Do intake manifold bolts need thread sealant

[lbuch40]

I just replaced the intake manifold gaskets on my 302. Everything is stock. I am getting intermittent coolant leaks at the front and rear of the manifold. Do the four bolts on the corners enter into the water jacket? Should they have thread sealant of any kind?

Also have been having to re-torque the bolts several times. What is the reason for this?

Just trying to figure out the source of my leaks and whether I am going to have to pull the manifold off again. Any suggestions are much appreciated.?

 

[jamesroney]

I just replaced the intake manifold gaskets on my 302. Everything is stock. I am getting intermittent coolant leaks at the front and rear of the manifold. Do the four bolts on the corners enter into the water jacket? Should they have thread sealant of any kind?

Also have been having to re-torque the bolts several times. What is the reason for this?

Just trying to figure out the source of my leaks and whether I am going to have to pull the manifold off again. Any suggestions are much appreciated.?

OK, you got me thinking. So I had to check.

The bolts at the end of the intake do not enter the water jacket. I checked an early C4OE head, and you can see that the threaded hole is actually all the way thru. I also checked the oddball 14 bolt C9OE 351W head with the extra bole in the water jacket. It also does not thread into the water jacket. Then I checked an E7 head from a 5.0, and it does not thread into the water jacket.

So if you have a leak bubbling around the head of the bolt, it is because the gasket seal in inadequate. Obviously, if the bolts are loose, then it is going to leak.

The Small Block Ford intake manifold bolts are vertical in the engine, and at 45 degrees to the head. So as the intake gets tighter, it also gets "shorter" which loosens the bolts. I usually torque the 12 bolts in the intake about 6 times (in the correct sequence) before they all come to equilibrium. I am not exaggerating. 6 times is about right. Always use a good sealant around the water jacket passages, and RTV the end seals at the lifter galley.

SBF intake bolts should be grade 8 cap screws. Do NOT use butter bolts. Even Stainless is questionable. The early cast iron intakes on the 221 and 260 used an aluminum washer under the flanged head of all 12 bolts. They only lasted once. I have no idea what they were intended to do. They were eliminated by 1967. pics to follow.

 

[lbuch40]

OK, you got me thinking. So I had to check.

The bolts at the end of the intake do not enter the water jacket. I checked an early C4OE head, and you can see that the threaded hole is actually all the way thru. I also checked the oddball 14 bolt C9OE 351W head with the extra bole in the water jacket. It also does not thread into the water jacket. Then I checked an E7 head from a 5.0, and it does not thread into the water jacket.

So if you have a leak bubbling around the head of the bolt, it is because the gasket seal in inadequate. Obviously, if the bolts are loose, then it is going to leak.

The Small Block Ford intake manifold bolts are vertical in the engine, and at 45 degrees to the head. So as the intake gets tighter, it also gets "shorter" which loosens the bolts. I usually torque the 12 bolts in the intake about 6 times (in the correct sequence) before they all come to equilibrium. I am not exaggerating. 6 times is about right. Always use a good sealant around the water jacket passages, and RTV the end seals at the lifter galley.

SBF intake bolts should be grade 8 cap screws. Do NOT use butter bolts. Even Stainless is questionable. The early cast iron intakes on the 221 and 260 used an aluminum washer under the flanged head of all 12 bolts. They only lasted once. I have no idea what they were intended to do. They were eliminated by 1967. pics to follow.

Thanks for checking and verifying.

Attached is a photo of the gaskets with RTV right before placing the intake manifold. I put RTV on both sides of the gasket (Mahle) around the water ports. The yellow arrows indicate where I have determined the leaks to be coming out.
Do you see any potential problem areas where coolant could be following a path out?
From what I can tell so far, water does not seem to be getting into the oil......i.e. no frothy/milky stuff on the dipstick.

 

[jamesroney]

Thanks for checking and verifying.

Attached is a photo of the gaskets with RTV right before placing the intake manifold. I put RTV on both sides of the gasket (Mahle) around the water ports. The yellow arrows indicate where I have determined the leaks to be coming out.
Do you see any potential problem areas where coolant could be following a path out?
From what I can tell so far, water does not seem to be getting into the oil......i.e. no frothy/milky stuff on the dipstick.

Are you sure those are the correct gaskets? Those look like later model 5.0 gaskets. Take a really good look at the gasket to head interface, and the gasket to intake port alignment. I think that there's an earlier style gasket that will match better.

Your yellow arrows have nothing to do with water. That interface just keeps oil in the engine. If you see coolant there, it is leaking from somewhere else.

You have to have a LOT of water in the oil to get the milky frothy look. Like about a quart. A tiny amount of coolant will not get you to milky any time soon.

I have never used RTV on the water jacket interface. But I'm a dinosaur. Lots of people use RTV successfully. So I'm not the best person to ask. Maybe @DirtDonk can help you. I use 3M 08001 Super Weatherstrip Adhesive on the water jacket mating surfaces. I use RTV on the end seals.

Keep at it, you will get there.

 

[lbuch40]

"Your yellow arrows have nothing to do with water. That interface just keeps oil in the engine. If you see coolant there, it is leaking from somewhere else."
Yes, that's what I thought too. But can't figure from where.
The gasket is a Mahle MS15172. Supposedly fits as OEM.

 

[ntsqd]

I believe that those aluminum washers were there to act as crush washers - to seal the bolts to the intake so that any oil that might work it's way up the bolt threads couldn't get out. As improbable as that sounds, and it does to me too, that is the only thing that I've been able to come up with.

Hardware store stainless bolt are no better than a Grade 2 steel bolt. NOT good enough for an intake manifold. ARP stainless bolts are a different story entirely.

No ideas about the leak.

 

[lbuch40]

Are you sure those are the correct gaskets? Those look like later model 5.0 gaskets. Take a really good look at the gasket to head interface, and the gasket to intake port alignment. I think that there's an earlier style gasket that will match better.

Your yellow arrows have nothing to do with water. That interface just keeps oil in the engine. If you see coolant there, it is leaking from somewhere else.

You have to have a LOT of water in the oil to get the milky frothy look. Like about a quart. A tiny amount of coolant will not get you to milky any time soon.

I have never used RTV on the water jacket interface. But I'm a dinosaur. Lots of people use RTV successfully. So I'm not the best person to ask. Maybe @DirtDonk can help you. I use 3M 08001 Super Weatherstrip Adhesive on the water jacket mating surfaces. I use RTV on the end seals.

Keep at it, you will get there.

In my experience, Dinasours are the BEST knowledge base! I showed my picture to a shop friend. He thought maybe I had too much RTV around the water jacket ports. He said use just a thin film - enough to fill in the pitted pock holes in the head and manifold.
Picked another gasket-Felpro this time. Will give it another shot today.

 

[ba123]

In my experience, Dinasours are the BEST knowledge base! I showed my picture to a shop friend. He thought maybe I had too much RTV around the water jacket ports. He said use just a thin film - enough to fill in the pitted pock holes in the head and manifold.
Picked another gasket-Felpro this time. Will give it another shot today.

I was just gonna write that. WAY too much.

It has to go somewhere after you toque down and it's not going to go anywhere you want it to go. You really only need a very very light coat, enough to fill small voids if anything at all.

And if that is the right gasket, it's too low and will go even lower once you put the heads on.

There is a huge debate over what to put on your gasket to keep it in place, you could use RTV, Spray Copper, High Tack...the list is long, but you want the ports on your head to match the port openings on your gasket after you put your intake on and torque down.

Find a way to make that work for you. Maybe a little mark with a sharpie on each side where you can see it and make sure it stays aligned before you torque down or eyeball it if you feel confident, but ditto on what James said, no water there on the block but that doesn't mean it isn't coming from your intake right above that. Your intake will have coolant in in and you could just have a loose fitting or freeze plug in the intake.

Some coolant will glow under blacklight. It's not a super bright glow, but if darn enough, you might be able to trace it from your intake. They do make a UV dye for coolant I think as well, if you want to try for a little extra but you shouldn't need it.

 

[m_m70]

Picked another gasket-Felpro this time. Will give it another shot today.

Hoping you got the Fel Pro 1250S-3 gaskets and not the Fel Pro 1250. Lots of bad juju with the 1250 intake gaskets.........

 

[neilvonarb]

Hoping you got the Fel Pro 1250S-3 gaskets and not the Fel Pro 1250. Lots of bad juju with the 1250 intake gaskets.........

1250S-3 gaskets didn’t work on my ‘74 302 original heads. The holes for the water jackets are too big and hang just barely past the edge of the heads, causing it to leak. That was fun to find out.

 

[lbuch40]

I had read something about that. I don’t see either of those numbers on my gasket set.
Package says MS 90103-1.

 

[ba123]

I think the 1250 is just 5.0 and pretty sure the problem isn’t so much the gasket as much as it is how people have put it on, but that’s just my guess.

I had the 1250 on my 5.0 rebuilt but never ran it, that’s what Trick Flow said to use with it. This time I got the FEL-PRO MS 93334 cause it looks better and the valley sides are better, I just don’t need the upper intake gasket it comes with.

 

[pcf_mark]

Since you are taking it off again anyway..when the gasket surfaces are all nice and clean lay the intake into position w/o any gaskets etc completely dry. It should sit firm and not rock side to side or front to rear. Check it for any dings or burs that could keep it from sitting flat and doing its job. Drop your distributor in too and make sure it still bottoms out and is not sticking out of the block.

Then get some threaded rod or cut the heads off some 3+" long bolts that are the same thread as the intake bolts. Put them into the two holes on each side to act as stud guides. Put the gaskets on dry and then slip the intake on dry as a trial run. It should sit down flat and easy. Once you know you are good a thin wipe (not a bead just a consistent smear) around the water ports on head and install the gaskets on the heads. Then a bead along the front and rear block walls that extends into the corner where the head meets. Then a smear on the intake surface water jackets and slide it down the studs into place. Torque sequence!

 

[lbuch40]

Good suggestions! Thanks!

 

[m_m70]

1250S-3 gaskets didn’t work on my ‘74 302 original heads. The holes for the water jackets are too big and hang just barely past the edge of the heads, causing it to leak.

Interesting. I didn't have those issues on my stock heads or my TFS heads I currently run.....
I use ARP intake manifold studs instead of bolts but I don't think that would make any difference in fit. They do however help with alignment during install. Only drawback I see using studs is I have to remove the distributor to pull the manifold but I'm OK with that.

 

[lbuch40]

Can anyone tell me the difference between these two above mentioned Felpro gaskets and the MS 90103-1 that I am about to install?

 

[Oldtimer]

Looking at pictures on Summit web site, the coolant ports and exhaust cross over ports are different shapes.

 

[neilvonarb]

Looking at pictures on Summit web site, the coolant ports and exhaust cross over ports are different shapes.

View attachment 902965

Look at the difference in distance between the edge of the coolant port and the slotted hole for the intake bolt - that was the issue when I tried the S3’s. The edge of that hole was basically at the edge of my head and coolant could get out. On the standard 1250’s, that hole is narrower, but still the right size so it doesn’t block the coolant port (the rest of the gasket you see inside the coolant port is meant to be cut off). The S3’s also have a steel core.

 

[lbuch40]

Very interesting comparison. For what it’s worth, the Mahle gaskets that I botched the install on are exactly the same as the mS 901031-1

 

[ntsqd]

Look at the difference in distance between the edge of the coolant port and the slotted hole for the intake bolt - that was the issue when I tried the S3’s. The edge of that hole was basically at the edge of my head and coolant could get out. On the standard 1250’s, that hole is narrower, but still the right size so it doesn’t block the coolant port (the rest of the gasket you see inside the coolant port is meant to be cut off). The S3’s also have a steel core.

From memory, and it isn't as good as it used to be, the 1250's look to match the 351W C9OE heads that I have around here somewhere. With those heads if you cut that inner section out of the coolant ports and made the opening roughly rectangular you would have coolant leaking into the lifter galley and bubbling up out from under that bolt head.