SharkSkin

Anyone know what alloy the 85/6 manifolds are made of?

I've been thinking of having my brother fabricate a flange to mount the EGR valve out of stainless and weld it to the 85/6 manifold, with the objective being to make it look like it belongs there. I'm assuming that the smog techs will have no clue what it's actually supposed to look like, and will accept it as unmodified. I understand that they are double-wall, but I don't know if this applies to the individual tubes, the "log", or both -- it does seem like a solvable problem though, but with stainless it's very important to match the alloys, both in the added parts and in the filler rod.

Another less savory option would be to build a flange that will fit at the end of the manifold and sandwich between that and the Y-pipe -- this flange would then have the mount for the EGR valve attached -- but I haven't looked closely at this option. It would look like an add-on for one thing, and there may not be clearance.

Before any of you in non-smog check states tell me to just rip out the EGR: No. I don't want to be fiddling with this every time I come due for a smog check. Also, the engine was designed to run this way -- if I remove the EGR then I will have to fool with the ignition curve via the distributor and perhaps fueling as well. Not interested in that approach.

Headers are a non-starter for me as well, for the reasons mentioned above plus the fact that they block the lower bellhousing. I would like the few extra horsepower that better exhaust would yield, but I don't want to be paying for it over and over, whether it's paying in $$$ or blood & sweat.

I found a good pic of the 85/86 manifold, anyone have a good pic of the 78/79 EGR-equipped manifold?

PorKen

I would do the flange. You need something to bridge the gap between the 85-86 headers and the Y-pipe on the passenger(?) side anyway.

You could start with the adapter (Motorsports sells)and add a pipe to position the EGR valve.

You could route the airpump to the cats, like on later models, and connect the air injection pipe that goes to the heads, to the EGR valve with a flange.

SharkSkin

Thanks for the Pic, Ken. Below is a pic lifted from another thread (thanks Big AL from Virginia ) of the 85-86 manifold. Looks like it may be a little tough to tuck the EGR back in there -- I'll have to look at clearances this weekend when I've got the car in the air for bleeding the brakes. Seemed to me there was quite a bit of room in that area but I'll look again.

lorenolson888

Hi,

I think they are stainless... probably 304... they corrode but not to the point of rusting through...

LO

SharkSkin

I realize they are stainless -- may have to have a sample analyzed to find out which alloy. Does anyone have an unusable manifold they are willing to part with for experimentation?

PorKen

Is it magnetic?

lorenolson888

I highly doubt they are anything but 304...

LO

Optimator

I believe 409 is commonly used for exhaust manifolds. Not that that answers your question, or even helps.....

SharkSkin

Thanks guys, looks like I need to find someone who has one of these, or something like it:


Click pic for link

I'm going to a local welding supply and see what I can find out.

fst951

If you are welding something made out of 304SS to the exhaust manifold, use 308L welding wire or rod. If you are using a carbon based mild steel to weld to the manifold, use 309L. The manifold is very similar to 304SS but slightly different. I still requires the use of the above mentioned welding wire.

Good luck and get it really clean.

lorenolson888

I know for aluminum recyclers commonly use a laser gun to ionize the sruface of the metal in question and sniff for the compostion... a LED screen then says which alloy it is...

Not sure if they have this for steels... (maybe ask some scrap metal guys)

You may want to talk with a welder as the above reply is correct... 308 filler for 304... and there is some slop and overlap in what fillers and parent alloys can can be joined... I welded some 316 with 308 and it worked fine... thought I think this is not the recommended metal

So talking with the person doing the welding may be the key as these things are a mix of science (metalurgy) , experience, art and voodoo...

Also I think that cutting the metal is the hardest part as a nice clean cut will be key to putting your EGR on... metal circular saws are good but typically stainless cutting is done with a blade soecifically for stainless... I think I priced on recenly for a little over $200... for the blade...

Hopefully it is 304 and you can simply fusion tig weld the parts together. I find this gives the best internal finish and is more than strong enough.

Will you be doing the welding yourself?

Loren

Fogey1

Dumb 928'ophile question here:

Which are the two manifolds pictured in # 2 & 3 above? Both 16V, nicht war?

US and Euro?

SharkSkin

Have you actually done welding on one of these? Is this from experience, or is this an educated guess as to manifold material, combined with knowledge of how to proceed based on the assumption that the guess is correct?

SharkSkin

It will be my brother -- he does mostly prototype , short & medium-run work in his own shop, though he used to work for NASA, welding airframes, pressure/vacuum vessels, etc. -- later he worked for Varian, welding various vac chambers & parts from stainless & other alloys. He's been doing his own thing for a couple decades now, give or take. He knows this end of the business very well, but usually the material in hand is known. He has not held one of these SS manifolds in hand so cannot do more than guess at the material, and would in any case prefer to know with certainty what the material is. He does not have any fancy way to discern different alloys.

SharkSkin

Both US -- Ken's pic is of a 78/79 US with EGR valve. The one I posted is of an 85/86 32V manifold -- I believe there was no US/Euro version for this.

BTW, I looked, and there is not a lot of room in there -- maybe ~1" each side of the EGR. Also, I won't want to make a new EGR tube to the plenum, or fuss with it much. My plan now is to make a rough jig with a cast manifold to locate the EGR mounting flange relative to the exhaust ports. Then I will put the later manifold on the jig and see what's what.