Part Number for Mercruiser 420 Cylinder head...?

[Hondo Jet]

Does anybody know what the GM part number is for the cylinder heads on an '87 model Mercruiser 420?

Thank you!

 

[Don S]

Re: Part Number for Mercruiser 420 Cylinder head...?

Never heard of a 420 model Mercruiser.

 

[zbnutcase]

Re: Part Number for Mercruiser 420 Cylinder head...?

And that better not be cheap automotive fuel line connected to that cheap auto fuel filter feeding an engine protected by a crappy Fram oil filter! 'nutcase

 

[JustJason]

Re: Part Number for Mercruiser 420 Cylinder head...?

It looks like it says 420HP on the valvecover from my house. I also see serial numbers on that sticker. Give us the serial numbers and we'll run them and see what you have and need.

 

[Bondo]

Re: Part Number for Mercruiser 420 Cylinder head...?

Ayuh,... If that's a BBC,..
You'll have to pull the valve cover,+ find the Casting #...
Then start Seaching....Used heads...
As I doubt you've going to find a Match, New...

 

[ErieRon]

Re: Part Number for Mercruiser 420 Cylinder head...?

MCM 420, Service Manual #9, 1986, 454 production performance, 420 HP. Never heard of it either, but there it is.


EDIT: Check your S.N. with this description;
OEM P.N. 938-816778T3 HEAD, Cylinder Superceded from 938-816778 SN# 0A398941 THRU 0D725499

This link may help; http://www.mercruiserparts.com/Show...bnbr=200&bdesc=Cylinder+Head+And+Rocker+Cover

 

[Hondo Jet]

Re: Part Number for Mercruiser 420 Cylinder head...?

This is a boat parked in a storage lot that I've had my eye on for a long time, now I have a chance to buy it. Went out to do a compression check on it, found it locked up and the number 8 plug has been hit hard from the inside . Most likely dropped or broke a valve. I cant imagine the lower end of it coming apart. No holes in the block or oil pan, also no water in the oil. Valve cover cant be removed without removing the exhaust manifold. I know the GM number wll be there under the valve cover, I just thought it may be published somewhere what GM number was original equipment.

Thanks ErieRon, I had already found the Mercruiser number, 938-816778T3, but was hoping for a GM number so I could at least know whether it was a rare or common piece in the event that I would have to find a used replacement.

'nutcase, I'm with ya on the mickey mouse fuel lines and Fram filter. If I get it you wont see that again.

I'll go ahead and pull the exhaust manifold and lift the valve cover to see whats going on under there. Then I'll have the GM number.

 

[zbnutcase]

Re: Part Number for Mercruiser 420 Cylinder head...?

Chances are good its a standard open chamber rectangular port head. 'nutcase

 

[Hondo Jet]

Re: Part Number for Mercruiser 420 Cylinder head...?

Yep, has 990's on it.

 

[Bondo]

Re: Part Number for Mercruiser 420 Cylinder head...?

Yep, has 990's on it.

Ayuh,... So'd,.. Ya get her Runnin' yet,..??

 

[RicardoMarine]

Re: Part Number for Mercruiser 420 Cylinder head...?

And that better not be cheap automotive fuel line connected to that cheap auto fuel filter feeding an engine protected by a crappy Fram oil filter!

Ditto! Set yourself up with the corret parts here.