Hi guys,

You know how they say that you learn something new every day? There is a lot to that! lol

So I just picked up a 1983 F250 4x2 extended cab with a 460 and C6. I swapped the stock (mostly dead) Holley carb off for an Edelbrock 750 Performer. When I did, I discovered that Ford switched from Spreadbore to Squarebore manifolds at some point. Every stock manifold I had seen to this point was a spreadbore...they must have all been from the 70's I guess, the 1 I have access to at the moment is from 1978, so it seems reasonable.

I am having a hard time getting the idle to drop below 2000 even when it is hot as a pistol. I have gone over the vacuum lines and checked for cracked lines (found a few), checked the timing (was off a bit), made sure the choke was full open and linkage was not on high idle cam, basically done all the usual stuff.

Here is the question: I just mounted the carb to the manifold with a standard paper gasket. Do I need one of those thick...composite? gasket/spacers under it to make the vacuum ports work right? I don't know what to call the silly thing, they are like 1/4" thick.

Opinions? Also, if you have any other theories, I would love to hear them!


Thanks!

 

Cars had spread bores.
All the trucks I've seen since the 460 reappeared in 1983 came with a squarebore 4180 Holley for Motorcraft carburetor.

Tell us about your manifold.
What are you doing to block the EGR port if you are only using a paper gasket?
Have you tried spraying some carb cleaner around the base looking for vacuum leaks?

How is your linkage geometry and cable routing if you have no spacer?
I would definitely look and see if it bottoms out on the manifold (I know the 4180 would)

 

I have seen quite a few 460 manifolds in my time...but I think they were all from the 70's. I know there was 1 pickup and 1 van...the rest could have been cars or trucks, I do not know. It never occured to me that the 80's were different...being mentally lazy again I suppose! lol

Not blocking the EGR....it is still all there. I was wondering about that. That is one of the reasons I was wondering about the composite gasket...amongst others.

The carb cleaner netted me no results, but with that big a$$ fan blowing hot air back across the engine, I think it was unlikely to work well. (it was hotter than the hinges of hell yesterday.)

The carb throttle plates move freely, no bottoming out that I can feel or see.

Linkage is good, cable is attached to it's factory bracket on the manifold, and to the carb with a stud/ball kit from either Edelbrock or Holley, I forget which name was on the package. (bought it years ago, have moved it from carb to carb and rig to rig ever since.) The kickdown is not attached currently, it is zip tied out of the way to keep it out of mischief until I buy the kickdown kit for it.

Think I may pull my old Bumpside out of the nettles and start it today to verify that the carb on it is still in running condition. (Holley 750) If it is, I think I will pull it to verify the problem is not a setup issue in the carb...if the composite gasket doesn't fix it. (going to buy one of those when I go to town in a few hours.)

Thanks for the suggestion!

 

When you said I figured you had done away with the EGR spacer because.... it only makes sense that way.

If you have the EGR spacer, the linkage should line up but you may have a leak in the high temp gasket beneath that plate.

I'm sure you'll have it figured out in no time.

 

that is what is weird, there is no EGR plate, it goes into the manifold, not into the plate under the carb like I am used to. I will try to get a couple pics in a bit.

 

I stand corrected...I just went to take a picture to show you, and realized that the EGR plate IS there, it just looked like a part of the manifold. I changed the carb about a month ago, then had to work on the wife's rig, so I obviously forgot a few details....my bad! I hate making myself look like a schmuck, but I guess everyone get's to now and then! LOL.

 

Well, changing the carb base gasket to the 1/4" thick composite gasket did not help...but it did not hurt either, so at least it wasn't a fail.

However, I discovered the culprit:




See the Cruise Control Chain? Yeah, that was tight before. As soon as I loosened it, the idle dropped by 1000 RPM. Now it idles around 1050-1100 in Park, and 850 in Drive. Much Better! I intend to fix the Cruise Control in this rig, and I will set this up properly when I do.

When I went to take it for a test spin, it started to pop back thru the carb. It is low on fuel (below 1/4, above Empty), and I have no idea how old the gas was in this thing when I bought it...I know it had been sitting for a long time. I had filled that tank all the way up when I brought it home...if the gas was only kind of skunky I was hoping it would mix and I could burn it out. But, looking at the stuff I am getting in the filter (clear G2 Fram), I am thinking it did not mix, and this stuff is BAD. Going to pump the tank out and give it a shot with fresh fuel...next weekend. I start work at 4AM, so I am done wrenching for this weekend.

If the fresh fuel does not fix it, I will try swapping in a known good coil from my '86 just to isolate the problem. ( I plan on installing an entire ignition system in the not to distant future, just for preventative maintenance reasons, but I want it running solid before I do so if I pick up any new malfunctions, I will have a solid baseline to troubleshoot from.)


I will keep this updated, since I do not like it when I find a thread dealing with a problem of mine, and the resolution is not given.

Cheers!
If anyone has any other suggestions, let me hear what you have!

 

Ok, I had posted another question and kept it updated, but forgot about this one.

-Had no fuel pressure to speak of. Installed aftermarket electric rotary vane pump.
-Still popped and banged, would not run. Installed gauge after pump, 4 psi steady.
-Pumped both tanks dry...gas was REALLY skunky.
-Poured 5 gallons of fresh gas into front tank. (last one selected.)
-Still bad.
-put a 2nd pressure gauge in line after vapor return doo dad. had .5 psi to carb.
bought some more 3/8 fuel line and bypassed the vapor return gizmo. Voila!
-Runs pretty good!

The truck Idles, cruises good, 1/2 throttle acceleration good. It is still boggy at WOT. I think it needs a rod change in the carb...but before I go there I am going to tune it up. (Plugs, wires, cap, rotor, coil, oil change, and another new fuel filter.)

 

Update to the update! lol

Pretty sure I isolated the WOT bog. I went to change the spark plugs and wires, and the #1 and #2 wires disintegrated in my hands when I twisted them to pull them off. Discovered that part of the exhaust leak the truck has is BOTH exhaust manifold gaskets, #1, #2, and #5 the gasket was completely gone on the upper side...which cooked the sparkplug wires.

Haven't been able to verify this was the entire problem. When I went to pull the manifolds, I had 6 bolts snap. I had to push the truck to the back burner for the time being. I will update this when I know for sure.

Cheers!

 

Can you elaborate on this?
Your saying you had 1/2 psi pressure (vapor pressure?) going into carb? I assume at the bowl vent.
What did you by-pass? Picture please.

You have my curiosity peaked.

 

A lot of the 460's had a hot fuel handling package on them. They supplied fuel to the carb and at the carb there was a special tee fitting with a orifice to let some of the fuel return directly to the tanks. This kept the fuel moving and circulated which prevented vapor lock and other problems during very hot weather idling. He took that special tee fitting out and made it into a conventional single line system.

 

Ahh - that makes sense.

 

Bumkin,

Here is a diagram that was sent to me on my other thread showing the vapor return routing:




Frankin posted it. Here is the other thread: https://www.ford-trucks.com/forums/1...ric-pumps.html

Cheers!

 

i have nothing to add to this, but im subscribing because im getting ready to drop a 750 edelbrock on my 460.