Hey
I am pretty new to this list and everyone has been awesome about helping me out. So thanks

If you saw my post yesterday you know I am in the middle of a super six conversion and was pretty flustered to find out my exhaust manifold was warped as I went to put it on the head for a test fit.

I have been milling through my options and thought of one low cost possibility that might allow me to be on the road very soon.

I have a big honking drill press in my shop. My manifold is just barely too short to fit on the end studs in the block. What if I drilled out each of the end mounting holes on the manifold ever so slightly stepping up the hole size until it is just enough to fit onto the studs?

I know warpage is also bad beacuse it reduces the ability to seal between manifold and block but I put the manifold on a piece of glass and used a feeler gauge to check the clearance between the flanges (ports) and the glass and it looked pretty snug to me. There was about .01 gap on one or two of them but it just didnt seem too bad.

So, I am curious as to the opinion of the seasoned vets out there. Should I drill it out and move forward or should I source a new manifold, go to a header etc.

Thanks in advance

Dr Wheelie

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Dr Wheelie

Oh I forgot.
When test fitting the manifolds to the head, what is the acceptable amount of space that one can have between manifold and head to feel comfortable with the abilit of gasket and sealer material to keep a nice seal going?

Thanks
DW

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Dr Wheelie

It sounds like this manifold can be made to work.
Use the gasket as a template to try to figure-out where the warpage is, is it mostly on one end or split evenly between both sides?

Once you know how it is warped you can adjust by grinding-out the holes in the proper direction(s).
One trick I have used is to file on the heat riser mounting area in order to change the relationship between the intake and the exhaust ports. Most of the time I end-up taking some material off the outer - forward corner / edges so the rear intake ports are raised to follow the warped exhaust ports. (usually the end exhaust port(s) drifts higher.

It is "widdle and fiddle" time, with a grinder and a big flat file, you should be able to get this unit to match-up. Use some high temp. sealer when you assemble and follow all the little tips in the manifold install article, screw this sucker together.
DD

Cool
I am glad to hear your positive thoughts about this problem.
I can do the drill out easily enough.

I would like to try to avoid any extra grinding though.
I dont have an air powered die ginder and it makes me nervous to remove too much material. Also, I am not sure exactly where to grind or what warpage looks like when you compare the head to the gasket.

My question is, what is the upper limit of tolerance between manifold and block in terms of gaps where manifolds mate to the block?

Once drilled out I plan on loosely assembling the 2 manifolds and test fitting them, using a feeler gauge to check for possible areas where there will be a sealing issue. Problem is, when it comes to space, I dont know how much is too much.

I am really into doing things right the first time and I dont want to build this thing all back up only to find an exhaust leak or intake leak.

-DW

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Dr Wheelie

I suggested warpage inspection and selective die grinding just to reduce the amount of material removed. The holes on the end "ears" can get pretty close to the edge and will sometimes crack open.

As for sealing, dead flat and clean is always best but as you know, the gasket and sealer can take-up the some mis-match, it is really hard to say how much will create a problem but .010 should be fine.

Again, a big - long flat file does wonders, show you where all the high and low spots are and allows you to work the high spots down some.
Give it a try.
DD

I wish the block to manifold sealing was the issue because I am fine in that area.

It is the gasket and port to manifold match that seems to be the issue.
Upon playing with the gasket and the manifold on my bench, it became clear that there is no way to make the ports line up to the gasket. If the front ports line up, the back ones are shifted out and down and if the back ones line up the front ones are shifted down and in. The scary thing is that it doesnt matter where the end holes are, even when they dont line up with the end holes in the gasket so that I acutally have more play to make adjustments, there is no way to line the gasket up with the ports.

This just seems way out of whack to me. Guess I am going to have to begin looking for a new manifold, no?

I am actually thinking of getting a mopar performance header (there is a guy perptually selling them on ebay) and a lokar throttle, kick down set up and running an open choke on the thing.

Its going on a 76 volare that I dont see us using for more than a few more years at the most (no ac and we live in Lousisana) so long term issues arent as much of a concern.


Thanks for any advice

Dr Wheelie

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Dr Wheelie

Look back a few weeks worth of posts and you'll see I had the same problem with an exhaust manifold I bought at the boneyard (second one)
I wasn't as educated about this as you and Doc are, so I suspected the manifold was off a different size block. According to Doc, the heads are all the same size for 173, 198, or 225. My holes don't align by about the same as yours, 1/4". I thought about superheating the rear runner and trying to "bend" it back into position, after all, that's how it got that way, right? I like your idea much better, wallow out the stud holes to give more room to align everything.

Sounds like what Doc was explaining is to mate the gasket to the manifold in a "best fit" configuration, then mark the location of the port holes and grind out the interfering material. Am I close, Doc?

I think I'll spend a little time trying that first, before I start looking for another (third) manifold. I've already had my machinist resurface this one, and I sandblasted and painted it already. What a waste, if I can't salvage it.

Jerry

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There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Your idea sounds good. I just hate to grind away on my block to fit a messed up manifold. If you ever want to use anything else in the future, your block will then be permanently altered to fit the warped piece and say a nice new offy dual weber conversion would not fit right.

I always get wary grinding away material becuse it shure as hell is hard to put back.

I may go with a header although I have heard they have problems of their own with sealing and flange warpage.

Anyone else have some thoughts here?

Dr Wheelie

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Dr Wheelie

You got it.
You need to get the "best" alignment you can and start grinding away any interfering material. Be sure to bolt-on the intake without a gasket to see how those ports align and split the difference on the warpage. As noted before, some adjustment between the two manifolds is possible by grinding at the heat riser mounting surfaces.

If the manifold is badly warped it is hard to get good gasket "crush" so it is better to find a different unit. Doing that just save you time and effort plus you get more gasket contact surface so the gasket won't "blow-out".
DD

Oh, so you grind the manifold to match the gasket, you dont grind any of the block at all.

I think I get it now.

Nothing to lose but time since the manifold is pretty close to junk already

What makes the best grinding tool? Air powered die grinder I am guessing.

-C

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Dr Wheelie

Ok
I looked at it and looked at it and there is just no way to make it work.
Even getting happy with a grinder wont work because the front and rear "arms" are so far from being horizontally aligned that there is almost no way to get the gasket on there and matched up.

Hi Ho Hi ho off to the boneyard I go. (unless someone has a good super six manifold for sale!)

Dr Wheelie

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Dr Wheelie