I don't think that anyone is suggesting that Merc developed or even helped to develop the 502. That was all GM. That said, you can order the 502 with different heads on them right from GM (iron ovals, iron rec. port, aluminum ovals).


I'm sure Merc did plenty of R&D before they choose what castings to have GM bolt on them.

By bolting on a set of aluminum heads with the same size CC chamber as the ones you take off, you can actually lose 1/2 a point of compression.

wjb, OK now I understand what was said. The reason I asked is because I was in the motor plant here in Western NY in the engine cells a couple of times during it's developement. I was told by the engineers at that time it was being developed for the truck and marine industry as an alternative to a diesel power plant.

When I was looking into heads for my project I learned a fair amount, I think... The 502 is going to use a large rec port head. In reality this is not a very good head for your engine. The flow is going to be poor until the upper rpm range, and acceleration from midrange up is going to be poor becuase of the port size and shape. A great head for your engine would be the AFR 290 oval ports. These have fantastic flow numbers across the board. I have the AFR 265 ovals on my boat and its unbelievable how great these heads are. Either way I wouldn't buy a set of heads just because there a good deal... There are a lot of variables to take into consideration.

Thanks for all the replies everyone. A few clarifications, the heads I believe are GM performance aluminum ZL1 heads (I could be wrong about this). The guy I know owns a machine shop and has bugging me for years to let him do some work to my motors. I have been hesitant because I want my motors to be reliable, but since I cannot sell my boat to buy a faster one, I thought maybe I could make mine a bit faster. He can do anything to the heads as far as porting and what not as well as crank and cam work. I really don't have a clue about this stuff, so I thought I would ask for some input before I commit to anything. Thanks.

I haven't seen this mentioned...I thought you could run a little more timing or compression on lower octane fuel because aluminum heads disapate heat better and are therefore less prone to detonation. Am I misinformed?