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Exhaust manifold needs machining


Rodney_Hamon
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I removed my manifold this am and here is the question. The 4 bolts holding them together are frozen. The butchery done in splitting the exhaust has the welds so close to the bolts I can’t get a box wrench or socket on two of them. I had a helluva time finding a machine shop that will resurface it but found one. Is it crazy to have the mated pair surfaced together so it sits flat up against the block ?   Or do they need to be separated and then machined?  I usually have installed manifolds in the past with the two slightly loose and then tighten. But this one is quirky 

11389802-5EE2-4F8B-BB36-868D20F8DC9C.jpeg

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I had a mess with mine: all 4 bolts were broken off.  The machinist removed them, but I can't remember what he said he did for repair (whether he tapped the existing holes or installed helicoils).  Then, between being warped and probably not bolting together perfectly after the repairs, he had to weld a couple surfaces to build them up, and then machined it all flat.  When I picked it up, it was all assembled with new bolts and machined.  He said to just install it as-is.  Based on that, I'm guessing you'll be fine to just have it machined as an assembly.

 

 

Edited by belvedere
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1 hour ago, Rodney_Hamon said:

I removed my manifold this am and here is the question. The 4 bolts holding them together are frozen. The butchery done in splitting the exhaust has the welds so close to the bolts I can’t get a box wrench or socket on two of them. I had a helluva time finding a machine shop that will resurface it but found one. Is it crazy to have the mated pair surfaced together so it sits flat up against the block ?   Or do they need to be separated and then machined?  I usually have installed manifolds in the past with the two slightly loose and then tighten. But this one is quirky 

11389802-5EE2-4F8B-BB36-868D20F8DC9C.jpeg

No. In fact,nothing else makes sense with your setup because it is NOT a "split" ehaust. It is just a regular exhaust manifold with an extra outlet welded to it.

 

I have no idea why you had a tough time finding anyone to resurface it. Maybe you should ask about getting it surface ground instead of milled?  

Edited by knuckleharley
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I am in agreement that this manifold was butchered. Several machine shops said they didn’t think they had a jig to hold it in place. Some shops closed and others were short staffed that make for long waits. Even Napa let me down. Maybe I should have just brought it in without calling but I live pretty far out of town. But, you two are saying that maybe as an assembly it’s ok to surface. I’m going in tomorrow to try a shop who wants to see it at least. I have another manifold assembly that the 4 bolts will come right out but the rear dump is not in the same place.  Thanks for replying and wish me luck.  

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Machine shops which do a lot of this kind of work are never hesitant to take on this job.

As usual if you have the right tool it is easy money.

They don't have to jig it up and mill it or grind it. It's much easier than that!

They use a really big Belt Sander made for just such a job.

They only use a milling machine to do spot facing of the two manifolds bolt bosses.

 

I've had trouble getting the exhaust pipe to seal at the manifold.

The previous owner had a muffler shop bend up the exhaust and they put a flange which has oversized slotted holes in it.

When tightened it flexes and misaligns so it never seals.

Walker Exhaust makes a two piece bolt together repair flange for a problem flange on GM cars.

I had to modify it slightly to fix my problem. The flared part which contacts the old flange and the flared pipe wasn't flat so I used a belt sander to get it flat. Now it contacts the flange all the way around and since the bolt holes are smaller it aligns much better when tightening. Walker P/N 36132

 

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My machine shop guy would not machine my ex. manifold, says it is too hard and destroys his cutter bits. He sent me next door to the exhaust specialty shop, as Loren stated, they have a large belt sander that trued up my manifold for $40.

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11 hours ago, Rodney_Hamon said:

I am in agreement that this manifold was butchered. Several machine shops said they didn’t think they had a jig to hold it in place. Some shops closed and others were short staffed that make for long waits. Even Napa let me down. Maybe I should have just brought it in without calling but I live pretty far out of town. But, you two are saying that maybe as an assembly it’s ok to surface. I’m going in tomorrow to try a shop who wants to see it at least. I have another manifold assembly that the 4 bolts will come right out but the rear dump is not in the same place.  Thanks for replying and wish me luck.  

Try using a Dremel tool with a small grinding tip to grind down those welds so you can put a socket or wrench on them. Do no more grinding than absolutely neccessary,though.

 

As for the machine shops "not having a jig to hold it so they can machine/grind the surface" goes,they are blowing smoke up you ass by telling you in a polite way "We just don't want to do it." Or even worse,and in YOUR favor,"Weeze jist two stoopid to figger out stuff like dat.",and you are lucky they aren't willing to try/.

 

Here is the reality of machine shops. Their surface grinders and every other machine in their shop is level,so ALL they have to do is level whatever they are grinding in both dimensions,and let the machine tool do the work. Just how freaking difficult CAN it be to figure out how to level a freaking cast iron exhaust manifold? After all,the damn thing ain't what anyone would call flexible.

Edited by knuckleharley
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Years ago the most common tool and technique for resurfacing was a specialized grinding machine.  I had a large, horizontal grinding wheel. That wheel protruded in the center of a cast iron top and the level of protrusion could be adjusted. 

 

  The good thing is that no jigs or holding fixtures are needed so it is quick.  The bad part is that the part will be flat end to end and side to side but may be tapered if the operators skill level wasn't quite what it should be.   Not a problem with manifolds, but quite an issue with heads!

 

Maybe some old machine shop has one of those???

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2 hours ago, kencombs said:

Years ago the most common tool and technique for resurfacing was a specialized grinding machine.  I had a large, horizontal grinding wheel. That wheel protruded in the center of a cast iron top and the level of protrusion could be adjusted. 

 

  The good thing is that no jigs or holding fixtures are needed so it is quick.  The bad part is that the part will be flat end to end and side to side but may be tapered if the operators skill level wasn't quite what it should be.   Not a problem with manifolds, but quite an issue with heads!

 

Maybe some old machine shop has one of those???

I had a local friend in his early 40's that had one of those grinding machines and was still using it when he died a couple of years ago. Brain cancer.

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Rodney,

I took a piece of Flat Metal 6" Wide and about 4' Long and laid it on my garage floor in the flattest spot I could Find.

Then with 80 Grit Belt Sand Paper I (Leaving the Maniflods Bolted together) rubbed the whole heavy mess back and forth several times until I could see I evened the flanges out flat and evenly. Then I went to 160 Grit Belt, then 200 Grit Belt. It goes real fast because the two manifold do all the work - you are just basically guiding them back and forth in quick short motion say 8" to 10" motion. Wala finitute! It is a perfect mating serface done dirt cheap. Drill out Bolts (4 at center) and replace with new ones to make it perfectomundo.

Tom the git er done cheapskate

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Loving all the replies. I took it this am to a small machine shop and he said he would do it. A sole proprietor who does work for local dealerships. Vibe felt good. One machintshop that turned me down said their belt sander wasn’t set up. I agree some did not want to do the job. They are backed up in jobs, along with the guy who I just dropped off my assembly to. I pick it up next week. I ordered a rebuild kit and base gasket from rockauto this am.  Time to be patient once again. I am intrigued with belt sanding my own manifold and I will get a new grinding bit for my Dre Mel and carefully grind around those welds in order to set a wrench on the bolts when I get it back.  Btw, The machinist didn’t think it was an issue to resurface the assembly as a whole.  Strange times we are in that something so basic as it has been stated has become a pain in the ....

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Just so you are aware ;  On the larger engines the four bolts that hold the two manifolds together go all of the way through and have nuts on the bottom . On the smaller engines the bolts  terminate inside of the bottom manifold and often break off and then you will need to deal with that . 

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Tom Skinner, that is a nice looking manifold you got there! I may havta paint mine now. I did not know larger engines had the bolts with nuts. Interesting.  On that subject of the 4 bolts holding these 2 manifolds, I may need to rob them from a spare assembly I have or buy new. My local local hardware store which had a fantastic fasteners section turned into an Ace hardware store which decreased their selection. Where could I buy good replacement bolts ?  And the gasket?  Do I buy some sheet hi-heat material and cut my own?  

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Gasket source and parts # is good to know. Thanks!  Gonna buy different belt grits for sure. Have a good straight edge.  I will search for good grade bolts also.  I’m trying to loosen the drain pipcock in the bottom side of the block as it’s frozen. Gives me angst on this one. I slowly let the water drain out of the 3 bolt holes holding on the manifold prior.  Messy, and I want to correct that.  

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  • 2 weeks later...

Just returned home with my machined exhaust assembly.  Super nice guys but very busy.  I think they felt sorry for me and only charged $50.  .0070 taken off. That’s a lot.  First they put it on the belt sander for short periods of time to keep from heating up and warping. In the end it was taking too much time so they milled the rest. I’m thankful they did it.   I will clean, paint, and install next week.  Everything is set up for this manifold: pipes and tapped holes for the linkage. Eventually I’ll get another manifold to split correctly.  Success. 

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Glad to hear that you had success in getting it resurfaced.  It sounds like you now plan to separate the intake from the exhaust and replace the gasket, check the heat riser valve and likely replace the four bolts holding the two manifolds together. 

 

How do you plan to get those two freshly machined surfaces back in plane with each other when you reconnect the two manifolds?  I suppose you'll install them somewhat loosely onto the block, with the four middle bolts (the ones that connect the two manifolds to each other) also being a little loose, and then carefully snug all bolts in small increments?

 

Another option might be to reconnect the two manifolds to each other (those four center bolts), making sure the two manifold surfaces are flat and double-checking on a granite countertop or a machinist's straight edge (or both) before attaching them to the block. 

 

The first method may be best, since the manifolds will be mated to the block, with whatever inconsistencies it may have. 

 

I just wanted to bring this up, so that you don't just bolt the two manifolds back together and try to install them right to the block, thinking the two machined surfaces are still in plane with each other ("coplanar" is the word I was looking for).  You could crack them if you tighten them up against the block when they're no longer coplanar. 

 

You've probably thought of this, but I just wanted to be sure.

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32 minutes ago, Sniper said:

Matt brings up a good point.

 

One other thing to remember is installing the hardware.  Mopar used special washers and nuts in specific locations to ensure the manifold could move with out cracking as it heated up.  Here's a good thread on that

 

 

I had forgotten all about that.

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