dennis rider

I recently rebuilt my GM 502/502 Crate motor. Last year I had trouble with water and oil mixing. I eventually destroyed the motor and have since rebuilt it. We changed cams due to the fact the original equipment was not marine friendly. My mechanic wasn't available tonigt so i'm not quite sure what the specs of the cam are. The engine has been bored 30 over and we added roller rocker arms and and an edelbrock air gap intake with an 850 Demon carb. This engine block is a genV1 model. We used universal Mark 1V head gaskets (fel-pro). I've done some reading up on these head gaskets and am not convinced they are the right one for the application or at least i'm hoping so. This engine has been totally re-worked and i'm still mixing water and oil. Another problem we have encountered is with the timing. I have to advance the timing to 48 BTDC before it will take gas. I realize this is a problem and have shut the boat down for now. Does anyone have any suggestions as to why this engine is mixing water and oil? I'm very frustrated at this point.

Ps. The exhaust system is Gil magnun headers

thanks,

DR

MACDAD260

Did the oil and water mix since the motor was new or did you get some time on it before that happened? What kind of exhaust are you running? That is the first place to look as reversion will happen if there are any leaks there. You could have a bad riser gasket or an internal leak. It could be the cam if you do a lot of idleing. It may be a porous block but, I would think that would have showed up when the block was rebored. Why did you use the universal gaskets? They may be OK but there should be a set just for Gen VI motors. Maybe not, too. Do you have an oil cooler? Maybe that is leaking internally. It could also be that the intake manifold is porous in the water passage area. Just throwing out some possibilities. Hope you get it figured out. Good luck.

jpclear

Dennis Moore's book on BBC Performance Marine Engines goes into lots of detail in three different chapters on just what you can and cannot mix as far as blocks, heads, and gaskets are concerned and it sounds like you may have fallen into one of the traps. The wrong combination, although it will go together just fine, will leak water into the valley under the intake manifold. Get a copy of the book and check it out! Luck to you! --- Jer

Dave1972

May also want to check water pressure as that was the culprit for my new motor. The other guys offer good advice to check out Dennis Moore's book....I just happen to have a copy if you need it drop me an email or PM.

Let us know what you find out!

convincor

you din't mention the part # for the gaskets???

Dave F

use Fel pro 1047 head gasket. The intake gasket may be leaking and as has been said, check water pressure.
If proper gaskets have been used, check surfaces and make sure they're flat and true.
DAVE

dyno

What heads are you running? My Merlins have two bolts that run through to the water passages if they arent sealed they will wick water up the threads I've had this in one of my motors and SuperV had one that was close but never leaked.