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'36 Dodge D2 Intake/Exhaust Manifold Problem

1936 D2

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Finally, my turn to ask a question!

I had a rather severe exhaust manifold leak (very rear opening) for a bit and finally decided to work on it. My mechanic friend said the whole set (intake and exhaust) had to come off so have the gasket set available for it - and be sure to include the exhaust pipe flange gasket and the intake to exhaust square gasket. We drained the coolant and took all that stuff off (including the carb and auto choke). The manifolds were stripped down of all spare parts except the linkages and they were separated by means of the four bottom bolts. All surfaces were cleaned of old gasket material, all studs were wire brushed so threads were clean. Two at the very back came out of the block and one at the front came out. They were wire brushed their whole length. (Eventually the two long studs were removed from the block and fully wire brushed too). The manifold was sent out for planing.

My experienced mechanic said that the manifolds ALWAYS needed to be separated at the four bottom bolts (by the heat riser) so they could be planed separately and later tightened onto the block evenly. The four bottom bolts would then be tightened at the end to pull the two manifolds together at the heat riser. He said the machinist (with 42 years of experience) would agree.

The parts went out and were planed separately. My mechanic said when he came back that the exhaust manifold needed almost a quarter inch planed off of it to make it flat again. It was warped badly, hence the leak. Not as much needed to come off the intake though to be flat. I started to wonder about that. How would the four bottom bolts fit if the two were planed differently? This is just the reason I asked him, before they were planed, if they should be planed TOGETHER and not two separate pieces. He assured me at that time that they are ALWAYS planed separately.

When they were back, my mechanic drilled out the four bottom holes in the exhaust manifold (only) just a bit, maybe 1/16th larger. He said this would allow for the difference in planing. I set the two manifolds together at the heat riser and saw that the intake manifold face stuck out closer to the block at the bottom of the face but was the same distance AWAY from the block at the top! The mechanic said it would all come together. I then noticed an OLD hairline crack in the exhaust manifold at the inside of the bend, on the bottom of the last header bend toward the block at the back. It does not seem like it goes all the way through. I pointed that out and asked about repair. He said it would have to be welded if it leaked but that would require it to be re-machined as it would warp again. Great!

Long story short from this point (and I can't say unexpected), once back on the block and the radiator filled, the thing vacuum leaked at the top of the intake manifold at the block, especially at the front lobe and there was a severe exhaust leak at the gasket by the heat riser and the gasket could be moved! (Those four bolts were as tight as he felt comfortable with).

The plan now is to remove the manifolds again, tighten the four bottom bolts fully so the gasket at the heat riser seals fully, and have the two manifolds machined AS A SET (like I felt they should have been at the get-go). Then hopefully the whole thing will fit tightly to the block as it should.

OK - now for comments - what do you think of this whole story? Should they be planed together or separately? Does the idea of keeping them together and re-planing sound feasible at this point? (Oh, by the way, the crack was cold fused with "JB Weld" at this time.)

Thanks for any comments!




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First of all, let me say how very sorry I am for your predicament. Second of all, my wife is sorry, too. We both groaned loudly as I read your post. The hair on my arms even stood up. The air was sucked out of our living room by the both of us as I read the awful part about drilling the bolt holes out. Thirdly, you will probably need to find a new manifold set to work with. Last, but not least, I NEVER would have separated those two pieces PRIOR to surfacing them. Maybe afterwards if a gasket was needed. Just my opinion and others may not agree. In any case, I will search for a manifold set for you if you like. John

Let me add that you might want your "experienced" machinist to chip in on the new manifold set. There's a whole 1936 DB engine on ebay right now...$200.00 in Lapine, Oregon.

Edited by keiser31 (see edit history)
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totally agree , why would you seperate them? they have to fit as a set , there may be a difference between "experience" and actual knowledge.....I too would ask for donation from your "machine/mechanic.....I do have a set of 33 dodge as well as 34 dodge manifolds, but I am not quite certain they will fit and I am willing to say I honestly don't know, I would not tell you some thing will work in less I am absolutely sure , I am 1 of those people who hate to spend other peoples money on a hunch"........... "double thinking is free"

sorry to hear your predicament......

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Guest DodgeKCL

I agree with everyone. You've buggered your manifold and will have to find a new set. They should NEVER have been separated at the heat riser box. The faces should have been planed together as one unit. And of course if there is a small crack it would have to bronze welded 1st and then the manifolds planed. I'm sorry but my opinion is to not take these 'mechanics' advise again. Ever. The gasket set BTW is available at NAPA for $9.

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Thanks for all the input so far. The current plan is to take them off again Tuesday and have them re-planed as a unit. I will see if there is someone available in town that can do a TIG weld of the cast iron exhaust manifold BEFORE I have the last planing done. Hopefully that will put the least warp into it.

I had to go with my mechanic's comments at the beginning when he said he has done this same job on a few Willy's Jeeps in the past and all those (except the first one) had the manifolds separated before planing. The first one, he said, had a problem where the manifolds were put back together first and then, with the manifolds being pulled up unbalanced to the block surface, a crack occurred. So ever since he has had them done separated, mounted them very close but loosely to the block, started to tighten the four joining bolts, fully tightened the manifolds to the block and then pulled up the four joining bolts fully tight last. He said this keeps tension balance even across both of the manifolds and prevents cracking.

I still didn't see how they could be machined separately and still fit evenly but I deferred to his experience, compared to my lack there of, and followed along with his plan.

Well, lessons learned. I will be trying to save as much cash as I can at this point by doing the plan as stated in the first paragraph here and see how it comes out. There also have been some delays to this project as the manifold gasket set I had for years turned out to be wrong for this engine. I had to order another set from an eBay vendor (which also came in as the fully wrong set than what the auction said :mad: and then had to wait another 5 days (including weekend) to have the right ones in hand. (I will be checking with my local NAPA next time!) I need to have the car on a show grounds Sept 17th so the pressure is starting.

Again, keep the comments coming if there are any further ideas out there! :o

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Don't wanna be a downer, but I would still be looking for another manifold set so as to start from scratch. After the drilling out of the 4 holes as mentioned earlier and the mis-shaving of the surface AND the crack, you may not be able to correct all of those things without a lot more expense than it may take to find another set that does not need shaving.

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My condensed parts list has inlet and exhaust manifolds (and heat control) listed as one assembly, part #651277. Should fit 36-38 Dodge. Even the detailed D8 parts list only has one part number for the whole assembly. I think it suggests the manifolds should be machined as one assembly.

My advise is to also post your question on the P15-D24 forum - tons of flathead 6 knowledge to benefit from.


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OK. I took the whole manifold set, as one piece, to the machine shop and got the setup RE-planed. (Nice job by the way!) The machinist said he was wondering what my mechanic was getting at when he had them split up to be machined. (But the "customer" is always right!) When I was there with the setup to have it redone he seemed much more comfortable with that. He knew it was going to take a while and was not sure if his equipment would be able to work that much material off (was thinking it may need a milling machine to get it close first) but after further discussion he went ahead. 1/2 hour later it was looking NICE and I was thinking I may be able to pull this off yet!

Back at the car, I could not get the manifold on with the long studs in place. I found the back one was offset about 1/32". That means the warp in the manifold goes all the way up to the rear long stud hole! I took out the long studs from the block and the manifold set went right back on TOTALLY FLAT with the block! (OK - really close now!!!) I was able to hand thread the front stud back in but the rear one was still a problem. Long story short, I finally got the rear long stud in (by using jamb nuts to turn it in) but then, as the inner nut was coming OFF, it messed the threads up on the end of the stud!

So close - only one nut away from success (all twelve other nuts / washers were in place and the manifold snugged up to the block) and FAILURE.

OK, so now I finally give up on the old warped manifold. Tom S, I would like to thank you again for the tip on the where-a-bouts of a NOS MANIFOLD ASSEMBLY! I have made that purchase and it will hopefully arrive next week. (Geez, I feel a little broke now!!!) This is supposed to be the same SET as listed in my '36 Dodge Parts Manual as the "Manifold Assembly". It should bolt right on.

Now I just have to figure out how to get the old set off the engine! It is REALLY on there! Pretty much think I will take out the four heat box bolts to separate the manifolds and try to get them off separately. That's today's project anyway.

Final report later!

Edited by 1936 D2 (see edit history)
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  • 3 months later...

Oops. Sorry for the delay.

The manifold set arrived and was as expected. Brand new, in the original box, still covered in Cosmoline! (See attached). Except it arrived in the evening only two days before the show. So earlier that day I had re-mounted the old set on the car (to make sure it was ready for the show on time), crossed my fingers and started it up. It was a battle to get them on but it worked! No leaks!

I was able to drive it to the show and present the car (with my helper - daughter) to the delight of many show attendees. (See pics). It was a very nice day and sort of a different feel to this show, being in a State Historical Park constructed for public education. We were in "costume" and spoke of the car as in "present day". Fun!

Now it is back in the garage till spring as they have spread road salt already (I don't drive it on the salted roads - ever). I will have time to change out the manifold, carburetor and fix the distributor by the next time it is out! :cool:











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Glad to hear you're winning on both sets of manifolds. That's amazing to find a NOS set! 2wks ago, I had a stuck heat riser and pulled the manifolds off, got a busted stud in the block, and one in the intake too! The grinch came to my house early.:(

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