Silicone as an exhaust manifold sealant??

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Princess Valiant

Princess Valiant

A.K.A. Rainy Day Auto
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So I was car chatting with a guy this evening. As usual I'm going on and on about cars because if you give me the idea you want to car talk, then you better pull up a seat and get you a snickers bar, you're going to be here awhile.

I'm building a hyper pak slant six for a valiant wagon. I took the head to a machine shop on march 5, 2020. A little after that, the shop closed due to the whole thing with covid-19. So now its the end of June and the shop is still closed and I can't ever find anyone there and they still have my cylinder head.

So I mentioned that I am going to put my slant six Clifford headers and intake on a different slant that is a good running stock original engine just to get the car running.

So I don't want to spend good money on a Clifford brand intake/ exhaust gasket because the engine is temporary until I can get my performance engine built.

I mentioned I am going to use a standard fel pro gasket with the Clifford stuff but I'm not sure if it will hold up.

He suggested using the felpro gasket with silicone. Standard household silicone.

What do ya think??
 
Princess Valiant said:
So I was car chatting with a guy this evening. As usual I'm going on and on about cars because if you give me the idea you want to car talk, then you better pull up a seat and get you a snickers bar, you're going to be here awhile.

I'm building a hyper pak slant six for a valiant wagon. I took the head to a machine shop on march 5, 2020. A little after that, the shop closed due to the whole thing with covid-19. So now its the end of June and the shop is still closed and I can't ever find anyone there and they still have my cylinder head.

So I mentioned that I am going to put my slant six Clifford headers and intake on a different slant that is a good running stock original engine just to get the car running.

So I don't want to spend good money on a Clifford brand intake/ exhaust gasket because the engine is temporary until I can get my performance engine built.

I mentioned I am going to use a standard fel pro gasket with the Clifford stuff but I'm not sure if it will hold up.

He suggested using the felpro gasket with silicone. Standard household silicone.

What do ya think??
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Not hardly. Put it on dry, it will last plenty long for what you want.
 
RustyRatRod said:
Not hardly. Put it on dry, it will last plenty long for what you want.
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I have used Fel Pro intake - exhaust gaskets on slants with the stock intake, Clifford intake, Dutra exhaust and Hooker headers and never had an issue. Just make sure the mounting surfaces are clean and flat.
A week a go Rock Auto had one of their manufactures close our sales on the Fel Pro manifold gaskets. It may still be going on. IIRC the gaskets were less than $5.00 each. I bought four of them.
 
my68barracuda said:
I have used Fel Pro intake - exhaust gaskets on slants with the stock intake, Clifford intake, Dutra exhaust and Hooker headers and never had an issue. Just make sure the mounting surfaces are clean and flat.
A week a go Rock Auto had one of their manufactures close our sales on the Fel Pro slant six manifold gaskets. It may still be going on. IIRC the gaskets were less than $5.00 each. I bought four of them.
Click to expand...
 
Princess Valiant said:
So I was car chatting with a guy this evening. As usual I'm going on and on about cars because if you give me the idea you want to car talk, then you better pull up a seat and get you a snickers bar, you're going to be here awhile.

I'm building a hyper pak slant six for a valiant wagon. I took the head to a machine shop on march 5, 2020. A little after that, the shop closed due to the whole thing with covid-19. So now its the end of June and the shop is still closed and I can't ever find anyone there and they still have my cylinder head.

So I mentioned that I am going to put my slant six Clifford headers and intake on a different slant that is a good running stock original engine just to get the car running.

So I don't want to spend good money on a Clifford brand intake/ exhaust gasket because the engine is temporary until I can get my performance engine built.

I mentioned I am going to use a standard fel pro gasket with the Clifford stuff but I'm not sure if it will hold up.

He suggested using the felpro gasket with silicone. Standard household silicone.

What do ya think??
Click to expand...

I`d at least use the hi heat stuff, if I were going to use sillicone , used to use it on my 406 sbc. Haven`t had to use anything w/ the TTI headers now tho.
 
My power wagon/318 has just silicone. No gaskets. When i pulled original manifolds there were no gaskets.
 
Rani, leave a note on the door instructing owner to call. Maybe you can arrange to get the parts back.
 
Tooljunkie said:
My power wagon/318 has just silicone. No gaskets. When i pulled original manifolds there were no gaskets.
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^ This. It was the same with my 383's HP manifolds. I did have them trued on a big sander when I had them off. Actually, it's likely a must. Check across them all with a straightedge.

How much are the Clifford gaskets? Flange leaks blow:lol: (pun intended), it's worth the expense to be leak free.
 
doug 371 said:
we'll pretend he meant hi temp rtv
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I once had a set of Sanderson Headers on a SBC and their recommendation was to use a bead of Permatex Ultra Black RTV in lieu of a gasket. I went with a gasket, but I suppose it'll work so long as the mating surface is flat and true.
 
Ultra Copper would be my choice. B/RB Motorhomes came without exhaust gaskets IIRC something to do with heat transfer. I wouldnt think header flanges would be rigid enough to seal with just RTV though unless they were 3/8.
 
I have used the felpro gasket on a few slants. never had an issue. just make sure you follow the torque spec. if I remember correctly it is really low, like 10ft lbs.
 
I recommend Hylomar AF for manifold gaskets. It is a sticky blue goo that doesn't dry — it stays pliable so the manifolds can slide as they expand and contract, but it really fills all the gaps, even with the low torque. And it is super easy cleanup compared to anything that hardens up — it just wipes off. You can even re-use the gasket, if you want.
 
Do what you gotta do, but for my money, I would use a high temp. RTV for extra insurance instead of the generic household stuff which isn't designed to take any heat at all.
For under 10 bucks a tube, it has a lot of uses down the road, so you won't be out anything in the long run.
 
Your best bet is to use a gasket. Slant Six manifolds can be tedious to install, no sense in making it any more tedious than it is. Clifford and Remflex are both great options, but they are the most expensive. Mr Gasket #320 was another option, but they seem to be hard to find now. Fel-Pro will work fine, and the price is right.

I believe your best option for what you want to do is the Napa Mahle MS16030 Should be around $10.00 and is an excellent gasket.
 
Johnny Dart said:
Your best bet is to use a gasket. Slant Six manifolds can be tedious to install, no sense in making it any more tedious than it is. Clifford and Remflex are both great options, but they are the most expensive. Mr Gasket #320 was another option, but they seem to be hard to find now. Fel-Pro will work fine, and the price is right.

I believe your best option for what you want to do is the Napa Mahle MS16030 Should be around $10.00 and is an excellent gasket.
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Its not so much that Clifford gaskets are expensive, it's trying to avoid with having to deal with Clifford.

They will tell you their gasket is the ONLY option, so it's nice to see the alternatives available.
 
Princess Valiant said:
Its not so much that Clifford gaskets are expensive, it's trying to avoid with having to deal with Clifford.

They will tell you their gasket is the ONLY option, so it's nice to see the alternatives available.
Click to expand...

Did you actually talk to them ? Is that what they told you ?
 
vitamindart said:
I have used the felpro gasket on a few slants. never had an issue. just make sure you follow the torque spec. if I remember correctly it is really low, like 10ft lbs.
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And following the torque spec is true when using the stock one piece cast iron exhaust. The one piece cast exhaust manifold needs to have the ability to expand and move.
When I used cast iron dual Dutra's and the steel two piece Hooker long tube headers and this would also apply to the steel Clifford two piece headers, I tightened the mounting bolts pretty tight with no bad effects. I was using my 1/4 inch drive socket set, so I did not get huge torque, but I was more than 10 ft lbs.
 
mvh said:
I recommend Hylomar AF for manifold gaskets. It is a sticky blue goo that doesn't dry — it stays pliable so the manifolds can slide as they expand and contract, but it really fills all the gaps, even with the low torque. And it is super easy cleanup compared to anything that hardens up — it just wipes off. You can even re-use the gasket, if you want.
Click to expand...
I used the halomar on a 406 sbc, dam stuff just ran oFF and didnt do squat . MAY HAVE BEEN A BAD BATCH , BUT i WONT USE IT AGAIN, ON ANYTHING!
 
Princess Valiant said:
Its not so much that Clifford gaskets are expensive, it's trying to avoid with having to deal with Clifford.

They will tell you their gasket is the ONLY option, so it's nice to see the alternatives available.
Click to expand...
I have Remflex on mine and no issues.
 
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