Hello,

I own a 1973 F100 2WD with a 360 FE and a C6 tranny. When I originally bought it, it had a broken exhaust maniflod bolt, causing it to make a puffing leak sound when it was running. It needed some work anyhow, so I took the intake and both heads off to replace leaky gaskets and head gaskets, while the right side head was off, I drilled out the broken bolt stub and re-tapped the hole. Then I re-installed everything, heads torqued to 85 Ft/Lbs and intake torqued to 45 FT/Lbs per Haynes manual, and I installed 2 new exhaust manilfold gaskets and torqued both exhaust manifolds to 12 FT/Lbs per Haynes manual... to make a long story short, it STILL puffs during acceleration , the same way it did before, from the right side exhaust manilfold, but I cannot detect a leak, what is going on here? a cracked exhaust manifold? or a cracked head? I give up.... lol

 

I'm sorry to say this is why I wouldn't buy another FE engine. I'm real luck however. My 390 is as tight as new. I know the FE's had problems with the intake and exhaust seals. I would think by now that a company would make over sized gaskets to take up the slack. If you don't have a cracked manifold then it has to be coming from somewhere? First thing is to find the leak. Then go from there.

 

Did you get the heads and manifolds resurfaced while they were off?

Did you use 2 exhaust gaskets on each side?

You can find the leak by running a small amount of ATF in to the engine thru a carb vacuum line or pour a small amount slowly down the carb. This will create a whit smokescreen in your neighborhood but it will show every exhaust leak.

 

Unfortunatly I didnt have them re-surfaced, but I am willing to try the ATF Idea to find a leak, and when I do, I will try to use 2 exhaust gaskets instead of 1, hopefully this works out or I may have to have a re-surfacing done. Thanks guys for the info!

 

put high temp copper rtv in between both gaskets and on the engine and manifold side ,if you use two , install with both metal sides facing out that will seal even the worst leak , bob

 

Thanks for the tips guys, thats good to know

 

While you're checking the head/manifold surfaces, check that it's not the donut that's leaking.

Barry

 

i have about 7 exkaust leaks on my truck and it annoys me. I can't wait for some new headers and redoo the exhaust.

 

I took the exhaust manifold off today and verfied that the leaks are coming from the mating surface of the manifold and the head, there were black soot marks where it was leaking, I am going to go with Bob Arrington's idea tommorow and get me some copper rtv to seal it up, along with using 2 gaskets, I think this should seal it up good. I appreciate the help guys!! this is my 2nd F100, I used to own one while I was in the army as a Tank/truck mechanic for uncle sam, that old truck I used to have was immortal!!! never died!! it explains why I purchased a second one to date

 

I have used the hi-temp (red/copper) RTV many times on my 360 and 390's, and never had a blow-out or leak.

Here's my trick:

Take a 330 (or is it generic FT?) exhaust manifold gasket (they usually come in the full gasket set). They are a metal composite, not just plain sheet metal.

First, notice the holes are too small. Cut them out to match the head, and test fit to the manifold to make sure it lines up correctly. DO NOT crease the gasket.

Smear the gasket on one side with red RTV and MAKE SURE YOU LET IT SKIN - this is the most important part of working with RTV - letting it cure for a little while until there is a cured layer on top - that layer stays intact and does the actual sealing - if you don't, it will just squeeze out.

After putting down the gasket to let it skin, do the manifold, same thing - let it skin.

Bolt the manifold to the head, and I had NO problems.

I did this 330 gasket trick with regular manifolds and even my headers. The last time I did it was 12 years ago, and they are still sealed up tight. And yes, it does actually work with headers.

And while your in there, get stainless bolts of a good grade - stainless "gives" more than standard bolts, and you don't have to use the torch (too much) to get them out of the top bolt holes - the design of my headers requires I use those small-headed bolts that came with the headers, on the bottom, but the bottom holes are usually not a problem.

 

Today I took the exhaust manifold off and bought some permatex copper RTV and used 2 gaskets as well, I put copper RTV on all mating surfaces, even between the 2 gaskets like Bob Arrington said, and then bolted it back up and let it dry for 2 hours, then I started it and ran down the street at low speed, I am happy to say that there isnt a leak at all!!! It sounds SOOOOO good now, no more puffing exhaust sounds anymore!!! YAY!!! Thanks guys for the help, I am very grateful!

 

RTV is like duct tape, just more permanent

 

That high temp RTV is good stuff. I have two FE's and it's the only way to go. I couldn't believe it when I first heard it. But it works and lasts.

 

your welcome, bob

 

I was told by a Locktite sales rep to use the Ultra Black for exhaust leaks. I have used it for both my race truck and my tow rig, both with headers and neither with exhaust leaks. Just some input......