It says to toss the end seals in the trash and use RTV.  I just installed one this morning using that method.  It will never leak.  Be sure to put that paper thin wet layer on the bottom of the intake end seal surfaces, then the bead on the block.  The paper thin layer makes sure that if there is any irregularity in the joint, you have full coverage on both surfaces so the RTV will flow and adhere to both.  The intake I took off had (someone else's installation) RTV but there were gaps everywhere.

Steve's way definitely works well but you can also use the end gaskets if you take the time to make them fit correctly.  Most of them are just a bit too long so they tend to squeeze out after they are installed.  I found that if you test fit them (no RTV, just dry) and trim them a little at a time until they lay flat on the end flange, they do not squeeze out after being installed.  Do use a thin layer of RTV on both sides of the end gaskets and a thicker blob at each end where the block meets the heads when you install them "for real" though.

Last edited by John Ha (7/11/2014 8:02 AM)

mrputz1 wrote:

How do i become a member Perpetually Bewildered Society?

I'm not sure - I don't even know how I became a member  

:-)

The problem with the end gaskets is they have to be compressed in order to work.  RTV is just THERE once it hardens up, so it will never leak.

A gasket that is compressed has one of two things going on... First, it is compressed to the point where it deforms enough to be squished out of its position.  It spends the rest of its life trying to get compressed the heck out of there.  The other thing that can happen is it finally gives up being compressed and then just quits working altogether.  Once it loses that elaasticity, it is gone and creates gaps.

RTV will never shrink, is not compressed and does not lose its adhesion if the surfaces are properly cleaned prior to installation.  Plus it is just alot easier.

If the manifold is old or after market, it may have been machined at some point to match heads that had been milled or it may have been bad out of the box.  If it is not compressing against the stock gaskets, any RTV you put in there to seal it will not hold up over time or even a few minutes as RTV products generally are not gas friendly.  You need to find out why it didn't seat.  The end seals will often prevent the intake from seating but if you indeed did not use them about the only thing that comes into play is either the complete wrong gaskets, machining of the intake, or some casting bosses on the underside that are hitting something.  There are several companies that make thick gaskets for this purpose and this is the proper correction over RTV.  Try setting the intake in place with no gaskets to see how well it seats and to determine if there are any obstructions underneath that are preventing it from sitting properly.  You may be able to measure the intake to head gaps if wth feeler blades but this may be tricky.  If you do need a thick gasket set, I can check with my local engine guy to see what brand he recommends.  I had to use a set on my 428 after some head machining and they worked great.

intake manifold sizes are exactly the same  new vs old. DO NOT DO NOT use universal Fel-pro gasket set for multiple engines. A 351 is not a 302. The 351 has slightly larger openings. Just enough to alow air leaks form area under the maniflod. Alas no drawing fuel through the carbs. Will not run.

Expanding on GPatrick's response, I would think that the manifold was milled to fit heads that had been milled to a significant amount, like 0.040-0.060".  This is necessary or the manifold will not line up properly with the ports in the head.  You can try to double up the manifold gaskets to get back to the correct alignment ... and I still would use RTV instead of the end gaskets.

Use some modling clay on the head gasket sufaces. vaseline the intake,,set it in place and snug it down not torque then remove the intake you can cut the clay and measure how thick it is compare it top of ports to bottom side to side etc.

Milling heads on a SBF can really mess things up.  Things like port alignment and water jacket port alignment, as well as the bolt holes.  That is why I have always said, for anything I work on, the heads cannot get milled more than 0.040" without causing problems.  Stock intake will still bolt up.

If heads are milled, the intake will still sit at the same elevation in relation to the engine block, so the end seal gap will not change.  Milling the intake there would gain nothing since the head and intake ports are still misaligned after milling heads. 

If BOTH SIDES on the intake AND both end seals were milled, the intake could then sit a little lower to match the repositioned heads.

I am glad I have never run across that issue.

MS, regarding your last post, agree w/everything stated.  In my case, I was racing a 289 w/351W heads that were milled a significant amount (I do not remember the total), the intake manifolds sides were milled for port matching, but the manifold ends were not milled.  When assembling the manifold the end gaskets they were pushed out of alignment (due to the manifold sitting lower the normal), this is when we stopped using end gaskets, and just RTV.
Also, w/o the end gaskets and just paper thin RTV on the manifold surfaces eliminated the intake manifold bolt "loosening" issue as you indicated.  And, I follow the same torquing method you described.