M90 l jet head identification

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griffo
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M90 l jet head identification

Post by griffo »

I am a out to buy another m90 l jet head but i want to know how to tell if the head is in fact a l jet head? Thanks and need help asap!!
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Re: M90 l jet head identification

Post by GRNSHRK »

griffo, got this photo from a fellow Big Couper, M90 should be in the casting, I think behind the cam sprocket :-k
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M90 on head.jpg
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griffo
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Re: M90 l jet head identification

Post by griffo »

Thanks so the m90 heads are the same from motronic to l jet heads yea?
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zinnocoupe
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Re: M90 l jet head identification

Post by zinnocoupe »

I believe the m90 on the head doesn't really mean much. I have an m90 engine and the head doesn't say m90 on it. And I have a m30b32 engine and the head says m90 on it. Both heads appear to be the same. The head gaskets when laid on top of one another line up identically. Or close enough I see no difference.other than the larger bore for the m90 engine
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Re: M90 l jet head identification

Post by bpoliakoff »

griffo wrote:Thanks so the m90 heads are the same from motronic to l jet heads yea?
The last year of the M90 was model year '81. It was the first year of Motronic . The block did not have a raised water passageway on the drivers side. I also believe there wasn't a difference in the design of the head and the manifolds, intake and exhaust, would bolt to either head but the water passages in the cylinder head were close to the combustion chambers and cracking was an issue.. The 82 engine on did have different water passage configuration and the later heads are interchangeable with an M90
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
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griffo
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Re: M90 l jet head identification

Post by griffo »

bpoliakoff wrote:
griffo wrote:Thanks so the m90 heads are the same from motronic to l jet heads yea?
The last year of the M90 was model year '81. It was the first year of Motronic . The block did not have a raised water passageway on the drivers side. I also believe there wasn't a difference in the design of the head and the manifolds, intake and exhaust, would bolt to either head but the water passages in the cylinder head were close to the combustion chambers and cracking was an issue.. The 82 engine on did have different water passage configuration and the later heads are interchangeable with an M90

So the later ones "not l jet" had m30 style water ports compared to the m90 block yea? See mines a l jet motor.
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Re: M90 l jet head identification

Post by griffo »

zinnocoupe wrote:I believe the m90 on the head doesn't really mean much. I have an m90 engine and the head doesn't say m90 on it. And I have a m30b32 engine and the head says m90 on it. Both heads appear to be the same. The head gaskets when laid on top of one another line up identically. Or close enough I see no difference.other than the larger bore for the m90 engine
So for a cheaper alternative i can take a m30b32 head and put it on a early m90 and all the water ports will match and i can run m90 or b35 valves? Would be alot cheaper lol
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