1977 PK41U and PK41P: exhaust set-up

[PeugFra]

U-code engines were dual exhaust, P-code engines single, but were there other differences? Did they both have mini-converters?

And if U-code engines had mini-converters, did they have only one on the left side, accompanied by a manifold crossover with a heat control valve, or did they have two of them, one on each side? Remember, "true dual exhaust"!

 

[Davea Lux]

U-code engines were dual exhaust, P-code engines single, but were there other differences? Did they both have mini-converters?

And if U-code engines had mini-converters, did they have only one on the left side, accompanied by a manifold crossover with a heat control valve, or did they have two of them, one on each side? Remember, "true dual exhaust"!

'77 U code should be dual convertors with true dual exhaust. Do not remember any of the U codes using a crossover to a single convertor if the car had the "Police Special Order" exhaust system.

Dave

 

[75LandYacht]

Off subject: I see your “Armed Forces Italy” plates in your avatar.. I have my set from when I was station in Naples.. brings back memories..

 

[PeugFra]

I have no doubt about two main catalysts being present on the U-code engine, one for each exhaust line. But I'm less sure about mini-converters, the ones that on certain configurations were installed in addition to the main catalyst and closer to the engine for faster warm-up.

 

[commando1]

I recollect that for 1975, at least, the police package with the 400 dumping thru dual exhausts and NO cats.

 

[PeugFra]

By 1977 the 400-4 HP had a main catalyst and ELB, as they come with N94 on the fender tag.

The mini-converter was introduced in 1977, the last year for full-size Dodge and Plymouth pursuits. So I guess examples are hard to come by.

@75LandYacht: That's interesting! What is the number on your plates and when were they issued to you?

I bought mine for car shows: they're American and Italian at the same time.

 

[75LandYacht]

I was stationed in Naples from 90 to 94, the black plates were on my motorcycle and the white plates were on my car. And! I have ALL the plates from every car I ever owned in my garage Posted up on the wall.. cool reminders of days gone by..

 

[Davea Lux]

U-code engines were dual exhaust, P-code engines single, but were there other differences? Did they both have mini-converters?

And if U-code engines had mini-converters, did they have only one on the left side, accompanied by a manifold crossover with a heat control valve, or did they have two of them, one on each side? Remember, "true dual exhaust"!

Google "Muscle for the man!-Plymouth Fury A-38 Pursuit"-Hemmings

Dave

 

[PeugFra]

An interesting and in-depth read, thanks!

The statement about grass shield being included in the A38 package is quite intriguing. That would apply to both P- and U-code engines then.

There is no mention of mini-converters in the text, so that remains undecided.

 

[CBODY67]

The "mini"converters were for cold start emissions. Being smaller, they'd fire-off soon after a start, before the larger "main" cats would be up to temp and working. Possibly your best reference might be a FSM for that model year? Or a Chrysler parts book for that model year?

Electronic Spark Control is NOT the same as Electronic Lean Burn. NO HD, HP, or HO engines were "lean burn". 1977 would be the first year when the 400 and 440 HO engines would have had ANY catalytic converters under them from the factory. PLUS no filler neck restrictor in the fuel tank filler pipe as with no cats, they would not have been "Unleaded Fuel Only", either.

At this point in time, finding ANY mini converters and related pipes they were in would only be in the realm of NewOldStock. Nobody reproduced them, back then, so probably not now, either. You CAN get replacement cat converters from a few places, as Walker Exhaust, though. Need to get in their online catalog to look at the size and pipe size specs. If anything happened when the cars were out of factory warranty, the cats were removed and forgotten about. There was a hidden provision in the Clean Air Act that allowed law enforcement agencies to make some of those changes to the "as-produced" vehicles, if desired.

CBODY67

 

[CBODY67]

The statement about grass shield being included in the A38 package is quite intriguing. That would apply to both P- and U-code engines then.

There is no mention of mini-converters in the text, so that remains undecided.

The "grass shields" or "environmental shields" were placed under the converters, to prevent grass or similar from contacting them directly. Similarly, there were heat shields on the underside of the floorpan, full length of the passenger compartment on sedans.

By observation, the exhaust of the 8.2CR motors was noticeably hotter than the prior higher compression motors, HO or not. Don't recall seeing any shields on non-cat cars, HP or ELB.

CBODY67

 

[PeugFra]

If anything happened when the cars were out of factory warranty, the cats were removed and forgotten about.

So pics without the expected cats and/or grass shields don't prove anything, unless you are clearly dealing with an original, intact set-up.

 

[CBODY67]

So pics without the expected cats and/or grass shields don't prove anything, unless you are clearly dealing with an original, intact set-up.

Very possibly.

The grass shields hung down about one inch below the converter itself. Attached with normal muffler clamps to the pipe in front and behind the converter. As such, they were probably the "lowest-hanging" item on the exhaust system. Which would make them vulnerable for contact with earthly objects the car might run over. Once squashed, no longer viable for their intended purpose.

These shields were used into the 1979 model year, possibly beyond.

At the present time, 40+ years later, finding an unmolested intact police vehicle might be difficult . . . all things considered. Especially in the "catalytic converter years", I suspect, when performance had decreased from prior times. I highly suspect the mini-cats/pipes were not produced other than by the OEM, rather than any replacement parts suppliers. Once out of the OEM warranty, they were probably quietly replaced by normal non-cat pipes. Cold Start emissions was not an operational parameter which was tested outside of the basic EPA certifications done by the OEMs.

There is a National Police Car Owners' Association in the USA. Plus, there are two great books on Mopar Police Cars. Great reading. Some factory pictures, as I recall, too. One neat story in Vol 2, of a proposed turbo Daytona police car which will make you better appreciate the performanc engineering which went into Chrysler "economy" fwd cars back then.

CBODY67

 

[PeugFra]

You know what keeps me awake at night? Recall #77V131000!

It concerns the 440-4 HP B-body with California emissions and the way I read it, they imply the presence of one mini-converter. There goes the "true dual exhaust"!

 

[CBODY67]

The mini converters were placed in the y-pipe on single exhaust and in the "head pipe" on dual exhaust cars.

Chrysler and Ford honeycomb monolith converters were generally smaller in size than the GM "bead" converters. But the true "mini" converter was quite a bit smaller in size than the normal Chrysler-spec cat converter.

What "true dual exhaust" means is that each exhaust manifold has a pipe attached to it, which leads to a separate muffler and tail pipe for EACH side. Rather than going into a single, main cat converter and then splits into a "dual outlet" exhaust system (as in the '77-'81 Camaro Z/28s, for example).

On most genuine Police TorqueFlites, there was a "low gear blockout" mechanism. So you effectively only had "P-R-N-D" available. Reason? To prevent a driver from going from "P" to Manual Low when a pursuit was initiated, and continuing on as if the trans was in "D", when it was in "1" instead. So access to any lower gear, manually, was blocked to prevent such a "heat of battle" situation.

As for the plastic bushings melting, it's something that's not going to happen in a short time period, but from longer periods of WOT or extensive idling, while parked in a tail wind situation, possibly.

The Ford Fairmont police vehicles had issues with "smells" from the rear seat foam, during normal patrol work, which was claimed to be from heat from the dual exhaust mufflers under the rear seat area.

I highly suspect that police vehicles which just patrolled and were generally in motion would not produce the situation the TSB describes. There might also have been some pipe clearance issues that also were part of the particular situation, too.

It would be better to lose sleep over the rear tires not "barking" at a WOT 1-2 shift than that linkage bushing melting, to me.

CBODY67

 

[PeugFra]

The mini converters were placed in the y-pipe on single exhaust and in the "head pipe" on dual exhaust cars.

In the case of one mini-converter on a dual exhaust system that would mean that in a cold-start condition one exhaust line would be cut off and all gasses are diverted, by means of the manifold crossover, through the mini-converter in the other line. Than the heat control valve opens and the true dual exhaust starts operating.

 

[PeugFra]

Just in case:

Does somebody have a 1977 Parts Manual with drawings of the equipment we are talking about here (manifold crossover, exhaust head pipe with mini-converter)?

Also, the parts number list could contain extra info on the type of cars/engines/emissions packages these parts would apply to.

Thanks!