308 Manifold Corrosion Problem

Discussion in 'Technical Q&A' started by bwassam, Aug 19, 2005.

  1. bwassam

    bwassam Formula Junior

    Jan 3, 2005
    North Bend, Oregon
    Full Name:
    Robert Wassam
    The problem with my '77 308 GTB started when the idle would go to 2000+ RPM after the car warmed up to operating temperatures. I thought there was a possibility that there was a vacuum leak in the system someplace. I thought it could also be the acelerator circuits in the carbs. I don't understand everything I know about Webbers, but I know they have adjustments for accerlation. Anyway, I took the car in and the mechannic said that there was a leak in the manifold gaskets and that I would need to change them. Now he has the manifolds off and they are a mess. There is corrosion where the antifreeze goes through opr past the manifolds.

    I think this problem was caused either by the antifreeze or an electrolsis problem.

    I'm having a machinist weld some material onto the manifold and then he'll resurface them to make them useful. This should fix the immediately problem. On the off chance there's an electrolsis problem, I'm going to put a new grounding strap on the engine and use distilled water for the antifreeze. I'm changing antifreeze brands to one that does not have any phosphates in it.

    I purchased the car in January '05. I'm still getting things dialed in with it. It has had this problem since I bought it. Incidently, I've driven it less than a hundred miles since I've bought it, other than bringing it home.

    I'm putting this on the list so that everyone can benefit from the knowledge of this problem. At some point, someone else will run into this problem and now they can have a heads up.

    Bob Wassam
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  3. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
    Full Name:

    I have this very same problem, although with mine the corrosion is at the head side. I hate the idea of removing metal to get a better surface, and am entertaining ideas in an attempt to get around it, but in the end thats probably what I'll do.

    Are you thinking of bonding the manifold's to the heads with a bonding strap to stop the electrolisis? I wonder if bonding the heads to the block wouldnt be a good idea as well. My heads came right off fairly easy, but there was aluminum oxide all over the studs and some appreciable corrosion within the stud holes of the head. But I also wouldnt care to see it accelerate electrolisis if we guessed wrong. Would a zinc anode placed somewhere be a better choice?

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