Sealing Manifold to Head

[oldtuckunder]

As I'm waiting for the new crank, turning attention to a few other problems emerging from the strip down.

 

It appears from the soot marks that I have a minor exhaust leak on three cyls where the manifold joins the head.(pic attached)

 

 

It obviously wasn't major as I never heard anything, and there is a posibility that it occurred early on after fitting and a subsequent nip up may have cured it. But as gas getting out also means air getting in, it may mean my AFR readings are being affected so on this rebuild I'd like to ensure that there isn't a leek.

 

The manifild is tubular, so like all tubular exhausts getting all the bits 100% paralell is almost impossible. Plus the fact on the MK1 head everything is held with clamps that act on both the exhaust and inlet manifold, so its possible that whilst the inlet side is firmly clamped the exhaust might not be quite so tight.

 

In the past I have only ever used grease on manifold gaskets, it usually works and even means at times (as it did this time) that the gasket is still good when you remove the manifolds again. But looks like I need to sacrifice that possibility for a better seal.

 

Any recomendations for a high heat resistant jointing compound that wont bake on like concrete, possibly with a bit of flex to allow for expansion & contraction?

[peejay4A]

I've only ever fitted the gasket dry but I did modify those clamp saddles on my 6 to take into account the different flange thickness of the tubular exhaust and standard inlet manifolds. I relieved them a little with an angle grinder so that the dimples were much more prominent. No sealing issues.

[peter clarke]

your comment that ""gasket is still good"" ...............never re use a gasket and with manifold re torque as soon as manifold heats up..

[oldtuckunder]

your comment that ""gasket is still good"" ...............never re use a gasket and with manifold re torque as soon as manifold heats up..

 

On my MK1 if working on the carbs and inlet manifold sometimes its far easier to undo a few clamps and remove the complete assembly, destroying a port matched gasket (that takes about 2 hours to make) in the process is a pain, especially as to replace means then removing the exhaust manifold, which means removing the starter motor..... So sometimes a reusable gasket is a major benefit!

 

However yes I think this time I will check the clamps not long after the initial start up.

 

As from the soot the leaks appear to be head side rather than manifold side, i was just wondering if some magic compound might help with the sealing on that side.

 

As for dry gaskets, many decades ago my father taught me to fit every gasket - paper, copper whatever with a smear of LM and touch wood I have never had an oil leak from one, or a head gasket leak (even on engines renowned for them). Mind you he always insisted we fitted heads with greased bolts not studs & nuts (a practice which I know others hate). Four decades on some habits are hard to break :-)

[Noel Maule]

Hi,

I experienced very significant leakage problems when I fitted a stainless extractor manifold. Like you say, the differing thickness between the inlet and exhaust manifolds causes problems. I cured mine by placing thick copper washers between the clamps and manifolds. Then, when thoroughly hot, nipped them up again. Job sorted and no further problems.

Noel

[oldtuckunder]

Hi,

I experienced very significant leakage problems when I fitted a stainless extractor manifold. Like you say, the differing thickness between the inlet and exhaust manifolds causes problems. I cured mine by placing thick copper washers between the clamps and manifolds. Then, when thoroughly hot, nipped them up again. Job sorted and no further problems.

Noel

 

Neat idea, I'll cut half a dozen copper strips to go behind the clamps, much better idea than trying to gunk the gap, thanks!

 

You know what they say "if you cant raise the bridge, lower the water"

[peejay4A]

My suggestion has the same effect and no fiddling of washers into place. If the difference in thickness of the manifold faces is large then you just open up the hole in the saddle so it rocks a little when tightened.

[Noel Maule]

I don't think "fiddling a few washers" is as big an ordeal as taking an angle grinder to the clamps or enlarging the holes with a drill and essentially changing the design of perfectly good items and rendering them unfit for purpose if or when further down the line someone wants to change back to a standard cast iron manifold. But each to his own I guess.

Noel

[oldtuckunder]

My suggestion has the same effect and no fiddling of washers into place. If the difference in thickness of the manifold faces is large then you just open up the hole in the saddle so it rocks a little when tightened.

 

Sorry should have explained better, the clamps on the MK1 2L head are a bit wierd see attached picture. There is very little width to play with, there is only about 1/8" of the clamp on either face so not much wobble room. A copper strip should work nicely.

 

[peejay4A]

Yes, my mod would not work with those clamps, only the saddle type. Each to his own. If washers works for you then so be it.