M151 engine head differences?

[WIZ87]

Hello everyone I trying to find some information as to the key characteristics between the Light duty and Heavy duty engine heads the the M151s. I was advised that I have an early head and if it requires too much work then to replace with a Heavy duty head. I believe my A2 is an early AMG and the next question is when did the Heavy duty heads start being produced?

 

[nattieleather]

I am not aware that there was a light and heavy duty head. As far as I know the heads were the same on all M151s from start to end. I've used heads off of A1 motors on A2s and vice versa. Please if someone has more information please share but as I said I don't know of any difference of light duty vrs heavy duty.

 

[CBrinker]

I’ve always heard that all a2 heads had heavier duty valve seats than a1 heads, but I don’t know for sure if that’s true

 

[FilBonica]

The heavy duty head was introduced as a retro fit to any 151 .
as was mentioned they have hardened valve seats.
The other improvement was a
much larger boss that holds the exhaust manifold.
typically an improved gasket is used to seal the exhaust manifold not just moly grease.

Fil Bonica

 

[nattieleather]

I know that at one time a kit was available for the exhaust manifold which had four square gaskets made out of a fiber metal material, new clamps and bolts and this kit solved exhaust leaks at the manifold, but how knows if any still are available today.

 

[WIZ87]

Awesome thank you for the responses. I have an A2 that I am refurbishing. Have the early head and it just received a check and valve job. If it flunked I was going to get the updated head.

 

[FilBonica]

If you refurbished the head then you should be all set.
Fil Bonica

 

[WIZ87]

I have seen the exhaust kits similar to your description nattieleather on ARMYJEEPPARTS.COM the picture shows square gaskets for the exhaust manifold. I did read a thread on G838 referring to the different torque specs between gasket and non gasket set ups. Another user did mention the doubling up intake manifold gaskets to make up the difference made by the exhaust gaskets. I'll see if I can find the link.

 

[FilBonica]

I mentioned doubling up the intake gasket.
someone told me but I never tried it .
all my heads were late style so no need.
apparent the saddle size is just a bit snaller.
Fil Bonica

 

[WIZ87]

Here's the link http://g838.org/viewtopic.php?f=3&t=10954

 

[nattieleather]

NAPA use to make an exhaust manifold sealant that used in conjunction with the gaskets kit would make an exhaust manifold leak never happen again on a m151. I know cause I used it with the gaskets and it work miracles on my old 151. I also had broken the bolts off the head and when I talked to the old Motor Pool SGT what to do he said drill them out and use a nut and bolt. It will make your life easier and is what they did back in the day.