1990 vs 1992 4.3 block swap

[Chris51280]

I have a 1990 4.3 non balance shaft maercruiser with the 2bbl carb and fluid mounts. I found a 1992 4.3 automotive engine from an s10 for $50. I would like to have a backup maybe something to work on over the winter. I know I can only use the head and block with crankshaft the intake should still be the 12 bolt right? Does the balance shaft pull horsepower? I know the cam should work. Change tje freeze plugs.
any other things to consider? I have the mechanical fuel pump. Does that still work?

 

[Chris51280]

Will there be a problem with the flywheel from a non balanced engine to a balanced engine? I think the non balanced engine had sone counterweights on the flywheel. Will this give me trouble

 

[Scott Danforth]

either stick with the same generation, or change everything. DO NOT try to mix and match rotating components... that viper will bite you in the back side.

heads, intake, exhaust are the same, however everything in the short block is different, including the engine mounts

here is some reading on the 4.3

https://forums.iboats.com/forum/eng...history-of-the-4-3-liter-with-casting-numbers

 

[Chris51280]

I see that the only difference is that 1992 has the balance shaft. That is better anyways, right. So I can install the mercruiser camshaft and change freeze plugs and seals and have a marine engine.

 

[Chris51280]

The fluid mounts should still work with a balanced engine. The manual #7 is good until 1993

 

[Scott Danforth]

thats because in 1993 they were still using motors left over from 1991 and 1992

no, the difference between the balanced and non balanced is significant

damper is different, flywheel is different, cam is different, block is different, timing set is different, timing cover is different.

because the damper and timing cover is different, the accessories - specifically the accessory drive brackets and pulleys on the front of the motor are different.

when they went to the balance shaft motors, the damper, flywheel and mounts became common with the 5.0 / 5.7 motors

 

[Rick Stephens]

I will echo Scott. Rotating assemblies must be matched.

 

[Chris51280]

I asked the seller for the c/n to be sure. but sounds like there are just too many variances to make it work correctly. thanks for the help. I guess i'll stick with 87-91 models

 

[dlogvine]

Also you need to get a different oil pickup, oil pan, camshaft has different lobes in automotive engine vs. Mercruiser. All gaskets must be marine instead of the automotive. In 1993 they also changed the fuel pump from mechanical to electrical, so newer block with balanced shaft might require you to get a new fuel pump. Distributor must be also marine and not automotive. these are just a few differences I can think of on the top of what the other posts said.

 

[Chris51280]

I would have just used the block and heads as a short block assembly. everything else will come from the old block. Combined with a mercruiser rebuilt kit should have given me a marine engine with balance shaft.

 

[Scott Danforth]

I would have just used the block and heads as a short block assembly. everything else will come from the old block. Combined with a mercruiser rebuilt kit should have given me a marine engine with balance shaft.

No it wont. your not understanding

your short block assembly is the Block, crank, rods, pistons, cam, balancer, timing assembly, flywheel.

that all must remain together. you cant mix and match parts.

and because the timing cover changed and the balancer changed from GM, Mercruiser had to change the accessory drive when they went to a balance shaft motor.

only the heads work on either block until 1995

either stick with all components from a non balance shaft motor which means get a different shortblock or rebuild the one in the boat now

or switch everything over to the mercruiser parts for a balance shaft motor which means getting all the stuff to bolt on the balance shaft short block to make it a mercruiser - accessory drive pulleys, brackets, belts, manual transmission flywheel for a balance shaft 4.3, cam would be close enough to use.

 

[Chris51280]

Thank you Scott. Was about to get the wrong engine.

 

[Chris51280]

Scott Danforth I found another 1987 block which I will confirm the block casting numbers. Its an automatic. Is this a problem?

 

[Scott Danforth]

the block doesnt know what the crank has bolted to it

however with a 32 year old block, you have about $700 in machining (cleaning, line-hone, decking, boring, honing) prior to assembly

 

[Chris51280]

I was just wondering since the unbalanced engines were tested and balanced at the factory. Drilled at the dampener and or flywheel. As long as I keep the rotating parts together. Like you said.
I wasn't planing on doing a complete overhaul. just rings and bearings if needed. New oil pump

 

[Chris51280]

sure beats a cracked/welded block. I also need new exhaust risers. So I need to stay in some kinda budget

 

[Scott Danforth]

non balance shaft motors use different dampers and flywheels than balance shaft motors

if you are buying a different block, you cant use pistons you have laying around. so not going to be able to just do bearings and rings. while you may be able to slap it together, longevity wont be there and it would probably smoke like crazy

make sure your 87 block is a true 1987 block and not a left over 1986.

 

[Chris51280]

The block has casting h103 on it where mine is a 011. From rapid marine I get a match for the 103 number

 

[Chris51280]

http://www.rapidomarine.com/default.aspx?p=/casting_numbers_43.aspx

 

[achris]

Automatics tend to have flex-plates, not flywheels, so you'd need to source a flywheel for an non-balance shaft engine.

Chris.....