472 intake end seals

[DeVillain]

Alright boys I got one for ya. Are you guys using the rubber end seals for the intake manifold or just running a bead of rtv? Id like to hear your preference and suggestions. Im replacing a leaking end seal and wonder if I should just do away with them and use rtv. The engine is from a 72, 7.7 w/stock cast intake. 
       

[Scot Minesinger]

Yes use the rubber end seals and RTV.  Get the corners really good because that is the primary leak source.  Also, don't just seal the 8 intake ports, seal the entire aluminum gasket all the way around.  Be generous with the RTV.  Rehearse the placement of the intake manifold dry several times, then add the RTV.  When I properly sealed my intake after talking to MTS in CA, my 1970 Cadillac ran way better.  When I placed the intake manifold on the block with the RTV in place - I heard no metal to metal contact -nice.  You will need to reset the timing because it changes as vacuum leaks develop over time.  May also have to turn down idle too.  Recommend replacing all vacuum hoses too if original or in the slightest doubt - now is the time (especially carb to PCV on valve cover).

I think this is why there are a lot of complaints from posts where a 47/500 Caddy engine runs rough at idle after an engine rebuild - poor sealing of intake manifold.

[DeVillain]

That's what I was looking to hear. Thanks Scot.

[cadillacmike68]

Not only is it required for a good vacuum seal, if you don't get it sealed good, and you live in a humid environment like here in FL, then you invite what happened to my engine which was a rusting of the bottom of the intake manifold which proceeded to rust out the intake gasket which nearly ruined the engine. I'll dig out the post and link it here if you want some reading.

Here is the link, some pics in it as well:

http://forums.cadillaclasalleclub.org/index.php?topic=145138.0

[Scot Minesinger]

Mike,

The intake gaskets are aluminum now, so no rusting them out.  However rusting of interior of the intake manifold is no good I agree.

Is that what caused your engine issue that was recently rebuilt?

[cadillacmike68]

Mike,

The intake gaskets are aluminum now, so no rusting them out.  However rusting of interior of the intake manifold is no good I agree.

Is that what caused your engine issue that was recently rebuilt?

Yes, somehow, moisture got in there and here its 90%humidity all the time, so that's what did it.  I can't think of any other reason. I'm sure having it never get a good run for 5 years while I was deployed and it was getting the body work done didn't help it either. The car just got moved from one part of the shop to another, and this was most likely a large contributing factor.

I didn't post pics of the manifold bottom and huge hole in the gasket earlier?