Fueling issues with 51 ford ????

R

Rollingmenace

Member
I just ran all new fuel lines filter and rebuilt the holley94 that was in the car... It starts and idles good .. I think it may be a bit rich.. When starting cold 40 deg F or so it doesn't like the choke.. Just give it 3-4 pumps and hit the key and she fires right up...
Now the problem I'm having is when driving down the road at a constant throttle the car kinda bucks and stumbles.. Almost like it's running out of fuel .. It backfires a bit if I clutch it and hold on the throttle down it sputters backfires lurches and almost dies... I pull over and the car seems to clear up and idle fine . if I let it idle a min or two it seems to clear up and will run fine especially at lower speeds and with little throttle input... I'm kinda stumped here any ideas????
 
I haven't checked anything yet.. Have to drive home first.. I'm basically looking for leak from vac port on carb to vac advance module on dizzy.. Anywhere else I should look .. The manifold vac shouldn't affect anything should it... I'm kinda a noob when it comes to working on these old cars
 
Could be a leaky or blown Power Valve. Most DIYS people buy china made kits and or kits locally and usually contain the wrong # PV in them and rubber cup accel pumps and lousey inlet needles . Lots of wrong parts in them. Backfiring through the carb will blow one out. ken ct.
 
You can check the power valve by turning in the brass mixture screws. If the engine doesn't die or even bog down, then the pv is kaput. Contrary to the above post, the wrong number power valve (usually 7.5 in over the counter kits vs. a 5.5, which works better) won't cause these symptoms.

Ignore the DIYS crack. If you do have some lousy parts contact Charlie NY here on the 'barn. He can set you up with a good power valve. That's where Ken gets his fixed up, you can cut out the middle man.
 
Well drove the car home didn't have any issues on the ride... I did buy and install a over the counter kit.... Had a rubber pump and whatever pv came with the kit... I reused the old steel needle with the new seat I was told to run seat in and then give the needle a nice firm tap with the hammer to seat it
I tested for a vac leak on vac port on carb and dizzy.... I used carb cleaner if there was a leak it should've pulled idle down.. Is this correct or is there another method...
It seems the problem seems to be after the motor builds a little heat... It could be totally unrelated though.. I have an aftermarket temp guage on car in top of passanger head it never reads above 160-170
 
ken ct said:
Could be a leaky or blown Power Valve. Most DIYS people buy china made kits and or kits locally and usually contain the wrong # PV in them and rubber cup accel pumps and lousey inlet needles . Lots of wrong parts in them. Backfiring through the carb will blow one out. ken ct.
Click to expand...

Well Ken, are you going to help him or tell him that DIY people are just incompetent?

Lonnie
 
Some some of the rubber cups on the accelerator pumps are okay. There are different grades of viton, some are adequate for today's fuel. There are some kits that apparently have the rubber cups that don't like today's fuel. Kind of a crap shoot, however. You may have lucked out with yours. I'm sure you'll report back if the described problem resurfaces. Perhaps some small particle needed to be passed?
 
I will report back... It has kinda stumped me a bit...
I was thinking issue due to heat or possibly a float issue
I may pull top horn off and double check float height
So how can I test to make sure the pv is good and not leaking might as well check it out and eliminate that as an issue
 
I didn't say the guy was incompetent,a lot of people buy the wrong kits with incorrect parts in them because they don't know any better. At least he went with ole-school needle. Even the blue accel cups are no good.I'll help him any way I can,all he has to do is ask. ken ct. Set float @ 1 7/16" if it backfired through carb it will be all burned,fire + rubber don't get along to well. ken ct.
 
Ill look Into getting another accel pump and a correct pv.... I don't think it backfired through carb.. Mostly out exhaust just a couple times ...
Ill double check everything when I pull it apart
I set float level with horn upside down to 1 11/32
I can't remember what I set float drop at
Idle screws out 1 1/2 turns...
Does that seem right
 
Rollingmenace said:
Ill look Into getting another accel pump and a correct pv.... I don't think it backfired through carb.. Mostly out exhaust just a couple times ...
Ill double check everything when I pull it apart
I set float level with horn upside down to 1 11/32
I can't remember what I set float drop at
Idle screws out 1 1/2 turns...
Does that seem right
Click to expand...

Quick test, turn in idle mixture screws, if engine really bogs or dies, pv isn't blown. If it doesn't make a difference, pv is toast. This will not diagnose a slow leak due to poor pv to bowl seal.
 
Ill check it out a little more tonight I'll check the pv like Henry stated above ... I'm also planning on pulling air horn off carb and doublecheck float height ect..... One of the guys I work with is into older trucks and cars, he seems to think it could be a issue with the fuel pressure or volume to the carb... As I'm cruising along the fuel level gets low in the bowl and it leans out (or basicly runs out of gas) at idle it catches back up.. He said he would help me look at it If I can't figure out on my own....
 
Ok a little update pulled the air horn and rechecked float height... It was pretty good... Right at 1 11/32 where I set it... I did work on getting the drop a little better I'm thinking that could've been part of the problem .. Not enough drop and it wasn't getting the enough fuel to replace what was being used at cruising speed... It's just a theroy but we will see... I checked the pv like Henry said by using the air screw method turned drin screws in and it bogged down.... The size of the pv is unknown ... I pulled the accl pump and the rubber looked ok still

What size power valve should I run.. I'm still planning on getting a new one and a leather accl pump as well as a few jets so I can dial this in...
Also noticed a small leak on the fuel pump coming out the weep hole in side of it.. Looks like it's time for a new pump I'll get that coming tomorrow... I'm hoping that that could be the cause of my issues...
 
You should use a 5.5 power valve. Most otc kits come with a 7.5, but as stated, that wouldn't cause the issues you had. Check with Charlie NY here on the 'barn for good, quality USA carburetor and fuel pump kits. He will stand behind his products.
 
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