doing some testing.

In other words, don't use anti-seize. Doing so will risk over tightening the head bolts. Better to just buy some thin AN washers and use them under all head bolts, even the short outer bolts.

Jim

[Ken A.]

Re: Small washers under iron head bolts

Fellows, no dry threads and no antisieze, unless you want water leaks. No thin washers, either. Use hardened washers and thread sealer as the FSM tells you to do.

[Ian G.]

Re: Small washers under iron head bolts

Good to know, thanks!

[Jim L.]

Re: Small washers under iron head bolts

Fellows, no dry threads and no antisieze, unless you want water leaks. No thin washers, either. Use hardened washers and thread sealer as the FSM tells you to do.

You are absolutely right about the thread sealer. Most SBC blocks do not have blind head bolt holes. My mistake; I have several blocks that do have blind holes.

What is your rationale for not using thin (meaning .032) AN washers?

Jim

[Ken A.]

Re: Small washers under iron head bolts

What is your rationale for not using thin (meaning .032) AN washers?
Jim, experience-the real thin ones distort.

[Michael G.]

[Edward M.]

Re: Small washers under iron head bolts

Michael;

Great info, thank you.

The concern is that the twisting friction / galling that can occur has, in the past, caused the outer head bosses to crack or break altogether. It may have been becuase they were over torqued, then again, it may not.

The idea, which I got somewhere (and can't remember where) is that there is a small diameter flat washer (I thought it was stainless) that can be used under the head bolt to help this situation. This washer is small enough to be virtually undetectible when installed.

I am trying to minimize that possibility of an expensive set of heads.

I appreciate the info that everyone has provided.

[Joe L.]

Re: Small washers under iron head bolts

Michael------


As long as we're on the subject of washers, the most vexing question I can recall that I've ever had is why GM used external tooth star lock washers on the flywheel-to-crank retaining bolts? These washers are very soft material and are highly susceptible to breakage. The bolts, on the other hand, are GM 300M material grade, so why they would use the star washers in this system has always mystified me. Perhaps, with your experience and knowledge you could shed some light on this?

[Michael G.]

Re: Small washers under iron head bolts

Joe,

Sorry, I haven't a clue why they were selected for this usage.

They certainly don't serve to keep the bolt head from backing out. Maybe they were intended to keep the flywheel from sliding under the head, but, if you've lost enough clamp-load to allow this to happen, its too late anyway. They add to the grip length somewhat, a good thing on such short bolts, but normal hardened washers would have been a better choice, in my estimation.

Perhaps I'm missing something, but I never specified star washers for anything other than breaking the paint on electrical grounding attachments.

[Jim L.]

Re: Small washers under iron head bolts

"AN" is short for "AN960", a type of washer used with airframe bolts to correctly establish the grip length of the fastener. Racers also use them. Very common:

http://www.aircraftspruce.com/menus/ha/washers.html

and

http://www.specialty-fasteners.com/images/SpecialtyCatalog-14.pdf

Jim

[Joe L.]

Re: Small washers under iron head bolts

"AN" is short for "AN960", a type of washer used with airframe bolts to correctly establish the grip length of the fastener. Racers also use them. Very common:

http://www.aircraftspruce.com/menus/ha/washers.html

and

http://www.specialty-fasteners.com/images/SpecialtyCatalog-14.pdf

Jim

Jim and Michael-----

Yes, and the "AN" actually stands for "Army-Navy" which established the original specifications for this fastener series. I think it's an early "aerospace" specification from the days when there was only "aero" and no "space".