zenith 40 enrichment circut bypass?

7483cab · 7483cab's Garage

I have been told that some mechanics remove the enrichment circut hoses and cap the fittings on the sides of the zenith 40 tin carbs. Can anyone tell me why? Thanks

PhatRedHead · 09-06-2005, 12:03 PM

i'd like to know as well, please someone help !

SMC · 09-06-2005, 12:38 PM

Me Three

tswaney · tswaney's Garage

Why would you want to get rid of that beautifully engineered octopus?

Are you talking about just getting rid of the hard lines and hoses or the whole diaphragm device? I just rebuilt mine and left everything in place and capped (4 or 5 mm) the vacuum lines (1 on each carb). I also left the solenoid on the right side carb.

But I guess you could get rid of the hard lines and hoses and cap the six nipples with 7 mm (I think) caps and leave the house-shaped diaphragm housing. I wouldn't have a clue on how to plug the hole in the carb body if you got rid of that mechanism. Maybe a very small rubber cork?

Brant · 09-06-2005, 02:27 PM

Tom,
can you explain why this is done...

I'm very ignorant regarding zeniths (especially)

brant

tswaney · tswaney's Garage

Just my guess, but if you don't need the emission control that the Aux. Enrich. Dev. provides (i.e. emission testing for registration...), then why have all that excess plumbing? It is definitely in the way while making mixture adjustments.

I have never found out where the vacuum fitting is supposed to attach anyway, so that's why I plugged it. But I do like the original look with the brass(?) piping and cloth braid lines.

There are definitely guys with way more knowledgeable about Zenith's than I....hope they speak up here. Allen, Mike.....?

tforri · 09-06-2005, 04:54 PM

FWIW, I found JB Weld in the diaphragm area on the right bank during my rebuild. I removed it because I couldn't figure out why it was there and why only one side. Engine wasn't running when I got the car so I don't have any way to compare how it ran before vs. how it runs now.

Todd
_________________
1971 911T

Allenk · 09-06-2005, 05:12 PM

Allenk · 09-06-2005, 05:15 PM

rw7810 · rw7810's Garage

You can remove this as it was for smog, etc and doesn't add anything to performance. I've had mine off for 5 years or so and no difference in running. See pic after recent rebuild. you can cap or cut off the little tubes, tap and plug. Cleaner look too.

tswaney · tswaney's Garage

Excellent. But what are the results if you shut this circuit down, beyond increased hydrocarbons through the tailpipe during decel? Popping/backfire? Are there advantages to plugging up everything?

project 911 · project 911's Garage

Not sure if this helps anything, but I removed the housings and tubes from the sides of my Zeniths and pluged the lower vacuum tubes. I filled the holes where the side housings where with epoxy (I think). I still have the solinoid on the inside of the passenger side carb, and it is hooked up to the switch that is activated when the throttle is closed (on the driver side carb). I week or so ago I noticed backfiring on deceleration and generally more carb popping. I found that the RPM transducer on the electric panel was dead. I replaced that and the popping went away. I think most people remove these parts too, and some say you can tune out the backfiring.

7483cab · 7483cab's Garage

According to Bruce Anderson (911 perf. handbook) these were installed in order to suppliment fuel at higher rpm's in order to avoid detonation but offered no increase in hp or performance. According to people i've talked with these were over eng. and troublesom. I would like to know the problem symtoms these will show?