A couple of Techie questions on Stainless HEs, since I need to have one of the manifold lug ears welded anyway...

1. Can I have the welder close off the ends of the heat shroud at the front & rear of the HE around the exhaust pipes??

They don't appear to need to be open for air flow to the cabin heater loop, but are notorious places for exhaust gas & oil spatter to get in &

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2. What's the best way to have the welder replace the mild steel end flanges at the muffler (which are welded in), with the new SS flanges from Engman - so I don't end up too short for the 2L muffler bracket position??

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Easy way to line things up is to bolt everything including the (stock) muffler togetther, Still won't perferct so it may need some tweaking, bending, clamps, etc.
If you use the stock muffler it should keep things straight. Tack it up then take it off and weld.
I have an old jig engine (empty block, just old cylinders and heads w/good exhaust studs) and a scrap trans, that I set upside down for a jig.

You shouldn't need to weld up the seams, if you smell exhaust you have an exhaust leak....just like if the cab is filling with smoke you have an oil leak.
Welding the clamshell may be tricky as it's very thin SS.

i am curious to see how the flange replacement goes and cost??

i would think you would at least want to mount them to a scrap head - to keep the lined up as the tin won't help much.

jim

They are not welded for a reason ... To keep you alive ...
Andy

How so Andy? ...please educate me!

I had assumed that they were not closed off like the sides are because of cost/difficulty reasons only, since the warmed fresh air-flow comes in one pipe & out another, & those open ends don't appear to serve a purpose in that scheme.

However, I see the point Mark is making above - as to the difficulty in welding the thin shroud SS sheetmetal to the thin sheetmetal exhaust pipes.

The other option which I considered was that aluminum exhaust tape to close them off, but I thought that having the welder close them off with the rod material would be the better solution, since I need one ear repaired anyway, so it wouldn't add much to that cost if done at the same time.

The SS Flanges are $29.95 each side + Welding TBD, which I won't be doing myself.
No skills/experience in - nor the equipment! I try to know my limitations!

Since the engine & transaxle will need to come out for repairing, restoring & repainting the body shell, it could be set up on the actual engine & flanges.

I just wasn't sure whether to just have the pipes cut-off at the inside of the old flanges, or to cut the flanges off the pipes to preserve the length of the pipes - if that's even possible??

BTW ALL -
These are used 2L SS HE's which I picked up because my 36+ year old OE ones are now rusted out & need to come off. So they've never been "fit" to my 2L engine & muffler on the car.

They are probably not welded because of the additional cost of the welding labor. I don't see why it's necessary unless the heater doesn't get warm enough. Stuff getting in is as bad as moisture that can't get out. I'm sure there is some condensation there. When you weld ss tubing it will twist and warp pretty bad unless you go real slow. Also there may be a different expansion and contraction length between the two pieces when the exhaust gets hot and the loose ends allow for the different lengths. The movement might be observeable on the tubing.

I do know that long ss exhaust does grow quite a bit on bigger cars.

The only way I see to keep the exact same length is to cut the welds loose inside the old flange and hope the tubing is still good enough to weld the new flanges to. I would think it all needs to be bolted together to get it to align back up. As in the whole car, motor, and muffler unless you have the motor, tranny combo as someone has already mentioned.

Thanx for the tip - as noted in reply to Andy, the engine & transaxle will be out, so it can serve as the jig.

The reason I want to seal them off, is that every time a small oil leak comes up - & all 914s eventually get them, it gets sucked/thrown into those gaps then cruds them up, as can be seen in what the seller hasn't cleaned up on this used set before selling it to me!

Also, small amounts of exhaust gases get sucked in there via the airstream, which can be enough to give mild cases of carbon-monoxide poisoning. If you've ever had headaches while driving your 914 when using the heater, that's why!

According to my long time factory trained 914 mechanic Hans in Huntington Beach CA, that was always one of the biggest complaint he had from 914 owners, along with oil leaks!

Looking at the current state of my OE HE's now - mine was probably starting by the time I put it into storage in my SoCal garage in 5/85, but our warmer climate probably saved me form having to use them much!

This is the end of one - all 4 ends are bad + holed along the shroud at several places! Although the SS shouldn't rust away like these end, I do want to eliminate the gaps if I can & it's safe to do so.

One end of one OE HE:

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Can't find now who asked "...why replace the flanges?" - but the pic of one of the mild steel flanges on the SS HEs above, clearly shows that it has been rusting away where the pitting shows, but the seller wire-wheeled everything to clean up the HEs - so they now "look" nice-n-shiny.

Since I'm putting so much into repairing/restoring my early73 2L, & that everything is coming off to do so anyway, & that I need one mounting lobe/ear repaired/welded at a crack - I might as well get this right now, so it will all last another 30 years without trouble!

Same idea on using SS HEs - rather than OE carbon steel ones, as well as why I want those ends sealed up - if it's not otherwise a problem/safety issue (pending "Sir Andy's" answer/clarification)!

So that's my story anyway, & I'm stickin' to it!

I think Andy's point is that weld beads can crack, and a crack lets CO into the cabin.

Thanx Charlie - all good points on why the ends are left "loose"!

As I said, the engine/tranny unit will be out of the car for some time - so it could be used as a jig to weld the flanges. Also, the new SS flanges appear to be a bit thicker - leaving some wiggle room.

And you may have stumbled upon a replacement implant solution for guys needing Viagra in your second point!? ....just imagine an SS "Tool" that grows when you get "Hot"!!!!

i have a set that was welded as you are contemplating - see pic

Thanx Jim!
How did that work for you?

I don't know if there is a difference in SS vs. carbon-steel expansion rates to cause the cracking noted above?

Not just expansion rates... a weld bead introduces a stress riser, and over time, vibration can cause a crack. Hydrogen embrittlement due to the weld is also a possible cause of cracking.

I don't know how likely a crack is, but the possibility is there.

Just my two cents, the flanges do have some pits, could you grind of file flat, the gasket should then take care of any leaks?

i did not have them welded and never had them on a car - my cars don't have heat plumbed anyway - but i agree - if you flanges are not paper thin ( and thye don't look thin at all ) they should be ok with gaskets and some copper permatex - no need to grind them off - really.

jim

Good input on both the flanges & ends sealing questions guys!

I think I'll take it up further when I get it over to my mechanic & may not do either, or only what's best.

In any case, it sounds like the hi-temp aluminum tape which can flex may be the answer to sealing the end gaps, since it can flex - so long as there isn't some metals' interaction problem with them!

I look at that type of reaction, after the head corrosion problems on the 2.1L Vanagon Water-boxer heads on our 88 Westy!

And I agree with Andy. With the flex that occurs in the whoe exhaust sytem, cracks are bound to happen. Will CO sneak in? Could be. I would leave it alone. My SSI's are 35 years old. Yeppir, there is some degredation of the red sealing compound they originally used on the ends. Until the shell rattles I'll leave them alone.
Pat

You know I just now remembered when we changed the headers on my sons sti we used a red high heat sealer on the flanges to help seal them as they didn't look exactly parallel with the head surface. That stuff would probably work on the ss shell to pipe surface and would probably stay in place if the surfaces were cleaned real good.

Aha! So mine apparently has lost the red sealing compound at some point, or it got cleaned out with the wire wheel by seller. So I can follow the suggestion above of using the Red Heat Sealer, to recreate what Pat's talking about!

So long as I'm essentially tearing apart & rebuilding this car, I might as well see that it's correct going in to start with, rather than just putting stuff back in a "half-fast" job!

Anyone Recognize the brand of these?? Don't know if they're SSI's or another mfgr., and seller didn't know either - since got them with a couple of boxes of parts for a 2L core engine taken apart.

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They are SSI's, they changed small things each production run. Early SSI's (like mine) had mild steel flanges and are the ones that are usually rotted.

You need to be careful welding stainless...

Some grades will crack years after after welding...

My metalurgy teacher always cautioned about that and cited a law suit for a stainless steel fire extinguisher filled with dry powder. The bottom of the extinguisher was seam welded onto the can.

All the overpressure tests at the factory showed the welds were fine.....

However, about 5 years later, when somebody activated the CO2 container in the fire extinguisher to blow out the powder on a fire, the bottom blew off the can and embedded itself in the operators foot.

Metalurgy tests showed that the stainless used weakened over time at the seam weld and broke...

Not knowing the types of stainless, would you like to risk a crack in the pipe inside the hot air shroud after you welded the shroud to the pipe?

30+ years ago, I made my own HE's on a 914 turbo exhaust sytem. The fabricated sheet metal HE's were brazed (not welded) to the header. Worked great, completely sealed, and no cracking of the braze joints.

Andys

I think something else you get with the normal crimp fitting is a ltttle adjustability with the heat shrouds on the pipe so that you can ensure the other heater parts attach. If you weld and it warps, you could be in for fun.

An old engineers saying: "if it aint broke, don't fix it"

I used Permatex Red High Temperature Silicone to close up the gaps in my H.E.'s. So far so good. Why not, GM uses it on all there exhaust manifolds!!! Before changing the ends to SS I would consider using the HT Silicone to seal up the gasket surface and fill in the rust pit marks.
BTW I beleive the header pipes and the HE shrouding have a different rate of expansion therfore you can only weld up one end. If you don't then they will crack for sure. Silicone will allow quite a bit of expansion and contration.

Thanx for the plethora of tips guys! ...just what I was looking for!

Thanx for identifying them as SSI's as well!

It sounds like the safe & sane solutions for the HE shroud end gaps is to seal with HT flexible exhaust sealant, to maintain flexibility for expansion/contraction & to avoid potential cracking!

And possibly that or copper permatex on the existing flanges, unless the old ones can be properly replaced with the new SS flanges that I've already bought!

The one dog-ear to attach to the head ex-manifold is cracked as in below, which I've been told can be welded to repair - TRUE????

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That one is an easy fix. 2 minute job, just be sure the welder uses SS welding rod.

I might have missed it, but I didn't see anyone mentioning passivation. Once stainless is welded, it looses it corrosion resistant properties at the weld bead/heat effected zone. To regain these properties it must be passivated. It’s a relatively simple process, but uses some acids and chemicals and so is (IMHO) impractical to do at home. Without passivation the joints will rust. I'm used to working with deionized water which is very tough on metals, but I would imagine that road salt has equal corrosion capabilities.

Personally, I wouldn't be too worried about the weld bead cracking (though it would be a concern). Once again, my main concern would be the loss of oxidation resistance. Anywhere that jacket is welded will have an increased propensity for rusting. IMHO its not really a big deal fixing the mounting ears, and running without any treatmet because of their location. I would leave the rest of the heat exchanger alone unless it really needs help (which it doesn't look like from the picture). Like someone above said, if it works, don't fix it.

I had the same crack on the ears, just weld them up.

Another thing you have to look out for on SSI's is that you don`t over torque the exhaust nuts. I`ve seen the tube around the ears start to deform if you over torque the nuts. This is also the most likely reason the ears are cracked.

Thanx - hadn't heard of that effect before, but will ask the welding shop which does the work about "passivization" treatment afterward - especially if I end up replacing the exhaust flanges.

I think I'll go the HT Red Silcone at the Jacket end joints as apparently SSI did originally, rather than either welding or brazing - after they're cleaned up from what apparently was a very leaky 2L, given all the burnt oil crud on them - of course.

Having lived in Pittsburgh PA as a kid & visiting since - I know what you're talking about with road salt!

Fortunately here in mostly sunny SoCal we don't have any road salt concerns!

However, when I lived closer to the beach - sea salt spray in the wind was a bigger concern, particularly on the top-side!!

So you Easterners & Midwesterners might keep that in mind when you're looking at supposedly "clean & rust free" CA 914s - & ask: "Where in CA did it live?".

BTW - as an Architect, I too know the "...if it ain't broke...." ethic, but keep in mind that I'll be essentially rebuilding my 914 & want to get the used parts back into close to new condition before it all gets hung on a very expensive job! There's also a saying about doing it right the first time & "You can do it fast, or you can do half at a time, but NEVER do it 'half-fast'!!!!" - so you're not redoing it again later - over & over & over............trying to find what you missed!

Thanx for the tip! I think that was the same with the OE HEs as well as on the soft alloy heads & manifolds & case of the engine itself too!

So Pat, for your CW perfection 72 - did you paint the SSI SS HE's to the stock HE & Muffler flat HT Grey, or leave them shiny??

If left shiny, does it work against you on concours points??

I need to clean up & repaint my muffler, so I could do both at the same time if that's the case!