Carburetor Quest for my F250

[Hamilton Felix]

I picked up an old '77 Ford F250 Camper Special a little while ago. It's my $500 truck, intended to save my older International from the ravages of highway miles. According to the VIN it left the factory with the 351M engine and a 4.10 locker axle. It has an automatic transmission.

I've replaced a power steering hose, installed a fresh RV battery in the second battery tray, and put in a domelight cutout switch.

But my real problem is the carburetor. I have learned that these 351M engines (visually indistinguishable from the 400) came stock with a 2 barrel. Mine has an Edelbrock Performer 400 manifold and a Holley 4 barrel.

The Holley is in bad shape. Not only is there no accelerator pump function, but the top edge of the carb appears to have been heated and slumped to where the vent tube hits the choke so the choke cannot close. It can be a real bear to start, and winter is coming.

I've done a little online research, and called a place or two. I'm trying to find my best possible deal on a small 4 barrel carb for that application. Doing the cfm calculations for this engine/application, I find I'll never flow 500 cfm. So a small 4 bbl, with vacuum secondaries would seem to be the ticket.

Any thoughts? Would looking for a junkyard carb be too risky?

Thanks.

 

[twohawlks]

I would go with a used carb from a junk yard and rebuild it, no problem

 

[toothless1]

How does it run when its been warmed up?
I think I would try to rebuild the holly.
But thats just me.
T

 

[Hamilton Felix]

Look at that bottom closeup picture of the Holley. I may have a challenge there. However, I think I WILL try to get it to where the choke can close.

If it's running down the road, it runs OK. But step on it quickly and it falls on its face. Ease into the throttle until it's wide open, and you'll feel it kick down and it doesn't take long to be going 75-80. But the combination of NO accelerator pump action and no choke (not to mention the hot air ducting for cold start & warmup is missing), really makes it a bear to start and keep running in cool weather.

Before I run to the junkyard, I need to figure out what I'm replacing. I am not looking for the correct original carburetor, unless I want to buy a stock intake manifold and swap back to a two barrel. But I want a SMALL four barrel on this Performer 400 manifold. Nice small primaries, plenty of mid range torque, not over-carburetted, because it's not a high rpm hotrod.

I don't know enough about what is available today to say whether Edelbrock or Holley -- or others -- represent the best deal.

You know, I should root around in my basement. There should be an old 4 barrel from a 392 International -- Nope, just an old Holley 2 barrel from a 304 International.

Maybe I should make the effort to swap back to a stock 2 barrel manifold. I can probably get a manifold and old 2 barrel carb for next to nothing from a friend who likes to upgrade his Fords.

It just seems simplest to get a small 4 barrel that will fit what I have now. I'll keep my eyes open for a deal.

 

[toothless1]

If you get the choke to close, great
a new accelerator pump plunger should be avalable with the rebuild kit.
I would try that first,
it would be the easiest.
T
got block heater?

 

[intothatgoodnight]

Hamilton,

If my eyes are not deceiving me, it appears that the Holley was a victim of a carb fire at some point in its life.

A Holley 600 cfm with vacuum secondaries, coupled with --- mmm -- say, jetting in the high 50s or low 60s should do the trick -- what you might want to do is pull the jets out of the old Holley and see what size they are -- stamped on the jets is a number -- may be different between the front and rear jets -- could use in the replacement Holley.

Could also use a Carter AFB-style (Edelbrock) carb as your replacement -- good design and reliable, also.

See if you can find an electric choke (if you don't have one already) -- much easier to set up.

Gas mileage on that vintage 351W motor was never too good to begin with, in my experience -- particularly in a truck, and especially with the 4:10 differential ratio.

A decent towing cam, perhaps some head and valve work, and headers plus free flow exhaust would free up the induction system to produce more power and better gas milage -- lot of work and money, though.

If you are not using the truck for towing or carrying heavy loads, I would swap the rear differential/pumpkin unit out (it should have a 9" Ford rear) with a junkyard replacement that has a mid-three gearing -- say something in the 3:40-3:65 ratio range. -- will need to swap the speedo gearing to resynch the speedometer -- easy enough to do -- pumpkin swap should take a few hours with a second set of hands.

YMMV


intothegoodnight

 

[Hamilton Felix]

It's a 351M. I've been told the 351M/400 family (no relation to 351W or 351C) has a bad rep. But I gather most of that is because of when they were made, all handicapped with first generation emission controls and too-retarded, too-mild "smog" cams.

Yeah, I think I'll do some online price research at Summit Racing. A friend was telling me today that Carter and Edelbrock are the same these days. Maybe I should bite the bullet and look for my best possible deal on one of them. I know my present carb is in very rough shape.

Thanks for the help.

PS: I've figured out it's NOT a Camper Special, despite what the seller told me. It's a basic F250 custom that's had a few things added by a former owner.

 

[intothatgoodnight]

Hamilton,

My mis-typing -- meant 351M.

Could find a decent running FE motor (previous generation of Ford big-block) and tranny (352-360-390-410-428 + C6) and plunk it into the engine bay -- that power train combo will run forever, and deliver miles of smiles.


intothegoodnight

 

[toothless1]

You should be able to find a new air horn for that holly at a wrecker.
Do they run propane where you are?
Where I am a used auto propane system costs what a new carb does.
but auto propane is about 2/3 the price of gas.
It's useless to entertain the idea unless propane is readily available.
T
whoo hoo we driving the barby...

 

[Roger Thornhill]

Hamilton, I've got a Holley like yours in my parts bin. PM me and I'll send it to you.

Oh boy, more stuff cleaned out of the garage!


Now we've just got to figure out how to get some of those M38A1 parts to you...

 

[Synap]

Tend to agree about the possibility of a past fire. If so there are several possibilities. Most obvious may be that the carb body has warped..leading to vacuum leak(s). The other is that there are several internal ports and guides that are !plastic! lined IIRC (been a few years). Seems I remember there were extra holes/ports drilled in the casting (for other models) that were sealed by the gasket o Either along with the accelerator pump already mentioned could cause the stuff your seeing. This last could be either the leather has wimped out (usual)..or..someone used the wrong rebuild kit. IIRC, there were different shaft lengths available. (don't have my MOTOR book handy). This could also not cover those "extra" holes...back to the vacuum leak potential.

Heh..I'd prolly seriously consider Tom's offer. If only to have a working unit for direct comparison to see if the bad one is fixable. Heh..backup plug&play carbs make yer truck smile a lot!