Author Topic: Exhaust Manifold Gaskets  (Read 1311 times)

rcgt350

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Exhaust Manifold Gaskets
« on: February 15, 2022, 05:32:04 PM »
What do most do when it comes to the exhaust manifolds on a 289 HiPo? Do you use them or bare metal only surfaces ?

JD

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Re: Exhaust Manifold Gaskets
« Reply #1 on: February 15, 2022, 05:51:44 PM »
I think the BB's were metal to metal, SB use gaskets.  Others will chime in...see below

Many debates as to the best gasket to use vs concurs "correct" gasket to use, can you say which you want?
« Last Edit: February 15, 2022, 09:22:44 PM by JD »
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Bob Gaines

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Re: Exhaust Manifold Gaskets
« Reply #2 on: February 15, 2022, 06:13:42 PM »
No gasket is needed or used from the factory. It is confusing because gaskets are included in most BB and SB gasket or engine rebuild kits. SB was metal to metal like the BB. The manifolds should be machined for flatness if possible. I also smear a little high temp silicone around the exhaust port for insurance against leakage. Not too much so as to squeeze out when bolted down and be noticeable. If that happens once cured you can take a sharp tool and pick away the visible extra.
« Last Edit: February 16, 2022, 10:41:30 AM by Bob Gaines »
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Royce Peterson

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Re: Exhaust Manifold Gaskets
« Reply #3 on: February 15, 2022, 08:16:45 PM »
Like Bob said - don't use one. They tend to fall apart, then someone tries to fix the resulting leak by tightening the now - loose bolts. Then the manifold cracks. Bad day.
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J_Speegle

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Re: Exhaust Manifold Gaskets
« Reply #4 on: February 15, 2022, 09:32:42 PM »
You can also us graphite between the two surfaces to help seal like the factory did. Worked well for me the last couple of times I've used it

No tell tale signs of the bright colored silicon that often turns up in those tight "they'll never see that " corners and hiding places  ::)
« Last Edit: February 16, 2022, 01:01:42 AM by J_Speegle »
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rcgt350

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Re: Exhaust Manifold Gaskets
« Reply #5 on: February 16, 2022, 12:00:30 AM »
Ok, Iíll have the manifolds gone over first, I have graphite in a spray, so sounds like thereís a plan now.
Thanks everyone!

J_Speegle

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Re: Exhaust Manifold Gaskets
« Reply #6 on: February 16, 2022, 01:03:31 AM »
For the graphite. I sprayed some in a spray can lid, let some of the liquid evaporate then when it was more watery paste like applied it to one of the surfaces with a small brush then torque everything down
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Bossbill

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Re: Exhaust Manifold Gaskets
« Reply #7 on: February 17, 2022, 03:16:54 PM »
Are you guys using shops that use large sanding belts,  threading a few holes for a fixture and a using a surface  planer or an old school flat table resurfacer?
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Bob Gaines

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Re: Exhaust Manifold Gaskets
« Reply #8 on: February 17, 2022, 03:30:36 PM »
Are you guys using shops that use large sanding belts,  threading a few holes for a fixture and a using a surface  planer or an old school flat table resurfacer?
Flat table resurfacer is what I thought was the standard way to do the exhaust manifolds. At least it seems more logical for best true flatness compared to a large sanding belt. 
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Royce Peterson

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Re: Exhaust Manifold Gaskets
« Reply #9 on: February 23, 2022, 04:17:39 PM »
I've never done any of that. I just put my favorite RTV on the flange - very sparingly! - and assemble them. I do get the manifolds blasted clean first, and the cylinder head gasket surfaces on FE's are masked. On small blocks or big blocks you need to make sure there is no oil on any of the exhaust manifold surfaces.

I have used clear basin tub and tile RTV one night when I had to drive to work the next day because we didn't have anything else and it was 10 PM. It worked well for many years afterwards. Best practice would be lithium grease like the shop manual recommends.

Are you guys using shops that use large sanding belts,  threading a few holes for a fixture and a using a surface  planer or an old school flat table resurfacer?
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Bob Gaines

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Re: Exhaust Manifold Gaskets
« Reply #10 on: February 23, 2022, 04:30:00 PM »
I've never done any of that. I just put my favorite RTV on the flange - very sparingly! - and assemble them. I do get the manifolds blasted clean first, and the cylinder head gasket surfaces on FE's are masked. On small blocks or big blocks you need to make sure there is no oil on any of the exhaust manifold surfaces.

I have used clear basin tub and tile RTV one night when I had to drive to work the next day because we didn't have anything else and it was 10 PM. It worked well for many years afterwards. Best practice would be lithium grease like the shop manual recommends.

Are you guys using shops that use large sanding belts,  threading a few holes for a fixture and a using a surface  planer or an old school flat table resurfacer?
The machining of both services is the ideal however there are all kinds of degrees of effectiveness in between that will get the job done too. I remember the days when I used the rough sidewalk as my flat "machining table" to make sure things were flat ;) . That was in there there somewhere as far as within a range of effectiveness goes.   ;D
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Bossbill

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Re: Exhaust Manifold Gaskets
« Reply #11 on: March 17, 2022, 09:37:19 AM »
There was a machine shop I used in the 80s that had a large cast iron table with a hole in the middle. A grinding stone with height adjustment was located in that hole. One simply held the manifold flat to the table and ran it over the stone, back and forth. I can't remember the name of it.

My issue is that the Hipo manifold I bought was stored badly and the mating surface has too many pits to use as is.

Found it. It's a Peterson grinding table.
« Last Edit: March 17, 2022, 09:48:08 AM by Bossbill »
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Royce Peterson

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Re: Exhaust Manifold Gaskets
« Reply #12 on: March 17, 2022, 10:00:59 AM »
That old grinding table looks like it might do the job. But really if the manifolds or heads are that pitted, the best results would be obtained by a machinist using a Bridgeport - style vertical mill. Should be a relatively inexpensive job.
« Last Edit: March 17, 2022, 07:23:15 PM by Royce Peterson »
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Bossbill

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Re: Exhaust Manifold Gaskets
« Reply #13 on: March 17, 2022, 11:49:53 AM »
I agree on using a Bridgeport or similar.
A lot of machine shops have resorted to sanding belts hoping the gasket will do the rest. But, we don't use gaskets!

Bill

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warwick

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Re: Exhaust Manifold Gaskets
« Reply #14 on: March 17, 2022, 04:41:39 PM »
A lot shops will just use a lapping plate.  They are often used for motorcycle heads. Inexpensive and you can you can use at home.