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Discussion Starter #1
Here's the picture:

Used motor swap in my 86 s-10 w/2.8, dropped in an '87 2.8 . I got to run the motor before I bought it. Checked out fine.

I installed the motor and experienced Tremendous vibration at idle and going down the road. I went to the chev dealer and they said the mounts were hosed.

OK, now I have BRAND NEW motor mounts and a BRAND NEW trans mount, all of which were totally shot. The vibration still persists. It is terrible to endure for my one hour commute each day.

I changed the harmonic balancer because it had a little wobble to it. Still the vibration persists. I used my old motor's balancer (identical but it had 320km on it, looked good, doesn't wobble)

I am also experiencing a high rev low rev nonsense from the motor. Some days it idles great some days it idles really high and I don't need to use the gas pedal at all, some days (sedom) it idles way too low. It makes my water temp climb of course. I noticed that when all of this happens, my water hose to the intake manifold is hard as a rock, completely under intense pressure.

I thought the thermostat was shot so I replaced it. Still it gets really hard. Is there soemthing wrong with my water pump? Could the killer vibration be coming from there? Maybe the impeller on the pump is screwing things up?

Help!!!

P.S. - The entire water syatem just got a rad flush with chemicals last week to make sure nothing was pluggin up stuff.
 

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sure you got the right harmonic balancer and fly wheel.... the 2.8s went from internally balanced to externally balanced and even though the one motor is out of an 87 doesn't mean its an 87..... someone else may have had it rebuilt......

also a friend of mine had a 2.8 sbanger that had a bad torque converter, tranny ran fine just shook like crazy especially under load...

other than that....dunno.... just make sure everything is firing good and no bad plugs or wires
 

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Discussion Starter #3
I compared the two harminc balancers, both had the identical castings, ther would be a big difference between the two if they were different. Regardless it made NO change in the vibration, better or worse, just the same.

No torque converter on this one, its a manual trans, but good point all the same.

I've seen a picture of an externally balanced flywheel in my haynes manual, both the old and the new flywheel (both used) we not of the external type, they had hardly any external weighting, the real external flywheel looks like it must weigh a ton, not the two I have used so far.

Any more ideas?

What about the water pump? Any thoughts on that being the problem?

I don't like how hard that the upper rad hose gets when the motor decides to run hot. It makes me think that the pump isn't properly working, maybe the impeller is doneand that's where the vibration is coming from?
 

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When did the 2.8 go to reverse turn water pump? Did you use accessory drive from the replacement engine, maybe a mismatch. Try running engine with belt off. Radiator cap controls system pressure, put on lower pressure cap and see what happens. Check motor mounts closely. Look for metal to metal contact where the cup shaped metal mount is right next to frame mount. Pretty tight clearance at best and if it makes contact you'll have vibration. Was the replacement engine from a standard transmission truck? Did it have a pilot bushing in the back of the crank, and was it in good shape? Running out of ideas here. If the harmonic balancer and flywheel are correct and in good shape, a major vibration would have to be internal. Ouch.
 

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Discussion Starter #5
Very good questions, here's my responses:

Re water pump, I wasn't thinking, I disconected ALL belts and ran the truck to eliminate this possibility, vibration still existed. Therfore, its not the pump.

Not sure what you mean by accesory drive. I am using the alternator, emissions pump, power steering and water pump off the crank pulley.

There was a prob with the pulleys. The new 87 motor had the serpentine belts. The new motor didn't come with the alternator or power steering pulleys. I retrofitted my older pulleys. They are just slightly offset from each other which isn't good, but it isn't the problem because like I said, I have disconnected the puleys to troubleshoot.

I will try a different cap, I had to put in a new rad last week, I went from a single core to a triple core. The vibration prob was there before and after. The new rad came with a cap, I could try my old cap. How do I identify the cap pressure? What could the cap pressure be affecting?

Replacement motor came from a standard trans truck.

Re motor mounts. They are brand new a most definately make metal to metal contact from cup to frame mount but I can't see how you could possibly avoid this just shy of introducing rubber washers. The mounts are supposed to bolt up that way aren't they? So long as the through pin is boited up really tight then the vibration should be transfered into the rubber mount? Yes, No?

I found upon installing the new mounts, my upper metal cup on the pass side was sitting offset from the mount, it took some persuarsion to get it lined up. I blamed this on running the new motor (new upper mount cups) on my old frame motor mounts which had fallen. I figured thats why the two halfs of the mounts didn't quite line up.

Re the pilot bushing:

I had no idea there was such a bushing on the truck. Until now, I have always re & re'd motors with auto transmissions. The standards I have worked on were VW's and they don't have a pilot bushing. My haynes manual says to grease the bushing upon clutch install. I didn't know this at the time.

Could this bushing make all that vibration? Its pretty bad yet it doesn't affect performance or drivability, it just rattles my teeth loose.

I have to drop the trans to inspect this don't I?

Thanks for all this input, this forum produces more results than my local GM dealer.
 

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if the torque converter nipple is interferring with the bushing there is a possibility that the flex plate bowwed toward the torque converter when you tightened the flex plate/converter bolts. This could lead to a cracked flex plate (fly wheel) and I would imagine vibration
 

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Discussion Starter #7
Both motors came from STANDARD transmissions, there isn't any torque converters.
 

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This is a REALLY obvious thing, but have you checked you gas mileage to make absolutely certain that the there isn't a misfire problem. (I only mention this because many years ago I nearly drove myself nuts trying to get a GM v-8 to stop vibrating, only to find that I had a bad plug wire).

Just out of curiosity, since you had a v-belt truck and you swapped in a serpentine motor, you had to swap front cover (timing chain covers)?
 

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Discussion Starter #10
Good point on the milage. I don't really get great gas milage right now, but I attribute that to the high rev, low rev problem I get off and on throughout my day. The motor likes to rev up a thousand or two rpm more than it should sometimes. Almost like it thinks its cold. I just changed the thermostat, no fix.

The plug wires are also brand new as of two weeks ago so that rules that out. The motor was also timed by a mechanic.

Re: the V-belt setup. My v belt is only on the power steering and bottom crank pulley. The 86 motor had sort of a serpentine belt but it was skinnier. The new motor came with a true serpentine belt but I didn't get the alternator or water pump pulleys. I mixed and matched the pulleys by using the 87 fan to bolt to the water pump, and I took my 86 water pump pulley and drilled it out a bit so the bolts would line up. I know it spins true becuase the 86 and 87 had the same center holes so it has properly centered itself.

What is wonky, is the offset the pulleys now have from one another. The pulleys are out by about 1/4" but the belts still stay on. I have disconnected the belts to make sure the vibration isn't coming from there.

The front cover didn't have to be changed as a result of my retro fitting.
 

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did you swap intakes when you put this motor in?

im wondering if the over heating problem is causing this.... high combustion temps are causing a knock that the knock sensor is picking up and telling the EST to go nuts on retard and that will cause a vibration and a change in timing will cause high to low idles as the timing changes

even though the gauge doesn't read high temps, the head may have a pocket that is getting hot and causing this

im assuming that you still have this high water temp problem when your water pump has the belt all hooked up.

Im also assuming that all your heater hoses are all hooked up and not plugged off too, sometimes if you plug them off the heads dont cool properly

the system could also be air bound, its unlikely but possible.... usually unthreading the temp sending unit on the intake untill it starts to leaks can help this

Make sure the temp sending unit is good.... might be giving the computer false readings and the computer might try to mess with timing to counter the overheating problem by retarding the timing

remove the thermostat and see if that fixes the high pressure problem..... maybe its stuck, put in backwards, or just defective.

this is obviously all with the assumption its TBI
 

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The part about the 1986 belts seems odd to me: I thought that 1986 and earlier rotated the water pump in the opposite direction, so that you'd get into trouble mixing the part like you did? I haven't even looked under the hood of a carbed one for a long time, so it might not be a problem. Did the 1986 have a different belt setup than the earlier carbed trucks? Hopefully someone with better knowledge of the belt systems can answer that?


I take it that you aren't getting any computer codes? If you have a friend that has a real scan tool, it would be about time to scan it while it is doing the high-low buisness and check for the various sensor values.
 
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