Ford 351W won't idle when cold

[jfw432]

It's a Ford 351W and it has a Holley 4bbl carb on it. It used to crank right up instantly and idle fine whether it was cold or warm. Now it takes a little gas to crank up every time. The biggest problem though is that it simply will not idle until it's had 5 minutes or so to warm up. If I adjust the idle so that it'll idle cold (500-600rpms), it'll idle around 1200-1300rpms once it warms up. It will idle just fine when it's out of the water though but I guess the water puts extra strain on the engine.

I've done a lot of work to this boat and engine lately so it's hard to pinpoint exactly what the cause could be but I haven't made any real modifications and only done minor improvements. I've changed the plugs with standard copper plugs (I know this isn't the problem b/c it ran good afterwards), replaced the exhaust manifold gaskets, valve cover gaskets, and cleaned up some wire connections that were done poorly by the previous owner. The electric choke still warms up and opens but if I let it open before the engine warms up, it makes the issue worse.

I'm kind of at a loss as to what could be the problem.

 

[Don S]

Re: Ford 351W won't idle when cold

You adjust the idle MIXTURE when the engine is warm only, not cold.
Does your engine have a water seperating fuel filter? Has it been changed and the old filter checked to see if there was water in it?
Does the choke work properly?
When was the last full tuneup including compression check and timing check. You can't adjust a carb on an engine with weak ignition or improper timiing. or low compression.
It's also very possible you have dirt or water in the carb, and a complete rebuild is in order.

 

[Fireman431]

Re: Ford 351W won't idle when cold

On that Holley, is it a manual or electric choke?

 

[jfw432]

Re: Ford 351W won't idle when cold

The carb does have an electric choke and it does work properly. I haven't changed the fuel filter lately but I have replaced the spark plugs. I have not checked the timing or the compression. The cap and rotor are in good shape.

FYI... I wasn't adjusting the fuel mixture on the carb. I was only touching the idle speed screw and was only touching that because it wouldn't idle normally.

 

[Don S]

Re: Ford 351W won't idle when cold

Carbs take some warming up and the choke off before they will idle right. It's not going to idle like todays cars with EFI.

 

[grumpy old man]

Re: Ford 351W won't idle when cold

You say holley carb. I am assuming you are talking about an end bowl 4bbl. Don't know for sure about boat applications but the normal holley has a power valve in the metering plate, the plate that is about a half inch thick between the bowl and the carb body. If the rubber diaphram ruptures it will dump raw fuel right into the manifold. It doesn't affect the runninng noticibly but will definately screw up the idle. I don't know how mechanical you are but if you have never worked on an end bowl holley a boat is not the first one you want to try. They have their idiosyncrasies, one of which is leaking if incorrectly assembled. Gas in a boat bilge equals disaster.