New (NOS) Pinz Carb Install / Tuning

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oilcan
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New (NOS) Pinz Carb Install / Tuning

Post by oilcan »

Hey all - i ended up getting NOS carbs from EI as the idle screws on the old carbs were driven right through the throttle body and you can buy a new carb for close to the price of a throttle body.

They are beautiful - its like if Marty McFly delivered christmas presents - brand new, wrapped, shiny, and 40 years old. I got them installed and got the rig up and running but am having a hard time dialing in their idle (I think). I've got them pulling the correct amount through the synchro tester, and the idle seems smooth but according to the laser tach, the idle is way too fast (about 1400 rpm). I'm calculating the speed off of the rotate of the fan bolt. so 2 questions -

1st, the easy one -
does the fan rotate at a faster speed than the engine? i'm assuming no, but that would explain this away easy

2nd - what special steps should i take to get these new to the beast carbs dialed in? i've followed whats in the repair manual and Jim's page (http://www.goatwerks.com/carbarticle.htm) but it's just not doing it.


thanks for all the help
rich
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pcolette
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Re: New (NOS) Pinz Carb Install / Tuning

Post by pcolette »

1 - yes, I think so. The fan pulley is smaller than the crank pulley so the fan pulley will rotate more than 1 complete rotation for each rotation of the crank pulley. Try measuring the rpms on the crank pulley.

2 - check your timing. It may be too advanced (more than 3-5 deg or so) which would increase the rpms.

New carbs are very nice!
Paul C.
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Re: New (NOS) Pinz Carb Install / Tuning

Post by pinzinator »

Are the return springs installed and working properly? I the choke partially on? You should be able to set the idle so low that the engine would stall, just a few hundred RPM. Are the carbs jetted exactly the same?
sproket6
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Re: New (NOS) Pinz Carb Install / Tuning

Post by sproket6 »

Oil Can,

Congratulations on your new Zeniths. What a great carb design that is! I think they were originally developed to support a military requirement but Porsche liked them so much they were selected for the 356. There is a lot of information on fine tuning them if you search in that direction.

My first thought on reading your post was did you disassemble and clean thoroughly? Lots of gunk could get in those passages in 40 years, gaskets go bad, seals fail. All warehouse conditions are created equal.

Are the jets the same size as in your old carbs?

Also: Sounds like your engine may have a vacuum or other mechanical problem. What leads me to suspect that is because your vehicles previous owner apparently had a similar high idle issue (and responded by forcing the idle adjusting needle through the carb body!) May want to rule that possibility out first.

John
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Haf-e
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Re: New (NOS) Pinz Carb Install / Tuning

Post by Haf-e »

If you are going to the expense of putting on new carbs you probably should replace the gaskets at the bottom of the intake manifolds and the rubber hose between the two manifolds as well. Also, checking the manifolds for cracks is worth doing while you have them off. Any problems with the manifolds, gaskets or hoses could result in it being hard to properly set the idle level and overall mixture.

Good luck!
Haf-e

1971 Pinzgauer 710M

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oilcan
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Re: New (NOS) Pinz Carb Install / Tuning

Post by oilcan »

all, thanks for all the help / thoughts. a couple of things -

Both carbs have new gaskets under them and with the exception of the the throttle linkages, all return springs and parts are reinstalled. I've had the old ones on and off a few times trouble shooting them so i'm fairly comfortable with how it all fits together.

i did not adjust the timing - this along with adjusting the idle butterfly settings seems to be my weakest link. i will be honest and say i've never attempted anything like this but i am very mechanical and a pretty quick study and am hopeful that with the help from everyone on this forum i can figure it out. there's just not a lot written about new carbs, everything assumes you put your old ones back on.

as far as jets, the new carbs had the same (125) as the old carbs but i put the old main jets in anyway - after cleaning and blowing out with compressed O2. i did give the new carbs a once over.

I will get a timing gun this weekend and see how it goes. I'll check out the manifolds for crack haf-e and look at the gasket / hose situation too.

hopefully its not a more significant mechanical issue like has been suggested, but i will figure out. If i can't get it going smoothly, i'll take it to the local old porsche guy.... i assume he could fix it in his sleep (he's already somewhat fascinated by the truck). Its still the original distributor, I'm doing the truck one piece at a time and teaching myself how a car should work...

thank for all the help

rich
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pcolette
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Re: New (NOS) Pinz Carb Install / Tuning

Post by pcolette »

One other area to check - occassionally the engine tin beneath the throttle linkage on the rear carb becomes bent upward and interferes with the full return of the throttle linkage. Here's a photo with the offending area circled:
IMG_3156.jpg
IMG_3156.jpg (62.25 KiB) Viewed 9308 times
Make sure that the throttle lever is returning all the way to the idle speed adjusting screw stop point.
Paul C.
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'89 Puch 230GE
undysworld
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Re: New (NOS) Pinz Carb Install / Tuning

Post by undysworld »

Hi Rich,
Paul C. is quite knowledgeable about carb settup, and a great resource. :idea:
BUT. :shock:
Do your local old Porsche guy a favor (and yourself a HUGE favor) and take it by his shop anyway. He'll love the truck, plus you'll probably get it fixed quicker and better too. You'll also might learn a bunch from him. (Take beer too, because you two will probably become buddies, I predict, and a lot of Pinz-friendly guys like beer. :lol: )
Then, if you still have questions, call Paul. Heck, call him anyway, because he's also a good guy to chat with!
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Haf-e
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Re: New (NOS) Pinz Carb Install / Tuning

Post by Haf-e »

One easy mistake to make is not removing the rods from the carbs when setting the idle speed - they need to be removed! Then once the engine is idling correctly - try to put them on without affecting the engine speed - which will require adjustment of the rod ends...

I hope it something as simple as that...
Haf-e

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ExpeditionImports
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Re: New (NOS) Pinz Carb Install / Tuning

Post by ExpeditionImports »

Hi Guys,

My guess is it is going to come down to simple setup. You are not likely to get NOS carbs out of the box that will NOT need to be adjusted.

I would suggest anyone doing this have the following things available at a minimum:

Timing Light - Preferably one with an RPM readout - 12V is fine.
Carb Sync

I would go about it in the following way:

#1 - Mount the new carbs, get the truck up an running. Needs to be running well enough to come up to operating temperature. Do not mount the throttle rods, do not mount the air horn, do not run the choke cable.

#2 - Adjust the timing. Stock points 4-6, Pertronix about 10 degrees advanced. @ 900 RPM = Target

#3 - This is where it turns into a balancing act because as you increase or decrease timing your idle RPM is going to change.
Advance Timing RPM Goes UP
Retard Timing RPM Goes Down

#4 Now we are going to add a third variable - Carb Sync. Take your sync tool and move it between the two carbs and adjust them so that their throttle bodies are pulling the same reading. Doesn't matter what that reading is...just needs to be the SAME between the carbs.

Once Carbs are Sync'd, Idling at around 900 or your preference, check/adjust the timing again to confirm nothing has changed.

#5 Hookup the throttle rods one at a time noting that RPM does not change. "Snap Test" the carbs. Fast Hard Throttle...any popping, any stumble? Slow throttle advance, any stumble/dead spots.

#6 Ultra fine tuning. Your carb idle mixture screws should have started out about 1.5 turns out. For most of us it is very difficult to make this adjustment without practice or an exhaust sniffer. What I will do is with the engine running, turn each idle mixture screw VERY CAREFULLY all the way in one at a time until they stop. Their should be a noticeable decrease in RPM if they are working properly. Bring it back out to the 1.5 turns. Adjust/Set for smoothness.

Finally a last run thru......RPM 900 Check, Timing 10 Degrees (Pertronix) Check, Front Carb/Rear Carb Same Vaccuum - Check. Snap Test - Check, Smooth Acceleration Check ==== Put it back together.

It is not uncommon for us to spend 30-40 minutes "tuning" a new set of carbs.

Final Note - The NOS carbs being delivered are the latest version of the Pinz Carb setup for better emissions in Europe. IE they are jetted for cleaner burning. Some may or may not like this and would prefer their original jetting. I personally prefer them, however if I were jetting for performance I would probably run with an earlier set of jets. Take a look at the manual, and it clearly discusses the jetting.

In the next month or so I will try and put together a quick video showing the tuning.

Cheers,

Scott
Expedition Imports Corporation
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sproket6
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Re: New (NOS) Pinz Carb Install / Tuning

Post by sproket6 »

any updates? I hope your new Zeniths are now running smooth as silk.
oilcan
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Re: New (NOS) Pinz Carb Install / Tuning

Post by oilcan »

I got them on, got it running, ran it over to the artists at the classic european car workshop... i'm told they had it running like a dream, it was even possibly cast in a documentary (more to follow on that).. and then... ignition system woes. more to follow, hopefully this weekend.
sproket6
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Re: New (NOS) Pinz Carb Install / Tuning

Post by sproket6 »

That's good to hear. Those are really great carbs and once fine tuned they should give you years of good service.

I had some issues with mine not running well, missing out, hard starting. Turned out to be the tired old ignition. Replaced that and it was a huge difference.
oilcan
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Re: New (NOS) Pinz Carb Install / Tuning

Post by oilcan »

picked the truck up from the local european shop on monday am... they had the carbs running great, and they installed a Pinz SSI system while they were at it. That was on my planned upgrade schedule for the next year so I just went ahead and did it versus replacing old ignition parts here and there. They also installed a new voltage regulator. Truck starts right up now and almost sounds civilized. I won't say its faster, but is definitely more responsive and the smell of gas / oil is probably 25% of what it was previously. It is tough for me to attribute the performance / smell differences between the carb tuning / Pinz SSI since they were both done without me being able to drive it one after the other.

truck is much better behaved overall, glad i did those upgrades. will keep everyone posted as to how it continues to perform.

I had it in my possession for a few sweet hours and then... dropped it off at screen gems studio for its roll in an upcoming history channel mini series...
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TechMOGogy
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Re: New (NOS) Pinz Carb Install / Tuning

Post by TechMOGogy »

oilcan wrote: SNIP

I had it in my possession for a few sweet hours and then... dropped it off at screen gems studio for its roll in an upcoming history channel mini series...
Wow cool - keep us posted on this and when we can watch/see it!
72 Pathfinder | 75 710M 2.7i | 96 350GDT Worker
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