Exhaust Manifold gasket job 3838

Billccm · Oct 3, 2017

Hello:

I'm going to start the next job on my Road Runner of replacing the exhaust manifold gaskets. Plan is to remove the manifolds and have a machine shop check the decks, then reassemble with either copper, or good quality FelPro gaskets.

Other than soaking with penetrating oil a few weeks before I dig in, any other advice, or tips? This is a job I have not performed before, and will call in help if I get stuck, but looking for any advice for a newbie in this area.

Thanks, and have a nice day.

moparnation74 · Oct 3, 2017

Originally, there was no gasket used but I have not been brave enough to attempt that....Especially, on these old manifolds..

For me was staying to near original look and takes a keen eye to be able to notice I have a gasket. I took a fel pro standard metal gasket and cut it down for each port/ports area. Sprayed both sides with copper sealant and slowly tightening while alternating around until full torque was reached. Don't crank one bolt down and then jump around. Be sure to let it sit up 48 hours before firing it up...

If I was not staying as close to original. I would use a copper gasket IMHO but the tightening process is the same for any gasket....

I also placed anti seize to the outside threads of each stud....

If any of your studs come out with the nut or are loose....I use Indian head sealant when I replace them....Also, check the ones in the water jackets if you see any stain/leaking.....

miller · Oct 3, 2017

moparnation74 said:
Originally, there was no gasket used but I have not been brave enough to attempt that....Especially, on these old manifolds..

I checked both my head surfaces, and HP manifolds, all was within .001", so no gasket.
Seems to be working fine, no leaks.

moparnation74 · Oct 3, 2017

miller said:
I checked both my head surfaces, and HP manifolds, all was within .001", so no gasket.
Seems to be working fine, no leaks.

Good info and thanks for sharing......I haven't been brave enough to attempt that....

miller · Oct 4, 2017

Sure thing. Do need a surface bar, or some way to accurately check it. I have my own.

Billccm · Nov 20, 2017

I finally got around to tackling this job. As an experiment, used a homemade penetrating oil (see link below).

https://www.engineeringforchange.or...2015/12/ENGR103-WD40Alternative-FinReport.pdf

I used a gun oilier bottle with a needle dispenser and a flux bottle to apply the homemade penetrating fluid. Flooded the long tube nuts and threads every evening last week. Drove the car Saturday morning and got it hot, brought it back to the garage and soaked again.

Sunday afternoon soaked once more and began the job.

Drivers side everything broke loose and could disassemble with just fingers. Exhaust pipes broke loose easily.

As with every job I tackle, there is always a show stopper. The passenger side has one of those tube nuts that will not budge. I tapped, soaked, tapped, soaked for two hours. Can't break it loose. Really trying to avoid breaking a stud.

I guess heat is the next step?

miller · Nov 21, 2017

Billccm said:
The passenger side has one of those tube nuts that will not budge.

Not typical, but can happen on those long nuts. Either rusted, or threads are jammed.
Might try tightening first, then see if it will back out. If the stud comes with it, so be it, as long as it doesn't break.
Too many times those dang nuts are one run, then needs to be replaced. If the stud does break...operate.

Billccm · Nov 21, 2017

Thanks, Miller. One of my Mopar friends came over and we got the sleeve nut out. We tried some heat, more atf+acetone, tapping, etc, etc. He had a really nice Cornwell tools flex ratchet with a long handle, and finally we just man handled it and it broke loose. Stud did not break thankfully.

I've ordered from Mancini a manifold fastener kit with new studs, sleeve nuts, nuts, etc.

Going to check for flatness and see if the manifolds need decking. I've also ordered REMFLEX gaskets.

Hopefully all will go well getting it back together.

5wndwcpe · Nov 22, 2017

The last motor I did I did I used high temp RTV and no gaskets. Follow the directions and wipe off the excess. No leaks and no worries, just a re-torque after a few heat cycles.

beanhead · Nov 24, 2017

The remflex gaskets will work good with no sealers, even if your surfaces aren't perfect...at least they have for me in the past

Billccm · Dec 13, 2017

So, looking for some tips on torque for these remflex gaskets with my stock exhaust manifolds. Remflex states 20 ft lbs which is straightforward, yet I can't get a torque wrench between the shock tower and two of the nuts on the passenger side. I assume you just 'hand tighten until it's tight'? I guess this is where the men get separated from the boys when you have that intuitive feel for tight enough.

Trying to get this job done before Christmas.

Thanks for all of the help and advice.

oldbee · Dec 13, 2017

Well 20# isn’t all that much, “snug” with a 6-8” handle(wrench/ratchet handle) with a tad more? My 68yr old ‘torque’ elbow knows almost exactly where it’s at! Seriously it’s not a whole lot from snug.

beanhead · Dec 13, 2017

Yeah, I got them tight as was comfortable with a 3/8 wrench...then re-snugged after a good heat cycle...20 is fairly firm with a small wrench, not gorilla tight though (wear thick/leather gloves if you have them you can get a little more power..)

Billccm · Dec 17, 2017

I was amazed at how great these remflex gaskets worked! I really like they way they seal. The manifold crushes the gasket oh so slightly and seals easily. What a fantastic product. I started the car after the job was completed and just loved the sound of a leak free exhaust. Thanks for all of the help.

MoparGuy68 · Apr 12, 2020

Billccm said:
I was amazed at how great these remflex gaskets worked! I really like they way they seal. The manifold crushes the gasket oh so slightly and seals easily. What a fantastic product. I started the car after the job was completed and just loved the sound of a leak free exhaust. Thanks for all of the help.

I think I am going to put stock HP Exhaust Manifolds on my car, like you have on yours. Is your Road Runner a 383?

I already have a set of Remflex gaskets (RFL-6002 Mopar V8 Big Block) that I bought to go with my headers. I also got Permatex High Temperature thread sealant in a small tube. I already put the sealant on my 4 studs (in first and last position) that I mounted in the heads in preparation for mounting my headers. Since I now cannot use the headers, I will be getting a Manifold Fastener Kit from Mancini Racing.

Here is my shopping list:

Mancini Racing Exhaust Manifold Flange 2.5”
#MREHFAX0029-250 $11.95 each ($23.90 pair)

Mancini Racing Exhaust Manifold Flange Gasket
#MREHF029 $7.50 each ($15.00 pair)

Mancini Racing Exhaust Manifold Fastener Kit
1967-74 Big Block 383/440 B & E Body Only
#MREHF8065 $38.95

Are these Mancini items the same parts that you bought for your Road Runner?

Did you make sure your header exhaust port surface was totally flat. Mine has some of the paint worn off of it, and carbon deposits here and there. I wonder if the Remflex would seal to my surface as seen in the photo, of if I will have to try scrap all of that off with a razor blade or some other scraping tool?

My existing exhaust pipes bolted up to 3.5" header collectors and are welded to the input side of Flow Master mufflers. I will need to have new pipe run from the manifold exit flanges to the mufflers. I hope the existing pipes can be un-welded from the mufflers and new pipes welded back on to them.

Billccm · Apr 12, 2020

Yep I've got a 383 and am in the minority of preference of exhaust manifolds over headers. I used felpro flange gaskets with a generous bead of ultra copper.
One of my manifolds is flat and the other was slightly warped. The remflex sealed great. Don't over torque.

5wndwcpe · Apr 12, 2020

Remflex gaskets do work well but be forewarned, they're fairly thick and you might need longer studs if you plan on using the stock wire looms. I ran into this on my Sport Fury GT.

beanhead · Apr 13, 2020

5wndwcpe said:
Remflex gaskets do work well but be forewarned, they're fairly thick and you might need longer studs if you plan on using the stock wire looms. I ran into this on my Sport Fury GT.

Yes great point....AND as good as they are, their one drawback is they are very fragile. Be careful not to bend, drop or smash them inadvertently. Just need to be a little extra careful, once they're installed they're awesome..

Exhaust Manifold gasket job 3838

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