New Head Gaskets but Low Compression 52 Flathead 239

passenger side all 60psi
driver side all 70psi

wet test same results

I did all the following...

cleaned all holes with chaser and oil
cleaned both surfaces and final rub with acetone
the surfaces were not smooth originally in 52, they have machining marks all over them


Used Fel-pro 7525 and 7525B installed dry as recommended
used Fel-pro sealant on all bolts (but without the activator since it was no where to be found)
used Cat 5 bolts
they did have longer threads than original but only 4 threads on longer bolts
the shorter bolt were the same
torqued down to 70lbs in sequence in three steps

now... the motor did turn over and race for 5 seconds once... and never more

 

Would have to ask why the head gaskets were replaced. Valve job, rebuild, why?
[I]now... the motor did turn over and race for 5 seconds once... and never more[/I]
Does this mean the engine started and went to wide open throttle and now will do nothing? Please explain.

 

Please clarify the longer bolts. "But only 4 threads on longer bolts" Do you mean only 4 threads longer?

I'd have to go look at a bare block, but some of the longer bolts are in blind holes as I recall. You may have been bottomed out -- not good!

Did you put in new rings?

PS -- the flathead gurus on the Ford Barn recommend going no more than 55-60 ft-lbs on these with modern gaskets. The decks are not overly thick, you risk pulling threads at higher values, and the gaskets seal fine at the lower values.

Are you at high altitude (>5000')?

 

Low compression is from a lack of a seal in the cylinder. Could be from head gasket, piston rings or valves not sealing.

The concern seems to be if the new bolts are allowing the head to clamp down on the gaskets. If they are and no change with wet or dry test, the valves not seating could be an issue.

 

Valves have been reseated and appear to be fine and much better than before.

The bolts are not longer, they just have 4 thread towards the head of bolt more than original bolts.

original test wet and dry indicate the rings were not the issue

I am at a 3000 ft.

 

Are you doing the test will all spark plugs out? Does the tester have a hose and fitting that threads into the spark plug hole or the type you hold a rubber tip into the hole?

Does it seem to be spinning up the same speed for all cylinders? Not getting slower due to starter or battery as you go along?

 

Not exactly true on the wet/dry comp test. If the rings are stuck, or really worn, oil won't help. Did you have the throttle wide open when you did the tests?

You aren't that far off. Mine fully rebuilt, just broken in, is in the high 90's at 5300'.

 

I replaced a chipped valve and reseated them all. they are much better now...
Yes, the engine roared because throttle was stuck. I have since fixed that.
now the engine will not fire again.
it gets fuel and spark hence the compression check

 

I have the rubber hose threaded with removable compression gauge.
I checked each cylinder separately keeping the plugs in until removing for the comp check.

the turning over does not slow down

 

The starter working against compression on 7 cylinders may explain the lower numbers. You should have them all out and throttle blocked open.

 

Thanks...

What about sealing this fel-pro gasket? should have I?

 

No, they don't need it. That was needed with the older engines with copper head gaskets.

 

Is this something you just started working on or has it been running and now its not?

Mine was running but not very well when I got it. The carb needed to be rebuilt, I replaced the plug wires with solid core original type, new plugs, cap, rotor, points and condenser.

The distributor was not advancing so I disassembled and cleaned it. The starter was turning over slow so I rebuilt it. Replaced the coil because it would fail when hot.

It would run and die at times and I found stuff in the fuel line. Cleaned tank and lines. Also got rid of the 2 year old gas that was in it.

Fired it up, set timing and adjusted carb and it runs great. I have low compression on a couple cylinders too. Burns some oil but fires right up and runs great now.