Posted by PARTSMASTER on December 01, 1998 at 22:28:19:
In Reply to: 7.4 GEN VI Marine Heads posted by Dave G. on December 01, 1998 at 15:58:21:
: Hi,
: maybe you can answer a question that I have been struggling with for a few weeks.
: I have a 1997 Mercruiser (standard, not Mag)7.4 L that per the serial number is a Gen VI block. Does this
: automatically mean that it has the Vortec heads or is it a GEN VI block with the small
: port heads? Can I tell by looking at them (without removing the intake)? The intake is
: my next question. I had a HiRel (now Holley)MPI system installed on it recently.
: Hirel offered oval or rectangular port intakes. Would you think that the oval port intake
: would be the larger ovals and not the small ovals. If I have the small port heads I will
: want to change to the larger ovals such as Merlin or anything else "you" may suggest while
: keeping the costly intake set up in tact. I've been told to stay away from the rectangulars because
: in marine use you are trying to create the most power and torque while remaining under
: 5000 rpm making the large ovals a much better choice than the high rpm rectangulars.
: If any of this makes sense, I would appreciate any input.
: Thanks,
: Dave G.
Pull a valve cover off and give me the casting #'s we will be able to tell real quick.
Intake ports are usaully the larger size .
Rect. verse oval ports depends on what RPM levels you want your engine to run. Why does GM build all their marine HP engines with rect. heads.