New TC exhaust manifold not plane

martinblum007

martinblum007

New Member
I bought a new-old stock TC exhaust manifold off EBay. When it arrived I noticed that it wasn't perfectly plane :? . It drops off on the final zylinder by about 1, or 1.5 mm. I then brought it to a plateing company to have it put in the acid bath to get rid off any surface rust. When I discussed my concern with the plateing company they reckoned that this kind of tolerance should be compensated by the gasket. I am though still a bit apprehensive about fitting it. Can anybody reassure me about what kind of gaps the gasket rings can cope with? Thanks again for your much appreciated comments.
 
Certainly not 1.5 mm! Perhaps 0.25 mm. But I'd prefer you not to be able to measure it.

This goes to the heart of the problems with the TC exhaust manifold. It would appear that as constructed, they are not properly stress relieved after the welding. Plus it is also common for them to be assembled to the car in such a way that the exhaust system is able to apply further stress to them.

So first of all, I would take the maifold to a competent welding specialist - not necessarily an exhaust specialist, although it could be. Have the manifold as is stress relieved. This is likely to include cooking it at high temperature in an oven. See what the mating face looks like afterwards. If still obviously not true and flat, have the mating face skimmed by a machine shop. Then when you come to fit it, be prepared to have to modify the exhaust system to make absolutely sure that the system simply lies up to the manifold without any pulling, pushing or twisting. Plus make sure that small movements of the manifold, engine and system are possible in all directions, to cope with the engine shifting on its mountings as you drive.

And you thought you'd just be able to bolt it on!

Sorry!

Chris
 
chrisyork said:
Have the manifold as is stress relieved.
Click to expand...

Thanks Chris. Not the news I wanted to hear but think you are right. Would you expect the mating plate to straighten up under heat? I just think that having it planed, especially with the exhaust stubs in the way, will be a difficult and probably expensive job.

Has anybody on here done this?

Thanks
Martin
 
I can't see how you're going to find anyone who can plane across the whole length, but around the ends of the pipes that locate the sealing rings.
 
I was thinking the same think as Harvey. Wondering if it might even be cheaper to get one made rather than sort things out or try and buy another one?
If it's running out just at the edge of the mating face, you could maybe trying fitting it to see if you get a good enough seal round the copper gasket washers - it might work OK?
 
Wondering if it might even be cheaper to get one made rather than sort things out or try and buy another one?
Click to expand...

Normally I would also look at this option. It is only that I paid £ 150 for the manifold and then unfortunately £ 70 to have it acid bathed and plated. So now I have this beautiful shiny thing that is slightly off, I really want to rescue it.

I am not sure I quite understand the option of just plaining around the exhaust stubs? So if I milled down around each, well 3 of the 4 stubs, of say 1,5 mm - would that not result in the washers just being partly compressed? Would that be ok? Difficult to talk about without drawing it...

Thanks
Martin
 
I would give it a try, nothing to loose. I have just renewed the crush rings on mine. It has a genuine Rover exhaust manifold and its not true as the rings were not crushed equally. I only changed the rings as I had to remove the exhaust to get at the side plate.
 
Chrisyork above has nailed it.

Branched exhaust manifolds need to be carefully assembled in the factory with close attention paid to sequential welding so as to minimise heat-induced stress and distortion. Each finished part should then be QC tested for alignment on a gauge before being packaged for shipment. Assuming this NOS part was knocked out under the strained industrial circumstances prevailing 30-odd years ago it's not surprising its one of those "Good enough, Jim" parts who escaped into the market: indeed, this could also explain why this part was never fitted by a chain of its previous unhappy owners.

A custom exhaust fabricator would be able to make a new manifold - no problem.
 
I bought a second hand TC manifold off eBay that had the exact same characteristics - I just stuck 2 sets of exhaust manifold gasket rings around the offending cylinders, that was couple of years or so ago, it's been working fine ever since.

Cheers,
Bri.
 
If you wanted to go to the trouble, I'd drill a heavy plate, or use an old head, to line up with the manifold, loosely bolt if together, get out the gas torch, heat up the offending branch red hot and tighten everything up.
Cheers
Tony.
 
I've wondered this before... anyone know what would happen if you cut the plate into 4. Each section would be held by 2 bolts with a little more flexibility than the single heavy plate. But would that be a good or bad?
 
anyone know what would happen if you cut the plate into 4
Click to expand...

Mmmmm - out of the box - genius? Maybe I would actually just section off the one offending cylinder exit. Basically 3 of them are pretty true. It drops off after cylinder 3. So as you say, possibly just cut that section and tighten it separately. The tube is quite likely to have enough give to allow that section of the mating plate to bolt tightly to the cylinder head.
Does anybody know why this is not a good idea?

This is the manifold which should explain why I want to safe it. It turned out far more shiny than expected. I only asked it to be rust proven.....But it also means that if I put any extreme heat to it, it will flake.
 

Attachments

  • manifoldp6tc.jpg
    manifoldp6tc.jpg
    68.4 KB · Views: 568
:shock: That looks glorious.........truley blinging........... needles to say I like it.......you've got to get that on :mrgreen:

I would go with what brian surgested "manafold gasketts"
 
+1 for Brians approach :D

Cheap as chips option with no bling loss 8)

What's the worst that can happen? :mrgreen:
 
I did cut the 4th tube in the end and had it installed last week. I am very happy to report that it worked and it is running well. I also had a stainless exhaust installed at the same time, so the whole thing looks and sounds very good indeed. So, happy in the end :D
 
Result! But you should make especially sure that none of the exhaust joints or mounting points are putting any kind of strain on the manifold as this will cause it to crack at the welded joints as I found out with Bruiser who cracked two manifolds for me before I spent an afternoon hanging the exhaust properly. If you didn't fit the exhaust then it's really best to do it yourself. I can't quite remember the procedure but I'm sure Harvey wouldn't mind reiterating the advice he gave me. :mrgreen:
 
Glad to hear of your success Martin.
I welded up the cracks on an otherwise decent manifold last week. This one was fairly straight, but to keep it that way I bolted it tightly to a scrap cylinder head (without the doughnuts) before welding and am convinced that it made a difference.
Trouble was, when I fitted it to the car, the lower end was too close to the engine for the rest of the exhaust to fit. I had to use some gentle pressure from a scissor jack to bend it outwards. This actually worked without further cracking and the next pipe now fits perfectly with no strain anywhere, so hopefully it will last a while.
manifold1.jpg

manifold2.jpg

Incidentally, as you can see in the top photo, I hadn't fitted the sleeve that takes the hot air duct. I only remembered it after refitting the carbs which had to come off again for access to the bolts. :x
 
You must log in or register to reply here.
Back
Top