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Topic: Off with the Intake......Again !

in Forum: C3 Engines


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Off with the Intake......Again !

Posted: 4/16/07 2:13pm Message 1 of 11
deeboy59
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visalia, CA - USA
Joined: 10/27/2006
Posts: 641
Vette(s): 1981 red with silver interior,350(L-81), 350TH, glass t-tops, aluminium rims, 1980 Black/ Black int., 350 GM crate engine/350TH, 1976 black/ saddle int., L-82 w/headers, holly carb, Hypertech ignition

Had to pull the intake off my '81 again cuz of vacume leaks. I just this about two months ago.   It starts  sucking air  and oil internelly( looks like it starts at the ports for the EFE)   and then works its way externelly.  Am having intake resurfaced  this time and switching to hi-performance gaskits.  Is there anything else I should be looking for?  I've installed my share of manifolds,  but never had this much trouble keeping them sealed.  Any info would be nice  Thanks

 Daniel



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Off with the Intake......Again !

Posted: 4/17/07 5:10am Message 2 of 11
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Adams' Apple
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Make sure you do NOT use the rubber end seals that come in the gasket kit. Use silicon there instead. If the rubber end gaskets are used, they can keep the intake from bolting down completely, and can contribute to leakage, both external and internal.
Be careful of how much the mfld. sealing surfaces are machined...don't want them too thin. That will make it much easier to crack the manifold.
Of course, be sure to torque the mfld. to specs, in the correct criss-cross pattern.
If you must, you can use a small amount of 3M weatherstrip adhesive around the intake gaskets, but be forewarned...it will be a major pita to clean that crap off if you have to take it apart later.
Use a small amount of Permatex Aviation sealer on the bolt threads. This will keep oil from "wicking" up the threads to the outside, and getting on top of the mfld.
Good luck! Let us know if the machining helps with the leakage problems.


Joel Adams
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Off with the Intake......Again !

Posted: 4/17/07 5:40am Message 3 of 11
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lukesvette
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Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
In terms of the silicone for the end seals, look for a product called "Right Stuff". It's the best I have ever used. Apply a 1/4" bead on the front and rear sealing surfaces of the block and put an extra blob on the 4 corners where the heads, intake manifold and block meet. I also use a very thin bead around the coolant ports on the heads and manifold.
 
Make sure you're on target when you set the manifold down and start all of the threads on the manifold bolts before you run any of them down.
 
Good luck Wink
LukesVette2007-04-17 05:41:26


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Off with the Intake......Again !

Posted: 4/17/07 10:53am Message 4 of 11
deeboy59
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visalia, CA - USA
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Vette(s): 1981 red with silver interior,350(L-81), 350TH, glass t-tops, aluminium rims, 1980 Black/ Black int., 350 GM crate engine/350TH, 1976 black/ saddle int., L-82 w/headers, holly carb, Hypertech ignition
Thanks guys for your help.  Joel, I think you hit right on it.  The ends were way too tight to use gaskits.  Told the he machine shop to go easy on it.  They  said they had to take off  about  .007".   Will be putting it back together today as instructed. Will let you guys know how it turns out.  Thank you both for the help Thumbs%20Up 
 
Daniel



Off with the Intake......Again !

Posted: 4/19/07 2:34pm Message 5 of 11
deeboy59
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visalia, CA - USA
Joined: 10/27/2006
Posts: 641
Vette(s): 1981 red with silver interior,350(L-81), 350TH, glass t-tops, aluminium rims, 1980 Black/ Black int., 350 GM crate engine/350TH, 1976 black/ saddle int., L-82 w/headers, holly carb, Hypertech ignition
Got it all back together and it seems to be working.  Had to take off more material on the front and back of the manifold to get it to fit right and thats just using silicone.  Joel was right,  there was no way that thing was going to seal the way it was.  The car has way more power now and runs smoother.  Now on to the next item on the list !  thanks again guys Thumbs%20Up


Off with the Intake......Again !

Posted: 4/19/07 3:08pm Message 6 of 11
Chips58
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I've got an Edelbrock performer and am using Felpro gaskets WITH the rubber end seals with no problem at all?  Sounds like your heads have had too much machining on the intake faces if your end seals are holding the manifold away from their mating faces.  When I put my SB back together I had some oil leaks from the rocker covers, dumb me forgot to tighten them down properly but after that, no problem at all.


Off with the Intake......Again !

Posted: 4/19/07 6:59pm Message 7 of 11
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Adams' Apple
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Glad ya go it going again, Daniel! Just keep an eye on it for a few days...you may need to re-torque the intake bolts after a while. Doesn't hurt to check them, anyway.


btw...
There are a lot of different reasons why some engines can't use the rubber end seals. Sometimes it's because the heads have been machined too many times, or the intake just isn't totally right. One thing most folks never think about, tho, is if the block has been machined/decked. If you take metal off the top of the block, where the heads bolt on, then you are actually narrowing the distance between the heads...bringing them closer together. This will also cause the intake to sit goofy, in relationship to the block, than it normally would. Most machinist do not machine the flat area on the TOP of the block where the intake end seals go when they deck the block. This is where the thickness of the rubber end gaskets can mess your day up, and why I haven't used them in 30 years or so. GM stopped using them a long time ago, too, just because of the mass production tolerances they have anymore. It's just better to use the sealer instead...and cheapr too! Adams' Apple2007-04-19 19:09:38


Joel Adams
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Off with the Intake......Again !

Posted: 4/19/07 9:10pm Message 8 of 11
Gale Banks 80
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Vette(s): 1980 with a Banks Twin Turbo 1969 Convert Big Block 1996 Grand Sport Convert
  As the original owner of my 1980 I'll admit that I was surprised to see that the General Used RTV instead of Gaskets when it rolled off the Line. I have found that the Trick to success with RTV is to Clean carefully with Brake Cleaner and then put the RTV on at the last Minute and assemble before it can Skin over. Richard....


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Off with the Intake......Again !

Posted: 4/19/07 10:58pm Message 9 of 11
deeboy59
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visalia, CA - USA
Joined: 10/27/2006
Posts: 641
Vette(s): 1981 red with silver interior,350(L-81), 350TH, glass t-tops, aluminium rims, 1980 Black/ Black int., 350 GM crate engine/350TH, 1976 black/ saddle int., L-82 w/headers, holly carb, Hypertech ignition

 I think you guy are right on about the excessive machining and I think it is  the block.  The reason I say that is, it's just like Joel discribed,  the manifold sat on the engine goofy.  One end was closer to the block then the end and stuff like that.  The other reason is,  on the small pad thats up front on the right side of the block where GM stamps the I.D. #,  there is no number.  How much would you have to deck the block  to erase the vin/I.D  #'s off that pad?  I even took a magnifing glass and looked for the #'s( it sucks getting old)  and there's nothing .  I know the engines been out of the car by PO, for what, who knows?  maybe someone was trying to raise the compression?




Off with the Intake......Again !

Posted: 4/20/07 3:53pm Message 10 of 11
Chips58
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Australia
Joined: 5/6/2004
Posts: 535
Vette(s): 71 Coupe Black on Black
Mine must be just right 'cause they don't leak at all.


in Forum: C3 Engines


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