plug analysis Options

[last337]

I was having a hard time getting the carbs tuned and I had a hard time getting the car started when cold too. I finally got running again today and tried to adjust carbs again only to find that two carbs would be pulling much harder than the other two at different throttle ranges. There didn't seem to be a way to get them synced correctly so I pulled plugs and found those two to be very heavy in carbon. Is that what was happening? Can someone explain why this was happening how it did?

[brant]

did you use a sync tool?

you need to sync the carbs by measuring the air
and there is also an adjustment to tune between barrels on the same side...

but have you sync'd your linkage? are you using some type of snail to measure?

[last337]

Yes I synced them with a snail type sync tool. I have been cutting my teeth on these carbs the hard way though just learning so maybe I fouled them during my trials.

[brant]

so when you say that the 2 carbs pulled harder than the other two
do you mean one bank (say right) pulled harder than the other bank (maybe left)?

if that is the case then adjusting the linkage arm on right versus left should equalize the two banks

there is an air adjustment on the car for equalizing forward carb to rear carb on the same bank..... but that doesn't sound like your problem as I read it.

sometime the linkage is worn or sloppy (or of poor design) and makes that balancing of right and left more difficult. Also try balancing at a certain rpm.. say 2200rpm instead of idle


you might have carboned them during your adjustment some...
but the two banks have to be balanced. Otherwise your going to keep getting more air to one side than the other causing one bank to be lean the other more rich in comparison. This assumes that the jets are the same in all of the carbs of course.

[brant]

and don't feel bad or discouraged.
fighting linkage can be a major pain in the butt!

[last337]

It was actually one carb on each bank. Those were pulling more air through than the others when I had a good idle. I had some bad timing issues awhile back when I changed the distributor. I wonder if that was the initial cause and then maybe I made it worse by adjusting the carbs to account for it.

[messix]

2nd from left doesn't look to have been getting anything no fuel or fire

1st looks good

3 and 4 look really rich and might be washing the cyclinder down with fuel.... check your oil for the smell of gas, if it does change you oil or the cam and bearings wont live much longer.

go see a carb guy soon to get some schoolin'


those weber and weber type carb are a mother effer to learn and get right and then it's fiddle fest to keep them right.

[last337]

First and second actually look almost exactly the same. Why do u say it doesn't look like it was getting fuel or fire? These plugs are almost brand new.

[messix]

plug 2 doest look to have had any heat to the insulator, plug 1 has some light discoloration indacating it has had some heat.

it should be light tanish gray.

[last337]

What does that mean? I know its getting fuel and the engine wasn't really missing until lately. Could it be that I just created problems when I had ignition problems and that's why carbs wouldn't adjust and why that plug doesn't show wear? Actually looking at pic I think the flash may have made it look that way. Plug one and two look almost identical

[messix]

since the are so new it wouldn'd have enough time to show a true lean condition but the chart here should help you.

[Jake Raby]

Carry out a throttle plate open compression test. If the numbers are good start chasing tuning issues.