My 1971 Ford F-600, 300 c.i. in-line 6 cylinder has blown an exhaust manifold gasket on an overhauled engine with less than 3,000 miles on it. The gasket on this model has the intake manifold gasket laid on top of the exhaust manifold gasket, making that area thicker than the rest of the gasket so it seems like the exhaust gasket area cannot be tightened as tight as the intake area. What would be wrong with removing the intake manifold gasket, applying some good high temp sealant in place of the intake gasket and putting it back together?

 

Moved to the Ford Inline Six forum.

 

Many Fords do not use an exhaust gasket. Check both your manifolds for true, and see if it will bolt up with just the intake. I would want a gasket for the intake, not just goop in there.....

 

you're gonna need a gasket...hands down. unless you want to run into other headaches down the road. the engine may have been "overhauled," but without exact definition, the word itself can be meaningless. as much of a hassle it may be to remove the manifolds, do it. use a good straight edge to check how true they are from runner to runner with feeler gauge. if its not warped too bad, a machine shop should be able to straighten it out with a couple passes on a flat belt. a manifold stud kit helps the installation, especially if you're doing it by yourself. snoop around and find a good gasket...you get what you pay for. torque it all down to spec, run it, let it go thru a few heat cycles and torque check. factory thick manifold washers are the way to go, even when using a stud kit. yank them out of a stock setup at the junkyard. using a light coat of sealant to help hold the gaskets in place for installation can be helpful, but I've had better luck installing them clean and dry. if you have any other issues/questions, shoot me a PM. i'd be glad to help. best of luck to ya!

 

I had the manifold(s) off when I started this thread. They are cast as one unit. The gasket that was put on after the engine was rebuilt (pistons, rings, inserts, main bearings, valve job, oil pump, seals, etc.) and the gasket on #2 cylinder was blown out at the bottom of the manifold. I had purchased a Fel-Pro gasket and after exploring the internet for answers on how to prevent this from happening again I decided to fight the temptation to take off the thin, extra intake gasket and put some Permatex Ultra Copper sealant on the exhaust gasket. If this doesn't work, I will order a copper seal gasket from Mr. Gasket. Thanks for your input.

 

"They are cast as one unit."

Not so on 240/300 engines. The intake and the exhaust manifold logs are bolted together under the carb area but are not cast together as one unit.

 

Some have reported having good luck with installing the factory intake and exhaust manifolds somewhat loosely bolted together. Once positioned properly, the bolts under the carburetor area [as mentioned by Harte3] can then be properly tightened.

 

Good to know! I had never disconnected the exhaust pipe from the manifold and did not see the bolts that held the two manifolds together. Tightening them individually would be the way to go. Many thanks!

 

That would be the right way to go. Thanks.

 

there is an appropriate torque sequence in the engine manual. wouldnt be hard to find a pdf or jpeg of it online somewhere. it may seem excessive, but it will help.

 

Thanks, Dude; According to the Chilton manual, the bolts are supposed to be torqued between 13 and 18 ft. lbs. starting from the center and going out to the ends. That didn't seem like much but I tightened them a "strong" 18 ft. lbs. using the sequence they suggested. After letting it sit for approximately 24 hours, to give the K&W Copper Coat high temperature sealant a chance to dry, I started it and let it idle for several minutes then re-torqued them. No leaks, yet but it way too soon to tell if it is going to stay fixed. Do you think I should re-torque them after a few hundred miles? I might torque them again when the engine is cold. Do you think it makes any difference - hot or cold?

 

be careful when using terms like "retorque." it generally suggests completely breaking torque on the fastener and then torquing them to spec all over again. i think a torque check will.be more than enough for your application. to answer your question about temperature...yes it makes a difference. the torque specs listed in factory manuals generally apply to cold torques, unless otherwise specified. metal, and just about any matter will expand as temperature increases...if u torque it hot, as the block cools down, the potential for leaks increases. on the other hand...if its torqued properly cold, then the leaks most definitely will remain closed after she heats up. you're headed in the right direction, and using your resources...you'll be good to go. take your time, pay attention to the details and it'll turn out just fine man.

 

Upper pic.

Notice that while there's an intake manifold gasket (9461), there's no exhaust manifold gasket...as Ford never installed one. It was 'metal to metal' as original.

 

" Do you think I should re-torque them after a few hundred miles?"

That is something that certainly does no harm at all. I usually recheck the torque at about 500 miles and about 1000 miles.

 

Bill, Thanks for the beautiful pictures. The only problem is this is not the engine I am working on! Is it possible the engine has been changed at some point?! The blown gasket I took off has 12 holes in it, six for the intake manifold and six for the exhaust. The gasket I replaced it with - Fel-Pro #MS90157-1 INTAKE & EXHAUST SET, from O'Reilly's - has 12 holes, just like the old one. The application on the box it came in says: FORD Products 6, 240, 300 Eng. 1965-86 (Int. & Exh.). Your illustration says '65 to '72, Fel-Pro says '65 - '86. The Fel-Pro fits so I have to believe the illustration is wrong. Not the first time "the book" has made a mistake. We just keep on learning, don't we? Thanks. PS I have another problem with this engine. When I disconnect the vacuum line to the distributor it idles fine (timing is right on the mark) but when I connect the vacuum line it idles way too high and the timing mark cannot be found! Is the vacuum diaphragm "shot?" Should I start a new thread for this question?