EVO Head Gaskets blowing
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From: UK
EVO Head Gaskets blowing
I have a 1991 FLSTF and have recently had issues with just the back cylinder blowing. It has blown 3 times in the space of 3,000 miles. I have installed the fancy, so called, high strength gaskets the last time (these seem to have some sort of steel reinforcing in them, and this one has blown too. When i had a chat with a Harley Mech a few months ago, he mentioned something else needs to be done to prevent this from happening. I have checked both the cylinder and the head side for warping and these are both fine. I have replaced the holding studs, and they have very definitely been torqued correctly. Any ideas what I need to do to stop this, as I am about to melt the unit down and sell as scrap!!
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Joined: Oct 2010
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From: Near Frankenmuth, MI
Don't have the answer, just some information on how it related to my recent issue on my '86 FLTC.
On my 86 the base gaskets leaked for some time until the head gasket started to leak on the rear cylinder. Had a top end rebuild over winter and we discovered a single cylinder stud loose. I did a lot of reading up on this and discovered that there were some variables in the types of studs used. Some had a flange on them. If the flange was at the top there was the issue of not seating the bottom of those studs properly, and the flange made it impossible to torque the heads correctly in conjunction with the assembly. If the flange was down it could only go so far into the case but allowed the head to be torqued correctly. The best studs had no flanges to hamper the proper torquing.
Also in studying up on this, it was discovered that the rear cylinder stud holes on certain models developed a crack in the case near the lifter opening ruining the case.
My trouble was 1 cylinder stud that was loose effected properly torquing of the head. Once the base gasket started leaking it took a while before the head gasket began to fail.
On my 86 the base gaskets leaked for some time until the head gasket started to leak on the rear cylinder. Had a top end rebuild over winter and we discovered a single cylinder stud loose. I did a lot of reading up on this and discovered that there were some variables in the types of studs used. Some had a flange on them. If the flange was at the top there was the issue of not seating the bottom of those studs properly, and the flange made it impossible to torque the heads correctly in conjunction with the assembly. If the flange was down it could only go so far into the case but allowed the head to be torqued correctly. The best studs had no flanges to hamper the proper torquing.
Also in studying up on this, it was discovered that the rear cylinder stud holes on certain models developed a crack in the case near the lifter opening ruining the case.
My trouble was 1 cylinder stud that was loose effected properly torquing of the head. Once the base gasket started leaking it took a while before the head gasket began to fail.
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Gents, thanks for the comments. Some years ago i ended up changing the crank case because the stud hole got stripped and i messed up putting the inset in. What a mess that was! But this has slayed me completed, because, as I said, I am doing everything correct. So I am going to start again, get heads and the cylinder top and bottom checked out, get new studs and (obviously) new gaskets and see if this will work, if not we're off to the scrap heap :-)!
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