Driver's side exhaust manifold

Bearman · Post by **Bearman** » Tue Apr 19, 2016 8:39 pm

I just purchased a set of (Crown) manifolds for my 81' j10 360. The passenger side looks like the original one but the driver's side is different. I am aware of the pre 74ish style and have also read in 1980 AMC moved the 4x4 over and they changed the manifold again. The vendor page specified it for an 81' but I'm afraid I got the older style anyway. A post on here about a month ago said it will work if a smaller starter is used. I will be installing a new exhaust system.

My question is, will the earlier style manifold work if I'm installing a new exhaust system. I plan on keeping a factory starter and want to be able to access everything like I did before. I hope this makes somewhat sense to y'all. It's getting late and I'm about to call it a day. Thanks for any help by those who have had experience with this.

Renodemona · Post by **Renodemona** » Wed Apr 20, 2016 12:12 am

The passenger's side was the same from 71-91 as it fit with a passenger drop of the early years, so no need to change it. as far as I am aware the driver's side changed but not significantly and you should still clear the diff. However, if the one you pulled off was original is is different, you might have to have or bend up a different Y-pipe to meet the manifold. I doubt you'd be hitting the diff but I guess I'd have to see pics...

REDONE · Post by **REDONE** » Wed Apr 20, 2016 6:27 am

Like the OP said it's not the diff or driveshaft that cause problems, it's the starter. When Jeep switched to the 727 the starter changed sides. Jeep didn't need to reengineer the passenger side manifold, which already exits at the very back of the motor. The 79 and older drivers side manifold exits under #5 cylinder and points right at the 727 starter, that's why they went to the "log" drivers side manifold in 80.

Hopefully someone that's done it will chime in, I have no pics of what needs done to clear the starter, I only know that a handful of people have done it and I'm pretty sure they used a high torque clockable mini starter to do it.

HeavyMetalThunder_81 · Wed Apr 20, 2016 6:43 am

Every FSJ I have seen with the AMC v8 has had the starter on the passenger side. Irregardless of the transmission it had, TH400 or TC727. Ford style starter or Mitsubishi style starter.

REDONE · Post by **REDONE** » Wed Apr 20, 2016 7:11 am

Your right, it's been years since I had an 80s FSJ, I'm not sure what the clearance issue is then.

derf · Post by **derf** » Wed Apr 20, 2016 8:39 am

I think the clearance issue was the front driveshaft. Clearing the starter meant clearing the passenger side driveshaft. Drivers side used to not have to clear anything. When they moved the driveshaft over they probably had clearance issues.

Bearman · Post by **Bearman** » Wed Apr 20, 2016 1:56 pm

While searching for a solution before I send it back I have found this http://m.summitracing.com/parts/rnb-674-393

Anyone have any experience with the Dorman manifolds? The picture looks to be correct. Application says they fit 1987-1988...? Must be a glitch or something.

carnuck · Post by **carnuck** » Sat Apr 23, 2016 5:34 pm

Emissions requirements probably. Or angle of out pipe? Should be '80 to '91 AMC V8s in FSJs. See if they have a front pipe to fit and what years. Before '87 was AMC numbers and Chrysler added a J in front of the old ones to make new "unconfusing" numbers.

Bearman · Post by **Bearman** » Sun Apr 24, 2016 1:47 pm

I forgot to add that my old exhaust system did not have a y-pipe. It consists of just two exhaust pipes to dual flow masters. We have no emission test where I live. Hoping to just be able use the new manifolds and rely on the exhaust tech to come up with something. I will be installing the same exhaust setup or I hope so. I thought about calling Summit about the Dorman manifold but I guess they could tell me no more than the application chart says. Just looking for someone with firsthand experience with this. Thanks fellows for your input.

derf · Post by **derf** » Wed Apr 27, 2016 8:16 pm

FWIW, 80's on top, 70's on the bottom.

will e · Post by **will e** » Fri Dec 31, 2021 5:57 am

Looking at the pic it would appear the 70's ones would have flowed better.

tgreese · Post by **tgreese** » Fri Dec 31, 2021 7:13 am

will e wrote: ↑Fri Dec 31, 2021 5:57 am Looking at the pic it would appear the 70's ones would have flowed better.

Correct. The earlier factory manifolds flow well for cast iron manifolds. The '80-up log manifold is more restrictive.

will e · Post by **will e** » Fri Dec 31, 2021 8:11 am

tgreese wrote: ↑Fri Dec 31, 2021 7:13 am
will e wrote: ↑Fri Dec 31, 2021 5:57 am Looking at the pic it would appear the 70's ones would have flowed better.
Correct. The earlier factory manifolds flow well for cast iron manifolds. The '80-up log manifold is more restrictive.

I am going to get rid of the air ports on my manifolds. I assume it won't go well. I know a guy with a bunch of Jeeps in his back yard. I might just go pull an earlier passenger manifold and with my lift and mods I think the earlier drivers will fit fine too. Yes, the exhaust will need to be redone on that side but it needs some rework anyways. Maybe I will grab one of each for the drivers side, plug the spare and then see how both fit.

1978J10REDWHITE · Post by **1978J10REDWHITE** » Sat Jan 01, 2022 2:53 pm

Good timing on this revived article.
Subject ~ 1976 J20-360-TH400-D20, Stock exh manifolds.
Located a pair of good clean 'smog" 1971 Exh manifolds and considering putting them on the truck.
Perhaps a small performance might be one benefit to this , not really sure.
I will redo the entire Exh system anyway.
$300 for the pair, then the real fun begins.
My manifolds are fine as is.
Any Fitment Clearance concerns about swapping the car manifolds into a Truck, that I should weigh in on this upgrade??

AccrateDelivery · Post by **AccrateDelivery** » Mon Jan 03, 2022 10:05 am

Great flowing manifolds pre-1980. Best in my opinion.

1978J10REDWHITE · Post by **1978J10REDWHITE** » Mon Jan 03, 2022 6:04 pm

They design looks like a step up from the logs that are on there now. If these are straight & not cracked then for the $300 seems reasonable to me.

tgreese · Post by **tgreese** » Mon Jan 03, 2022 8:26 pm

Looking at the parts book, the Jeep 360 manifolds for '71 are different from that, more log-like. However, the '72 manifolds have the same shape as these car manifolds, though they have the bosses cast-in for the air injection and not drilled. '72 could have come with or without the air injection. Apparently AMC took this design and modified the casting so it could be machined for air injection. Looks like the seller wrote 3216158 and 3210160 (?) for PNs, which do not appear in the Jeep parts book. Instead you'd have 4488899 and 8121271, without AI.

1978J10REDWHITE · Post by **1978J10REDWHITE** » Mon Jan 03, 2022 8:33 pm

His ad says he has another set, with the air fittings in them, yet are capped with proper Allen key plug/bolts.
He is close by my location , if they are flat on head mating area and no cracks and bolt holes are ok, then I feel this might be worth asking price.
Hopefully I will know solidly their fitment, yet my views on the area appears like they might be a goof clearance fit.

will e · Post by **will e** » Tue Jan 04, 2022 7:01 am

What year did the air injection start on our rigs?

tgreese · Post by **tgreese** » Tue Jan 04, 2022 8:59 am

will e wrote: ↑Tue Jan 04, 2022 7:01 am What year did the air injection start on our rigs?

Some 327s got air injection; I don't have any reference that says which years/models/equipment did. Apparently the 350 did not. Looking at the exhaust manifolds (see above and the parts book), it seems that 1971 did not get it. Some 304-360s got it in 1972 - according to the TSM, all '72 304s with a manual transmission and all 360s with a manual got air injection. I don't have a TSM for '73, but there is only one V8 exhaust manifolds listed for '73, so I presume all V8s got a smog pump that year. '74 shows air guard (air injection, smog pump) for all models except the 232/258 CJs. Each year's TSM has a table in the emissions chapter that shows which devices were applied based on model and equipment.

Note the table changes from year to year, and does not uniformly get more strict by year - my 49-states '77 J10 with a 258 came with no smog pump and no vapor recovery. The requirements were changing from year to year and by locality in the 70s, and the manufacturers improved their strategies as time went on.

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