Re: 4.3 Mercrusier Cracked Block Swap-Over
Things are going good. I picked up the 1999 4.3 Blazer motor on Tuesday of this week and the block is IDENTICAL to the one in my boat. It even came with the cast aluminum oil pan that was identical to the mercruiser one (my marine one was cracked as well).
First Things - I bought some brass casting (freeze) plugs and prepared to swap them into the automobile block. The Blazer block ALREADY HAD BRASS PLUGS!!!
The timing covers were slightly different. There was a knockout at the bottom of the Blazer timing cover that wasn't knocked out in the marine motor. This had to be swapped in. To do this we had to drop the oil pan first!
While we had the oil pan off we compared the difference between the cranks. The crank rods & the crank itself were slightly different. They looked like they were weighted the same, but they did have different numbers stamped on both the crank and caps.
We didn't pull pistons from each motor for comparison. (I didn't really want to have to buy rings & bearings to drop the marine pistons in even if they were different).
I've been told that the marine cams are different than the automotive 4.3 cams, BUT that the truck cams are as close as you can get. Some say that they're identical. But I elected not to swap in my marine cam.
We flipped the engine back over and prepped the mating surfaces on the heads. Installed the ($45! per side) marine head gaskets, and mounted the Vortec MARINE heads onto the block.
The heads were slightly different. The rocker arms from the Blazer had roller bearings at the rocker pivot point. I went ahead and bought the rocker arms from the salvage yard for $10 to see if they would fit my head. (I didn't buy the heads b/c he was asking $35 each and I wanted to use my KNOWN marine heads). The rocker arm stud bolts were too small to swap in for the stud bolts for the marine rockers... so no bearing rockers on this engine. Would these be considered roller rockers, or do roller rockers just have the roller just on the tip where it pushes the spring down?
THE HARMONIC BALANCER WAS DIFFERENT. The marine engine one was at least 3 pounds heavier.
We installed heads, rocker arms, lifter rods.
The top end of the Blazer engine looked identical to the marine engine. The lifters had a guard on both engines (I suppse to keep them from flying out in case of a failed lifter rod).
I reused the intake manifold gaskets. They looked perfect and were a plastic gasket with a rubber bead that looks like they could easily be reused. We cleaned them up, carefully used a knife to clean up the fingers on each end of the gasket, and used gasket silicone for the front and rear of the engine. If they fail, they'll not be too difficult to replace, but get this... they're $100 for the pair!
All of the marine components bolted up to the Blazer engine perfectly.
1) Engine Block Plugs -> Marine L & R Drain Plugs
2) Engine Block Plug where oil filter screws into block -> Marine oil pressure sensor? 3) Blazer Engine Oil Dipstick -> Marine Block Plug
4) Blazer Engine Drain Plug - > Marine Dipstick Tube
5) Blazer Oil filter - > Blazer Oil Filter (Don't worry, We'll swap it out after we do a 5 min oil cycle to flush out the engine for the first time.)
6) Alternator, PS Pump, Fuel Pump, Pulleys, Starter, Distributor are all different but bolted right up.
7) Intakes were differenton (on my setup). Blazer was fuel injected, mine was carb.
8) Water Pump Was Different but it bolted right up.
9) We didn't get the Blazer flywheel, so I don't know if it was different. The marine flywheel bolted right up to the Blazer's crank perfectly.
10) Rear housing was different (obviously), but bolted up perfectly
11) Motor Mounts from the marine engine bolted right up.
I dropped the engine in the boat, connected wire loom, water hoses, fuel line, sensors, etc, and everything is ready to run baby. I'll do another post for this because I have some questions... don't want them to get lost here.
