Intake manifold Not seating properly (?)

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bighammer

bighammer

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I don't know if I have a problem or not... Is the intake manifold supposed to make even contact on the block as well as the heads? I just set the intake on there, without gaskets, and it makes good contact at the heads, but seems like it is elevated off the block. Is there something wrong here, or what am I missing? This is the only pic I have at the moment, it was taken before I realized there may be a problem.
 

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they do not sit on the end rail...use a good bead of Rtv to seal the ends...

make sure the dowel pin or locating pin on the block is gone..
 
Hammer, do you have the thick cork gaskets that are supposed to go under the intake at the front and rear?
 
Thanks guys. Yes, I have the correct gaskets, from Summit, but they are at my work, not with the engine yet. Thanks again.
 
Don't use the cork end gaskets, they are nothing but trouble. Just use a big bead of silicone like blue Permatex on those ends.
 
The end gaskets are not an issue if installed correctly. I use a light smear of "The Right Stuff" on both sides and they seal just fine. I only use them when there is a large gap, other wise its just the bead of silicone.
 
The bad reputation of the cork gaskets was caused by another component. They worked fine from the factory, until the pcv system got clogged. Crackcase pressure is what pushes them out. the fact that they are nearly cut in two by the dowl pin hole is a contributing factor. ( The same "PCV caused a failed Gasket" condition was at outer rear corner of GMs right valve cover ). Anyway... I do throw the cork away, remove the dowl pins, clean those pin holes and fill them with RTV as I build a RTV gasket. This makes the RTV stronger ( better fastened ) in this one location. The only thing even better we could do is mill a groove in intake or block to secure the RTV. See Honda or other T shaped profile vulcanized rubber gaskets for example. Bottom line.. If the PCV system isn't maintained, that pressure is going to escape somewhere.
 
On my small block LA 360 after removing and replacing the intake manifold I used a bead of RTV at the front and rear end rails like you are recommending. I am getting some oil seeping out of this area at the front of the motor. Maybe I did not use enough RTV in that area? Or could this also be a sign of a clogged up PCV valve allowing pressure to build up in the block?
 
Problem I have had with the cork end seals is that they seem to hold the manifold up too high, making it difficult or impossible to get the bolts started without crossthreading them.
 
The pcv valve itself was rarely the location of fault. Most cases the port ( metal tube ) at the carb was totally clogged. I've found the rubber hose connecting the two filled solid a few times also.
I'll place the intake clean and dry and use a sharpie to mark where the RTV bead belongs. Clean and dry is very important. Allow 24 hours for RTV to cure is just as important. A heavy bead of the stuff aint going to cure in a minute like whats on your fingers. I said that because surface finish matters. Ever notice how a thin coat of RTV will slide off a putty knife blade a lot easier than off your fingers. Your finger print ( surface finish ) is the difference.
Here's a good example. Take a very close look at the factories finish on OEM heads and you'll see tool marks )))))) left by their shell mill. Same finish appears on the block rails, OEM intakes, etc.. Sure they could have produced a mirror like finishes. That's not what engineering called for. If you were to magnify the surface you would see peeks and valleys like vvvvvv. There is what's called R.M.S. spec on engineered drawings ( details on that get too technical ). My point is, Getting the valleys clean and dry isn't easy but they do need to be there and they do need to be clean and dry.
 
I always use black hi-temp on the front and back rails. The last two intakes I pulled I used the engine lift and a carb plate to get the intakes un-stuck. That silicone sticks so well it seemed close to lifting the tires off the ground before I started in with a razor blade! I'm scared of prying that hard on aluminum.

Fwiw I never used the corks- and never had a leak there.
 
The instructions with the edelbrock intake i put on my LA 360 stated to just use a bead of rtv silicone on the end rails
 
I was planning on using the cork gaskets on my stock 340 intake. The machine shop didn't return my front and rear dowels. I purchased 3/16 dowels but they are too loose. Are these supposed to be 3/16 roll pins?
 
While you're at it, with the intake on the long block, see if the bolt holes line up.
If they line up perfectly without gaskets, then they won't when you add gaskets and you'll need to mill the thickness of the gasket off of the heads or the intake. Any other misalignment differences you'll have to estimate milling accordingly.
 
Franko said:
I was planning on using the cork gaskets on my stock 340 intake. The machine shop didn't return my front and rear dowels. I purchased 3/16 dowels but they are too loose. Are these supposed to be 3/16 roll pins?
Click to expand...
Don't know, but the pins are not needed if you just use the RTV as recommended.
 
Locomotion said:
While you're at it, with the intake on the long block, see if the bolt holes line up.If they line up perfectly without gaskets, then they won't when you add gaskets and you'll need to mill the thickness of the gasket off of the heads or the intake. Any other misalignment differences you'll have to estimate milling accordingly.
Click to expand...

This can be misleading. The factory used thin metal like shim stock for a gasket so with or without those would hardly make a noticeable differencein bolt hole alignment.
( Crush allowance for shim stock is only .003 )
Aftermarket gaskets are typically a composite ( I use felpro print-a-seal ) that is several times thicker than the OEM. Even so, if the heads haven't been milled the bolts will go.
Torqueing the bolts to spec will crush a composite gasket considerably more than the metal. ( crush allowance for composite gaskets varies with makeup, application, and torque spec ).
 
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