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CVO Technical => Twin Cam => Topic started by: JMK on November 16, 2020, 08:38:43 PM

Title: Head gasket seating surface
Post by: JMK on November 16, 2020, 08:38:43 PM: Installing my 117 kit, getting heads ready to reinstall. I finally got all the old gasket off and the rear cylinder head has areas that appear to have been depressed by the gasket. The front has some but not as bad. see the attached pics. The new gaskets are the 4.125 and the old were the 4.0 stock fiber so the new ones ridge may sit right on the edge of the rough area. I would have put it back together if I was using another fiber gasket, but I haven't used this type of gasket before.
My question is will the 0.030 cometic gaskets seal this type of surface imperfection? Cometic says 50 RA surface finish which is hard to determine.
Thanks in advance for the help!
Title: Re: Head gasket seating surface
Post by: JMK on November 16, 2020, 08:40:11 PM: front head pic
Title: Re: Head gasket seating surface
Post by: HD Street Performance on November 17, 2020, 11:10:31 AM: Will probably be fine but why not mill them. Good time to clean everything and put in new seals too
Title: Re: Head gasket seating surface
Post by: JMK on November 17, 2020, 12:36:53 PM: Thanks, I don't know of a good local machine shop (near Chesapeake VA). Suggestions appreciated since google hasn't been much help . I'm guessing shipping would be expensive. Trying to build on a budget and my tendency is: well its there anyhow so why not do the works!
Title: Re: Head gasket seating surface
Post by: stuart1270 on November 22, 2020, 10:37:41 PM: Try this method
https://youtu.be/UDPsEwXXbMg
Title: Re: Head gasket seating surface
Post by: stuart1270 on November 22, 2020, 10:47:38 PM: https://youtu.be/qCMZGaLSO8w
Title: Re: Head gasket seating surface
Post by: JMK on November 23, 2020, 10:29:13 AM: Thanks that is basically what I did. I called a local machine shop the Harley Parts guy recommended. He said he could do it but first try Drywall sanding screens on a flat surface. I did it on the concrete in my garage with some plastic down, wish I had thought of the table saw. It worked great. The cross hatch pattern is much better than the picture shows. Flat when checking with a straight edge. There is no discernible depth to what looks to be scratches in the pic.
Title: Re: Head gasket seating surface
Post by: HD Street Performance on November 23, 2020, 12:16:31 PM: Guys can do many things at home some work some do not. That is nowhere near a 50 RA
This is how I do it and I end up with a <10 RA true and flat. I have another fixture I made for the M8 that is more complex.
Title: Re: Head gasket seating surface
Post by: JMK on November 23, 2020, 02:20:27 PM: Thanks, do you think it is too rough? The lighting really makes it look like there are scratches but there is nothing that will catch a fingernail. It is much smoother than after I cleaned it up prior to the "sanding". The existing factory milling marks were deeper and I could catch my nail in them. I will post if it holds up. I am keeping my fingers crossed.
Title: Re: Head gasket seating surface
Post by: johnsachs on November 23, 2020, 05:04:44 PM: Quote from: JMK on November 23, 2020, 02:20:27 PM
Thanks, do you think it is too rough? The lighting really makes it look like there are scratches but there is nothing that will catch a fingernail. It is much smoother than after I cleaned it up prior to the "sanding". The existing factory milling marks were deeper and I could catch my nail in them. I will post if it holds up. I am keeping my fingers crossed.
You should be fine.
John
Title: Re: Head gasket seating surface
Post by: JMK on December 06, 2020, 09:02:02 AM: 100 miles on it so far all is good!