Compatability

S

Sugo

Petty Officer 2nd Class
Joined
Nov 11, 2008
Messages
160
When replacing a cracked 4.3L mercruiser block (gm casting 867) that was produce late 80's early 90's, can I use a newer 4.3L Vortec short block ? Will my heads (768) and intake fit the newer block? Will my flywheel bolts on ? Does it make a difference that the newer block is set up with a balance shaft? The only visual difference I can see is that I will need to add an electric fuel pump as the newer block is not set up for a mechanical fuel pump. This option is being explored as it is hard to find an older short block with low hours and my heads and manifolds are in good shape. Any input would be helpful.
 
Bondo

Bondo

Moderator
Staff member
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Messages
70,524
Re: Compatability

Sugo said:
When replacing a cracked 4.3L mercruiser block (gm casting 867) that was produce late 80's early 90's, can I use a newer 4.3L Vortec short block ? Will my heads (768) and intake fit the newer block? Will my flywheel bolts on ? Does it make a difference that the newer block is set up with a balance shaft? The only visual difference I can see is that I will need to add an electric fuel pump as the newer block is not set up for a mechanical fuel pump. This option is being explored as it is hard to find an older short block with low hours and my heads and manifolds are in good shape. Any input would be helpful.
Click to expand...

Ayuh,... As long as the old 1 is newer than '87, the crankshaft/ flywheel is a non-issue...

The heads, 'n manifold, as a package will also swap, no problem...

The timing cover is the only difference on the balance shaft motor...
 
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Struc

Chief Petty Officer
Joined
Jul 27, 2011
Messages
409
Re: Compatability

Post the casting number on the back of the block, so we can make sure which block you have. Looks like this:

IMG_2736s.jpg


But yeah, unless you have an old block with 2-piece rear main seal, things should be fine.

The intake manifold is not compatible between the Vortec heads and non-vortec. The Vortec heads have 8 mounting bolts for the intake manifold, the non-vortec have 12. So, if you want to use the Vortec heads for the power gains, you'll need to get a new intake manifold. They can be had for around $200. If not, use your old heads on the new block, and you'll be fine.
 
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Sugo

Petty Officer 2nd Class
Joined
Nov 11, 2008
Messages
160
Re: Compatability

Thanks for the info guys. I will check out the casting #'s tonight
 
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