Using a Scrap of Wood to Replace a Porsche 924’s K-Jet Injection With an SU Carburetor

Fuel injection is undeniably a Good Thing in the car world. While carbs occasionally offer an advantage or two under very specific circumstances, injection plays a central role in things like 200 mph Corvettes that get 20-plus mpg and emit a fraction of the pollution of a 36-horsepower VW Bug.

So, given the choice, injection is the thing. But in Lemons, desperate times routinely call for desperate measures, and having your Porsche 924’s Bosch K-Jetronic injection go kaput in the middle of the race certainly qualifies as a desperate time.

After trying numerous unsuccessful fixes on their vintage K-Jet system, the brilliantly named It Won’t Get Better Unless You Pick At It Racing collectively uttered those familiar old-gearhead words while working on their Porsche 924: “Let’s rip off all of that injection crap and slap on a carb!”

There were a couple of problems with this strategy. One, they didn’t actually have a carburetor. Two, this was a Porsche 924, not a Camaro–they couldn’t just pop down to the local AutoZone for an Edelbrock manifold. But–and here’s where the desperate measures really come into play–the team figured they were surrounded by typically spare-parts-rich Lemons racers who had plenty of scrap materials (more on those in a minute) from which to construct a simple carb adapter for the stock 924 manifold.

A quick stroll around the paddock scored the team a trusty single-throat SU carburetor and a low-pressure fuel pump from the dark recesses of an Austin Mini enthusiast’s toolbox. An inventory of their own trailer produced a perfect, lightweight, easily workable material for the adapter: wood.

After a few passes with a drill and a jigsaw (both for fabbing the adapter and cutting a necessary clearance hole in the hood), along with a few minutes spent MacGyvering a throttle linkage, the 924 ran well enough (terrible, by normal standards) to get back on track.

Fuel injection blues? Only at a Lemons race: Just replace everything with an old SU carburetor.

Join Free Join our community to easily find more Low-Buck Tech, lemons and Porsche 924 articles.
Comments
View comments on the GRM forums
Agent98
Agent98 Reader
12/20/19 2:58 p.m.

Excellent trackside engineering! Hey we all use paper/wood pulp gaskets....

Stefan
Stefan MegaDork
12/20/19 3:11 p.m.

I used a block of aluminum that I drilled holes in to fit a Turbo-Dodge throttle body  on mine :)

The CIS and electrical implementation on the 924 is terrible and causes many to be parked and found for nearly free.

As I tell people in the 924 groups, carbs are better than that CIS nearly any day, but don't expect huge gains other than a running vehicle.

If they track down one of the carb intakes used on the version of that engine used on some AMCs, they could end up with a slightly better long term solution.

californiamilleghia
californiamilleghia Dork
12/20/19 3:33 p.m.
Stefan said:.

If they track down one of the carb intakes used on the version of that engine used on some AMCs, they could end up with a slightly better long term solution.

Hi , which AMC was that ?  and was that the only motor in the AMC those years ?

Thanks

ShawnG
ShawnG PowerDork
12/21/19 9:54 a.m.

"Organic carbon fiber"

jr02518
jr02518 Reader
12/21/19 10:26 a.m.

Did the they olive oil in the dash pot? 

mad_machine
mad_machine MegaDork
12/21/19 8:38 p.m.

isn't that also the same engine as in the Dodge Omni?

slowbird
slowbird Dork
12/21/19 11:09 p.m.

Hopefully they give the intake a nice coat of deck stain before the next race. Y'know, to impress the tech inspectors.

Vigo
Vigo MegaDork
12/22/19 12:48 a.m.

I thought about doing the same with my old 924 (which i no longer own but is still in my yard...) but with an actual DCOE. I'm not convinced it's NOT a good idea. 

My thing with the 924 engine is if you're not adding boost, you should at least be reducing complexity. If you want an amount of complexity commensurate with the 100hp you're going to get out of it, a carb starts to make sense. 

Stefan
Stefan MegaDork
12/22/19 1:18 a.m.
mad_machine said:

isn't that also the same engine as in the Dodge Omni?

Nope. 

https://en.wikipedia.org/wiki/List_of_discontinued_Volkswagen_Group_petrol_engines#EA831

The Omni used a 1.6L Peugot OHC, a VW 1.7L SOHC from the VW Rabbit and the Chrysler 2.2L SOHC.  The 2.0L in the 924 was from Audi 100LS and some VW LT vans, but was never used in any of the VW cars.  So it doesn't use the bellhousing pattern of the more common VW water cooled engines.  At least the 2.0L shares bellhousing pattern with the later Audi 5-cylinders, so there's hope if you can sort out the rest of the swap parts, but I5's are thin on the ground anymore and there are other challenges involved with that swap.

That said, the 924 was originally a VW project they were developing with Porsche, but the 70's oil crisis scared them and they sold it to Porsche and made the Scirocco instead, so the 924 has a LOT of VW parts in and under it and the 944 is an evolution of that, so there's lots of parts that can be swapped between them to make them better in many ways.

Stefan
Stefan MegaDork
12/22/19 1:21 a.m.
californiamilleghia said:
Stefan said:.

If they track down one of the carb intakes used on the version of that engine used on some AMCs, they could end up with a slightly better long term solution.

Hi , which AMC was that ?  and was that the only motor in the AMC those years ?

Thanks

The AMC Gremlin starting in 1977: https://ateupwithmotor.com/model-histories/amc-gremlin/

https://en.wikipedia.org/wiki/List_of_discontinued_Volkswagen_Group_petrol_engines#EA831

LanEvo
LanEvo Dork
12/22/19 5:06 p.m.

I swapped out the CIS/K-Jet on my racecar with a pair of Weber side-draughts. Makes perfect sense to me. 

Sonett323
Sonett323 None
12/26/19 5:44 p.m.

The AMC cars that used the Audi 4 cyl engine along with the earlier Porsche 924's were called the AMC Spirit. When buying parts for this engine I always looked at the AMC Spirit prices before Porsche prices, Example: Pirelli timing belt AMC=$9, Porsche=$50. You decide!

californiamilleghia
californiamilleghia Dork
12/26/19 6:03 p.m.

Anyone have a picture of the AMC /  AUDI / VW manifold ?

Sonett323
Sonett323 New Reader
12/26/19 6:19 p.m.

These AMC Spirits were made from 1979 to 1983

The standard engine on all models except the AMX was a 121 cu in (2.0 L) EA831 inline-four supplied by Audi.

The four-cylinder engine is the same overhead camshaft unit carried over from the Gremlin, and was also available on the Concord. It used the same cast parts as the Porsche 924 (both made by VW/Audi) but was assembled in an AMC plant in Indiana to different specifications than that of the Porsche engine; the AMC version was only offered with a 2-barrel carburetor while the Porsche unit had electronic fuel injection and a higher compression ratio.

GIRTHQUAKE
GIRTHQUAKE HalfDork
12/27/19 10:14 a.m.
californiamilleghia said:

Anyone have a picture of the AMC /  AUDI / VW manifold ?

Have you asked around on the AMC Forum? One of those wacky bastards probably has one, they hoard parts like ferrets hoard trash it seems.

aircooled
aircooled MegaDork
12/27/19 10:55 a.m.

It's a phenolic spacer!

I created a phenolic spacer out of red oak for my Lifan 200cc motor after creating a custom steel intake which left the carb an inch from the head with no insulation.  Works great.

Vigo
Vigo MegaDork
12/27/19 10:03 p.m.

Anyone have a picture of the AMC /  AUDI / VW manifold ?

I found a diagram of one from an autozone repair manual, not a real pic. I also found that the engines were tilted differently and that an amc manifold on a 924 would tilt the carb more than most like and may be a hood clearance issue.  

Streetwiseguy
Streetwiseguy MegaDork
12/27/19 10:17 p.m.

Maybe it's only in my part of the world, but I worked in an AMC dealership in 1980, and I only ever saw one Gremlin with the 2.0.  I presume them to be exceedingly rare.  The Spirits mostly had 242 inline sixes, and iron dukes for the four cylinder.

Our Preferred Partners
MlBZay4etDXfKDjv7n3kdFkdpY785N8ZaBXcTWp9PIkN2uHEXuD1LYUoiFbpdBbN