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Differences between 86 and 96 marine 350

A

Agarabedian

Member
My 1986 260/v8 block cracked and I recently got my hands on a free 1996 5.7 350 marine short block. I thought everything would be interchangeable and I could take stuff off my old engine and put it on my new while doing a rebuild on the new short block. I know I got this new engine for free but how screwed am I? What do I need to get to make this new engine work? Heads, intake, etc.?? Will anything match up??

new engine is;

MERCRUISER 1996 5.7L. 457B110JS. 5.7L/LX 350 MAG ALPHA/BRAVO
 

As per your thread title regarding the SBC 5.7L.

1986 cylinder block:
Std bore = 4.000"
Stoke = 3.480"
connecting rod length = 5.7"
same cylinder head bolt pattern as with other 5.7s, meaning that the Vortec cylinder heads can be used on this block.
if equipped with cylinder heads, it will likely be set up with the perimeter bolt pattern valve covers ('87 went to the center bolt pattern)
typically set up with the GM full dished pistons
rear crankshaft flange and block casting uses the 1 pc main seal
crankshaft flywheel bolt pattern is small diameter
typically not set up for the roller cam followers
will accept the mechanical fuel pump
starter motor bolt pattern will allow for the use of either style starter motor (i.e., 153 tooth or 168 tooth flywheel)
may be equipped with either 2 bolt or 4 bolt main bearing caps.

1996 cylinder block:
Std bore = 4.000"
Stoke = 3.480"
connecting rod length = 5.7"
same cylinder head bolt pattern as with other 5.7s
if equipped with cylinder heads, it will use the center bolt pattern valve covers.
typically set up with the GM full dished pistons
rear crankshaft flange and block casting uses the 1 pc main seal
crankshaft flywheel bolt pattern is small diameter
will accept the roller cam followers
no push rod bore nor oil return port for the mechanical fuel pump
starter motor bolt pattern will allow for the use of either style starter motor (i.e., 153 tooth or 168 tooth flywheel)
may be equipped with either 2 bolt or 4 bolt main bearing caps.

NOTES:
....... during some point in time, GM changed the location of the oil dip stick, meaning that the oil pan may not be capable of swapping.
....... the Vortec cylinder heads require the Vortec intake manifold.



quote_icon.png
Originally Posted by Agarabedian
My 1986 260/v8 block cracked and I recently got my hands on a free 1996 5.7 350 marine short block. I thought everything would be interchangeable and I could take stuff off my old engine and put it on my new while doing a rebuild on the new short block. I know I got this new engine for free but how screwed am I?
I'm not sure how you could consider being screwed if the block was free!


What do I need to get to make this new engine work?
A short block will include the rotating assembly, of which means that you received pistons with it, and possibly a camshaft.
You will need to determine which piston profile these offer, and then select cylinder heads accordingly.
(please read my write-up that I linked you to in your other thread)

The camshaft profile must also be correct for marine use.

If you plan to fit this engine with a Closed Cooling System, you can use high grade automotive head gaskets, and save a few dollars.
If you plan to Raw Water cool this engine, you will want to use the Marine set.

Heads,???
Again, please read the write-up.... it will help you with cylinder head selection...... in particular, the combustion chamber volume.
All exhaust ports are of the same configuration, meaning that your Merc SBC Marine exhaust manifolds will mount to them.

intake, etc.??
Depending on the year, the Pre-Vortec cylinder heads offer two slightly different mounting bolt angles.


Will anything match up??
Assuming that your 1986 5.7 is actually a 1986 5.7 w/ 1 pc rear main seal......... yes, your flywheel, your flywheel cover (bell housing in the auto world), engine drive coupler, your Marine Ignition System, your starter motor, your coolant circulating pump (what some call a "water pump"), your alternator mounting bracket, side engine mounts, etc.

Some early 1986 5.7s used the perimeter bolt pattern valve covers....... these will not work for the later cylinder heads that require the center bolt valve covers.


If you stay with the GM Full Dished pistons, make sure that the cylinder head combustion chamber volume is a good match for the piston dish volume in that the combination will offer a suitable static compression ratio.
Again, if you stay with the GM F/D pistons, DO NOT throw too much ignition spark lead at this engine.

Good luck and have fun putting it together.






.
 
Last edited:
Just looking at parts diagrams and cross referencing, seems like the following will fit:
Flywheel (same part number for both 86 and 96)
Flywheel bolts
Water circulating pump/gaskets/bolts
Water pump pulleys
Front cover crank seal
Power steering bracket (and power steering pump, by extension)
Alternator bracket (and alternator by extension)
Starter motor maybe, depending on block casting.
Engine supports (cast or stamped)
Exhaust manifolds and risers, gaskets and bolts.
Flywheel housing
Oil pan and gasket, oil pan reinforcements oil pan screws

so. not so much.

I would do a search on "non vortec heads on vortec" or something to see if the heads and intake can work on that block. If yes then you're in good shape.
 
RicardoMarine said:

As per your thread title regarding the SBC 5.7L.

1986 cylinder block:
Std bore = 4.000"
Stoke = 3.480"
connecting rod length = 5.7"
same cylinder head bolt pattern as with other 5.7s, meaning that the Vortec cylinder heads can be used on this block.
if equipped with cylinder heads, it will likely be set up with the perimeter bolt pattern valve covers ('87 went to the center bolt pattern)
typically set up with the GM full dished pistons
rear crankshaft flange and block casting uses the 1 pc main seal
crankshaft flywheel bolt pattern is small diameter
typically not set up for the roller cam followers
will accept the mechanical fuel pump
starter motor bolt pattern will allow for the use of either style starter motor (i.e., 153 tooth or 168 tooth flywheel)
may be equipped with either 2 bolt or 4 bolt main bearing caps.

1996 cylinder block:
Std bore = 4.000"
Stoke = 3.480"
connecting rod length = 5.7"
same cylinder head bolt pattern as with other 5.7s
if equipped with cylinder heads, it will use the center bolt pattern valve covers.
typically set up with the GM full dished pistons
rear crankshaft flange and block casting uses the 1 pc main seal
crankshaft flywheel bolt pattern is small diameter
will accept the roller cam followers
no push rod bore nor oil return port for the mechanical fuel pump
starter motor bolt pattern will allow for the use of either style starter motor (i.e., 153 tooth or 168 tooth flywheel)
may be equipped with either 2 bolt or 4 bolt main bearing caps.

NOTES:
....... during some point in time, GM changed the location of the oil dip stick, meaning that the oil pan may not be capable of swapping.
....... the Vortec cylinder heads require the Vortec intake manifold.



quote_icon.png
Originally Posted by Agarabedian
My 1986 260/v8 block cracked and I recently got my hands on a free 1996 5.7 350 marine short block. I thought everything would be interchangeable and I could take stuff off my old engine and put it on my new while doing a rebuild on the new short block. I know I got this new engine for free but how screwed am I?
I'm not sure how you could consider being screwed if the block was free!


What do I need to get to make this new engine work?
A short block will include the rotating assembly, of which means that you received pistons with it, and possibly a camshaft.
You will need to determine which piston profile these offer, and then select cylinder heads accordingly.
(please read my write-up that I linked you to in your other thread)

The camshaft profile must also be correct for marine use.

If you plan to fit this engine with a Closed Cooling System, you can use high grade automotive head gaskets, and save a few dollars.
If you plan to Raw Water cool this engine, you will want to use the Marine set.

Heads,???
Again, please read the write-up.... it will help you with cylinder head selection...... in particular, the combustion chamber volume.
All exhaust ports are of the same configuration, meaning that your Merc SBC Marine exhaust manifolds will mount to them.

intake, etc.??
Depending on the year, the Pre-Vortec cylinder heads offer two slightly different mounting bolt angles.


Will anything match up??
Assuming that your 1986 5.7 is actually a 1986 5.7 w/ 1 pc rear main seal......... yes, your flywheel, your flywheel cover (bell housing in the auto world), engine drive coupler, your Marine Ignition System, your starter motor, your coolant circulating pump (what some call a "water pump"), your alternator mounting bracket, side engine mounts, etc.

Some early 1986 5.7s used the perimeter bolt pattern valve covers....... these will not work for the later cylinder heads that require the center bolt valve covers.


If you stay with the GM Full Dished pistons, make sure that the cylinder head combustion chamber volume is a good match for the piston dish volume in that the combination will offer a suitable static compression ratio.
Again, if you stay with the GM F/D pistons, DO NOT throw too much ignition spark lead at this engine.

Good luck and have fun putting it together.






.
Click to expand...

Note: as seen before from poster...copy and paste.

1986 had a 2 piece rear main seal.
Not sure any of the info for 1986 is accurate based on the obvious copy and paste.


Ugh
 
.........
Note: as seen before from poster...copy and paste.
No copy and paste.... those were my words, no differently than any other day!

1986 had a 2 piece rear main seal.
You can find info showing that 1987 was the first year, and you will find info showing that 1986 was the first year.
None-the-less, the 1 pc rear main seal engine will have either the 5.0 or 5.7 cast into the #1 cylinder side at the very rear.

Not sure any of the info for 1986 is accurate based on the obvious copy and paste.
Again, no copy and paste.
I would challenge you to find a copy/paste source for my exact words.
Click to expand...
 
the way to tell,
Center bolt valve covers....1 piece rear main seal
Non center bolt valve covers ....2 piece rear main seal.

99.999999 % of you posts are copy and paste....we see them over and over and over and over and over and over and over and over again and then some....
Why do ya think everyone is sick of them
 
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