I have an 88 F250 that has had some big work done to it. It was a fuel injected 351 and now a carbureted 460. I pulled the 460 that was in the truck when I got it and put a fresh 460 in it. It has been running just fine up until a couple weeks ago.

Now for the problem...it starts up and idles just fine but when I give it any gas at all it bogs down and stalls. If I release the gas soon enough it will recover and idle again. I tried adjusting the mixture screws, but this didn't help the problem. This problem arose after I filled up with new gas, but it is the same gas that I put in my Excursion from the same station.

I have a Holley 4 barrel carb with 1850-4 stamped on it. I did some research and found that this is a 600 cfm vaccuum operated carb.

Like above, it runs just fine at idle, but once I push on the gas even just barely it bogs and dies. Can anyone give me some advice?? Thanks.

 

Sounds like the accelerator pump isn't. Remove the air cleaner, look down the front carb. throttle bores and advance the throttle. You should see fuel squirt out into the throttle bores. If not, your accelerator pump either has linkage that has come loose or off or the squirter or passages are plugged. Go here for tech info;

Holley Performance Technical Service Department

 

I did just as you said, and there is fuel squirting into the front 2 barrels. If there were too much fuel would that cause my problem? How can I measure this? Thanks.

 

Not likely. It takes a real lot of fuel to cause a stumble. First check you spark to make sure it is blue. Then check your timing and make sure it is set right and advances.

 

I'll check that tomorrow hopefully. I still don't understand how this happened. I ran it dry of fuel (fuel guage is fishy) and it sat for about a week. Then I filled up my fuel can when I put gas in my excursion and brought that can home, put it in the truck, and drove it around a little. I parked it and it sat for about a week again, now this problem. I'm baffled. Thanks for the help.

 

Is the vacuum advance line to your distributor the OEM fabric covered one?

Had a similar situation I though was just a bad carb. Rebuilt it, made sure the accelerator pump worked, idle adjusted. . .set the timing correctly. . .

Still bogged on acceleration, even while moving. . .you really needed to lean into the throttle. . .

Anyways, I popped the line off and plugged the other end and blew into it. No pressure Somewhere under the fabric the line was cracked. Replaced the line. . .idle came up, acceleration is great! Whoda thunk a vacuum leak and no advance makes for a crappy running truck. . .

Anyways, that's my little nugget of knowledge

 

Well, I don't think that'd be the issue. The idle is just fine, I mean perfect. The problem is that I can't give it ANY gas at all without it bogging. I'll try to take a video/sound clip tomorrow and maybe that will help. Thanks all.

 

Same here. . .I wouldn't dismiss something this easy to check just yet, you never know

 

Check your gas jug to see if anythings besides gas is in it, they seem to collect debris sometimes, then if its clean check your fuel pressure at the carb, at least pull the fuel level check plugs to see if the bowls are full.

 

Two possible problems;
1st and most likely the easy one, it sometimes happens that the vacuum advance is advancing so far that it is pulling the pickup out of wack. Pull off the vacuum line and see if it improves. If it does the permanent solution is to get an adjustable vacuum advance. Crane sells them, even if this isn't the problem they a good upgrade most ford distributors have to much advance.
2nd no fuel, somehow something got into the carb and is blocking the jet. Unfortunitly the only good way to conferm this is to tack apart the carb. But at least it's a holley and you can most likely remove the front bowl without removing the carb.

 

Thanks for all the help guys. I think I'm going to get a rebuild kit and tear apart the carb just for good measure. Hopefully that'll fix it.

 

Try the vacuum advance first it's really easy and could save you alot of agrivation.

 

You sure are hung up on vacuum advance. But it can't be his problem here and your lack of knowledge is become apparent. As to your carb contention. Wrong again, off idle is handles by the idle curcuit and the accelerator pump and not the main jets. Oh and the idle curcuit is fed fuel thru the main jet so it is not plugged.

 

I bring up the vacuum advance alot cause it is the most neglected aspect to making an engine run well.

The vacuum advance could absolutly be his problem, and it's so easy to check there's no reason not to. He said his problem happens as soon as he tips in to the throttle. This is exactly when the vacuum advance starts to do it's thing. As the throttle starts to open the throttle plate opens up vacuum to the ported vacuum line whitch should be connected to the distributor. This activates the vacuum advance alowing for good throttle responce. When the vacuum advances it turns the base plate in the distributor(that the pickup attaches to) and is the only thing that turns the baseplate. If there is a problem in the dist this can agrivate it causing the ignition to cut out abruptly.

A blocked jet could also cause his problem. While it is true that the idle circut draws through the jet the demands are low and there are other pathways. During idle the fuel could pass through one of the many emulsion tube ports, this flow would imediatly cut off as soon as the venturies started to pull vacuum. Causing fuel starvation and a stumble.

Now tell me how a timing issue other than from the vacuum advance could cause this problem as you stated before?

 

There is no point in giving you the facts as you already made up your mind it is either vacuum advance or a blocked jet. Have fun in your fantasy. I'm done.