what year i assume 4.3 (JTR MM?)does it have a balance shaft?if so is the shaft timed right?spark plug wires on the right cylinders? compression test?

 

its a 92 CPI w/ ballance shaft, it is timed right and built right, rebuilt motor, motor runs great, just has this bad vibration

 

anyone? i really dont know where else to start...

 

a mechanic? its gonna be pretty hard to figure out without seeing it. some one that can put their hands on it has a better chance of figureing it out than anyone here
i still think the balance shaft may be timed wrong

 

well i've been turnin wrenches for about a decade, and even took it to a friends shop (in the biz for 30 years) and we tried a few things on a hoist and no luck, just looking to see if anyone has had something similar?

 

Did you ever resolve this issue? I too have just put in a reman engine and have a pretty good vibration right at 2000 RPM, very noticable in neutral, just reving the engine up.

I also feel it somewhat less at 500 and 1000... so 2000 is a harmonic, but the most obvious. It's obvioulsy engine or converter related, but didn't do it before the engine swap. I've read in other posts here that it may be related to improper valve lash in a cylinder or to a mis-timed balance shaft and I will investigate these.

Does a 99 Blazer have the press in rocker studs that require valve lash adjustment?

Thanks in advance for any suggestions.

 

New engine bushings/ Mounts? Probally an engine miss.

 

i have had a few reman engines that have had vibrations in them. i disassembled one and found to have been bored and not had rotating assembly balanced. The fix was to send crank, rods pistons, flywheel, harmonic balancer to machine shop for balancing. This engine is was a 350 in a fullsize but it is still in service and is smooth after 75,000 miles

 

I had the same problem. I have a 1996 4.3 4wd. I assumed the same, but my vibration wasnt from something un-balanced or broke. Mine was electrical. I replaced the rotary button and distributor cap it helped alot, i still have a slight vibration i beleive it my coil is weak and is skipping fire around 2000 RPM. After i get passed the shift point it rides fine. I would get a mechanic with a diagnostics machine to see if your cylinders are skipping any. If so he should be able to tell you which cylinders if his machine is advanced enough. Hoped this helped some...

 

I would go to a garage and try to get some one to run a diagnostics on it. I already had new plugs, wires. When i changed my rotary button and distributor cap is when everything got better. Also i would check the motor mounts. Mine was also broke on the passenger side. After doing this my vibration is almost completly gone. My next step is the coil. When i go to start it sometimes it wants to lag real slow like its getting weak fire. Also it still vibrates slightly within 2000 rpm. good luck!.