The Portal Hub: All things Pinzgauer, Haflinger, Volvo 303 and more.

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 Stock Pinz exhaust questions 
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Joined: Mon May 11, 2015 3:10 pm
Posts: 14
Post Stock Pinz exhaust questions
I have recently upgraded to SSI ignition (why did I not do this sooner?) and newly rebuilt carbs. Vehicle runs great but has a popping in the exhaust on deceleration on a downhill slope. I suspected exhaust gaskets and poked around looking for carbon tracking around the manifold but found no sign of a leak. I did check the rest back and noticed some carbon around the two short pipes which join the exhaust manifold to the heat exchanger. Looking at the drawings in expedition imports I was surprised to see no apparent exhaust gaskets or donuts between any of these parts!...just a steel ring and some type of snap ring on either side of these two short pipes. I am aware that many are converting this setup to a kit made by EI but I would like to stay stock if possible. Is my exhaust leak a result of the expanding snap ring that may have rotted and blown out? or is there a gasket that I am unaware of? also I was able to spin those two pipes quite using only a finger is that normal?....thanks for any insight


Tue Sep 05, 2017 12:35 pm
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Joined: Sun Dec 10, 2006 7:38 pm
Posts: 1259
Location: Southwest Wisconsin
Post Re: Stock Pinz exhaust questions
All of what you found with the 2 short stock pipes is normal. The snap rings and "bell shape" are supposed to provide a good enough seal but over time they rust/corrode/wear and allow exhaust gases to escape. Consequently the exhaust back pressure decreases and causes the popping sound you heard. I understand your desire to remain as stock as possible but the flex exhaust kits really do fix the problem and contribute to a smoother running engine, especially with the PinzSSI installed.
Cheers!

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Paul C.
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'73 Swiss 710M
'72 Swiss 710M
'89 Puch 230GE


Tue Sep 05, 2017 1:03 pm
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Joined: Wed Apr 14, 2004 9:58 pm
Posts: 1401
Location: Idyllwild, CA
Post Re: Stock Pinz exhaust questions
Because the exhaust gasses are moving quickly, there is a negative pressure within the exhaust that sucks in fresh air through any openings. This fresh air adds oxygen that allows the hot, fuel-rich exhaust to ignite that produces the popping/backfiring. Because the rings wear against the bell ends of the short pipes due to engine movement, both need replacing if you want to stay stock. They are really well worn if you can spin them with a finger!

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Jim M.
712W and 710M


Tue Sep 05, 2017 2:12 pm
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Joined: Thu Oct 10, 2013 7:18 pm
Posts: 219
Location: Mt. Hope, Ont., Canada
Post Re: Stock Pinz exhaust questions
I recently bought a older (1970s) copy of Audel's Automotive Guide and started on page 1. (available from Abebooks) This is a great book to fill in knowledge gaps on older systems, their carb section is amazing! I can't find the exact quote right now but the gist of what I read is that the popping on the override is normal on engines without emission. Yes, a better seal will stop air (with oxygen) being drawn in and causing immediate increased combustion of unburnt fuel in the exhaust but it will not solve it completely.

Too often we seem to forget these are an old school (gun) tractors with no emission controls or computer modules. They cough, spit and fart as the beasts they are :twisted: and should not be compared to, or attempt to be tamed into, the docile, domesticated, urbanized pets modern vehicles have become. If that is what someone wants, Magna Puch offers the G on portals, seroids and with a pretty Mercedes badge and interior ready to look cool going for the kids' soccer practice and ice cream! :shock: Personally, I'll stick with the one I can "detail" inside and out with a pressure washer when it comes home dirty. :D

Each to his own.

Cheers, Clive


Wed Sep 06, 2017 8:43 am
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Joined: Mon May 11, 2015 3:10 pm
Posts: 14
Post Re: Stock Pinz exhaust questions
Thanks so much for the replies, I think I will disassemble and take a look how that expanding clip engages the pipe and perhaps a better seal could be figured out...if not then perhaps retrofit but that would be my last option. I am one of those purists that hate changing designs...the only change I ever made gladly and without hesitation was adding military LED headlights to the Pinz...one of the best upgrades I ever did...the SSI literally took me years to finally come to terms with...but so far it is making me happy...thanks again men!


Wed Sep 06, 2017 9:02 am
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Joined: Wed Apr 14, 2004 9:58 pm
Posts: 1401
Location: Idyllwild, CA
Post Re: Stock Pinz exhaust questions
Quote:
Too often we seem to forget these are an old school (gun) tractors with no emission controls or computer modules. They cough, spit and fart as the beasts they are :twisted: and should not be compared to, or attempt to be tamed into, the docile, domesticated, urbanized pets modern vehicles have become.
All true, but with a good sealed exhaust the deceleration popping will go away. Don't let the fact that they are old vehicles prevent anyone from properly maintaining and replacing worn or failed components. This is not "taming" our beasts, just maintaining them.

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Jim M.
712W and 710M


Wed Sep 06, 2017 9:21 am
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Joined: Thu Apr 02, 2015 1:11 pm
Posts: 58
Location: Indiana, U.S.A.
Post Re: Stock Pinz exhaust questions
Updating the exhaust is very rewarding. You should do it.


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IMG_4023.JPG exhaust1.JPG [ 127.58 KiB | Viewed 496 times ]

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75 710K
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Wed Sep 06, 2017 11:39 am
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Joined: Sun Aug 10, 2014 8:36 am
Posts: 15
Post Re: Stock Pinz exhaust questions
Looks excellent. You forgot to ceramic coat the clamp. :)


Wed Sep 06, 2017 3:10 pm
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Joined: Thu Jan 22, 2015 4:00 pm
Posts: 133
Location: San Antonio, TX
Post Re: Stock Pinz exhaust questions
I also lean towards the "don't change stock components" crowd. That said, I don't imagine a Puch engineer intended to have exhaust leaks in their system and they were limited with components they had at the time.

You can replace what is there with NOS parts or upgrade to a modern fix that people have come up with, tested and are happy with. It probably won't make a lick of difference if you were to sell the truck in the future. Stock exhaust components are probably not high on a buyers checklist. If it worries you, save the old parts so you or a future owner can take it back to absolute stock if they were wanting to go that way.

You can bet when it's time to cross this bridge on my truck, I will go for the modern fix. How could you not want a system like whitesik's? That's some exhaust porn right there!


Thu Sep 07, 2017 6:34 am
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Joined: Sat Oct 24, 2009 5:17 pm
Posts: 890
Location: arizona
Post Re: Stock Pinz exhaust questions
pinzgauerpete wrote:
Thanks so much for the replies, I think I will disassemble and take a look how that expanding clip engages the pipe and perhaps a better seal could be figured out...if not then perhaps retrofit but that would be my last option. I am one of those purists that hate changing designs...the only change I ever made gladly and without hesitation was adding military LED headlights to the Pinz...one of the best upgrades I ever did...the SSI literally took me years to finally come to terms with...but so far it is making me happy...thanks again men!


A better seal has been figures out. They are flex couplings. If you go back to the original, buy all you can. I have seen people do the exact same thing you are wanting to do. The stock exhaust seal rings don't hold up for very long. If you replace the rings you need to also replace the headers as the header pipe has worn also making replacing the rings a waste of time and money. funny people say the old design lasted 40+ years. That is just not true. Look how many miles/km's were on these trucks when released from the military and factor how many miles you will be driving and don't forget that these have probably already been changed while in the military at least once if not twice in fewer then 20K KM's


Fri Sep 08, 2017 9:52 am
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Joined: Wed Sep 30, 2015 5:03 pm
Posts: 31
Location: Boston MA
Post Re: Stock Pinz exhaust questions
I have to add that the stock exhaust with the slip joint is awesome. I was doing some serious wheeling and ripped out a huge stump which ripped my whole exhaust rearward the exhaust separated at that slip joint if it was any kind of hard connection I would have destroyed the whole exhaust! It took me 20 minutes 1 bolt and my winch to pull the exhaust forward and make it all good again!


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Sat Sep 09, 2017 1:34 am
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Joined: Mon May 11, 2015 3:10 pm
Posts: 14
Post Re: Stock Pinz exhaust questions
Brady 712k wrote:
I have to add that the stock exhaust with the slip joint is awesome. I was doing some serious wheeling and ripped out a huge stump which ripped my whole exhaust rearward the exhaust separated at that slip joint if it was any kind of hard connection I would have destroyed the whole exhaust! It took me 20 minutes 1 bolt and my winch to pull the exhaust forward and make it all good again!


I wonder if it were designed as a breakaway exhaust, I am certain that this vehicle was not designed in a haphazard manner and given its purpose and intended use to have an exhaust that could be snapped back together with a few spring type rings would be a great advantage in the field. I think you are correct in your statement that had you had a securely mounted exhaust much more damage would have resulted...imagine broken exhaust manifold...and the $$$ that would have cost.


Mon Sep 11, 2017 5:03 pm
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Joined: Wed Sep 30, 2015 5:03 pm
Posts: 31
Location: Boston MA
Post Re: Stock Pinz exhaust questions
Yes if it were the case that he headers were solidly connected to the rest of the exhaust I would have been in a heap of trouble money-wise! But since it was designed to slip apart literally loosening one Fastener and pulling the exhaust forward was all it took!


Tue Sep 12, 2017 12:03 am
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Joined: Sun Dec 21, 2008 10:50 am
Posts: 96
Location: Atlanta
Post Re: Stock Pinz exhaust questions
I've found that exhaust deceleration popping is very dependent on carburetor idle screw adjustment. Have you tried to lean a bit your idle screws? Based on the pictures I would assume you have done your homework on tuning that truck... Running too rich would do it.
Jerome

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Sun Sep 24, 2017 3:23 pm
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