airjunky

iTrader: (2)

Those pistons look like the orig 22 yr old mcm500's wow! If its 4.440 bore then you score !

airjunky

iTrader: (2)

Prob std deck bowtie 454 based unit .should be able to take some punishment (and boost ) not sure if there is lots of room for overbore .just a Retro roller cam and some good springs away from glory if your lucky .

Shibby1485

my crankcase oil was staying pretty clean, but i was getting alot of condensation milkiness in valve covers... and i THOUGHT this was bc i had no thermostat or a thermostat problem.... i never saw my temp guage go past 100 degrees. maybe if i ran the boat hard for awhile and then came down to idle i MIGHT see it hit 105-110 degrees if i was lucky. i thought it was running too cold maybe to burn up water vapor.... upon pulling out thermostat and crossover tubes i was fitted with a 144* thermostat i think it was? but this motor never got hot, or is it normal to only run at 100* water temp on guage? i have no oil temp gauge, but it is being fitted with one on my new dash i'm making.

upon taking off intake manifold, it was very evident water was leaking into motor at the front port side corner between the head and manifold. gasket corroded, aluminum pitted and missing from mating surface... i figured that was my water in the valve covers?

my calipers are MIA, i think they got thrown out after hurricane sandy, need to go buy new ones...

i measured "precisionly" with a tape measure ... it is definitely about just SHY of 4 5/8" bore...i was originally a capenter by trade, haha...

intake valves are 2.25"
exhaust valves are a touch larger than 1.75"

MILD THUNDER

iTrader: (3)

Ive ran without thermostats and cold water temps for years. I've never had standing water under my valve covers. I see people blame condensation when in reality, theres leaks. Not saying that condensation doesnt happen, but you should not have standing water or foamy chocolate shake on the rockers and springs after a run.

Have you verified the piston stroke?

Shibby1485

just measure the distance from top of piston at BDC to the deck?

and before you mentioned the rocker set screws.... meaning the black tall nuts that tighten the gold rockers down in place? if so, those were bottomed out tight all the way upon disassembly i'm nearly positive. i was checking valve lash before stripping everything and it was pretty much at zero lash and those rocker nuts on the studs were cranked down. if my terminology is wrong let me know which set screws you speak of

Thank you for continued response.... graciously appreciated. i'm a fast learner and thorough, just learning a "new-to-me" powerplant.

Budman II

iTrader: (1)

That seems small for BBC exhaust valves - would expect them to be 1.88".

MILD THUNDER

iTrader: (3)

I think he's using a tape measure.

For what its worth, the 502 Mag heads had 2.19 valves. The high performance engines, like the HP500, 500 bulldog, HP465, got 2.25 intake valves. Obviously they could have been changed out over the years.

But, mark IV bowtie block, 2.25 intake valves, flat tappet cam, sounds like it could have been a HP465 engine, or a 540 bulldog. A sneak peak at the connecting rods might tell a story. I believe the 540 bulldog had carillo rods, where all the others had GM I beam style rods.

Shibby1485

4.560 bore is what I measured

2.25 in stake

1.88 exhaust

I went and bought a digital caliper. I freaking forgot to measure the stroke though. Will do that tomorrow.

At this point ... Should I just flip it and pull the oil pan off ?

airjunky

iTrader: (2)

If it was leaking water in the oil wouldn't be a bad idea at all to pull the pan ,take a peek at bearings have some 12 point sockets of good quality handy just in case the lunati - h beam rod gods are smiling on you .

Meshikinquah

iTrader: (1)

I would pull the pan if for nothing else to replace the gasket....