Hello all,

I have an 86 d100 with a slant six/4 speed. The leanburn is gone and mopar electronic ignition has been installed in its place. I received the truck with just one cat on it and straight pipped (was a joy on the high way lol). All the emission stuff was deleted off (by the previous owner) so i been trying to unfubar the thing somewhat. I did go ahead and install new 2 1/4" pipe attached to the down pipe with a new high flow secondary cat (believe its a 3 way). My question is can i just have the one high flow cat without the smog pump hooked up or would it be beneficial to plumb in a new air injection line into a new down pipe minus the first cat. or when i go to fab up a new down pipe should i weld in another cat and plumb a new A.I.R line to that or just leave the smog pump/line off all together. I had my fill of exhaust fabrication for a bit lol so id rather not melt/toast the cat(s) anytime soon. Also if i should go the route of the smog pump should the diverter valve be hooked up to manifold vacuum or ported vacuum (the pipe going to the cylinder head wont be installed).

My 85 came with most of the same setup on it, but was otherwise badly butchered/cobbled. I totally redid the under hood wiring harness and did the lean burn delete the right way rather than the butchery done before I got it, (the lean burn was still there but only one of the pickups in the distributor was crudely connected, I have talked about how much of a fire hazard this truck was in older posts here, won't rehash it all here) and the rear cat was completely plugged with remnants of what used to be the front cat "brick", it runs great now but I'll just say that it can't ever have a cat go bad again with how it's currently set up....

I understand that the air pump will be beneficial to your converter lifespan..

viewtopic.php?f=19&t=33811&p=226729&hil ... or#p226729

You definitely want to keep the air pump if you're running a catalytic converter. And don't get sucker(punch)ed by so-called "high-flow" catalytic converters; most of them are a waste of money, time, and effort. A good catalytic converter—for definitions of "good" that apply to carbureted vehicles—will cost more but last much longer and be much more resistant to internal meltdown; see here.

Rest of the exhaust system (pipes, muffler) see here.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Oh awesome ill give those a read. Ill probably fabricate a line to hook up the air pump then to feed the first cat.

Ya thats what i been reading too. Ill probably end up fabricating a new line with a new front cat too. Seems to be more peepy with the new exhaust i put on it.

Do you have a pic with how you have it set up by chance

No but I'll just say that parts that aren't there, can't go bad

Keep in mind that unless you have to pass emissions equipment inspections where the original configuration must be intact, you can replace the factory two-separate-cats setup with a single 3-way catalytic converter with air injection tube (already linked to the good one), wrap your headpipe with the thermal wrap in the linked post, and wind up with lower restriction and cleaner exhaust.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I definitely dont have to pass emissions testing where the original equipment has to be there just need a cat in place. I believe what i have as the 2nd cat is a 3 way converter now. Would you suggest i run a line directly right before the 2nd cat or would it be good to put one somewhat where it originally entered right out of the manifold. Eventually ill probably hook up an air fuel ratio gauge.

This sounds like your air injection system is incomplete or hacked. You'll want to fix that. There are two locations where air is injected: to the port at the rear of the cylinder head on the manifold mounting face, and at the catalytic converter. There is a control system and vacuum-operated valve to switch between the two injection points. There is at least one check valve in the injection line(s) to make sure the flow runs in one direction only, from the air pump into the exhaust tract, and not the other way.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Ya it was completely removed by the previous owner. Should the vacuum operated valve be hooked up straight to manifold vacuum

No. This isn't a by-guess-and-by-gosh deal. You really need to get a factory service manual and put it together properly. If you don't, you can damage the engine (toast the exhaust valves) and/or quickly cook any replacement cat right to death.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

(update after much deliberating/attempt at part hunting) if anyone is looking for the down pipe without the cat. for the slant six on d100/d150 Waldron can custom order you one for a decent price (165 plus the ride). I believe its similar to the old walker exhaust 44958 that is no longer made. Looks like it should fit my 86 pretty nicely.

Waldron? Huh?
What's the pipe size(diameter) of that one? I made one from scraps for mine a while ago, started with an original stub I got with a super 6 manifold stack and raided a scrap dumpster at a local exhaust shop, had some stainless (whatever grade OE exhaust is on newer vehicles) 2-1/4 pipe in there that was taken off of who knows what, looked like it wasn't far from brand new, I cut all the elbows out of it (kinda like a summit or jegs DIY header kit) and eyeballed it on my truck and mig'd it all together. I did a decent job welding and positioning what I had but being it's 4-5 short sections welded together from manifold to muffler inlet, but it looks the part (cobbled)