Help needed: What’s going on here..???

Fullchat289 · #1 (**permalink**) 10-14-2010, 08:32 AM

Some engine info:

T&L 347 running Weber IDFs with Dart Pro1 heads and Hydraulic Lifters. Engine has 8300 miles on it.

Very recently noticed some stains on my freshly painted valve covers after returning from my 1300mi trip to the Dragon that appeared to be some fuel that burped out of the front RH front carb. (IDF’s) Took the air filter last night and noticed a bunch of carbon on the inside of the venturie stacks and underneath the air cleaner. The other three carbs aren’t showing this phenomenon. Any ideas what’s going on here? I have more of a backfire on the RH side of the car, but was attributing it to sealing on the header to side pipe slip joint connection. My exhaust manifold bolts all appear to be tight from a recent check. I’m noticing no performance issues other than a little carb spitting from time to time under initial throttle application. The car pulls very strong and all adjustment screws/linkage is secure and unchanged.

Here is a picture of the RH bank showing the stain on the valve cover and carbon in the stack of the front carb.

Here is the rear carb showing no carbon.

Here is the front carb showing the carbon.

Here is the underside of the air cleaners of the front and rear carbs.

Thanks in advance for your input,

- Allen.

dlampe · #2 (**permalink**) 10-14-2010, 06:11 PM

It looks like that carb is very rich. That would account for the popping. That can only be cause by a few things but my first guess would be a float level or needle and seat. If you start the car and look down the carb, is gas dripping throught the auxillary venturi? Check and see how those plugs look compared to one of the others.

dcdoug · #3 (**permalink**) 10-14-2010, 06:19 PM

Allen - if you have problems figuring it out, Zimmy is pretty good with webers and is part of CACC.

zimmy · #4 (**permalink**) 10-14-2010, 11:48 PM

Doug - thanks for the vote of confidence (something very rare for me in CACC

). I agree with Doug. I would first look at the float and fuel line valve. I had a bad fuel valve in one of my IDAs and it completely flooded the one carb (long story how I found out). Surprisingly didn't really notice it driving.

Best way to check float level is to remove all of the carb cover screws except a couple. Run the car for a few seconds to be sure carb is full of fuel. Shut off car and immediately remove the last two screws, open the cover and actually measure the top edge height of the float. It should be about 5.5 mm above the top of the carb (at least it is 5.5 mm on an IDA, I forget what it is on the IDF). Adjust if necessary and replace cover with the 2 screws. Test again. When done reassemble and enjoy!

Fullchat289 · #5 (**permalink**) 10-15-2010, 09:44 AM

I appreciate the responses, guys.

Since I'm not experiencing any performance issues, I'm going to clean up all the soot, and assemble it all back together, put a 100 miles on it or so and see if the soot returns before I start opening things up. I remember a time on one of the last legs of our Dragon trip where the car smelled extra rich, but has since gone away....I wonder if I might have gotten some dirt in that needle valve or something that would have created this issue...If the soot returns, I'll check the floats and try to find some IDF setting documentation in the mean time.

If anyone has a lead on some on-line IDF specific stuff, I'd appreciate it.

- Allen.

Gaz64 · #6 (**permalink**) 10-15-2010, 03:18 PM

I'd agree with the other boys, pull the tops off, at least of that carb.

I'd say some fuel hose debris has lodged in the needle and seat.

You have normal hose and hose clamps (not AN) and the offending carb is the last carb in the fuel line.

I'd also go back to studs and nuts for the airfilter base/ramtubes, you'll need longer studs than factory.

Rick Parker · #7 (**permalink**) 10-15-2010, 03:57 PM

I think the intake valves are leaking on those 2 cylinders. Does it run smooth, or rough? Does the roughness increase as RPMs rise?

bobcowan · #8 (**permalink**) 10-15-2010, 04:03 PM

first thing to check is the balance. If that carb is opening more than the others, this is what happens.

wolf k · #9 (**permalink**) 10-31-2010, 07:45 AM

Fullchat, what did you find?

zrayr · #10 (**permalink**) 10-31-2010, 10:33 AM

could be inversion ? Not uncommon with single runner induction and also vintage Paxtons. If inversion, cause could be varied. Anything from carb out of sync to valve adjustment or lifter/cam damage

Z.

Fullchat289 · #11 (**permalink**) 10-31-2010, 11:50 AM

Guys:

I'm thinking this is a carb sync issue, ultimately (glass half full and all). Reason for this is when I took reciept of the car, the idle was a low 500rpm. One weekend when I gave my dad the car, I also handed him a screw driver and showed him where the master idle adjustment screw was on that RH front carb. What I'm think is that the idle adjustment was taken up by this carb and with the slight tolerances in the linkage, there wasn't enough to overtake the overall spring tension and none of the other carbs followed suit.

Anyway, to prove the theory, I should be getting a syncrometer in the mail this week.

Does anyone know if you need to mess with the idle mixture at all when sync-ing the carbs, or can you just back off all the jam nuts and make sure all the carbs are drawing the same and call it a day? I was a little confused by this when reading some of the "best lean idle" documents I found on the Pierce Manifolds site.

Thanks again..I really have appreciated all the replys.

- Allen.