I have a 14096859 502 4.446 Generation V marine block with 4 bolt mains and thin main bulkheads

what was the deal for the thin main bulk heads in marine blocks?

Also I ran a radical cam in the car. It ate up the valve seals. Now the #3 cylinder is fouling. Should I expect the valve guides are bad to?

It has a puff of smoke when you first start it. It will burn a quart of oil every 300 miles. Also if you idle around too much it will foul the 3# cylinder spark plug, dark with oil.

Are new heads the way to go? Thank you very much. LACK

 

i cant really help you...but my dad has a chevy big block in his 98' boat and in the manual they claim that its very normal to go through a quart of oil a day....ours goes through none, but obviously a lot of big block chevy marine engines go through a ton of oil for them to put in in their owners manuals.

 

it has always been my understanding that the tollerances for the marine motors was not as tight as the auto industry. most of this is secondary to cooling problems. you don't exactly have 60 MPH air blowing across a nice big radiator in a boat. the more lax tollerances leads to increased oil consumption, etc. etc. but also give more room for heat expansion.

the air-cooled aircraft motors can go through oil REAL quick compared to cars. some of those motors are 300+ HP 6-cyl horizonally opposed air-cooled engines! they make the pistons on modern v-6 automotive motors look like 1st graders.

 

You don't have airflow across a radiator, but you have an unlimited source of of cold water for cooling. Unless you have a problem with the seapump, most performance boaters have a hard time getting to proper operating temps (160+), especially when crossovers are used instead of the conventional water pump.

The reason the clearances are a little looser on marine engines is due to the fact that it's not unusual for the engine to operate at WOT or near WOT for extended periods of time. I built a pair of Dart 540's for my 35' Cigarette and they're setup to run at 5500 rpm all day long, although with current gas prices that gets expensive quick!

Marine engines in general live a much more harsh life than automotive engines and are built to reflect this. Automotive engines make poor marine engines, without modifications, but marine engine would generally make a very durable automotive engine, albeit the operating range is different. Marine engines don't usually have to have good off-idle performance, with the emphasis placed on strong mid-range and high-rpm performance. Anything below 2000-2500rpm is generally not significant as long as it can sustain a good idle around the docks and doesn'y stall when shifting into gear. To get on plane the rpms are generally required to initially be above 2500-3000 rpm depending on the props. Once on plane you might be able to drop the rpms back down to 2500 or so, again depending on props.