Started for the first time in seven years runs rough. Where do I start

[thegreatjustino]

Started the 5.0 in my '67 for the first time in about seven years on Sunday. Running off a gas can. Starts right up and idles, but runs rougher than hell and is eye watering rich.

I've not pulled the plugs, but should and will this weekend.

Has an electronic ignition with MSD box.

Any suggestions on where to start?

5.0 out of a 92 mustang. EFI removed and running a Holley 4bbl carb. Electronic ignition with MSD box. Manual transmission. Not sure what other specs would help.

 

[Bitch'nBronco]

Since you have what sounds like decent spark, I'd start with the carb first. Most 4bbl holleys I've had sit for a while will run rough until you take them apart and clean them. Especially with CA gas, definitely doesn't keep as well as gas from other states (heard there's more ethanol content thats hard on the brass parts of a carb).

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[thegreatjustino]

I should add the throttle response is great. Just sitting in my driveway idling. No clue under load as it's not drivable yet.

 

[Jfryjfry]

Clean the carb, new plugs. That’s where I’d start.

 

[ssray]

I have an 1850 on my old beast....been a lot longer than 7 years since it’s run. I think I had to put a kit in it a couple times. I figured part of the problem was that it had a thin gasket under it because of hood clearance and would cook when shut off. Might be something with the power valve as well. Maybe the diaphragm that’s leaking or possible stuck? Probably been 25 years since I had it apart, hopefully someone can chip in. I do remember the stinking pain in the rear transfer tube and o-rings that never wanted to seal. I never did get around to changing that out.

P.S. It’s actually a model 4160, I am remembering the part number. I looked up a kit out of curiosity, 34$, thought it might be higher. If it’ is what you have here’s a link. Instructions listed as well.

https://www.holley.com/products/fue...omponents/rebuild_kits/renew_kit/parts/37-119

Scott

 

[phred]

I agree it probably the carb. Delco makes a carb conditioner spray. It’s not really carb cleaner but will lubricant and soften up seals and the like. It’s worth the cost of a can to avoid a full rebuild if you wanna try. but a Holley kit is cheap and easy to do anyway.


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[Bitch'nBronco]

Throttle response is different from the idle circuit. Your idle circuit is either out of adjustment or dirty.

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[Rustytruck]

Take a can of carb cleaner and spray all the little holes on the top of the carb while it is running. then kill the engine and spray carb cleaner through the idle jets after you take them out. count the turns in and out on the idle screws.. I usually spray carb cleaner down the bowl vents. seven years sitting I would check the mounting bolts and all the vacuum plugs and hoses for cracks. watch for fuel leaks on all the hoses. fuel lines don't hold up well just sitting around.

 

[Rosco]

Started the 5.0 in my '67 for the first time in about seven years on Sunday. Running off a gas can. Starts right up and idles, but runs rougher than hell and is eye watering rich.

I've not pulled the plugs, but should and will this weekend.

Has an electronic ignition with MSD box.

Any suggestions on where to start?

5.0 out of a 92 mustang. EFI removed and running a Holley 4bbl carb. Electronic ignition with MSD box. Manual transmission. Not sure what other specs would help.

This may be a stupid suggestion, but firing order correct for 92 block? or maybe timing causing rich situation?

 

[thegreatjustino]

Timing and spark plug wires have not been moved since the last time it was driven and running correctly.

 

[Darryl M]

If it hadn’t been started in 7 years, I think I would have started with some Marvel Mystery oil in the cylinders.

 

[Eoth]

Pull them plugs!! They tell a story... If they all look the same, then you have a carb issue. If one (or more) looks different then you usually have an ignition or valve issue.

 

[ssray]

Since you have what sounds like decent spark, I'd start with the carb first. Most 4bbl holleys I've had sit for a while will run rough until you take them apart and clean them. Especially with CA gas, definitely doesn't keep as well as gas from other states (heard there's more ethanol content thats hard on the brass parts of a carb).

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That’s a good point....I don’t know how long ethanol has been around in CA, we’ve had it here a lot longer than 7 yrs. and while I like it and haven’t had any problems fuel related over the years you do need a clean fuel system to start running it as it a good solvent and will flush out any crap that’s in the tank or lines and plug filters in the system or likely the carb if there wasn’t a filter.

Surely the carb kits have ethanol compatible parts now but it makes me wonder if these old carbs might need newer floats or or other parts that aren’t in the kits?

Scott

 

[ame]

For a quick carb clean with the engine running pull the air filter, use your hand to open the throttle all the way, let the engine get around 3500-4000 rpm and put your other hand over the carb intake, repeat 3 or 4 times. This puts all the vacuum into the jets and pretty effective way to clean them out quickly, have done it may times with good success aslong as there is not dirt and other thing in the fuel bowls.