Advice on exhaust manifold removal

[Guest 49 Dodge Dude]

I just bought a 1949 Dodge sedan that I'm fixin' to restore. The exhaust manifold gasket has a hole in it, so I need to replace it. As this is such an old car and it doesn't look like the manifold's been off in a month of Sundays, does anyone have any advise on how to take it off without breaking the bolts or causing any other headaches? Thanks!

[Chris Bamford]

Good morning Dodge Dude

On the '46-'48 Dodge/Plymouths, there is a "hidden" manifold bolt up and under where it cannot be easily seen. It is commonly missed during disassembly and has thus been the cause of many a broken manifold.

You would be wise to post your question on the P15/D24 (flathead Mopar) forum. Those guys are nuts about their old Mopars and will be falling all over themselves to help you out. Lots of other useful info on that site as well.

www.P15-D24.com - Powered by vBulletin

[Guest 49 Dodge Dude]

Thanks - I didn't know about the P15/D24 forum. I'll try there also. You mentioned 46-48 for the hidden bolt - does that apply to the '49s as well? Is there any trick to loosening really rusted nuts on manifold bolts?

[rocketraider]

Plenty of PB Blaster or heat.

I've heard that heating them and then dripping candle wax onto the threads works well- the wax wicks into the threads and loosens the bond.

[ply33]

Thanks - I didn't know about the P15/D24 forum. I'll try there also. You mentioned 46-48 for the hidden bolt - does that apply to the '49s as well? Is there any trick to loosening really rusted nuts on manifold bolts?

The manifold gasket set is the same for all Plymouth and US built Dodge cars with 6 cylinder engines from 1933-59 (and industrial applications to about 1972). Canadian Dodges and the larger Dodge trucks have a 25 inch long block that is closer to the DeSoto and Chrysler engine.

Anyway, the hidden fastener is on the bottom in the center of the manifold assembly.

Do follow Bamfords Garage's advise and visit the P15-D24 web site and discussion forum. While most of the people on there have 46-48 Plymouths and Dodges there are a fair number with vehicles outside that year range too.

[R Walling]

When attempting to remove rusted bolts or nuts, I always heat them quickly to red-hot and then let them cool. Then a day or so of penetrating oil, repeat the heating followed buy another shot of penetrating oil and cool. Then try to loosen with an impact driver (not an impact wrench) if it moves a little, tighten it back up a little and then loosen it up a little more.

Continue this process until the bolt comes apart. Lots of oil and patience.

NEVER try to remove it all the way the first time!

[Guest 49 Dodge Dude]

Many thanks for the advice! I've struggled with rusty bolts before - it is never an enjoyable task...

[ply33]

By the way, the nuts that hold the manifolds onto the block are supposed to be brass. And there are special tapered washers for the exhaust studs that allow the manifold to move slightly as it heats up and cools down. You can get them from Vintage Power Wagons.

If the original brass nuts are on there then removal of the manifold assembly should not be too hard. If some previous owner used steel nuts or replace them with steel bolts.... Well there are words for that.

The tough ones, at least for me, are the four bolts that hold the intake and exhaust manifolds together. If you don't have to open things up to repair the heat riser then just leave them be. If you do break that joint open, then when you are putting things back together you want to have those four bolts loose until the manifolds are firmly bolted to the block so that they line up straight and flat on the block. Then tighten those four bolts that attach the exhaust manifold to the intake.

[Guest windjamer]

On regular nuts and bolts that are rusted bad we use a torch to heat them cherry red and then spray them with cold water and a spray bottle to cool them fast. repeat once or twice and then spray with pb blaster (when cold) and work them with a ratchet wrench.

[Ivan Saxton]

Some penetrating sprays are much better than others. One that was much more expensive was called Reducteur H72; and everyone seemed to stop stocking it here because did not sell fast enough. I found that it was really worth having. The special fine thread narrow nuts that retained the pivot pins for the rear spring shackles in the A model Duesenberg chassis came undone a few minutes after I applied this, when I could not shift then even with heat.

Another technique which frequently works without damage is driving axially on bolt heads with a suitable punch and heavy hammer. This helps the penetrating lubricant. Similarly, if you can shock a frozen nut sideways exactly on as many of the six sides as you can access, the nut is slightly stretched to loosen the thread. You can often achieve the same by heating a frozen nut and the end of its stud or bolt , patiently, to a dull red with the oxy torch. Then quickly and carefully you cool the nut with water so that the stud or bolt does not cool as rapidly. The object is to make the nut contract while the bolt material is still expanded and semi-plastic.

If you have to deal with substantial rust in the thread, it sometimes helps to use a polar penetrant rather than one that is non-polar. Water is a polar solvent and it can be helped by acetic acid (vinegar), or citric acid from lemon juice. Citric acid is also a chelating agent, as is EDTA. These are pretty good for removing bi-valent positively charged ions from the oxide into solution.

You have to assess problems in terms of the principles of physics and chemistry, and make these work for you.

[Guest 49 Dodge Dude]

Excellent ideas, all. Thanks!

[tbirdman]

Actually PB Blaster apparently has good marketing but in real life there are btter things. I know the mag Skinned Knuckles did a test, a PB Blaster if I remember came in quite low in their ratings. I did find a post from another mag called Machinist Workshop that did some testing.

nothing 516 lbs

WD-40 238 lbs $0.25

PB Blaster 214 lbs $0.35

Liquid Wrench 127 lbs $0.21

Kano Kroil 106 lbs $0.75

ATF/Acetone mix 53 lbs $0.10 (1:1 mix)

Looks like I may go into business with the Acetone/ATF mixture.

[Ivan Saxton]

AFT-Acetone is good sense and good science. The polar end of acetone (which also makes it miscible with water) will wet metal/oxide with the automatic transmission fluid, which is an excellent low viscosity lubricant.

[Larry Schramm]

Agree on the ATF. ATF like Dexron has as much as 15% additives to the base lubricant.

[Guest 49 Dodge Dude]

I wonder why someone hasn't taken the ATF/acetone mix, relabeled it and sold it? Seems like a good idea to me.

[Ivan Saxton]

Agree on the ATF. ATF like Dexron has as much as 15% additives to the base lubricant.

Larry, the acetone is probably important, because it acts like a detergent for the ATF onto the metal and corrosion. Obviously you only need to buy the acetone if you have used ATF. (I'll have to get some used stuff from a friend and neighbour who repairs and services vehicles, and tell him the trick too. I dislike automatics and I will never own one, nor do I need to. )

[Larry Schramm]

Here is a great article talking about transmission fluids.

http://www.lubegard.com/pdfs/shiftpointersbyWayne&Pat.pdf