Differences in 350 engines

I have a CH270 Crusader which is a 350 c/i. According to the serial number it is a 1986 although I was told by the guy who sold it to me that it was a 1976. When I search for similar engines, the information I get is for 1985 and older or 1987 and newer, so I Wonder what is so different in the 1986 that it don't fit with other years? If I ever have to replace the engine is this mean that I am not going to be able to use the starter, alternator, fuel pump, etc... that I have on my 1986? Thanks for your help. Jean

I believe Andrew & company - our host here - have a serial chart on the crusader manual page -> just follow the link at the top of the page...

The break point is thru 1986 and then after...the big change is going from a split rear main seal to a one piece design. the hot rod (auto) boards have hundreds of posts on this topic and some go into ungodly detail...one caveat - most articles reference the year GM made the change...the engine marinizers almost always had "leftovers" so a marine 1987 engine could be a GM 1985 block...same holds true for the boat builders - very possible to have a 1985 block in a 1987 hull...

For the most part, most of the bolt on parts will swap...personally, if it is time to renew a block from the mid 80's, I'd think the bolt on pieces are just as tired...

Mark is correct regarding the boat builders not necessarily using year correct engines.
And I agree, the Hot Rod forum guys are fairly well versed in this. Just don't use their build techniques for Marine cruiser use.


Apparently the Martec web site has been taken down for some reason. However, somewhere out there you'll find an archived version of it.
Martec did a very good job at listing and identifying SBC cylinder blocks and cylinder heads via casting numbers and/or serial numbers.


In 1986 and 1987, GM made the change from the 2pc to the 1pc rear main seal for the 5.0L and 5.7L engines.
Apparently the 5.0L and 5.7L were one year behind the other, and right now I don't recall which one followed the other.

This is clearly identifiable by the casting number at the rear Port side of the blocks, which includes the engine displacement.
This one is a 5.0L.




Here's where we'll find the earlier 2pc rear main seal engine numbers.








Most all of your components will interchange.

Cylinder head exhaust ports and bolt pattern are unchanged.
Flywheel cover flange and bolt pattern remains the same.
Ignition distributors should interchange for the standard LH rotation engines.
153 tooth flywheel = straight across bolt pattern starter motor.
168 tooth flywheel = staggered bolt pattern starter motor.
Engine circulating pumps will interchange up the engines with composite timing chain covers.


Exceptions will be:

Oil pans are different between the 2pc and 1pc rear main seal engines.

Flywheel crankshaft flange and bolt pattern changes between the 2pc and 1pc rear main seal engines.

Intake manifold bolt angle changed at some point.

In/around 1991 or so, GM discontinued the mechanical fuel pumps, of which means that these blocks are not drilled for the fuel pump push rod.


As the year models become even later, there will be more changes that hinder some parts interchangeability.




.

Jean, a simple method would be to look for a casting number in this location.
If you find either a 5.0 or 5.7, it will be a 1986 or 1987 or later engine block.
If you cannot see this area, use a piece of modeling clay, and press it down onto this area.

If you do not see the displacement numbers..... then it's safe to say that it's earlier than 1986/1987.






Edit:
Also note that between the early and later engine block and cylinder heads, piston deck profiles and cylinder head combustion chamber volumes became subject to change.
This means that we cannot arbitrarily mix/match cylinder heads from one block to another, without considering this.



.

First, I want to thank you guys for answering my posting. The model number of my engine is CH270 and de eserial no is 59806, so according to the books that I ordered from our sponsor here it is a 1986. The motor run very well but I was currious about the difference as the references were always for up to 1985 or 1987 and newer. I already changed the starter, carburator, fuel pump, distributor, alternator and have a leaking water pump so will change it next spring. The boating season here is all over. So if I understand well, all of the above would fit on either 85 and older block if I ever have to replace it? By the way, it is a RH. Thanks again for your help guys.

sonama said:

By the way, it is a RH.

Click to expand...

RH as in Reverse Rotation???

This is a Rev RH rotation engine as viewed from the flywheel end.
(just opposite from car/truck application)






NOTE: some circulating pumps are not reverse capable. They will pump coolant, but not as effectively as will a bi-directional circ pump.


.

Hmmm is that a “marine” sbc Rick??? I’m just a dumb machinist new in the marine world. Since your a expert I’m hoping you can inform me

Rob0308 said:

Hmmm is that a “marine” sbc Rick??? I’m just a dumb machinist new in the marine world. Since your a expert I’m hoping you can inform me

Click to expand...

The images that I posted are generic and were grabbed from the Internet. There is no Marine specific SBC cylinder block. However, some castings are better suited for Marine use.

By the way, you have posted to a thread that was started way back in October of 2013.
It would be best to start a new thread with your specific questions.