1985.5 F150 5.0 EFI intake manifold gaskets

[sgauvry]

Gents -

I am going to use FelPro intake manifold gaskets for the lower intake manifold. I have read that I should use gasket sealant only on the end corners of the end rubber gaskets.

Is that what you recommend and if so, what sealant should I use?

Thanks!

Steve

[Gary Lewis]

I do not use the rubber piece on the dam at either end of the valley. Instead I use a 1/4" bead of RTV all the way across. And too much is ok, while not enough is bad.

But, regardless of what you use there, you need to ensure that the manifold goes down evenly and that you don't slide it around any when it goes down. So I have taken 4 long bolts that screw in the holes in the block and cut the heads off. That lets you slide the manifold down into place and ensures it isn't forward or backward, which causes you to have to slide it - which knocks the seals off and moves the gaskets.

Even then, you need to watch and make sure that the manifold is going down level - assuming your engine is sitting level. If it is angled too much to one side or the other you may not get it to pull down evenly. Don't ask and Brandon/Bruno2 won't tell.

Also, don't torque the bolts down immediately. Snug them down, which causes the RTV to be pushed against all parts of the block and intake, but wait several hours, and maybe over night, to torque them down the last little bit. That way the RTV sets up and when you do tighten down the last little bit the RTV is in compression.

Last, cleanliness is paramount. RTV won't stick to oily surfaces, and you want it to stick.

[85lebaront2]

I do not use the rubber piece on the dam at either end of the valley. Instead I use a 1/4" bead of RTV all the way across. And too much is ok, while not enough is bad.

But, regardless of what you use there, you need to ensure that the manifold goes down evenly and that you don't slide it around any when it goes down. So I have taken 4 long bolts that screw in the holes in the block and cut the heads off. That lets you slide the manifold down into place and ensures it isn't forward or backward, which causes you to have to slide it - which knocks the seals off and moves the gaskets.

Even then, you need to watch and make sure that the manifold is going down level - assuming your engine is sitting level. If it is angled too much to one side or the other you may not get it to pull down evenly. Don't ask and Brandon/Bruno2 won't tell.

Also, don't torque the bolts down immediately. Snug them down, which causes the RTV to be pushed against all parts of the block and intake, but wait several hours, and maybe over night, to torque them down the last little bit. That way the RTV sets up and when you do tighten down the last little bit the RTV is in compression.

Last, cleanliness is paramount. RTV won't stick to oily surfaces, and you want it to stick.

I second that on the RTV for the end seals. I used to use many nasty words on the end seals both on my 1964 Falcon 260 and the Cobra 289 in my 1966 GT350. At least on the Windsor engines the bolts go straight down. Worst intake manifold install, FE engines for the win! It damn near takes a crane to lift and set one in place, if it goes the least bit off, not only will it leak oil, it can move the side gaskets enough to drive you bats looking for the air leak inside a valve cover.

[Gary Lewis]

I second that on the RTV for the end seals. I used to use many nasty words on the end seals both on my 1964 Falcon 260 and the Cobra 289 in my 1966 GT350. At least on the Windsor engines the bolts go straight down. Worst intake manifold install, FE engines for the win! It damn near takes a crane to lift and set one in place, if it goes the least bit off, not only will it leak oil, it can move the side gaskets enough to drive you bats looking for the air leak inside a valve cover.

I am still amazed that I, as a 25 year old "kid", was able to put a 4bbl intake on my 390 by myself - and not have any leaks of any kind. Yes, it helped that there was enough room in the engine compartment to get in there, and enough strength in the fender of that '72 F250 to sit on it. But that intake was massive!

Dad used to say "I'd rather be lucky than good." I was lucky.

[sgauvry]

I do not use the rubber piece on the dam at either end of the valley. Instead I use a 1/4" bead of RTV all the way across. And too much is ok, while not enough is bad.

But, regardless of what you use there, you need to ensure that the manifold goes down evenly and that you don't slide it around any when it goes down. So I have taken 4 long bolts that screw in the holes in the block and cut the heads off. That lets you slide the manifold down into place and ensures it isn't forward or backward, which causes you to have to slide it - which knocks the seals off and moves the gaskets.

Even then, you need to watch and make sure that the manifold is going down level - assuming your engine is sitting level. If it is angled too much to one side or the other you may not get it to pull down evenly. Don't ask and Brandon/Bruno2 won't tell.

Also, don't torque the bolts down immediately. Snug them down, which causes the RTV to be pushed against all parts of the block and intake, but wait several hours, and maybe over night, to torque them down the last little bit. That way the RTV sets up and when you do tighten down the last little bit the RTV is in compression.

Last, cleanliness is paramount. RTV won't stick to oily surfaces, and you want it to stick.

Thanks Gary! Sorry for the delayed response.

It's amazing how so many differ on opinion with regard to this issue. But I believe the best course is to do it as you say. I have some Permatex Blue RTV Silicone Gasket Maker. Is that what you would use?

Thanks!

Steve

P.s. The use of stud guides is a good idea that I will also use.

[sgauvry]

I second that on the RTV for the end seals. I used to use many nasty words on the end seals both on my 1964 Falcon 260 and the Cobra 289 in my 1966 GT350. At least on the Windsor engines the bolts go straight down. Worst intake manifold install, FE engines for the win! It damn near takes a crane to lift and set one in place, if it goes the least bit off, not only will it leak oil, it can move the side gaskets enough to drive you bats looking for the air leak inside a valve cover.

Thanks, Bill!

[sgauvry]

I am still amazed that I, as a 25 year old "kid", was able to put a 4bbl intake on my 390 by myself - and not have any leaks of any kind. Yes, it helped that there was enough room in the engine compartment to get in there, and enough strength in the fender of that '72 F250 to sit on it. But that intake was massive!

Dad used to say "I'd rather be lucky than good." I was lucky.

I had discovered, after I removed the engine, that I had a massive leak of oil at the rear seal of the lower intake manifold. I had originally thought, prior to removing the engine, that the leak was from the rear main, but that was bone dry. It was all coming from the lower intake. Really pissed at myself for that one since I installed that lower intake 3 years ago. Live and let learn.

[Gary Lewis]

I had discovered, after I removed the engine, that I had a massive leak of oil at the rear seal of the lower intake manifold. I had originally thought, prior to removing the engine, that the leak was from the rear main, but that was bone dry. It was all coming from the lower intake. Really pissed at myself for that one since I installed that lower intake 3 years ago. Live and let learn.

Yes, the blue Permatex will work fine.

As for the leak, that is unfortunately very common. Rusty's 351M had the same problem. Big Blue's 460 has the same problem. But the procedure outlined earlier will resolve it - if all the parts are CLEAN. The RTV won't stick to oily surfaces, but if you clean the dam, the heads, and the intake well RTV will stick tightly to both and it won't leak.

[sgauvry]

Yes, the blue Permatex will work fine.

As for the leak, that is unfortunately very common. Rusty's 351M had the same problem. Big Blue's 460 has the same problem. But the procedure outlined earlier will resolve it - if all the parts are CLEAN. The RTV won't stick to oily surfaces, but if you clean the dam, the heads, and the intake well RTV will stick tightly to both and it won't leak.

Thanks, Gary!

I soaked the lower intake manifold in Purple Power, rinsed it off in hot water, dried it well and blew compressed air into all ports. Cleaned up well. All old gasket material is cleaned off and it is free from oil. I used a ceramic based, engine primer on it and painted it. I will remove paint from the upper surface where the plenum attaches.

I'm confident the RTV and methodology will take care of the leak.

Steve

[Gary Lewis]

Thanks, Gary!

I soaked the lower intake manifold in Purple Power, rinsed it off in hot water, dried it well and blew compressed air into all ports. Cleaned up well. All old gasket material is cleaned off and it is free from oil. I used a ceramic based, engine primer on it and painted it. I will remove paint from the upper surface where the plenum attaches.

I'm confident the RTV and methodology will take care of the leak.

Steve

Steve - Looks good!