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Discussion Starter · #1 ·
Hi I actually have a Oldsmobile Bravada the same thing as a Chevy Trailblazer. And the motor spins I have one cylinder which would be number four that has no compression and the Piston doesn't move up and down but the engine spins over fine doesn't make any sense I was wondering if I could take the Pistons out of a 4.3 and put them into the 4.2 if they were the same size
 

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Discussion Starter · #3 ·
Hi I actually have a Oldsmobile Bravada the same thing as a Chevy Trailblazer. And the motor spins I have one cylinder which would be number four that has no compression and the Piston doesn't move up and down but the engine spins over fine doesn't make any sense I was wondering if I could take the Pistons out of a 4.3 and put them into the 4.2 if they were the same size
[/ how do you figure the cam still rollover fine the motor still goes over fine it'll even start no holes in the block what else could it be if it's bigger problems in the Pistons
 

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If the piston is not going up and down it means that it is no longer connected to the crankshaft by the connecting rod. Odds are the bearing journal on the crank on both that cylinder and the one next to it are damaged. You will most likely need a replacement engine. A used one will cost less than the gaskets and bearings to repair your existing motor. By the time you buy rings, pistons, bearings, gaskets, connecting rods, a crankshaft, oil, filter, and antifreeze you'll have spent more repairing the original engine than an old Bravada is worth.
Least expensive route sometimes is simply get another car. These old beaters aren't collector vehicles like a Stutz Bearcat. They're cheap throw away transportation.
 

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The 4.2 I6 seem to be very reliable engines overall, depending on the overall condition of the vehicle I would consider getting a used engine, probably from a wrecked vehicle or one that has a guarantee from a salvage yard.

You just have to decide based on the condition is it worth it.
 

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Discussion Starter · #7 ·
never mind ..............
Ok n yea I get it but hear me out.. if the connecting rod broke like you say which I don't doubt one bit.. and I have this 4.3 carburetored engine that has just been sitting here why can't I take the rods and pistons out the bore of the inline 6 is 3.66 and the 4.3 is 4.00 just like a sbc.. why can't I hone and mic the block for those pistons and rods to work.. than I would only have to buy a new head gasket and oil pan gasket.. I mean I haven't hard of a rod breaking and NOT exiting the motor somhow.. but from bzkc to front the order Is 135246 and the number four piston is froze but 2 and 6 have over 150 compression.. N it will fire up and die
 

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So you are going to bore it out .340? over 5/16's of an inch. Seriously doubt the cylinder wall has that much material on it. Pull the head post pictures of the before and after.
 

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Simple fact. 4.3 parts will not work on a 4.2. Period. End of discussion. Can't be done. Not even close to possible. Entirely different engines with entirely different designs. I6 vs V6. As MBP points out, made from different materials.
Crank journal sizes are different, different size wrist pins, piston rings, bearings.
Gas Font Heat Pattern Event
 

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Discussion Starter · #12 ·
Aluminum block. You're not going to bore much of anything. Sleeve in that cylinder is probably junk too.
That's what I was asking you guys thanks guess it's back to the old beast 85 box s10 85 mind you they made legends that year! With the old 2.8 (which is original pushing 120 psi in all 6 cylinders and a bore n warner to 5 speed manual.. lost all spark one day and changed everything youncan think of n still wouldn't spark.. was showing to my friend the other day and one of the wires for the ignition was soldered and only 2 of the strands of copper was soldered
to the other 2 wires soldered together... inhope that fixed it
 
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