High compression head coolant leaking

[Ron W]

Backing off just a little on the nut is to break the friction "set" before re-torquing . Hot or cold would probably result in very little difference. I do it warm. In the service bulletins on page 289 it says "The nuts should be tightened with the engine thoroughly warmed up". Other sources say cold. Your choice! I think you will be OK either way. Ron W

[badal]

I realize the original poster stated this thread a while ago but one other thing to check is that the studs are threaded sufficiently to allow the nuts to properly clamp the head. If the head and or block have been surfaced then they are thinner than they were originally and there is a possibility the nuts may bottom out.

[daveymc29]

In the Marines we worked on Allison V12's. Torqued cold, backed the next torque slightly to break the friction. Never saw a head gasket failure. Not saying it was correct but that is what the manuals recommended* back in the mid 50's on those 1790 Cu. in. aircraft engines used in our amphibs.

*per instructors in the Mechanics School.

[Buddy Fleet]

I'm new to Model A engines. Just bought a Pietenpol airplane with a zero time rebuilt Model A/B. I did a short runup on the engine but when I checked it after it cooled down I noticed some water around the nut on the left side of the head third stud from the front. Should I put some RTV on the threads ? Any help would be greatly appreciated.

[hardtimes]

Originally Posted by Buddy Fleet

I'm new to Model A engines. Just bought a Pietenpol airplane with a zero time rebuilt Model A/B. I did a short runup on the engine but when I checked it after it cooled down I noticed some water around the nut on the left side of the head third stud from the front. Should I put some RTV on the threads ? Any help would be greatly appreciated.

Hey Buddy,
I would remove that stud and put a small screw driver or whatever down the hole to determine if it goes THROUGH into the water jacket. If it does then I would seal it on both stud and in hole . RTV permatex works for me.
I do this procedure with ALL stud holes. Some blocks have been abused to the extent that a lot of these holes have been broken thru.

Hmm, model a engine in an airplane !! How many 'backup' systems would that have to have to avoid Murphys law Parachute