Migrating intake gaskets

Discussion in 'Street/strip 400/430/455' started by puddle, Aug 31, 2020.

  1. puddle

    puddle Silver Level contributor

    This summer I got to change the intake manifold gaskets. As you can see from the pics, the #4 intake port developed quite a vacuum leak. Idled like crap and had a bit of a hesitation off idle. Anybody else have gaskets do this? Drivers side did the same thing only not as bad. Installed Mahle performance gaskets. They have a rubber bead around each port. Hoping that will help hold them in place. Hoping the ARP bolts will help too.
     

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  2. TORQUED455

    TORQUED455 Well-Known Member

    How long has the engine been together with those intake gaskets?
     
    No Lift likes this.
  3. No Lift

    No Lift Platinum Level Contributor

    I see you are using the China wall rubbers. Maybe they weren't allowing the intake to seat completely? Especially with a "0" deck and probably milled heads the intake should be sitting low on the ends. To get "0" you usually need at .020-.030 off the deck plus if there were any taken off the head. Was the intake face of the heads or the intake port face milled some to make up for the decking? Did you have to oval out the intake bolts to get it on the engine? Sometimes the locating pin holes will hold the intake up some. That could cause problems.
     
  4. puddle

    puddle Silver Level contributor

    Those intake gaskets lasted about 4 years and 6000 miles. The pistons I am using have a 2.10” compression height so .010” was milled off the decks. The heads just had a clean up cut, but they may have been milled previously. The intake faces were not cleaned up, and the problem may be that. Seems like I did the test to see whether to use the rubber end seals or gasket maker, and there was enough room for the rubber end seals as I recall, especially with the .060” thick intake gaskets.
    My theory is that I washed the engine at the car wash a few times and soaked the exposed top edge of the gaskets. Then when they dried, they shrunk at the top pulling the gasket up?
     
  5. puddle

    puddle Silver Level contributor

    Oh, and the bolts clear the holes on the manifold no problem.
     
  6. Bens99gtp

    Bens99gtp Well-Known Member

    wete all the bolts tight????? The ends looked to stay in place, the middle looks to be pushed up like msybe it was loose and pressure inside.......but that gasket is sure stretching
     
  7. puddle

    puddle Silver Level contributor

    I used cheap hardware store bolts with the thick washers that came with the manifold. You can see that the washers are clearly deformed. Torqued them to 50 ft/lbs as I recall. They all still felt tight when I removed the manifold.
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Aluminum intake to aluminum heads? 40 ft. lbs.
     
  9. TORQUED455

    TORQUED455 Well-Known Member

    Use a spray hylomar or other type of sticky spray gasket sealer on both sides of the intake gaskets, and Right Stuff around the water ports both sides. Use Right Stuff in place of the rubber end seals too. JMO
     
    DasRottweiler likes this.
  10. puddle

    puddle Silver Level contributor

    I am running iron heads and aluminum intake, and I think the torque spec for that listed in the TA Performance catalog is 50. Even so I torqued them to 45 this time. The instructions that came with the manifold specified only 25.
    I think I used Edelbrock Gasgacinch across the entire intake surfaces and gaskets on the head side only, plus RTV around the water ports only on the intake side last time. I will give spray hylomar and the right stuff a try next time I have the intake off. But I will see how long these Mahle gaskets hold up for now.
     

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