390GT exhaust manifold gaskets?

3947 Views 8 Replies 4 Participants Last post by 68gt390bench, Mar 9, 2001

68gt390bench

Discussion Starter · Mar 9, 2001

Hi all,
While my engine is out, I'd like to take the manifolds off (wish I had some CJ's to put on!! don't we all!!), have the surface machined nice and smooth and put new gaskets b/t them and heads. I know from the factory they did not some w/gaskets but right now there are some old rusty thin metal gasket deals b/t them. I am thinking of Mr. Gaskets? Anyone have any better ideas or know the best place to get a set of gaskets from? I had slight exhaust leak on my old 390Gt cpe and it got pretty annoying. The new FB doesn't have one, if it does it is soo minor I can't hear it! However, while the motor is out I want to make sure I don't have to worry about a leak ever surfacing!

tia,
Mike

Mike
Cortland Manor, NY
'68 GT390 FB, 4spd bench seat
http://www.geocities.com/stangman39/stangsho.html

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camachinist

· #2 · Mar 9, 2001

Personally, I feel, if the head and manifold surfaces are flat and not pitted, you don't need exhaust gaskets...
The manifolds have such a large sealing area and are so rigid that gaskets shouldn't be necessary, especially if you're running a free flowing exhaust system.

I've had more trouble with gaskets than I've had running either naked or with Hi-temp RTV for a seal...

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG

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68gt390bench

Discussion Starter · #3 · Mar 9, 2001

Hey Pat,
I think since there are some old metal gaskets in there now it might mean the surfaces are not that smooth. I'm gonna see if John who is working on my car has any advise on this issue or if he can smooth the surfaces down. I really don't want to take the heads off to smooth them down too. I just think if I take the gaskets out and put them back on w/o any new ones I might get the motor back in and have more problems then b4 - and I don't want that!

Mike

Mike
Cortland Manor, NY
'68 GT390 FB, 4spd bench seat
http://www.geocities.com/stangman39/stangsho.html

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camachinist

· #4 · Mar 9, 2001

Although you won't know until the manifolds come off, I wanted to offer a little advice in advance...

There's really only a few ways to make the surfaces smooth and flat if they're not....machining with a flycutting attachment or, in minor instances, using abrasive belting attached to a surface plate...

The FE heads lend themselves well to these approaches and, in my experience with mainly truck and industrial engines, remain smooth and flat in most instances.

The reason factory heads come without gaskets is that they are freshly machined on precision equipment prior to mating the surfaces...

Your eyes and fingers willl tell you smoothness and a straightedge and feeler guages will tell flatness...try to keep it under .002-.003...

Hope that helps a bit..

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG

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· #5 · Mar 9, 2001

IF you having them machined there is no reason at all to go back to gaskets on the manifolds. The use gaskets are one of the main reasons the manifolds warp in the first place

Greg B

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monk

· #6 · Mar 9, 2001

If you do decide to use gasket's, FelPro Performance gasket #1485 is for the 14-bolt GT head.I've had these on my engine for over a year with no leak's.Monk

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68gt390bench

Discussion Starter · #7 · Mar 9, 2001

Hi all,
thanks for the advice. As to what SuperCJ said. If I have the manifolds machined that is good, but don't I need to machine both the manifold and head? If I just machine the exhaust, there is chance they still won't fill nice nice with the head, right?
I'm not planning to take the heads off that is why I was gonna use gaskets..
thanks
Mike

Mike
Cortland Manor, NY
'68 GT390 FB, 4spd bench seat
http://www.geocities.com/stangman39/stangsho.html

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68390gt

· #8 · Mar 9, 2001

I've never had a problem using gaskets. Usually get them from Ford Power Parts in CA.

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68gt390bench

Discussion Starter · #9 · Mar 9, 2001

I am thinking of seeing what they have - I've heard of them b4.
Can you email me alittle about your car? i always like hearing about '68 GT390 cars especially

[email protected]

thanks,
Mike

Mike
Cortland Manor, NY
'68 GT390 FB, 4spd bench seat
http://www.geocities.com/stangman39/stangsho.html

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