Hello all, I have a 74 f100 v8 5.0 302 (or 304 can't remember).
it sat for 8 months or so and had a leaking in line fuel filter. Wouldn't start or get fuel. Replaced filter and fuel pump and sprayed carburetor and it started running. Ran well for 2 weeks, then started almost stalling, then revving, up and down at idle. Then stalling at deceleration. Changed carb fuel filter, added some marvel mystery to gas, and sprayed carburetor again. Ran Ok for a while but after a few miles wants to stall at idle and sounding rough. Made a stop and went to leave and it was real rough and stalling. More carb cleaner got me home. But the end of the trip same thing. Seems to get worse the longer it runs.

I did notice a substantial crack in the passenger side exhaust manifold.
All ideas welcome. Rebuild carb? Could exhaust build up in engine compartment mess with fuel/air ratio?

Thanks

P.s. I'm pretty inexperienced at wrenching am handy and can follow instructions well.

 

Fix your manifold, stop all vacuum leaks, take the carb apart and clean it. Also how old is that gas.

 

You replaced the in-line filter but what about the one on the carburetor? I over looked that one when I got my truck going. Have you already rebuilt/cleaned the carb or only spray cleaned?

I had a similar situation. Truck sat for awhile, new fuel hose, filters & pump, rebuilt carb, kept gunking up filters, finally cleaned rusty tank, new fuel filters and was running strong. Heard a pop one day while accelerating. Still ran well and then just starting bogging down on acceleration and felt an overall loss of power. Didn't seem to have an issue at idle though. Discovered the crack and could feel it pumping a good amount of air from it at idle.

Took it as a sign from the universe to go ahead and make the upgrade to headers it was an item on the truck's wish list.

My thinking says it might be an issue with the carb like a vacuum leak(per the idle surging you described). Might be an exhaust pressure issue?

I would start with little things like checking and replacing deteriorated rubber vacuum caps, hoses, and a carb rebuild with new rubber and gaskets if you haven't already done so. Once you're sure the fuel system is tip top revaluate and see if you have to tend to the exhaust. I hope it's a simple carb job for you and not a get under the truck 100 times job.

PSA: Keep in mind that those rubber belts/hoses/bits/gaskets are probably pretty old. The rubber of years ago is nothing to the rubber of today. Check the health of your radiator/fuel hoses if you haven't already and be proactive to replace things before they fail. You don't want to be on the side of the road with a busted hose or belt.

 

• Replaced both fuel filters and soft fuel line sections.
• Replaced fuel pump.
• Only sprayed carburetor.
• Fuel was pretty much empty when stored and filled with Ethanol Free.

Here are some pics.
I assume this is the stock Carb? So any rebuild kit for it. Any site sponsors to recommend?


Here is the cracked exhaust manifold. Can this be JB welded for a temp fix? Is replacing a doable job for me? PB blast the bolts for a week or so. Definitely do both? Worth upgrading from stock?


There are several hoses/lines that look to be not connected to anything. These two caught my eye. Have no idea what hey do but could they be part of the problem. They appeared to fit together at some point.


Here is where they terminate.


Thanks again, Sorry for all the questions but as you can tell I am very new to this, but excited to be learning.

 

You can weld that manifold crack despite it being cast. Any exhaust leaks won't affect the A/F ratio but it could lead to exhaust fumes getting into the cab at idle. Fix it before you fall asleep for eternity.

Find/fix all vacuum leaks....power brakes? Check the booster lines and booster swivel. Brittle/cracked vacuum lines?

Any vacuum leaks at the throttle plate/base plate?

One more check - the fuel pump. If yer battery is in good shape, disconnect the carb feed line...empty it into a clear container - a quart/litre sized plastic soda bottle - and have a helper crank the engine. You want to see a good, continuous squirt of gas.
If not, disconnect to fuel feed at the pump from the tank and emty it into a container....blow some air into the tank at the filler cap -about 10 psi - ....you should see a nice shot of fuel....if not, blow the lines out if not done already.

One more thing - pull the dipstick and take a whiff of the oil. If it smells like gas, the fuel pump is pooched....replace it AND change the oil and filter.
Be sure to add some ZDP additive to yer oil if you're not using an oil that has it in it already.

 

Here's a summary of what I've done already.

• Replaced in line fuel filter and carb fuel filter.
• Replaced fuel pump.
• Tank was pretty much empty when brought out of storage, so its been filled with ethanol free gas.
• Sprayed carburetor with carb cleaner.

All the hoses seem to have been replaced at some point. I don't see anything on visual inspection. Unfortunately I have no idea which ones to check for vacuum lines or exactly how to check them. I've been googling without luck. I did find a thin hard line in a braided cover that seems to have broken. I think it goes from the choke to the carb.
Here are some pics.


This is where each end attaches


So the crack in the header is probably not causing this problem, but clearly something that needs to be addressed. Is changing these out doable for a novice like me? I'm having trouble finding factory cast Iron type replacements. The reviews I read for these aftermarket ones are talking about grinding, cutting, and banging. Which I'm hesitant about. Is this a worth while upgrade?
here's a pic.


So I think this is a stock carb. Motorcraft 2100?


Thanks for the advice. New to all of this, but am really enjoying learning.

 

Here's a summary of what I've done already.

• Replaced in line fuel filter and carb fuel filter.
• Replaced fuel pump.
• Tank was pretty much empty when brought out of storage, so its been filled with ethanol free gas.
• Sprayed carburetor with carb cleaner.

All the hoses seem to have been replaced at some point. I don't see anything on visual inspection. Unfortunately I have no idea which ones to check for vacuum lines or exactly how to check them. I've been googling without luck. I did find a thin hard line in a braided cover that seems to have broken. I think it goes from the choke to the carb.
Here are some pics.


This is where each end attaches


So the crack in the header is probably not causing this problem, but clearly something that needs to be addressed. Is changing these out doable for a novice like me? I'm having trouble finding factory cast Iron type replacements. The reviews I read for these aftermarket ones are talking about grinding, cutting, and banging. Which I'm hesitant about. Is this a worth while upgrade?
here's a pic.


So I think this is a stock carb. Motorcraft 2100?


Thanks for the advice. New to all of this, but am really enjoying learning.

 

Thorough cleaning of carburetor innards and new gaskets should help. These days a carburetor probably needs it every 4 to 5 years, at the outside.

But I gotta ask, that thing doesn't have ignition points and condenser does it? '74 was about the tail end of that.

 

I have no idea, lol. It's f100 longbed v8, 302, 5.0. I inherited from my dad when he passed 5 years ago and its run like a champ the whole time until now. As far as I can tell its all original except fro paint and seat covers.

I'd be happy to look if, if you could direct me on what to look for.

Thanks. I think I'm going to try to rebuild the carburetor. Can't hurt, inexpensive and I found a really good video of someone doing it. Wish me luck.

 

'74 Duraspark came out, not sure about trucks though. Right in there though. Should have the large distributor cap, to handle increased spark energy. Regardless some new ground and start cables would probably keep the electrons happy.

 

Looks like the carb is a 2100 which is what I have. I found the rebuild kit at a local parts store, I think Oreilys. Still have the box, GP Sorensen - part number 96-215

Rebuild PDF - http://www.therangerstation.com/tech..._2150_carb.pdf

That braided pipe is supposed to pull heat from the exhaust area to the electric choke temp element. The other hose one seems to go to some sort of plug on my truck(see pic).

Based off the research I did when I had this problem you might find that JB Weld isn't designed for exhaust temperatures and cold/hot fluctuations.

Since it's cast you'd have to "braze" the pieces back together. I talked to my welding buddy and an exhaust shop guy and the consensus was that if you brazed the pieces back it would eventually fail again.

I couldn't seem the find the cast direct replacement either (checked eBay & auto part stores). The replacements I found on eBay were going for like $80-90 where the headers solution(both sides) ran $150. Figured another cast iron part would be same age.

I got generic flow tech headers from Oreilys and the driver side was relatively easy. Put truck in gear to move shift arms out of the way and disconnected clutch push rod and was able to align it in without too much difficulty.

Passenger side was a bitch. I dropped the starter, still couldn't finagle it and had to loosen engine mounts, raise engine, move mount out of the way, get header in, and then bolt engine back down.

I didn't have to cut/grind anything except the old exhaust pipe to make it easier to remove. Once you get headers in then you have to figure out a solution for mufflers which does involve getting exhaust piping back past the cab.