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help with my Ford 351 engine

I actually don't think this has anything to do with the actual engine; my guess is carb or timing. Reason being is that the engine is a brand new crate engine put into my 83 Amer skier. Just about everything is brand new - the carb is about 6 mos older than the engine, but still relatively new... here's the issue:

When the engine is cold, it runs great - full power, no hesitation. Even after running it for 20-30 mins, it is still good. Once I stop and idle for a few minutes and then try to get back up to power, I've only got about 1/4 throttle. After that, it starts back-firing and "starving". If I keep running, it eventually gets to the point where I can't even idle up without it starving and dies. I try to start it and it acts like it is not getting any gas at all. I remove the air cleaner/spark arrestor and confirm that gas is coming from the jets when the throttle is pushed. I let it sit for a few mins and then it will start again. But, still no power. I let it sit for 10 or 15 mins and then it starts up, has 90% power (still a slight hesitation at full throttle). Again, after a while of running and idle, it does the same thing.

I'm rebuilding the carb today to ensure there is no left over junk - I've already put a new fuel filter on and new water separator on. Plugs, wires, distributor - all new. Someone has suggested timing, but why wouldn't it act bad consistently? Anyway, I'm going to check that today as well.

Anybody else have any suggestions as to what else to look at?

 lets_ski
Apr 8
Putting a fuel pressure gage near the carb might be easiest cheapest way to pin it down. Could be the pump itself heating up. I've seen that electric pumps are the way to go for the 351 marine application but my experience is limited to 352 car engines.

--Vic

 Vic
Apr 9
If you can look down the carb, and you see fuel coming out when you pump the throttle, it's probably not a fuel problem. I would start looking at the ignition, check the points and distributor cap, replace the condensor. Pull the plugs out and take a look at them. Check the wires, are they laying on the exhaust manifold? Spray wire dryer on them and try it. Does the ignition system have a ballast resistor, try replacing it. How's the connections on the wires going to the distributor?

John

 Capt
Apr 9
I don't agree. Fuel coming out of the accelerator pump doesn't mean the main jets are delivering fuel. When you press the gas all you are seeing is the accelerator pump. The main jets need the engine to be drawing air though the carb in order to supply gas. But I won't argue it could be ignition as well.

It definitely sounds like it is heat related. Boat engines often get hotter when dropped to an idle after running a while. The cooling water supply gets reduced because of the drop in engine rpm's but there is still lots of heat accumulated in the block that needs to get removed. It could be detonation as well if the heads are heating up too much. Backing the advance off would be another good test.

 jamesgangnc
Apr 9
My guess is vapor lock. Get a fiber spacer to put uunder the carb.

<lets_ski@adelphia.net> wrote in message

James
Apr 8
Vapor lock. I believe you can fix it by using a spacer block under the carb, but I'm not sure. Short
Apr 8
   
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