Webbers

Atlee · 08-21-2006, 09:53 PM

So here's the situation.
'60 912, big bore, 40 IDF Webbers.
#4 cylinder is not firing.
The cylinder and piston are both O.K. and I got plenty of spark so it has got to be gas not getting to #4 even though I am getting gas to #3 off the same carb.
Just to confuse the issue further, I cannot make the engine stumble even with the idle screws full in on #3 and #4.
(#1 & #2 react as they should)
Incidentally, the car runs fine on three jugs, but don"t go uphill too good.
Any bright ideas?

Ron

Nige-912E · 08-22-2006, 12:31 AM

Could be a blocked jet, probably idle jet. Remove and give it a blast through with compressed air or carb cleaner.

Atlee · 08-22-2006, 09:14 AM

Nope.
checked the whole stack already, and tried replacing with some spares I had.
Any other ideas?

Ron

david c. · 08-22-2006, 10:21 AM

Have you checked compression on all four cyls.? With low compression the vac signal on that throat would be weak. Have you put a unisyn on all four throats? Is the suspect one drawing less?

Although you may have spark, the timing could be off. Are you still running points? If so, have those factors been addressed (i.e. dwell, timing, etc.)?

The two throats share the same fuel bowl, so this seems a bit strange if you've confirmed the idle and main jet passageways are not blocked.

Although probably not your problem, can you see gas squirting out of the accel pump jets (the nozzles near the top of the carb bodies)? If this is hard to see, you can do it on the bench. There are specs you can check against to make sure the volume of the spray is correct and equal, throat to throat.

Atlee · 08-22-2006, 01:21 PM

Syncrometer reads equal on all four cylinders, and the engine starts easy with only three cylinders firing so the timing and points should be good.
Float level is according to specs.
Couldn't get a view of the accelerator pump, but the carb is coming out for a looksee.

david c. · 08-22-2006, 02:22 PM

Have you swapped plugs?

I'd still do a compression test.

Atlee · 08-22-2006, 04:25 PM

Pulled the carb, used compressed air to blow out all the openings in the body for the variouse jets,and could see the air exiting inside the tube. The plugs are all new since the #4 died. Put it all back......NAADA.

I,m gritting my teeth here!!**#**#?

Ron

Atlee · 08-22-2006, 05:24 PM

All four jugs are firing..... and I haven't a clue why.

So I ain't ganna fix it 'cos it ain't broke.

Thanks for the sage advice.

Ron

david c. · 08-23-2006, 05:59 AM

Okay. I have to ask if you've made sure the valves are set properly, too. Glad you've gotten some results!

Atlee · 08-23-2006, 07:09 PM

Set dem valves on the bench before I slid the mill back in two weeks ago. It is easier than lying on your back. I could actually see what I was doing for a change.
Thanks for the suggestions........

Ron