935 gauges?

JJK78-951 · 05:07 PM

Good evening everyone,

I have some gauges I believe are from a 935 and looking for confirmation/additional information on them. These gauges came from the estate of a friend who was a Porsche racing mechanic. He also helped to restore the Martini #2 935 several years ago but can't say where these gauges came from as that is about the extent of the information I have on them. I'd like to have them tested and get them restored just wanted to get some recommendations, I've used North Hollywood and Palo Alto for standard gauges before but haven't spoken to them yet about these so looking for any recommendations/referrals.

Since this is the turbo forum i'll start with the boost gauge! Porsche VDO Ladedruck LED Boost gauge! .5-1.9 kg/cm2. 4 pin connector. Ink stamp very hard to read but possibly 2.77 date stamp? Has a hand written paper with "22" taped to the back. In researching it seems the part number for this gauge might be 935.641.503.00. The bad part is I do not have the sending unit for it. Is it possible to modify a stock 1.5 bar unit to 2 bar? Does anyone have an original 2 bar sender available??

Second gauge is a VDO 10,000 RPM Tachometer with tell tale needle. Has a blue and yellow warning lights. The instrument numbers themselves are printed onto the back of the plastic rather than stuck to the gauge face. It has a raised dimple in the center. On the back it is a mechanical drive and has an ink stamp dating it to 6.76. Also a little reset button presumably for the tell tale. No part numbers that I can see... I've looked through some pictures and appears to be correct but and info would be much appreciated.

Along with the tach I found what appears to be a custom tachometer drive unit setup. It has the 2 relays wired in as you can see, the unit itself is dated 7.71. Is this possibly the drive unit for the VDO tachometer? Any info would be great!

So I guess in summary...
Where is the best place to send the gauges for testing/restoration?
Does anyone have a 2 bar boost pressure sensor available or know where to get a compatible one?
Can a factory pressure sensor be modified to work with the 2 bar boost gauge?
Any info on the tachometer and electronics would be greatly appreciated!
Are these bits correct for 935s?

THANKS!!
John

1Bad86 · 05-16-2023, 09:24 AM

I can't help much with information but that digital boost gauge is a neat find as is the tach. Anytime old race parts pop up it gets my attention.
I had Palo Alto build me a 2 bar 934/935 style analog boost gauge and it looks and performs great.
I wouldn't hesitate to use them again for any gauge needs but they are pricey.
I'm sure they could help you with information and restoration.
I'd love to have those pieces in my car.
Good luck and keep us updated with what you find.

VZ935 · VZ935's Garage

Most of my 935s have both the VDO mechanical gauge and the electronic gauge you have pictured. In my K3 pictured below you can see them side by side
The issue with that boost gauge is that no one makes the sending unit and without that the gauge usually becomes a nice novelty to have or a bookshelf piece.
They were easy to see, specially for night races, but were not dependable so usually everyone had the mechanical gauge as a backup.
Hartmut at Palo Alto was never able to help with the sending unit.

All that being said I would be interested

JJK78-951 · 05-16-2023, 03:47 PM

Quote:

Originally Posted by 1Bad86

I can't help much with information but that digital boost gauge is a neat find as is the tach. Anytime old race parts pop up it gets my attention.
I had Palo Alto build me a 2 bar 934/935 style analog boost gauge and it looks and performs great.
I wouldn't hesitate to use them again for any gauge needs but they are pricey.
I'm sure they could help you with information and restoration.
I'd love to have those pieces in my car.
Good luck and keep us updated with what you find.

I appreciate the reply! Palo Alto will definitely be one of my first calls as I've always been impressed with their work. I'll update this thread with any info I get~
Thanks!
John

JJK78-951 · 05-16-2023, 03:57 PM

Thanks for this information! A bit bummed about the sending unit info but I'll keep digging around and see what I can find... I've got a buddy who is a bit of an electronics guru so maybe we can figure out a way to modify a standard sending unit to work.
I'm definitely jealous of your 935s! Must have been a hell of a lot of fun to race those beasts around!
I'll update this thread with any additional info I come up with~
Thanks for your reply!
John

Quote:

Originally Posted by VZ935

Most of my 935s have both the VDO mechanical gauge and the electronic gauge you have pictured. In my K3 pictured below you can see them side by side
The issue with that boost gauge is that no one makes the sending unit and without that the gauge usually becomes a nice novelty to have or a bookshelf piece.
They were easy to see, specially for night races, but were not dependable so usually everyone had the mechanical gauge as a backup.
Hartmut at Palo Alto was never able to help with the sending unit.

All that being said I would be interested

JJK78-951 · 06:42 AM

Well finally had some time to dig into these a bit more this week. They are definitely not your everyday gauges!

Hartmut from Palo Alto basically confirmed what VZ935 said regarding the boost gauge. Can't provide a sending unit or modify an existing one, and have no way to test it. Although they can cosmetically restore it. The tachometer can be tested, repaired and restored... but while I'm used to the standard Porsche tax when it comes to parts/repairs, the Porsche race car tax is beyond my expectations.

NHS also said they could handle the cosmetic restoration but not so much the functionality side, although pricing was much more reasonable. I may check with the Porsche restoration center here in Atlanta too just for giggles and see if they can help me.

My only other hope is that I have a friend of a friend with a 935 and 962 who I'm going to try and connect with. I'm hoping these gauges are a close match to the ones in his cars and may be able to test them that way. If that falls through then I'll probably just sell them as-is and let the next guy deal with it~

Edit to ad that it appears the correct part number for the boost gauge could be 935.641.502.00 although I'm sure there were different revisions so not sure how to tell.

Any other suggestions or recommendations would be greatly appreciated.
Thanks!
John