SOME of the early 4180's had four corner idling.
I never said they didn't.
Never seen them on ANY '86-'87.
Look at the secondary metering block and tell how that is even supposed to work.
If Beetle showed those bosses cut open to expose the screws I would say he has an early carb with 4 corner...

If this is going to be some stupid pissing match I'll just put him on ignore.

 

woodzee,
Just 'cause it's not "in store" doesn't mean it is not in the local warehouse.
Online inventory is BS at best!

I always have my counter guys look up the P/N in THEIR system.

 

New fuel, air filter, and additive = much better.

Vacuum reads at 17 and holds steady. Idle has cleared up. Only ran for about 10 minutes. Would like to put a full tank through it, but she may just get by smog without a rebuild. If things continue to improve as it runs I'm going to hold off on the carb rebuild, when I do decide to, I'll have the parts. I do have to get 1 new SV-CBV, the rear one was cracked off at the one of the tips. I hear that will cause it to fail smog.

 

That's great news!
The emissions limits for these trucks are pretty high.
It should not be hard to get it to pass if everything is in place and working.

Make sure to check the ignition timing and set curb idle before you test it.
The nylon cam gear tends to wear out and makes the timing even more retarded than the 4* it already was in '72 for emissions.

 

Got all the registration now taken care of, except for smog.

Holley rebuild kit and blow out protection check valve came in today as well. The truck of course is now exhibiting new symptoms. The truck is very hard to start. It sputters and sometimes I have to add gas into the carb to get it to start (Just added some more fuel to the tank so we have fuel). Once it starts it runs and idle fine. I raised the curb idle because it was dying when I put it in gear.

I'm hoping the rebuild on carb will fix this, but any thoughts?

 

I think a carb rebuild will resolve most of your early symptoms.

While you have the carb off check to make sure the EGR valve is sealing, as was already suggested.

As for needing fuel to start, are you not able to pump the gas pedal once or twice and have it catch?
Have you driven many carbureted vehicles before?

 

Pumping the pedal does not help the situation, at least is does not consistently help the problem. Could that be a symptom of a blown power valve? I did notice that if I give it a good goose it bogs a good bit and then revs up.

As for driving carbureted vehicles, yes, which I know is not common for my age as carburetors were going out of style before I was born . 80' 20R toyota, 1962 Scout 80, 1967 Scout 800, 1975 Scout II, 1975 IH 444,... lots of internationals, I have a thing for them. The '75 was my daily driver for a bit. I am relatively familiar with some of the quirks of driving a carbureted vehicle vs a modern EFI vehicle.

I will say that all the vehicles, save the 62 had solid carbs on them when I bought them, so carb work is a bit out of my normal mechanical dirty work. Rebuilding the Holley 1904 single bbl I don't think counts.

That being said, should I dive in and just rebuilt (or refresh as holley calls it) the entire carb or just start by removing the primary on the front and replacing the power valve?

 

I really have no idea of your age, and didn't mean to suggest anything.
But I know it's likely anyone under 40 has always driven a fuel injected vehicle.

You say you need to pour gas in the carburetor to get it to start.
There is an accelerator pump that should do that for you when you first set the choke before you turn the key to start the truck.
This and the fact that the engine stumbles makes me think the pump is not working.
Either the check ball or a passage is gummed up.

Let's try a little diagnosis.
Take the air cleaner housing off and get up above the carburetor.
Look down the primary bores and with the choke plate held open work the throttle linkage a couple of times.
Do you see a stream of gas being squirted into each bore?

Honestly, If you are good at keeping track of little parts, any carburetor of this age could benefit from a thorough cleaning.
A source of compressed air and a sealed container where you can soak parts in lacquer thinner is a lot more helpful than a few spray cans of carb cleaner.

 

Haha, didn't take it as an insult or suggestion I just forget sometimes. Let's just say the truck is older than I am .

I'll take a look and see how the pump is responding.

Thanks!

 

I had done this test early on when I first started this thread and there was some form of stream when you hit the throttle. Now there seems to be none, leading me to believe the power valve, accelerator pump (whichever flavor you use) had a leak and now is shot.

Will replace and see if that helps.

Will gas leak out of a blown accelerator pump causing rough idle, popping, running rich, etc?

 

Welcome to FTE.

Didn't notice if you have an electric fuel pump or a mechanical one.

Also didn't notice it you changed the fuel filter(s) but that's always a good idea.

With a carb that old I wouldn't mess around trying to replace just the power valve. Get the genuine holly kit and rebuild it.

FWIW, My 86 - 87 4180 does not have 4 corner idle mixture adjustment, only two up front, and due to their location and the rats nest of vacuum lines and hoses they are a real bitch to get at with a 3/32 Allen wrench.

If your carb still has the idle mixture adjustment anti-tamper plugs installed it has probably never been gone through and if that's the case it is probably time for a rebuild.

Your hard start could be any number of things; from choke not closing, accelerator pump circuit problems, and front fuel bowl leaking dry (happened to me) to ignition system issues (I once had an ignition module heading south that gave me intermittent hard starts).

If you do decide to rebuild the carb you might also want to get new floats (they are not included in the rebuild kit) and you will definitely need an EGR plate to intake manifold gasket which is also not included in the rebuild kit.

Also, if you have an electric fuel pump, you will probably have a hard line running from the hot fuel return device (I forget what it's called) to the carb inlet fuel filter and i had problems reassembling it leak free. Eventually I replaced the short length of hard line between the inlet and the "can" with rubber fuel hose and this has seemed to work in isolating the inlet filter from vibration and it has remained leak free.

 

The PowerValve opens when vacuum drops below a preset point (s).
The accelrator pump dispenses a set amount every time the throttle is opened.
Adjusting the idle mixture screws is a lot easier with a flex tool.
It looks like an octagonal handle on a tightly wound spring.

 

ArdWrknTrk

That makes a bit more sense. I thought the terms power valve and accelerator pump were interchangeable.

In the refresh kit neither term is used.

Power Valve = Primary Enrichment Valve
Accelerator Pump = Pump Diaphragm

Is this correct?

The power valve is then on the metering block and the accelerator pump is attached to the underside of the primary bowl assembly. The accelerator pump replacement would consist of replacing the diaphragm in the pump.

For Brnfree, I do not know about the fuel pump, I haven't checked it out. Based on the truck's condition, whatever came off the line is most likely what it has. Fuel filter change is on the todo list.

 

Yes that is correct.
The diaphragm is only part of the acc pump.
Without the check ball it will just push fuel back and forth.

If you have electric pumps you will see a metal can with three fuel lines between the ignition coil and the carburetor.
This is the vapor separator Brnfree is talking about.

 

I don't see the metal can, so I am going to assume mechanical.

Replaced the diaphragm and the power valve. Truck started up and then started running like junk, worse than before. Every rev up produced some type of horrible noise from misses to backfires. Wouldn't idle without 1 foot on the pedal and even then it had to be saved from bogging out. One time it even just shut off. Bogged and then started to rev up then just shut off. Took the carb back apart and stuck in the old power valve. Truck starts up pretty quickly now (does not crank forever) and idles alright, rich smell is gone. Truck runs well as long as I don't dump the pedal to the floor. I can do idle to 1/4 - 1/2 throttle and it responds well. Easing all the way up through the pedal runs nicely. Letting off the throttle decelerates nicely without any backfires or detonations like before.

If I give it a good dump to the floor is sputters and backfires and make a bunch of nasty racket (even saw some lovely fire out the top of the carb at one point on a backfire). I'm running new fuel out of the rear tank.

I know I need to replace the fuel filter, short of rebuilding the rest of the carb any suggestions? Any thoughts on why the new power valve (single stage) produces worse results that the old (2 stage) valve?