Howdy,

When I replaced exhaust manifold last year on my

300-6, I used a name-brand gasket. I now have some

small exhaust leaks which I can hear. Ford originally used

no gasket, and some recommend this. I have a '79 engine

with used manifold from '83---do you think I'd have problem

if I removed gasket ? Do they seal well without ?

Thanks. J.R.

 

As cast iron parts are heated and cooled they don't seal very well, they have a tendency to warp. 300 I6 exhaust and intake manifolds warp easily if they are not torqued down properly. I start on the inside bolts and work outward in a staggered pattern. I had similar problems with my 84s manifolds leaking, the best fix for it is to install two gaskets doubled up. I did mine over two years ago and haven't had a problem since.

 

Thanks---I did torque bolts according to factory manual,

but used one gasket set. Have heard of doubling gaskets, but

was concerned about durability. Do you use regular donut

gasket or sintered metal ? I used the metal thinking it might

seal better & last longer. Or does the '84 even use the flange

gasket ? Just remembered the newer manifolds changed

design... What brand gaskets do you use ? Think mine is

Fel-pro. J.R.

 

I'm in the same boat. Did mine a year ago, had both manifolds machined together. The intake sealed horribly with just the single piece (I removed the stapled intake one). I put the two piece set back on and one year later I have a minor exhaust leak. I blame myself for not retorquing the bolts shortly afterwards...or maybe my head is bowing that much. I'm doing the gasket job tomorrow...always easier the second time. My exhaust pipe is far from perfectly circular, the metal and sintered metal dougnuts are too rigid to fit my obround exuast pipe. The blue one is crap, I usually buy the shiney composite one. I have terrible sealing problems with those dougnuts... when I start plans on the aftermarket exhaust system for my truck I'll have to ensure there isn't a lot of stress at the union - I suspect the root cause of my dougnut problem. I'm not sure if you have a "Carquest" around, but the shiney is PN F17250

 

Oh I thought you were talking about where the manifold meets the head, maybe you were but that is the best fix for that problem. As for the down pipe from the manifold, mine does not use a donut gasket. I think I would use the sintered metal donut I would think it would be softer and would probably seal better.

 

Hey Pkupman---yes, was talking about exhaust manifold

originally. Just wanted opinion on doughnut, also---didn't

think yours used one... Thanks for info. Wonder how many

others have doubled gaskets. Did you use both intake gaskets

also, or just 2 exhaust with one intake ??? Good luck

Tetraruby with your leakage---let us know how it turns out.

Thanks again. J.R.

 

Did it today. As I suspected the dougnut was the major problem. There were no obvious leaks at the gasket, but I figured while I was at it to replace it anyway. Problem fixed...for now. Sounds a lot better.

 

I used double gaskets on both manifolds. An old timer engine builder told me the best way to install the manifold gaskets is to loosen the bolts that hold the two manifolds together, bolt the manifolds to the block, torque them down, then torque down the bolts that hold the manifolds together. Do it this way and you should have NO problems with intake or exhaust leaks for a very long time.

 

Forgot to mention I use Fel Pro brand gaskets I have had good luck with them, I used them when I rebuilt my engine...3 years ago and no leaks still!

 

i also use 2 gaskets sandwiched together. however, i also used the copper gasket material between them as well as on the block around the exhaust ports and on the header flanges.

not a leak and i haven't even tightened them since

 

This last Spring, had intake/out take manifolds ALMOST out. Couldn't get to that dad gum blot hidden behind the carb mt. 79 300 Inline 6. Left it to someone who said they knew…..Have metal type gasget in there now, but leaking, sounds horrible. Put on new 1 brl Carb, not sure had anything to do with….Really annoyed with same 'helper', who mixed up Alternator lines…*why take alter. out?*
Least I know now to have TWO gaskets on hand. As someone said, Should be easier the 2nd time and without the 'Jeep' helper…..Gggrrrrr
Now where did I put that 2x4 again? Nah, time to cut wood, will MAKE what is NEEDED for helpers!!

 

If you guys want a good exhaust manifold gasket, check out: FORD Header/Exhaust Manifold Gasket

Not cheap but a really good gasket.

 

IIRC some use a Mr. Gasket M260 with good results.

 

Yeah, they are a BIT more. Fall coming fast around here so will put off but save pg for spring, when firewood done. Going to look around for better gaskets also. Good point/option. Not like there aren't other things the old girl needs to have worked on! Thanks for the help, suggestions, yada, yada.
Oh, off topic, but with new carb got 11.4 MPG Pretty damn good for 300 I6 F150, right?
Tinker~

 

I would throw away the oem bolts (since they've been heated and cooled a million times not) and use grade 8 studs, 3/8" 18 thread into the head with copper anti seize compound on threads, and 3/8" 24 thread with a high quality crimp nut on that. I use the mr.Gasket 260, and three years later have zero problems. BUT, I installed by torquing to half torque first, working in an counter-clockwise spiral from center out, went back and torques in same fashion to full spec. After engine is run to full heat, let it cool completely and retorque, and repeat one more time and forget about it.

The gasket in the link looks super. I think the Mr. Gasket 260 costs $25 alone. For $20 more I'd certainly try that gasket.