O-ringed EFI upper intake?
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Postmaster
Joined: May 2002
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From: Broken Arrow, OK
O-ringed EFI upper intake?
As some of you know I do a lot of experimenting with my truck. As a result the upper intake comes off pretty often, which is a pain in the butt because the gasket must be cleaned off. Cleaning the gasket surfaces of the intake is usually the most time consuming part of what I'm doing. I was thinking of having a lower intake grooved for O-rings so I wouldn't have to mess with the gasket anymore. I figure I've had the upper off about a dozen times. The gasket is $2, so I've spent $24 on gaskets and a few hours of my life scraping them off. What does everybody think about installing the o-rings? It would mainly be to expedite and simplify things, the money saved on gaskets is not significant. I think it will be between $50 and $75 to get the grooves cut and buy the rings. Any drawbacks to this?
Posting Guru
Joined: Dec 1999
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From: Copley, OH
One BIG drawback: the o-rings seal so much better that you're going to be tempted to hang a turbo on it 
Because of heat issues, you may want to avoid the standard buna-n o-rings and step up to Viton (about twice the cost). The stock 90 duro buna-n rings are only good to 250° F; the Viton rings are good to 400° F. FWIW Silicone rings are good to 450° F but are not recommended with petroleum-based fluids. Even though the manifold is "dry-flow" I'd avoid them and stick with Viton.
Because of heat issues, you may want to avoid the standard buna-n o-rings and step up to Viton (about twice the cost). The stock 90 duro buna-n rings are only good to 250° F; the Viton rings are good to 400° F. FWIW Silicone rings are good to 450° F but are not recommended with petroleum-based fluids. Even though the manifold is "dry-flow" I'd avoid them and stick with Viton.
Posting Guru
Joined: Sep 2002
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From: Langhorne, PA
Are you talking about the paper gasket that sits between the 6 tubes of the upper and lower intake?? The one with two plastic pins?? I just took mine off for the first time(135,000 miles) it just lifted right off of the bottom intake manifold once I removed the upper intake. It is in one piece and looks like new. There are no signs of deterioration or leakage. It wasn't glued to either the top or bottom intake, and as far as I can tell it came from the factory that way. Maybe it doesn't need RTV, it's just plain old air running thru, what could hurt it?/
The Haynes says to "position the new gasket on to the lower intake and carefully lower the upper intake so you do not disturb the gasket position" I would assume that they mean for us to mate the manifolds without sealant.
Maybe this could be your next experiment to try..no sealant, that is.
The Haynes says to "position the new gasket on to the lower intake and carefully lower the upper intake so you do not disturb the gasket position" I would assume that they mean for us to mate the manifolds without sealant.
Maybe this could be your next experiment to try..no sealant, that is.
Senior User
Joined: Nov 2002
Posts: 298
Likes: 1
From: Kentucky
Mine lifted right off
I had the one off of my 1989 F-150 for the first time in 13 years. It lifted right off... Looked like a new one. The new one was installed withput sealer and I have had no leaks at all...
The O ring sound like an excellent Idea. I do not think that the .040 gasket thickness that would be missing from the setup (From the gasket not being there) should cause any problems...
I would retain the original plastic dowels to align the two pieces of the manifold......
Do you put sealant on the gasket when you install it?
What do you torque it to?
ftwfred
The O ring sound like an excellent Idea. I do not think that the .040 gasket thickness that would be missing from the setup (From the gasket not being there) should cause any problems...
I would retain the original plastic dowels to align the two pieces of the manifold......
Do you put sealant on the gasket when you install it?
What do you torque it to?
ftwfred
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Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
The first time I pulled mine off the factory gasket lifted right off the lower, but was damaged when I tried to pull it off the upper. Every gasket I've had on there since has stuck on both sides. I don't use any sealer on it and I torque it down to about 15 ft-lbs using my handy dandy 3/8 Craftsman ratchet and "feels 'bout right" meter.
I was actually planning to use copper, but it tends to flatten when torqued down and will eventually be too thin to seal. I also considered buying some soft copper and cutting a gasket from it, but that's work.
I was actually planning to use copper, but it tends to flatten when torqued down and will eventually be too thin to seal. I also considered buying some soft copper and cutting a gasket from it, but that's work.
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