Motorcycle Repair: shovelhead head gasket, cometic head gaskets, harley school


Question
Mike, a simple question for you. Let me start off with the specs on my bike:

specs:

early 1978 shovelhead 74 inch alternator style motor
bored .040 over
A grind cam
super e carb

DId a complete rebuild on the bike this winter. Motor completley rebuilt, but kept stock. Let me state here that all components were within spec and the heads were flat. Rings installed properly. Valves and such were lapped and did not leak. Pushrods were adjusted properly (solids).

installed the heads using cometic head gaskets (no gaskasinch used on them). Service manual says torque value between 65 and 75 ft/lbs and a minimum compression reading of 90 psi with a 10% difference.

took a compression test. Got 30 psi front, 60 psi rear.

Took apart and retorqued the heads to 60 ft/lbs. Got 80 psi front, 90 psi rear.

retorqued the heads to 65 ft/lbs. got 70 psi front 80 psi rear. Underestimated the importance of torquing sequence and value, I suspect then i am not torquing the heads properly. The heads are not sitting flat on the cylinders. So my questions to you are the following:

1. can i start over using the same head gaskets?
OR
2. can i just retorque to 70 ft/lbs and make sure that i torque them evenly.
OR
3. can i loosen the head bolts a bit and and start over
OR
3. can i leave them at those readings

Thanks Mike. Your help is quite appreciated.

stephane.  

Answer
You never said if you did the compression test with the motor warm or not. Your compression test shoud be done with the motor hot. Another thing is the rings are not seated yet so your compression will be a little low after the rebuild.
As to the torquing of the heads. All the years I have worked on shovel heads I have never torqued the heads. Even in Harley School, which my father-in-law attented in the late 60's, they never taught to use a torque wrench. They used the following method.
What I do is put the head on and snug each bolt. Then I tighten each bolt as tight as I can get it with a wrench. After starting the bike, letting it get to operating temp, I go back and retighten the head bolts and base bolts. You will find that you can turn them more.
I would leave the gaskets in that you have used as long as you have not started the bike and let it get hot. If you have I would replace them.
Good luck and happy riding
Mike