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View Full Version : Do exhaust manifolds need gaskets? '86 351 Indmar


djbartu
09-23-2005, 07:24 PM
When I removed the exhaust manifolds from my '86 tri star 351W Indmar, I noticed there are no gaskets (between the manifold and head) from the factory. Skidimm sells gaskets for this application ... do I need them?

H20skeefreek
09-23-2005, 07:50 PM
yep, shoulda been there.

Cloaked
09-23-2005, 08:10 PM
yep, shoulda been there.Agreed.....

BriEOD
09-23-2005, 08:55 PM
The reason the gasket is there is to prevent leaking water (merries the two surfaces). Is it leaking?

Workin' 4 Toys
09-23-2005, 11:02 PM
IMO there should not have been any from the factory. Again, IMO.

H20skeefreek
09-23-2005, 11:07 PM
IMO there should not have been any from the factory. Again, IMO.
any particular reason why you have that opinion?

Leroy
09-23-2005, 11:20 PM
I've never heard of this application without gaskets.

Workin' 4 Toys
09-23-2005, 11:25 PM
I don't see them being any different than a car engine manifold. And the ones I have done don't have gaskets from the factory. I have yet to pull a set of manifolds from a 351marine, but I wouldn't think they would. Like I said IMO. I have not done one. And when we bought aftermarket exhaust systems for cars/trucks in the past, they come with gaskets. Supposedly because the mating surfaces on after market are not as perfect as a brand new set of milled heads and brand new set of milled manifolds. Please correct me if I am wrong.

Leroy
09-23-2005, 11:27 PM
Which car and which engine did not? I'm surprised, but I believe you!



I don't see them being any different than a car engine manifold. And the ones I have done don't have gaskets from the factory. I have yet to pull a set of manifolds from a 351marine, but I wouldn't think they would. Like I said IMO. I have not done one. And when we bought aftermarket exhaust systems for cars/trucks in the past, they come with gaskets. Supposedly because the mating surfaces on after market are not as perfect as a brand new set of milled heads and brand new set of milled manifolds. Please correct me if I am wrong.

Workin' 4 Toys
09-23-2005, 11:35 PM
Small block chevys mainly in the 80's/90's.

Leroy
09-23-2005, 11:53 PM
Gaskets = cost! Guess they figured out how to build new engines without gaskets. I guess because we see a gasket with every repair, it's always expected.

djbartu
09-24-2005, 09:01 AM
I guess I'll add the gaskets to my Skidimm order. Thanks for the info.

kavants
09-26-2005, 07:30 AM
My 87 did not have any. Asked a local mechanic/machinist and he said it is common to not use gaskets in this type of application. Mine went back together with none and has never leaked a bit.

Engine Nut
09-27-2005, 07:57 AM
When I removed the exhaust manifolds from my '86 tri star 351W Indmar, I noticed there are no gaskets (between the manifold and head) from the factory. Skidimm sells gaskets for this application ... do I need them?

We (at Indmar) do not use gaskets between the cylinder head and exhaust manifold. There is no transfer of water between the manifold and head ... only exhaust. The head is water cooled and so is the exhaust manifold so there isn't a heat issue at that joint. All we do is put a small bead of black silicone sealant around each of the exhaust ports and mount the manifold. We have been doing it that way for many years.

Engine Nut

Hunterb
09-27-2005, 02:00 PM
I had mine off during the restoration process (1990 PS 190, 351 Indmar) and was surprised to find no gaskets in there as well. I put them back together using the Permatex Gold gasket goop and it worked fine.

Bruce

jimmer2880
09-27-2005, 06:07 PM
I've been told from someone that should know, that if you put gaskets on an engine that shouldn't need one - you can actually create an exhaust leak.

Workin' 4 Toys
09-27-2005, 11:30 PM
We (at Indmar) do not use gaskets between the cylinder head and exhaust manifold. There is no transfer of water between the manifold and head ... only exhaust. The head is water cooled and so is the exhaust manifold so there isn't a heat issue at that joint. All we do is put a small bead of black silicone sealant around each of the exhaust ports and mount the manifold. We have been doing it that way for many years.

Engine Nut
Thanks for the reassurance EN.

djbartu
09-28-2005, 09:53 AM
Well then, I guess I won't use them when I put the engine back together ... I think??

Workin' 4 Toys
09-28-2005, 11:16 PM
Well then, I guess I won't use them when I put the engine back together ... I think??
You be the judge. In theory you should not need them. HOWEVER, if the manifold and or head have even the slightest warp to them, and (you would never be able to see it by eye) then you will need gaskets (this is why they sell them aftermarket). You could of course have the heads and manifolds decked and then you would have fresh flat surfaces. However, if you are like most people, that is not worth the effort, and the money is better spent on a few gaskets every few years to keep the exhaust leaks to a minimum.
Perhaps you might want to try it without, and if it has a leak, then go to the gasket setup. (mearly a suggestion)