ZZ502 w 741 cam issues
 

I have a ZZ502 that has a Crane 741, roller rockers, cometic head gaskets, and a edelbrock airgap intake topped with a 850 holley. With Imco powerflow exhaust.
It fowles plugs, I think that it is due to a combination of carb and cooling. As it only foules the front two plugs. It has a bypass cooling system.

Would you add a recirc pump? Jetting, where should it be, it only has about 4.5 inchs of vacuum at idle. OR ultimately I have a friend who has a complete 525 EFI system, which would be the better setup, but I have oval heads, and I beleive it is rec.

Any help would be appreciated.

RT

Oh this is in my Sea Ray, it has NEVER run correctly.

Vacuum is very low. Check your ignition timing. Adding initial advance will usually improve a poor idle. Some ignition systems give you the option of changing the ignition curve. Msd uses a bushing and spring assortment to adjust the curve. Merc Thunderbolt can be adjusted by using a V-6 module with less advance. This allows you to turn up the initial advance without exceeding 34-36 degrees total. I don't know much about those carbs but I suspect something is opening early like a power valve because of the low vacuum.

I am trusting that you currently have a crossover water system attached to the front of the block? Are you using a thermostat? That's why you have the bypass hose connected?

Its in the tuning, most likely. When does it foul the plugs???? at idle or while running???? Where is the initial timing and full advance set???? How did you determine where to jet the carb in the first place???? What spark plugs???? What ignition system???

You can't just bolt stuff together and expect it to run right. The same goes with just bolting on a 525EFI system.

:DGiven the information, you may even have your head gaskets on backwards blocking the rear water passages and making the front cylinders run cold....has it always had this symptom?:eek:

It has a stainless marine crossover cooling system with a thermostat. I think that the COLD water is not allowing the front cylinders to build any heat. This I am sure is contributing to the front plugs going out. They are black as hell. It is not oil fouling, it is fuel.
The total advance is 36, I do not know what the initial is.
The Cometic gaskets were put in by Active Engines.
When running it never really gets much over 120-130 degrees, so I think the first order is to install a recirculating pump, and look at a V6 module.
The motor only has 20 or so hours on it, when it has fresh plugs it pushes the boat low 80's..... then if you idle more than a few min 60's. New plugs and away you go.

GOD I hate 4 strokes!.... and carbs LOL

RT

here is the motor, before installation, and while it was going it, it isn't complete here but you get the idea.

Crane 741, did you degree in the cam when it was installed? Are you bringing in water at idle.
I run a much larger cam than that from RMBUILDER and I have no issues. I also have Imco powerflow exhaust.
Like mentioned above I would start looking at tuning issues, like the jetting.

The cam was installed at Active engines, the motor was dyno'd there, but with dyno headers and cool fresh air. It now has the powerflows and mufflers. And a flame arrestor.

There is some milk in the tops of the valve covers, nothing down on the head, and the oil pan and oil is clean, I suspect that this has as much to do with there being no heat in the motor.
The original ZZ cam with the silent choice tops on the exhaust filled the motor. The longer tops seen in the pictures seem fine for reversion.

I belive the cam is in straight up.

RT