Weber balancing and stuff

[Martin S.]

Spent a happy afternoon twiddling with my webers. Set the balance at 900rpm then ran it up to 3000rpm to find the balance was way out, 10 grads on the guage on one carb and 14 on the other, so I balanced it at 3000 and rechecked at idle, 2 on one 3 on the other, not unsurprisingly! Are they usually this far out or am I expecting too much. It runs nicely on the road apart from the odd pop on part throttle openings which seems pretty normal for webers.

 

Dedion 2Ltr Zetec

 

Edited by - Martin S. on 4 May 2002 21:40:26

[ashaughnessy]

I think for setting throttle balance you should check it at a fast engine speed (like 3000, as you did) and not 900. My car at least (supersprint) doesn't idle smoothly enough at 900. However, if you find the balance at 900 isn't right after setting the throttle balance at 3000, perhaps it is your low speed mixture setting that is out? There is adjustment you can do to the low speed mixture that would presumably give the effect you're seeing - imbalance at low speed but balanced at high speed. I wouldn't try to use the synchrometer to set the low speed mixture though.

Anthony

[Martin S.]

Don't think it has anything to do with the mixture setting. My understanding is that the suck on each carb is down to the opening of the throttle plate only (and the air bypass screw which is factory set), irrsepective of mixture. Is that right Roger?

[ashaughnessy]

Yes, that sounds right. Ignore what I said then, I was talking rubbish (not for the first time and probably not for the last time either :-)

[Casbar]

I normally balance my carbs at around 1500, job done, don't bother checking at any other throttle openings.

 

As for accuracy, lots of guys use a piece of hose pipe, so, you will be able to set them closer with a gauge - in theory!!

[J.R.]

Martin.

 

I have had the same problem on my 2 litre zetec for 5 years also a high idle speed when hot.

 

I have just solved it prior to selling the car (isnt that always the way).

 

Mine was caused by the butterflies not being centralised on the modified throttle spindle (one with throttle pot) but could be on either.

 

When correctly balanced at 3k it is OK but when throttles shut one cant shut completely (misaligned butterflies) which either holds open the other (fast idle) or in my case the return spring on the spindle and the auxiliary spring pulled the throttles shut (on the correct spindle) by moving the balancing lever away from the screw and compressing the balancing lever spring.

 

Difficult to describe in print but easy to see.

 

After about an hours fiddling I had a good idle.

 

Before doing all the above make sure that the idle by passed screws are fully home as they can also cause the problem, but should be used to correct any imbalance after checking out the throttle spindles.

 

The way that I satisfied myself that one carb spindle was closing more than the other was to remove the screws from the progression drilling and using a torch I could see the misalignment, when I opened the throttle a tad they sprung back into line.

 

Very frustrating as I have lived with it for 5 years!!

[Martin S.]

Thought I'd found the problem, one of the manifold studs was missing, but after sorting that and rebalancing it's still the same.

 

J.R. I presume it's a carbs off job to check the butterflies as you suggest? 'Prgression drilling' is that one of the screws near the idle mixture screw?

 

BRG Dedion 2Ltr Zetec - Warrington

 

Edited by - Martin S. on 9 May 2002 20:11:04

[J.R.]

Martin

 

Can be checked without removing carbs by removing the progression drilling covers. Yes they are near the mixture screws, they are flattish brass screws (not with O-rings under, they are acc pump jet holders), remove them and you wil see the drillings as per last posting.

 

Carbs will have to be removed if you need to realign throttle butterflies.

 

Sounds like you have a Dunnell manifold as all my studs were loose & not loctited.

[Martin S.]

Thanks JR. Yep it's a Dunnell, as is the rest of the engine.

 

BRG Dedion 2Ltr Zetec - Warrington

[Martin S.]

Yesteeth.gif sussed it. Took the carbs off and couldn't believe what I saw. Some dork had drilled a hole in one of the throttle plates. Looks like they were drilling out one of the progression holes and carried on straight through the plate eek.gif. Surely not Dunnel when they built the engine??? Anyway soldered up the hole, refitted, set everthing up and it's running lovely + I know a lot more about Webers now. Thanks for putting me on the right track J.R.thumbsup.gif

 

BRG Dedion 2Ltr Zetec - Warrington

 

Edited by - Martin S. on 11 May 2002 19:49:57