Webers on 1600 Vauxhall

[ChrisJ]

2 questions

Does anybody know the best jet set up for these?

I read another posting talking about having the air horns in plane along with K&N filters. Is this the norm ?

Ta much

Chris

[Super_Rich_Bernie]

Chris

 

My car has bigger choke tubes (from 28 up to 32 IIRC), and was jetted to suit (bigger main jet, air correction jet & different emulsion tube, can't remember the sizes I'm afraid)

 

The work was done by Aldon automotive for the cars previous owner (Brian Lyall) who may be able to tell you more.

 

I have the original parts - the original choke tubes are very unimpressive, with a poor internal finish - it doesn't look like they were finished carefully from the original casting. Having looked at the olsd ones I checked the new 32mm ones fitted - these have a much better internal finish.

 

I haven't tried the car with the original jets in it so I can't compare, however as the car is now it runs extremelty well, with smooth power and no flat spots from 2000rpm to 6000rpm. It pulls strongly from around 3500rpm.

 

If I want to run the car in as a Grad spec in sprints I will have to put the original jets in. Will clean up the chokes first though.

 

As for the filters, there needs to be adequate (an inch?) clerance between the ends of the trumpets and the cover of the airfilter. Not something I have checked, just assumed its ok.

 

hope this helps

 

 

Jonathan

 

[oilyhands]

These settings might be a good starting point

 

chokes 28mm

mains 115

Emulsions F15/F9

Airs 160

Idles 45f9

 

For emphasis towards peak power

 

chokes 30mm

mains 120

Emulsions F15/F9

Airs 170

idles 45f9

 

These arent definitive, just a suggestion.

 

Oily

[Michael Peterson]

That car of Brian's was a fine example. I saw it up for sale, but could not find the quidsad.gif

[ChrisJ]

Oily

Thanks for the settings. I checked mine :-

main 115

air 195

idle 50F6

emulsion F7 (I didn't understand your nomenclature on this, are their 2 ?)

 

My problem is a very black sooty exhaust tail pipe. Is this to be expected looking at my set up or is it normal for this engine?

Ta much

 

Chris

[oilyhands]

Christ on a trike.. 50f6 idles!!, surely the act of a desperate man.. very very rich for a 1600.

 

Without knowing the choke sizes I cant comment specifically on the jetting but it would be reasonable for 28mm chokes. The only unreasonable thing is the emulsions, F7s are more suitable for engines of a much greater capacity (typically 2400cc 4 pot), F15 would be a better choice.

 

I'd get the thing to a RR rather soonish.

 

Oily

[Super_Rich_Bernie]

Interseting. I'm tempted to have a look at what idle jets are in mine - though given the car runs very well it is maybe best to leave them.

 

There are no idle jets in the bag of bits which came out. There are some pump jets though so I guess they were changed from Caterham's spec.

 

The idle jets control mixture at idle, and presumably have some influence at wider throttle opening too. The air bleed screws influence mixture at idle too. Can the two be used to balance each other out? The black art of Weber defeats me a little.

 

Are the carbs somehow checked & sealed on the grads racers cars?

 

 

Jonathan

[oilyhands]

The idle jets dont actually control the mixture at idle, they *supply* the emulsified air/fuel mixture to the idle circuit, it is controlled by the volume adjustment screws on the top of the barrels.

 

These adjustment screws are not air bleeds, they are a graduated tapered needle that sits in a drilling from which the fuel is discharged. Turning the screw in (clockwise) pushes the taper further into the orifice and reduces the annular area of nthe orifice and therefore the volume of fuel discharged. This in turn weakens the mixture. Conversely turning the screw out (counter-clockwise) has the opposite affect and enriches the mixture. This ensures that the idle mixture can pretty much always be corrected by adjustment regardless of the idle jet calibration.

 

The idle jets in conjunction with the progression drillings also supply and control the fuelling for the progression between closed throttle and main circuit. As the throttle plate/butterfly is opened the edge passes these drilling causing the airflow to draw fuel from them.

 

The progression circuit covers a major part of cruise and the critical transition between taking it easy on a light throttle and hammering it, getting the idle jet calibration right is they key to a smooth responsive engine. Get these wrong and you can have a kangarooing, stuttering, pig of an engine.

 

The numerical value of the idel jet ID indicates the size of the fuel orifice (50 being .5mm). The 'F' number on the idles indicates the size of the air bleed in the idle jet and therefore the amount of air emulsified with the fuel before it is delivered to the idle and progression circuits. F6 has the smallest air drilling and is the richest that Weber do. Couple this with a 50 jet which is probably oversized for a 1600 and you can see why I expressed some surprise.

 

Oily

 

 

Edited by - oilyhands on 19 Oct 2001 10:41:35