Truck:
F-250 Camper Special
390 v8 c6 Trans

I am not exactly sure just how many times I've replaced the exhaust manifold gaskets on this truck over the years but I know it has been several times.

I believe I have changed them for the final time. I used Remflex Gaskets and I think they are what I've been looking for. [No, they're not! They failed and Remflex did NOT stand behind their product and their customer service was very poor]

REMFLEX Exhaust Gaskets: Home Page

I don't know what the problem is but I understand that it is endemic amongst 390s. Perhaps the manifold had warped. Perhaps the bolts were old and stretching. Perhaps all the gaskets out there were just so much CRAP.

I replaced the gasket in stages. I did one side when I had the time and then (about a year later) I did the other side. The second side (driver's side) actually went pretty smoothly. I applied my favorite penetrating oil and patiently unscrewed the manifold bolts. Regardless of what gaskets you use I highly recommend getting new bolts for the manifold any time you replace the gasket. Few things suck more than rounding off the head of an exhaust bolt as you try to remove it.

Some tricks I learned:

- 14mm is a little snugger fitting that the 9/16 and can make a bit difference on rusted heads of 30+ year old bolts. And of course use 6-point sockets!

- Do not simply unscrew the bolts. If the bolt rotates at all you are almost certainly going to get it out but there is all sorts of rust and crap between the bolt and cylinder head threads that can build up and wedge the threads so the bolt won't come out. The secret is to rotate the bolts in and out to wear the rust and stuff down. On the bolts that were stiff coming out I'd rotate out until it felt stiff and then back in until it turned more freely and repeat until the bolt was out. It took a while to get some of the bolts out but not nearly as long as dealing with one that broke off.

- CAREFULLY run a tap through the top bolt holes and any others where to bolt was hard to get out. It is easy to cross thread with a tap but if you take your time you should be fine and the results are worth it. Be sure to use lots of oil. If you don't have a tap and can't afford to buy one I'd recommend taking a grade 8 bolt and filing it into sort of a chase bolt and run it it through (also with plenty of oil). The rule with removing the bolts applies here. Turn the tap or chase bolt in about a turn or so and then back of about 3/4s and repeat. Again it is slow but having smooth threads for the installation and any future removal is more than worth it.

- On one bolt the head rounded off and it simply WOULD NOT BUDGE. I applied heat and penetrating oil (I've read elsewhere on this forum that you can heat it up and melt wax into it. I wish I'd thought to try that) but it did not seem to make a difference. What it took was patience and a REALLY good grip on the bolt head with some vice grips. I then spent the next 45 minutes pushing and pulling, back and forth on the vice-grips with my upper body weight. The speed was just over one second to push, pull, push, pull. In fact about as fast as you can comfortably say, "push, pull, push, pull . . ." is about how fast I did it. Over time the vice grips wore into the bolt head and I had to re-tighten them so they wouldn't slip. Eventually the bolt turned, just a few degrees. At first I thought the head had split from the bolt shank. This is the point where you really need to be patient and follow the stiff bolt removal procedure I outlined above. This is also where the penetrating oil really makes a difference. Drench both ends of the bolt thread with oil (I prefer GM Heat-valve Lubricant but I don't think it matters much). As you rotate the bolt in and out it will help move the penetrating oil into the threads and help prevent the build up of crap and rust from galling the threads as you remove it.

- Hose all the holes out real well with Brakleen, and blow them out with some compressed air.

- Slobber a good coat of anti-seize on the NEW bolt that you put in. This will make all the difference in the future (I can't believe I forgot that! Thanks Slip ford man).

- Finally, use Remflex Gaskets. They are the Shizznit. They aren't cheap but neither is my time and I'd rather do the job once. [But if you want to do the job once you CANNOT count on REMFLEX gaskets or their customer service. See my post on page two.]


At this point I think the next time I take off the manifolds it will be to put headers on.

The manifolds are sealed up with no indication of a leak wanting to form. By now they would be starting to leak again.

The engine is so much quieter when it runs that I've heard some other things that need attention and been able to address them

That's what I learned. I hope someone finds it helpful.


Cook

 

You could save yourself from a lot of future problem's by applying a "never seize" type high nickel thread paste. Through out the years, I have always used a thread treatment on most bolt up operations, it really is a joy a few years out when you got a wrench back on it...thanks for the gasket tip!

 

I can't believe I forgot to include that but ABSOLUTELY. I added it in above so that post will be complete.

Cook

 

I should talk about the gasket. First off MADE IN USA.

It is thick, like an 1/8" or 3/16" and crushes down to about half of that. It is made of graphite and looks like it would be able to handle temps far higher than what a correctly set-up truck would put it through. They say longer bolts are not needed.

According to the propaganda on the package it is supposed to fill in warped manifold/cylinder head surfaces as well as pitting and so forth.

They look a little goofy after they've been torqued down and run a bit but the instructions say you can trim off the extra.

Instructions also say no re-torque is required. I followed these directions and, like I said, had no problems.

Cook

 

great post. thanks.

 

After replacing my exhaust manifold gaskets once a year, even after resurfacing the manifolds, I put in a set of Fel-pro metal heat shields with on other gasket. I have had no more problems now for over 5years. The engine is a 66 T-bird 428 in my 64 Galaxie.

 

I've used Remflex gaskets on my 390 with headers before. Remflex claims when you torque them down half-way they will rebound back 30 percent to help seal the surface. They worked good for a while, then I had to go back and retorque them again. I ended up replacing them when they started to look a little too squashed. But yes, they are good at handling the high temps.

OJ

 

Good point. I have no experience with headers and these gaskets. Just to make clear, my success was with the stock, crap flow manifolds.

Yeah, they look pretty squashed but they aren't leaking.

Cook

 

Thanks, my pleasure.

Cook

 

Good post about a good product.

Back in rhe day we got into the habit of glueing two gaskets together with 3M trim cement and then installing, this was mainly for headers or any application on cars that had leak problems. After the engine was run for a while, up to operating temperature and back to cold, we would re-torque the bolts. I don't recall ever having a problem after that if the procedure was followed exactly.

 

huh, I didn't remember seeing the Remflex advertisement here on FTE.

 

I must be missing something or else had very good luck .I had trouble getting my exaust manifolds to seal with gaskets after I went through my engine .I had my manifolds surfaced and mounted them with no gaskets prior to having a well thought out custom dual exaust system installed .So far no leaks .

 

Very informative post, for the 14mm socket, and the working of the bolts, thank you.

I have one slight issue and that the 1975 Ford F-250, Trailer Special, came with air conditioning and I am having issues with the last bolt; the one at the back on the top, I removed the exhaust pipe connection and still cannot access the bolt from below or above because of the evaporator. Apart from having to take apart my evaporator is there an easier way to access the above mentioned bolt?

 

My 75 does not have A/C so I don't know of any tricks. I will say this, getting the access you need is worth the time. If you have to disassemble the evaporator then that is what you have to do.

Good luck,

Cook

 

Yes, I am going through growing pains trying to sort out issues with the truck, from a blown power valve, cracked distributor cap, three missing bolts on the secondary throttle plate, over sized jets: Calgary is 2500 feet, sticky fuel float on the Primary, Accelerator pump leaver out of adjustment, too weak of a secondary diaphragm spring, and then finding the exhaust leak while I was setting up to do a compression test. I love my Ford.