f-85

I just got a 64 Super 88. The carb was OK but surging alittle. So i rebuilt the carb, set the dwell, adn timing. The car runs god and smooth. But when im full throttle it just falls on its face. 3/4 throttle its good but all in it just cits out. Is there any adjustment to the accpump? Any ideas?


Thanks Josh

BILL DEMMER

the accelerator pump does nothing in this operational mode. the accelerator pump only provides fuel when opening the throttle from closed to about 1/2 throttle travel or any point in between. and it only provides a short duration squirt to overcome the fuel-flow lag from the main discharge nozzles.

i would start by checking the fuel filter, and performing fuel pump pressure and volume tests. you may have a slight leak on the suction side of the pump from rusty fuel lines(all the way back to the tank), including the pickup inside the tank, or the strainer in the tank may be starting to clog.


bill

KQQLCAT

Also check the float in the carb. Sounds like you are not getting enough gas.

Olds64

I agree. If your float level isn't high enough then you could be sucking the fuel bowl dry during acceleration.

rocketraider

4GCs are very sensitive to gaskets between the throttle plate and float bowl, though it usually shows up as an idle or off-idle problem.

Also check the secondary float level and air valves.

BILL DEMMER

unless grossly maladjusted, the float level setting would not cause this.

does your carb. use the float counter-balance spring(s)?


bill

aristellier

Hi, I had this problem when I converted from 2 to 4 barrel carb. Thought I needed to buy a new fuel pump, but on talking to an old school mechanic friend of mine he suggested opening the mixture screws 1/16 each. Ten seconds to do and it fixed the problem.

BILL DEMMER

the only mixture screws on this type of carb. are the idle mixture screws. they only affect the idle operation of the vehicle. the problem stated is at, or near, wide-open-throttle.


bill

f-85

Hey Guys

Ok. Well this problem happens at any time i give it full throttle under load. So if im already half way in or im just idling, it will fall right on its face. I didnt see any springs when i had it apart. So i would have to say no. Just two brass floats. I have the iddle adjustment screws at 2-1/2 turns, and im getting 20inch of vacuum.


Josh

OLD SKL 69

I am having the same problem with a 4GC carb on a Buick. The carb has been completely rebuilt and the float levels are set to factory specs. I did notice that when I raised the secondary float levels that it improved the issue but I still have a little fuel starvation at WOT. I am going to raise the secondary float levels a little higher to see if that eliminates the problem. I'll keep you posted.

59-59-59

Is it possible you have a pinhole in the secondary set of floats? I had a similiar problem in a 57 with a somewhat identical Rochester before I got rid of it. Drove me nuts

Olds64

If you open up the carburetor it is a good idea to replace the floats. I replaced the float on my Quadrajet I just rebuilt. It is cheap and good insurance. Of course, I don't know if you can easily find the floats for a 4GC carburetor.

BILL DEMMER

unfortunately, floats for 4g-series carbs. are nearly or completely impossible to find. the better bet is to repair your old one, if possible. the 4g's used several different floats and none are interchangeable.

f-85, your secondary float should have the float balance spring, the primary does not have this spring, on this model number carb. i don't believe this is your problem though. the balance spring would cause idle and light-to medium throttle surging.


bill

59-59-59

I was kind of shocked that Fusick has them brand new for '57 - '58

BILL DEMMER

are those the brass or nitropyhll floats?
and if they fit your ride you better get a couple of spares.


bill

J-(Chicago)

I went out for a driv,e to F85's place yesterday to go check out the super. Cool car, and a really smooth cruiser to drive. As far as the carb issue goes, it doesn't matter if you're going 20 mph or 70 mph, if you stab the gas pedal down quickly, it chokes out for a second or 2.

rocketraider

Unplug the vacuum advance and see if it still does it. If so you have an advance weights problem. I've seen them stuck if car has sat for any length of time. WD40 will free them up.

If it still does it then, you have a secondary air valve timing problem or possibly a secondary throttle valve lockout adjustment problem.

Then again you could just have a rotten-*** 4GC. I've had more than one that no amount of adjustment or tweaking would straighten out. The BEST running one I ever had developed an unstoppable fuel leak at the fuel inlet nut, so it too became junk.

Believe me, if carb end TV rod adjustments weren't so critical to a HydraMatic's operation, I'd have probably thrown every 4GC I've owned in the trash heap. Switching to another carb entails a lot of fabrication and trial and error adjustment unless you have a TV rod length checking tool.

f-85

Well i figured i would mess with it on sat. Ill look at some of the stuff mentioned. Ill let you guys know how it gos. Thanks for the help.


Josh

Danny Wiseley

It DOES have the secondary air valves in it doesn't it? I have seen people leave them out, trying to improve WOT, but it causes the problem you're having. . .

Steve O

A lot of good ideas here

While Im not familer with this carb I have had this problem before...

First place to start is the ignition.

Check all of the wiring on the coil, distributor and points. A loose wire can cause this.

Since I know we just set the dwell on the old points and you have a new set in the box on the bench...

Put the new points in and clean and lube the mechanical advance weights.

Maybe try a different coil...

After that if you still have problems you can rule out the ignition.

Next check the fuel lines for rust/pinholes and cracked/loose rubber lines in the back by the tank. I've had this happen before and it never would leak on the ground. But there would be a wet spot on the line.

The line to the pump isn't under pressure so any leak will just allow air in and reduce fuel volume. Even just a tiny one...

If that's all good you could try a different fuel pump but they are probably expensive/hard to find for the 394...

On to the carb. Id make sure the floats are set right. If after all that it still does it yer focked

justinj

What does this tool look like?

I would love to get rid of my 4GC and replace with something else.

-Justin

Steve O

The floats were off a little

f-85

Yep it was the float for the sec. But its still not running right. I think im just going to take it apart and start over.


Josh

BILL DEMMER

float setting tolerance is +/- 1/32"


bill

f-85

Hey Bill

I got some new spark plugs, and im going to try and take another stab at the carb. Thanks for the tip. Ill check the floats one more time.



Josh

394olds

Something to always consider in a fuel starvation problem on any 61 to 64 full size Olds is the rubber suction hoses from the fuel pump going back into the frame on the passenger side (terminates behind the front frame torque box) into the steel line going aft. ALSO - the similar rubber lines that come from the fuel tank INTO the rear frame rail and exit connecting to the steel fuel line just forward of the right rear wheel.

I routinely replace these rubber hoses on every 62-64 Olds I own - a total of 14 over the past 40 years.

The 4GC is an excellent unit in the hands of a careful assembler. I have encountered internal interference problems when moving floats from carb to carb. Replacing the 4GC to solve a problem like this is unnecessary.

The 64 Super 88 is an excellent machine.

394olds

make sure your ignition timing is 4 to 8 degrees with the vacuum advance disconnected.

REMEMBER that the timing mark on the rubber damper may have slipped after 44 years and you may have to add in extra apparent advance to compensate for the consequent error to get a real 8 degrees.

f-85

Hey 394 olds

Well im going to go through it all today. Ill try and get this finally figured out. Ill check the balancer to see if its spun, the lines, im going to do the carb again, and then ill recheck the timing. Thanks for eveyones help. Ill post my results.


BTW Yes the 64 Super 88 is great!

f-85

Last night i put in the plugs. I took the car out to get coffee. The car ran much better. MUCH better. I think the carb still needs alittle work. But over all i am happy. Now jus have to stop the breather from spitting out oil.


Josh

70worm

wow im scared to touch my carb now

70worm

My 64 super 88 idles perfect but when you slam on the gas it does the same thing. I put a fuel cell in the trunk, new lines and rebuilt fuel pump. Now what about the vent tube for the fuel cell? It's bigger then the original so should I put a reducer on it? I'm also going to check my dwell & advance before I even think about touching the carb.