Cylinder 3 problem?

[peterman]

Hey guys,

I'm home from school and tuning my double webers after changing the idle jets to 45 F9's. The car has always ran rough and i thought it was mostly due to the jets, as some of you had pointed out that they were way too big at 55's. I'm using a borrowed uni-syn carb sync'er and was having some trouble getting the vacuums correct. There is a slight popping sound coming from the 3rd cylinder from the front (number 3?) and when I cover the back Weber the barrel of the 3 cylinder carb starts to fill with gas.

Could this be a bad valve guide? broken rocker (although I would have seen that)? I adjusted the rockers not too long ago. What would make the carb flood like that?

Any ideas what this could be?

Thanks,

Pete

[peterman]

Also, Cylinder 3 is pulling the same vacuum as 4 maybe just a little lower. I also just thought that it could be some internal to the carb but that does'n

t explain the popping sound.

[tim385]

I use my synchrometer to firstly get the linkages correct, do this first before you do anything else, your timing and valves should already be adjusted correctly, then ....easiest way Lamba/air fuel /wideband o2 up the exhaust and adjust the mixture screws till you get as close to 1 Lamba or 14.7 A/F.

I thought I was running the wrong idle jets until I did this and by adjusting the mixture screws ended up getting it spot on .

[c.d.iesel]

spitting(popping) thru the carb is too lean idle mixture just on that

one throat

recheck the idle mixture adjustments and your jets

sure that intake valve has clearance

[peterman]

spitting(popping) thru the carb is too lean idle mixture just on that

one throat

recheck the idle mixture adjustments and your jets

sure that intake valve has clearance

I opened up the idle mixture screw quite a ways and didn't see a difference. The noise I'm hearing is not a pop like a backfire but almost like a "clock" (noise not a tick tock). I turned the mixture screw to about 2 full turns before closing it down again.

I'm pretty sure its not a running lean issue because of the amount of fuel on my palm after I cover the throat to starve it of air. I could be wrong though.

[Jeff]

What is the engine idle speed?

It needs to be 1200 rpm or below for the idle circuit to be working properly. If you are adjusting the idle mixture screw and not seeing a change in rpm, the idle speed may be to high.

If your idle speed is 1300-1400 rpm you are out of the idle circuit on the carburetor.

Also make sure that the main throttle shaft in the rear carburetor is not twisted making one of the throttle blades open more then the other.

[oldguy]

Weber 40s or 45s?

[Arizona02]

intake valve is leaking combustion and you hear it in the barrel with side draft carb, Engines with a single factory type carb & intake you may not hear a slight leak.

[peterman]

Carbs are DCOE 40's I was at a high idle so I suspect I was above the idle circuit as suggested.

intake valve is leaking combustion and you hear it in the barrel with side draft carb, Engines with a single factory type carb & intake you may not hear a slight leak.

I thought it might be that. I guess I'll be doing guides and lapping some valves. Compression testing should confirm the suspicion so I'll probly do that before pulling the head.