i have one in my little shop right now,it is definitely plastic.

Weird, what engine is it? I just went downstairs to my little shop in the basement and checked 7 different ones, all aluminum. 575sc's, 502Mag, zz502, etc. I'll check some more when I'm at the shop tomorrow. Maybe there's some plastic ones on different years? I've ever seen one, but I'll check now 'cause I'm curios.

The gm performance gen vi covers are listed as cast aluminum. I have a stock gen vi 454 in my dually, ill have go out to my little shop and look at it. Lol

i have 2 96 454's gen 6 and they are both plastic with steel doo hickys where the bolts go through.. they may have changed it on the newer years..dont feel like digging in box's rite now..

Ok, did some surfing. Seems like the production gen vi engines, received plastic timing covers. The gm performance 454HO and 502HO crate engines got the aluminum covers. My guess would be look at a 7.4L mpi merc 310hp, and you'd probably see a plastic cover, since its more or less a L29 production engine. The 454 mag, 502 mag, HP500, and so on , would more than likely have a aluminum cover, since they were not automotive production engines in base form. Which would make sense why haxby is seeing the alum covers.

Here's the aluminum cover
http://www.gmpartsdirect.com/perform...CATID=344.html

this one is a gen 6 502,i dont know what year it is,it has been apart before because it has aftermarket hyd roller lifters with the link bars that would not be necessary with the stock 415 horse cam that was in it,also it was .030 overbore.

mine are the peanut port 310 454's

I bought 2 new crate engines for my Gibson a few years ago, Gen VI' have alum covers...

my 2000 model gen 6 502 mag's are alum.

my boat is a 1993 and was equipped with a 502. it had a manufacturer date of 1992 and is a gen 5. gen 5 engines in mercruiser setups have larger oil lines. it will have a flat tappet cam... mine had 5 flat lobes when i took it out a few years ago.