Omc 4.3? What did i buy?

[42 Clyde]

I just acquired a salvage 4.3 OMC motor with only 20 hours on the rebuild. But as im disassembling it to inspect everything im noticing some differences between this one and the motor i am replacing it with.

1. The new motor has a Flat tappet hydraulic lifters in cam. The motor from my boat has a roller lifters and cam.

2. All of the accessories still have the original grey OMC paint ,ie, water pump, intake, fuel pump, harmonic balancer and valve covers. But the engine block, timing cover and heads are painted with a cheep black paint. The harmonic balancer and valve covers wer over sprayed with the same cheep black paint. Did i just buy a truck motor in disguise? How do i tell if this motor will work? What els should i be looking for? Any advice would be appreciated.

I dont seem to be getting anywhere with the numbers on the block to tell me anything.
020
T050TUBC
TCB525065
C036
14088553
Cam EP 141 , CWC, E3, 23

 

[Lou C]

It could be a truck motor or even a Merc 4.3 since theirs were painted black instead of grey. The differences were stainless steel head gaskets and brass freeze plugs. If it’s a year older than your engine that could explain the flat tapper cam. I have a 1988 original OMC 4.3 and it has the roller cam. This won’t keep you from being able to use it unless it also has a 2 piece rear main seal. You really go by the casting # at the rear of the block behind cyl #6. And the cyl head casting #s as well.

 

[42 Clyde]

It could be a truck motor or even a Merc 4.3 since theirs were painted black instead of grey. The differences were stainless steel head gaskets and brass freeze plugs. If it’s a year older than your engine that could explain the flat tapper cam. I have a 1988 original OMC 4.3 and it has the roller cam. This won’t keep you from being able to use it unless it also has a 2 piece rear main seal. You really go by the casting # at the rear of the block behind cyl #6. And the cyl head casting #s as well.

Brass freeze plugs yes.....stainless steel head gasket no. Head gasket looks like a blue Felpro Auto Zone special. Rear main is one piece.
How do i cross reference the numbers on the block (from the first post) to find out what this is? Google has failed me on this one.

 

[Lou C]

You have to be more specific, which numbers came from where on the engine. You should be looking at the block casting # right behind cyl #6, and the cyl head casting #s that you can see when you take off the valve covers.
The marine Fel/Pro head gaskets are blue.

 

[42 Clyde]

You have to be more specific, which numbers came from where on the engine. You should be looking at the block casting # right behind cyl #6, and the cyl head casting #s that you can see when you take off the valve covers.
The marine Fel/Pro head gaskets are blue.

CO36 and 14088553 are cast on the block right behind #6.
.020 , T0502UBC and TGB525065 are punched into the block in front of #2
D237 and 14094768 cast on head #1
C307 and 14094768 cast on head#2

 

[Lou C]

Ok from the 14088553 the 553 is the actual casting #, that lines up with a 1986-1988 with one piece main seal.
The 14094768 head casting number lines up with the same year range
The .20 might be the size the cyls were bored during the rebuild. The T#s are probably a GM serial number, the T signifies the Tonawanda assembly plant.
So some 4.3s of this range had the roller cam, some did not. I think the year when it came on line might have been 1987, because I have seen several 1988s like mine and they all had the roller cam. So this engine appears to be from the same generation as your original but might be just slightly older than the original due to the flat tappet cam vs roller cam. The only concern of having the flat tappet cam is to use an oil higher in zinc than many modern oils tend to be, like Lucas Marine 20/50 which has a significantly higher zinc levels than is typical today.

 

[42 Clyde]

Ok from the 14088553 the 553 is the actual casting #, that lines up with a 1986-1988 with one piece main seal.
The 14094768 head casting number lines up with the same year range
The .20 might be the size the cyls were bored during the rebuild. The T#s are probably a GM serial number, the T signifies the Tonawanda assembly plant.
So some 4.3s of this range had the roller cam, some did not. I think the year when it came on line might have been 1987, because I have seen several 1988s like mine and they all had the roller cam. So this engine appears to be from the same generation as your original but might be just slightly older than the original due to the flat tappet cam vs roller cam. The only concern of having the flat tappet cam is to use an oil higher in zinc than many modern oils tend to be, like Lucas Marine 20/50 which has a significantly higher zinc levels than is typical today.

Well shoot, i was under the impression this was a 1996 motor like mine. So its about a decade older than my original motor. Will this still work? What are the possibilities of swaping parts over like heads, intake, carb, distributor , cam and lifters?

 

[Lou C]

Ah I don’t recall you saying you originally had a 96. Well it can be made to work depending on what accessory pulley set up the 96 has. You need to find out is your 96 a Vortec? Count the bolts holding down the intake manifold if it’s 8 bolts it’s a Vortec if 12 it’s a pre Vortec. The Vortec heads add about 20 hp. Did the 96 have V belts or a Serp belt?. There are some other difference as does the 96 have a balance shaft or not what timing cover is on it, tin, plastic or aluminum etc. There are many differences between the older pre Vortecs and the newer ones. If the rebuilt one is in good shape I’d put in a set of Marine HGs, and use it. You can use a 2 bbl or 4 bbl on these, I prefer the 4 bbl. Post up pix of the 96 and the rebuilt one you bought. Otherwise just guessing.

 

[Lou C]

(5) complete history of the 4.3 liter with casting numbers | Boating Forum - iboats Boating Forums

take a looky here....

 

[Scott06]

Well shoot, i was under the impression this was a 1996 motor like mine. So its about a decade older than my original motor. Will this still work? What are the possibilities of swaping parts over like heads, intake, carb, distributor , cam and lifters?

I think the flat tappet means the block is an 85-86. Will it work I would think yes but will make less power than a vortex 1996 and up engine.
the flywheel size maybe smaller on the older engine may cause a coupler fitment issue. I think in 91 went to a 14” flywheel From 12&5/8” starter is different between flywheel sizes too.

 

[Scott Danforth]

here is some light reading.

complete history of the 4.3 liter with casting numbers

thought I would post the complete history of the 4.3 liter that I could find. These are links and articles that I have bookmarked for my own use, however they should help many people. it may help some people when looking for parts or sourcing a salvage yard motor or a reman. keep in mind that...

forums.iboats.com

the block casting numbers "14088553" you have indicate its a 1986 block.

as Scott06 pointed out above, flat tappet motor makes less power than the roller motors and much less than the vortec headed roller motors.

 

[Lou C]

Even with the flat tappet pre-vortec block, you could probably add the vortec heads and a 4bbl vortec intake and perk it up a bit (20-25 hp). I actually prefer the older pre-vortecs with the roller cam for the simple reasons that they have an adjustable valve train, they can use a simple and trouble free mechanical fuel pump and they have the older intake with 12 bolts vs 8 which I think just seals better. It was very rare for those to leak whereas leaks were common on the vortec intakes. So what you have can be made to work, whether you leave it as is or convert to vortec heads.

 

[Scott Danforth]

adjustable valve train is as simple as pulling the studs and modifying for ARP thread in studs.

 

[42 Clyde]

So what ive ben able to gather on my own is that converting this motor over to a roller cam with the parts i have is not going to happen. This block does not have the necessary castings built in to accommodate the factory lifter guides. Yes i can convert it over with a Comp Cam roller cam kit Which would effectively blow my budget clean out of the water by tripling the cost. However this motor has the same accessory drive, fuel pump, flywheel, starter, intake, water outlet, distributer and everything els on the outside of the motor is the same.
The compression reading on 4 of the cylenders we all over the map and 0 psi in 2 and 4 so i pulled the head and found a half inch hole in the head gasket so the heads at least are going to end up at the machine shop.

 

[Scott Danforth]

you didnt read the link I posted in post #11, did you?

no way to convert the flat tappet motor you have to the roller you want short of this only 3-step method:
step 1 - sell what you have for a small pile of cash
step 2 - empty contents of wallet, bank account, etc onto small pile of cash, making it a bigger pile
step 3 - take bigger pile of cash and buy what you want.

 

[Scott06]

What you have is a 175 hp 2 bbl engine with rebuilt long block, likely was overheated causing the head gasket blowing.
I wouldn’t mess around with it, juice isn’t worth the squeeze. have the heads and block deck checked, take the pan off check the bearings out, plastiguage the clearances. If ok put it back in and run it. If you want more power buy a newer vortex reman you should be able to swap accessories over except the intake. With a 4 bbl intake and carb you’d have about 220 hp.

 

[Lou C]

When GM converted these to roller cams the block was changed they added 2 threaded bosses to retain the sheet metal guide that retains the lifters in the correct position. But of course millions of small block Chevys did just fine on their flat tapper cams. Just use an oil higher in zinc that what’s typically sold today.

 

[42 Clyde]

you didnt read the link I posted in post #11, did you?

no way to convert the flat tappet motor you have to the roller you want short of this only 3-step method:
step 1 - sell what you have for a small pile of cash
step 2 - empty contents of wallet, bank account, etc onto small pile of cash, making it a bigger pile
step 3 - take bigger pile of cash and buy what you want.

You are correct! I did not read your post untill just after my last post. Good read, very informative. Very detailed. As for the pile of cash...... i dont have one of those. So i will have to do with what i have.

 

[42 Clyde]

What you have is a 175 hp 2 bbl engine with rebuilt long block, likely was overheated causing the head gasket blowing.
I wouldn’t mess around with it, juice isn’t worth the squeeze. have the heads and block deck checked, take the pan off check the bearings out, plastiguage the clearances. If ok put it back in and run it. If you want more power buy a newer vortex reman you should be able to swap accessories over except the intake. With a 4 bbl intake and carb you’d have about 220 hp.

From the 2 motors i have 3 Possibly good cylinder heads. Im taking all 3 to the machine shop. Hoping i have 2 good ones to work with. Im trying to make this work with what i have. I was under the impression that all marine engines must be a roller cam to work properly and that is why i started this thred. I would love to have more power but i think im stuck with what i have for now. But if i do get ahold of the right long block where can I find a 4 bbl intake for a vortex head that wont break the bank?

 

[Lou C]

eBay, I found a couple of good pre Vortec ones there and the Vortec ones are probably easier to find