Inliners International Forums General Discussion Engines Rich on cyl's 3 & 4

My '67 truck has a 250 with Clifford intake along with Clifford shorty headers and an Edelbrock 500cfm carb. I've always had a problem with the 3 and 4 cyl's being too rich and fouling the spark plugs to the point that they become crusty and coated with brownish gunk and I have to clean them now about once a month. All the other plugs look fine and have a nice tan color to them with no build-up.

When I first bolted on the carb I tried different jets and rods using the Edelbrock tuning instructions, but never had good luck except with the stock jetting and rods. I've also tried the carb turned 90* to no avail.

The truck runs great and idles well otherwise. Anyone got any ideas?

Is the intake current production, or an early non-heated version?

Are you running heat to the intake?

It's an older unit that was converted by Larry in FL with a water box below where the carb sits. Hot water is run using 1/2" hose from a plug in the t-stat housing to the box underneath manifold and then on to a T in the top heater box water line.

Are you using a phenolic spacer under the carb?
Are there grooves, etc.. in the floor of the intake, and how are they oriented?
Are there times it starts hard?
What is your fuel pressure?
After a good hot run, shut it off and pull the air cleaner. Watch the carb, and see if it starts to perk gas into the manifold?
How's the compression?
How's the oil consumption?
Do you have a PCV valve installed, and where is it hooked into?

I'm using a steel spacer with 4 holes to raise the carb off the deck and simply to be able to mount it to the intake with the way the intake is designed.

Larry milled out the grooves in the floor where he could.
I don't think it ever starts hard.

I'm using stock fuel pump pressure-whatever that is.

I don't know the compression.

The engine does use oil.

The stock pcv valve is hooked up into the carb on one of the larger ports.

You say it uses oil? Oil residue is sometimes brownish rather than the usual black greasy deposits.

Yeah, that's were I was going with this...
While having a problem with two cyliners right next to each other might seem like a fuel delivery problem, it may just be a coincidence, and that the problem is really something else.
I would suggest doing a compression test on it. I wouldn't be surprised if the middle two were low, most likely due to bad rings, which is causing oil consumption in those two cylinders.

The only thing I was thinking about if it was the carb, is that its dumping fuel after shutoff, and that the grooves in the bottom of the intake were somehow directing most of it to the middle port. It's a long shot...

As for the PCV, another long shot, but if it was hooked into the middle runner,like the factory did it, and you had alot of blowby, you may just be adding too much oil vapor to those cylinders for the spark to overcome.

Or you don't have enough spark at those two cylinders due to a problem with the the cap or plug wires.


Do a compression test first...

I had a problem with my after market Offy aluminum valve cover. It had no baffles in it and thus it allowed oil to be sucked up into the carb through the PCV valve. It also caused oil to spew out of the breather cap. This may be causing your excess oil consumption. The cure is to install the baffles from the factory cover into the Offy cover.
Al

The runners in the Older clifford intake run from end to end.
Which over many have found out the worked all to well and the center two cyl. would be lean. So the trick was to remove a few.
which is what i had done for him while i had his intake.For the
added Hot water box.