GS400 top end issues & update

Discussion in 'Street/strip 400/430/455' started by Junkyardog, Nov 5, 2018.

  1. Junkyardog

    Junkyardog Member

    A buddy of mine bent #3 cylinder exhaust valve & pushrod on his original GS400 conv 4spd he bought new. When we took it apart, we saw a piece of pad missing off of the rocker which we found in a puddle of oil on the head. Finding info on this site for 400 is very difficult ! After asking a lot of questions to Buick owners, I found out there isn't many parts out there. I had to send the rocker assy. to T/A Performance for them to rebuild the shafts & rockers. The shafts had worn grooves where the rockers rotated. The heads were redone by Greg at Automotive & Industrial Machining in Souderton, PA and he did an awesome job. We reinstalled the heads, changed 2 lifters and ALL of the pushrods. The engine came back to life on Saturday and no leaks or issues. Here are some pictures I took along the way... In picture #2, you can clearly see the valve imprint. All the white grease is engine assembly lube. I'll take a picture of the pushrod. All of the balls on each pushrod were pitted so that it could have held a drop of liquid. #3 exhaust lifter where the pushrod touches was beat to hell from this mis-hap.
     

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    Bill Nuttle, Grandpas67 and Ziggy like this.
  2. Schurkey

    Schurkey Silver Level contributor

    White grease on the lifter sides and lifter bores is a big mistake. The grease may prevent the lifters from spinning, and that leads to flat cam lobes and damaged lifter feet. With luck, the white grease melted out and nothing is damaged--but I'd be pulling the valve covers to assure that all the pushrods (and therefore the lifters) are spinning while the engine runs. I've been told that white grease on lifter feet and cam lobes is OK, but I don't trust it to have enough high-pressure additive. Black "Moly-based" paste is what I typically use on flat-tappet cams. That stuff has it's own problems, as it'll plug an oil filter in ~20 minutes, requiring at least a filter change. I've also used Sta-Lube Engine Assembly Grease, which is a moly-fortified white grease, but much lighter-bodied that the typical Moly paste.

    RTV Silicone on the intake valley pan is a similar mistake. I don't like the idea of silicone blobs breaking off and falling into the pan. I'd have used some other gasket sealer. Gasgacinch is my favorite, but there's a dozen brand names of gasket sealers that work just fine. RTV silicone works "OK" INSTEAD of a gasket, or where two gaskets meet at a seam--but not as an ADDITION to a gasket. Given a choice, I'll take Permatex The Right Stuff, which I guess is not a silicone but rather a polyurethane--but with the same restrictions. Use it instead of a gasket, or where a gasket and seal, or two gaskets meet--but don't add it to a gasket wholesale.
     

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