Exhaust Manifold to Downpipe Gasket

[RickyJ]

At the moment I seem to be replacing the exhaust manifold to downpipe gasket on my VX at least every year and am looking for other possiblilties other than going the CSC/ANSA/GUY CROFT route.

I don't have the money at the moment for a 1-piece manifold and wondered if anyone has any thoughts on using/fabricating a gasket made of something other than what the standard ones are made from. The last one I had was (from memory without taking the thing off) some sort of foil type metal that's pretty flexible. I used firegum exhaust paste on both sides when putting it on and it lasted a while but is now making a rasping sound so looks like it's on it way out.

Anybody have any input on making up a gasket made from something a bit harder (steel??) I can't see that it needs to be that flexible as any differences in the surface faces should be taken care of by the exhaust "gum" you apply when connecting it all up. I guess it needs to be made of something able to withstand high temps because of where it is - Anyone have any thoughts on this?

Thanks
RIchard

[Will]

I've only had to deal with the ie 2pc manifold (has the odd undersize-head bolt holding it together). That thing annoyed the heck out of me until I finally took it out and WELDED the #$^%#$ out of it, making a nice 1pc manifold! :)

BUT it's CRITICAL that you make sure the spring-joint coupling after the downpipe is not overtightened, since you've eliminated the weak downpipe joint, which makes your exhaust studs into the head the new "weak point in the chain"!

AFAIK the only reason the downpipe is 2pcs is to make it easer to manufacture the castings, certainly the thing can be installed in 1pc without any drama.

-Will
PS> I thought I had found the ideal material in Zircar ceramic-fiber gasket material. Unfortunately, it packs out and has the fragility of a paper towel, so it's useless in any joint that combines pressure with any type of movement. So don't bother trying that. My.02

[RickyJ]

I hadn't thought of welding the 2 together - That IS a solution! Apart from different size bolts in the head I think it's essentially the same manifold/downpipe setup on a VX as any late Beta - Since I put the post on I mentioned the issue to a colleague and he's wondering if I should actually be using gum/paste on the joint as well as the gasket. In using this I wonder of I'm making the gasket slightly less effective as it's clamping on the "muck" I've put on rather than the gasket - Not sure what others do?

[Wallace]

I've often seen high temeprature gasket type material at autojumbles . . and not expensive either for a lump either. Thin copper sheet might be an idea as well.

I think it's important that the flanges are dead flat - on my Tipo, the gasket didn't last on the manifold and after eventually shearing off a stud, I got p*ssed off enough to take the thing off and skim them both flat on a mill - as well as replacing the studs !! It's probably more to do less with flatness, more of a gas tight seal not being formed due to scale, rust etc on the surfaces.

Anyhow, it's been fine ever since . .

[Gregory Smith]

When I had my Zagato, I had similar problems.

I finally took it all out and had the two parts MIG welded together. I removed the parts, beveled the edges where the weld would be to provide more depth for the weld, bolted it securely back together and my neighbor welded it. Problem solved forever!

[Wallace]

I take it all this talk of welding means the bits to be joined are the same material . . . . .. . ???

I'm not aware you can easily MIG cast iron to steel . .leastways not without coming appart again ! ;)

[Will]

Be careful of tossing aboiut the term "cast iron" too loosely- YES, I'm aware that there are those that claim the block is cast iron, the cams are cast iron, the manifolds are cast iron, et.etc.- and the same references can be found in print. However, I don't know of anyone having had a metallurgical analysis done on ANY or the parts to determine their carbon content or lack thereof, have you heard of anyone doing so? Are there records of this somewhere?

My point is that I suspect that some of the parts we (and I include myself in this group up until just a couple of years ago when I tried to spark-test a valve seat) enthusiasts have been calling cast iron are actually more likely cast steel. I've turned the camshafts and they don't behave anything like cast iron. I've made a hub for the Z-axis handwheel on my mill, valve guide tools, and other bits-those old Lancia camshafts behave like they are steel. Cast iron typically wants to be cut dry and turns off into a sort of crumbly powder, the cams turn off into clean spiral chips like they were made of tool steel, and a bit of research into cams indicates that A2 and S7 (both air hardening tool steels) have been the preferred materials for cams going back for decades, and lo and behold, they are both castable steels! YES I have pics.

I'm not saying the parts (and we are on the topic of the exhaust manifold , sorry) are DEFINITELY NOT cast iron, but I can tell you I managed to burn the two cast parts of my 2pc manifold together with only a Lincoln Weldpak el-cheepo wire feed welder, no MIG, TIG, or anything fancy.

Sorry to hijack the thread, just wanted to point out there are cast steels too and FIAT's foundry was considered pretty progressive circa 1970s from what I've been told, perhaps we should rethink the term "cast iron".

[1,6 HF]

Will's absolutely right. 'Cast iron' doesn't really exist anymore for applications like this; virtually all 'cast iron' automotive castings are actually cast steel.

[Hamish]

Interesting stuff.

Certainly the exhaust and the manifold are going to be two different metals, so welding it up might be tricky although it would be an interesting solution.
Does your downpipe have flexi-sections?

Getting a flat surface is the key but it's a pain in the a*se to get right. One interesting solution I came across was as follows:
1. The manifold (not the downpipe) had been sleeved (with a slightly narrower guage pipe) to fit intot he downpipe, maybe 3/4 of an inch.
2. The manifold gasket was doubled with a lead (yes, lead) piece in the middle.
3. Two different non standard flexi sections were present in the downpipe.

Top bodging ;D But it did work, albeit on a 1600 HPE and not a VX. Not sure what effect the sleeving would have on performance but the car went very well indeed.

I have learnt the following from experience with that particular joint:
1. De-stud the exhaust manifold and take it to an engineering workshop to level off the joint properly.
2. Don't double up on the gaskets or use too much 'gob'. It won't last.
3. Re-stud the manifold with new studs and use quality spring washers/fittings.
4. Make sure the downpipe flange is also absolutely flattened level.
5. Invest in a louder stereo when 1-4 make no difference at all :o

But seriously - although it grieves me to say it you will need to spend some cash and to be honest you could probably get someone to knock you up a copy of the Ansa manifold (if you can get dimensions etc) for a competitive price.

[SubGothius]

First, just to be clear we are all on the same page here, the late-model 4-2-1 exhausts had three sections between the head and the final union into one pipe: the 2-1 downpipe itself, and a sort of two-stage manifold, the latter comprised of a 4-2 section plus a 2-2 "extension" with a bit of twist (which IIRC usually carries the O2 and EGR bungs); both manifold sections are bolted firmly together (or often infirmly as we have read here ;) ), then attached to the 2-1 downpipe proper by a crude flexible joint -- really a modified butt joint with spring-loaded nuts'n'bolts so the flanges can spread as the drivetrain rocks under torque.

That lower flexible joint should NOT be welded and, as Will said, make sure those springs AREN'T so tight as to prevent that joint from flexing apart. I don't know what sort of gasket was used in that joint, if any, since I don't imagine any sort of material would do the job and yet last long with those flanges separating and closing against it all the time, which causes transient gaps anyway, so why bother with any gasket? That 2-piece manifold, however, can and should be welded together; they only gasket''n'bolted those at the factory because welding them would've been an expensive PITA for mass-production

The superior replacement for that primitive spruing joint would be a modern flexible section, which seems to be a sort of gooseneck inside a braided-steel jacket. That type, however, does not seem easily-adapted to the stock system, so you'd be into some sort of headers, then.

Speaking of which, who has had any flexible section(s) inserted in their headers, and where along the system -- i.e., just one after the 2-1 junction under the car, or two replacing both middle pipes beween the 4 and 1? I am specifically thinking in terms of the Ansa-type headers here, which I have heard rumors of cracking welds and/or pulling studs if attached too-rigidly. Seems to me that using the one flexi-section under the car, while easier to assemble and install, could allow the end to knock against the floor, and it still cantilevers a bunch of unrelieved weight off those exhaust studs; doing the two in the middle would seem more structurally-sound but trickier to assemble and install (maybe use clamped sleeve-fit joints at one end of the flexi-sections?)...

[Wallace]

You might have a point over what the manifold is made off Will - I know it didn't like a HSS cutter - which implies something a bit tougher than bog standard cast iron. But then, it's had years of heat treatment and nasty exhasut gases going round it so who knows ! You could always try belting it with a hammer to see if it's brittle ;)

Do try and fit stainless studs / bolts though. It makes it a lot, lot easier to undo if you have to in the future !!

[chrisc]

I had this problem as well in the past; had to have the faces on both milled flat for a lasting repair,

[Dmitry]

It is applicable FIAT palio (1.3) gasket. I can send you a photo .