1990 Mercruiser V6 Heads vs. OMC Heads

[incrediblened]

I was wondering if the 4.3 V6 heads were virtually identical on the Mercruiser and OMC. A couple of years ago a guy sold me "Mercruiser" heads to put on my motor. Well, my Mercruiser valve covers (center bolts) didn't fit, so I asked him for the valve covers that went with the heads (perimeter bolts). I come to find out that the valve covers said OMC.

The heads fit, they seemed to bolt on correctly, but it ran poorly when started. It could be many things... I just wonder if it's that the heads are just the wrong heads for my application.

Thanks,
Ryan

 

[Bondo]

Re: 1990 Mercruiser V6 Heads vs. OMC Heads

I was wondering if the 4.3 V6 heads were virtually identical on the Mercruiser and OMC. A couple of years ago a guy sold me "Mercruiser" heads to put on my motor. Well, my Mercruiser valve covers (center bolts) didn't fit, so I asked him for the valve covers that went with the heads (perimeter bolts). I come to find out that the valve covers said OMC.

The heads fit, they seemed to bolt on correctly, but it ran poorly when started. It could be many things... I just wonder if it's that the heads are just the wrong heads for my application.

Thanks,
Ryan

Ayuh,.... There ain't no Mercruiser heads, nor OMC heads,...

They're All Chevy heads,...

Sounds like you skipped down some Vintages in yer swap,...

 

[cliffblue]

Re: 1990 Mercruiser V6 Heads vs. OMC Heads

Yep, sounds like you dropped back from Vortec heads to non-Vortec heads.

 

[achris]

Re: 1990 Mercruiser V6 Heads vs. OMC Heads

Yep, sounds like you dropped back from Vortec heads to non-Vortec heads.

If that were the case, the intake manifold would no longer fit....

Peripheral bolts are much earlier than centre bolts... With Bond-o, you've gone back a few years....

Chris.....

 

[incrediblened]

Re: 1990 Mercruiser V6 Heads vs. OMC Heads

Yeah, I think they're both non-vortec. The mercruiser motor was a 1990. I was thinking that Vortec came out a few years later. But the "OMC" heads did bolt to the intake, so it sounds like I'll be alright. I just need to troubleshoot a few other areas to get it running right.

Thanks!
Ryan

 

[Volphin]

Re: 1990 Mercruiser V6 Heads vs. OMC Heads

Seeing as how "Vortec" heads didn't come out until 1996, you had 74 cc heads to begin with. I see so many people that think their '87-'95 heads are vortec heads because the center intake manifold bolts are at a different angle... SOOOO many people think they have some special "Vortec" head, which is just a buzz-word anyway for fast-burn chambers and raised intake ports.. An easy way to identify Vortec heads is to count the number of intake manifold bolts that hold the manifold down... Vortec heads will have two bolts in each corner of the engine, all of them are perpendicular to the ground with the engine sitting in the car.. So if you have 8 bolts, and they're straight up and down, then they are Vortec heads. All else is a 74cc head.

 

[Bondo]

Re: 1990 Mercruiser V6 Heads vs. OMC Heads

Seeing as how "Vortec" heads didn't come out until 1996, you had 74 cc heads to begin with. I see so many people that think their '87-'95 heads are vortec heads because the center intake manifold bolts are at a different angle... SOOOO many people think they have some special "Vortec" head, which is just a buzz-word anyway for fast-burn chambers and raised intake ports.. An easy way to identify Vortec heads is to count the number of intake manifold bolts that hold the manifold down... Vortec heads will have two bolts in each corner of the engine, all of them are perpendicular to the ground with the engine sitting in the car.. So if you have 8 bolts, and they're straight up and down, then they are Vortec heads. All else is a 74cc head.

Ayuh,... I Agree with what yer sayin',...

It don't help that Chevy was usin' the "Vortec" name on valve covers a few years, Before the fast-burn heads that are now known as "Vortec" heads even came out,...

Fast-burn, or Vortec, they're Kick-azz heads,...
Especially if ya put the Right short block under 'em,....