High Compression Head
- Thread starter jeepguy1948
- Start date
alexiskai
Well-known member
One caveat, getting psi numbers will give you some idea, but there are so many variables in a compression test that you should be cautious about trying to map a given psi number to a given ratio. The strength of the starter will be different from car to car, and you don’t know if, e.g., the guy who measured his 6.0 head did the test at WOT like you’re supposed to.
Marshall V. Daut
Well-known member
This is not my car. It came to me for major repairs, among which a rebuilt engine was eventually required. The FOM's were already there since the 1970's when the BIG thing was to install FOMs. With the old engine out, I just cleaned them and sprayed them silver so that they look like new. We just put in new rubber donuts and acquired the missing rear transmission yoke that so many FOM installations leave out (See photo. I know the U-joint housing bolts should have castle nuts, but we had to draw a financial line somewhere!). I prefer the original factory steel rear motor mounts for the frame rigidity they add. But we went with how this car came to me and improved the mounting with the new donuts and yoke.
I tightened the nuts on the center bolts until I could feel the donuts beginning to compress. These mounts need a little flexibility to be effective.
Marshall
I tightened the nuts on the center bolts until I could feel the donuts beginning to compress. These mounts need a little flexibility to be effective.
Marshall
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Terry Burtz Calif
Senior Member
Lots of missinformation on this thread.
All original heads have the 3 bumps. The 3 bumps are chaplet locations and all original heads have them. The heads were cast upside down and the chaplets kept the water jacket core from dropping.
Between the water pump and the water outlet, there may be no mark, a triangle, or a fore and aft line. These marks identified the source of the heads.
The oblong hole in the center of the head was added to help support the water jacket core. The oblong hole provides a short cut for cooling water and causes cylinders 3 and 4 to run hot.
The heads that are too short and not wide enough are because the shrinkage factor for cast iron was not incorporated into the patterns.
The new 6.5 head has the 3 chaplet marks along with a foundry mark. The new 6.5 head has engineered water passage holes that force more coolling water to cylinders 3 and 4.
The new 6.5 heads have not had points deducted in MARC and MAFCA blue point judging.
All original heads have the 3 bumps. The 3 bumps are chaplet locations and all original heads have them. The heads were cast upside down and the chaplets kept the water jacket core from dropping.
Between the water pump and the water outlet, there may be no mark, a triangle, or a fore and aft line. These marks identified the source of the heads.
The oblong hole in the center of the head was added to help support the water jacket core. The oblong hole provides a short cut for cooling water and causes cylinders 3 and 4 to run hot.
The heads that are too short and not wide enough are because the shrinkage factor for cast iron was not incorporated into the patterns.
The new 6.5 head has the 3 chaplet marks along with a foundry mark. The new 6.5 head has engineered water passage holes that force more coolling water to cylinders 3 and 4.
The new 6.5 heads have not had points deducted in MARC and MAFCA blue point judging.
Last edited:
jeepguy1948
Well-known member
Thanks for that information Terry (I’m on the Bert’s waiting list for one of your engines).