1979 Ford 302 Engine problem

Help someone, I have a Ford 302 engine in a 19 foot Shamrock boat, as it came with the boat I am assuming that it is the same age which is 1979, the boat was purchased as a junk item in 1996 and along with the engine was rebuilt by myself over the following two years, from that time on it performed well until this last year, when I started to have engine problems that manifested themselves as a very severe misfiring at around 2500 RPM associated with low compression on number two cylinder, (90PSI compared to the rest which were in the 125PSI to 130PSI range, not good but acceptable) four badly fouled plugs indicated that it was running rich on cylinders 1-4-6-7 which was traced to a split brass tube on the venturi cluster assembly in the 2 Bbl Motorcraft carburettor, oil pressure was also very low when idling.

At first I was informed ( by a supposedly knowledgeable friend) that the Ford 302 engine was susceptible to sticking valves which cause this problem, so I removed the heads and took them to be serviced, he company that overhauled the heads informed me that I was using valves that were supposed to have caps installed on top of them and recommended that new valves be installed that were slightly longer and did not require these caps, I was not too sure about this (having never heard of it before) but they were changed anyway, the heads were replaced and to my great annoyance the same symptoms manifested themselves again.

I then decided that as the engine had gone through some very rough service over the past 8 years, I would do a complete overhaul of it, changing out all of the valves, hydraulic cam followers, timing chain and associated sprockets, piston rings, crankshaft and bearings, oil pump, and camshaft bearings, all of the above items were found to be worn and in need of replacement.

External repairs consisted of repairing (soldering shut) the split on the brass tube in the Carb, a new water pump was fitted along with a new thermostat, also changed were all of the sparkplugs and HT leads and ignition points and condenser, I even installed a new flywheel as the old one was rusty and very pitted.

Last month I started the engine, and tuned and timed it, it idled perfectly with good oil pressure, and the timing set to 10 Deg BTDC, however at around 2500 RPM the same misfiring sets in again, and once more I notice that the same plugs are getting fouled, as the engine is on a test stand in my workshop it would not be a big deal to take it apart again if I have to, and as the idle jets on the carburetor do not seem to make any difference to the idling I know that I have to find a new or rebuilt Carburetor, but thus far have not been able to, does anyone out there have any ideas, do I have a carburation or ignition problem, or is it something else? I want to go out fishing again.


ARC

I know the Shamrock boat well, they built them right here in Cape Coral, Florida. I think you have nailed it with the carb situation. What is causing you to have a problem finding a replacement? If you are looking for the exact carb that might be tough, but you can adapt any MARINE carb to it as long as the bolt pattern is the same. I stress MARINE carb as you do not want to put a car carb on it under any circumstances (BOOOOOOOOOOOM!!! :eek: ) Same goes for fuel pump, distributor, alternator and starter.........use only those designed not to cause an explosion.

If the bolt pattern is the problem you can swap out the intake for any sbf intake, they are the same as the automobile versions. Then you can use a carb that will fit the bolt pattern. BTW, how old are your exhaust manifolds? Have them pressure tested because a leaking one will wipe out your new rebuild in a heartbeat if water gets into the cylinders.

For a little history on your Shamrock, I know George who started the company. He was in the Navy in WWII and saw the landing crafts with the protective keels under them. When he got home he started building pleasure boats with the same keel-drive system, primarily because of all the shallow water we have here in Florida. They have some unique handling characteristics because of it, and are not necessarily the driest running boat made, but they are built like a tank........especially the ones from your era.

I would also check out your ignition system, but the fact you say it is loading up leans me toward the carb first. BTW, you can switch to a four barrel if you swap the intake manifold too.

Don

Now I'm no expert but from my experience with a 302 I had in my Cobra I too experienced misfire and plug fouling between about 2000-2500 rpm. The engine was a mild performance rebuild, a bit hotter cam, roller rockers, etc.., induction was an Edlebrock performer and Holley 600 It would start and idle fine and about the above rpm would start to misfire on the same cylinders as yours, above 2500 or so it would just scream with no problems.

What I discovered after a long frustrating period was that it was a combination of too low of timing, I finally went to 14*initial, too cold of plug, and most especially a bad distributor and coil, curve would begin to drop out about 2k rpm . Once I replaced the distributor,coil, plugs and advanced the timing, then re-tuned the carb( I started getting a low rpm "stumble" then), I cured the problem.

The whole time I was thinking that when we rebuilt the engine we had done something wrong in the reassembly and was planning on pulling the engine again. Basically the engine had all new components, timing gear, chain, camshaft, Alum. heads, valves, pushrods, pistons and rods.
I'd check your dist.and ignition first off, then the carb...

Carb/ignition malfunction........unless its oil fouling?