Intake Gasket advice

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Rat Patrol

Rat Patrol

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I read somewhere that you cant use factory intake gaskets with aftermarket carb intakes - Or have I got the story wrong?

Something about them dissolving?
 
Maybe this will answer the question - does the factory intake have a groove to receive the rubber seal around each port hole on the intake gasket?

Kind of like an O ring?
 
That was my impression. The factory intake is individual O rings on each port that fit in a groove on the intake. The aftermarket carb intakes (at least my ModMan) are a flat bottom design that's designed to be used with a more traditional flat gasket. I got a set of phenolic ones with the kit. I don't think they seal as good as the factory ones would, but they seem to work fine so far.
 
The Eddy dual quad used factory orings. The fuel kept eating them up. I ended up filling the groves up with epoxy and making gaskets. My new stuff uses gaskets as well. Not sure about 6.1l. I haven't seen their gaskets so I don't know but if the factory uses the same silicone they will be an issue with a carb.
 
4speeds4me said:
It would make sense that fuel would deteriorate them. The OE system is dry...
Click to expand...

That's only sort of true. The injector sits right at the port opening, so some fuel is likely to get on the seals. Not as bad as a full wet carb intake I'll agree, but it's not perfectly dry. I can't imagine they would put a non-fuel resistant material in a place so close to fuel, but I guess stranger things have happened. The 6.1 intake is metal right? I was thinking maybe the factory seals just don't like the metal aftermarket intakes, but if the 6.1 is metal that theory goes out the window.
 
My 6.1 intake is aluminum with no o-ring receiver grooves. Im using a Cometic intake gasket though since they were slightly larger port wise than stock.
 
The reason I ask is Ive been chasing down some oil burning....

So I pulled the plugs and the threads were wet and the insulators were sooty.....

At first I thought it was the aftermarket valve seals -,so I pulled the intake to look for staining on the valve stem.

Forget the staining...it was clear the intake gaskets had deteriorated and oil was migrating into the ports!!!

Time for some FelPros!!
 
Hi Rat , as you have found out that rubber on the factory gaskets is not very fuel resistant , not a problem with injectors aimed directly at the the cylinder head , but on a carbed manifold with , perhaps an overfueling issue !! not so good . which is why silicone sealants should never be used to seal intakes .

My theory fwiw on the oil burning issue , based on your last post and following your progress.

could be related to fuel dropout , if it's bad enough it can result in bore wash , the excess fuel can wash of the lubricating film that is collected in the honed finish of the bores , some of it gets burned and with revision some ends up back in the intake side .
The bores and rings get polished and the whole situation just gets worse .

I don't want to sound so doom and gloom but I thought it worth mentioning .
 
I agree.........Bore wash was my first concern..especially at the tip-in....but as soon as I removed the intake it was clear how the oil was getting into the cylinders.

My AF gauge reads 12.8 at wot and 14.5 at cruise.
 
I would jet to 12.2 and see how it runs. I know on my BB with FAST EZ Efi I ran it at 12.2 WOT for a long time and over the summer it seemed like when running it HARD the thing got way hotter than it should on the temp gauge. So about a week before I pulled the engine to start this Gen III saga, I set the WOT to 11.8 just for a try. All I can say is I wish I would have tried that 4 months earlier because I might have just kept it.
 
Yes I was kinda jumping to conclusions there , but I am curious why oil would be getting in the ports
 
Oil in the ports would be from vacuum pulling it in from a crankcase ventilation system or getting past the guides. Some guys run oil catch cans to prevent oil in the intake.

If you have oil from reversion , that would be a serious ring sealing issue . If that is suspected best test would be a leakdown test and may be a good idea to run just to verify everything engine wise is ok.

An intake gasket leaking would cause a vacuum leak and pull air only and cause a lean misfire ,although the hemi has oil drainbacks between the intake ports on cylinders 1&3 and 6&8 those would be the cylinders effected and would have to be a really bad gasket to pull oil from there. .A sooty plug usually indicates a rich condition .
 
Thats correct 72Bb -

The oil vapour system is pretty basic - there are two " fill" points between 1&3 and 6&8 in the heads.

My intake has two vapour lines running from AN fittings over these ports to a catch can.

When I need to fill with oil...I just unscrew one of the AN fittings and stick a small funnel down the threaded hole in the intake.

The oil ports appears to be where the oil is coming from...the oil fill ports between 1&3 and 6&8.

Its basically condensed crank case vapours seeping past the gasket in those areas on the way to the catch can .....I suspect

Whether it was fuel or oil that dissolved the gasket seal Im unsure.

Anyhow- swapped in some Fel Pro gaskets tonight and the exhaust quality has improved immensely.

It never used much oil before - but Ill keep an eye on it and if it starts burning oil again in 12 mths time Ill use a cometic.
 
You're running the ModMan right? I may have to look into that myself. I got the gaskets that Indy sells with the intake and when I took it off a while back for some work I noticed it was a little wet around that fill port. Not really the best design and hugely annoying pouring 7+ quarts of oil down a straw to fill it. The tiny bolts that hold the intake down don't help the sealing matter in my opinion either.
 
As the 'O ring' style gaskets are re-useable...probably no harm in lifting the intake and checking - Im glad I did!
 
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