Check to verify that you installed the spark plug wire(s) correctly & didn't install or cross a spark plug wire(s).Did this problem exist before any of the work you did?Did removing belt change anything?Does the balancer wobble or shake while engine is running?

 

Thanks. I think I could manage that test.

 

You could also perform a Cylinder Balance Test using an old style SUN or Snap On Ignition Oscilloscope if either is available for you to use for testing.

A cylinder balance test done on these old Ignition system oscilloscopes will tell you if all 8 cylinders are contributing equally or not.

They perform a rpm drop test on a cylinder by cylinder or bank to bank basis, and measure the actual rpm drop(or + increase) when a chosen cylinder is dis activated.

If No Rpm drop is shown when that engine cylinder is shut down(ignition spark shut down in that cylinder) then you have isolated the problem cylinder. You can troubleshoot further into that cylinder.

Compression test next always good.


The cheap and dirty way of doing a cylinder balance test is a simple test light. The style with a tungsten filament light bulb inside.

Connect on end of the test light to ground, like the alternator bracket.

With the probed end of the test light, choose a spark plug wire and pierce though the insulation, if the engine speed drops, that cylinder is contributing correctly.

Using an old spark plug wire of at least 3 feet in length, you can replace it for the spark plug wire on your car for testing purposes only.

That way you dont ruin your good igintion wires intact.

Harmonic balancers do fail too. Usually you can see the outer inerta ring wobble around badly with the engine running if real bad.

BR

 

Thanks Brian. Lot of good ideas there. Now that my 87 is purring along nicely (with its charging problem fixed) the 84 can get my full attention.

 

I removed each injectors plug and saw the rpm drops, I think I have all 8 cyl working right ?

will do a compression test in weekend, what values should I have ?

 

I spent a solid year and a bunch of money trying to find a vibration, my advise is to pull the tranny back as was suggested....

My vibration ended up being a that my new SCAT cast crankshaft twisted on my first hard drag launch,,,it was balanced perfectly by the engine shop and ran great until I launched,,, I looked at the spark, the distributor, the cylinders the timing, the damper , the valves, plug wires, I mean everything because "no one" thought that a crankshaft could be twisted,,, pulled it our and the crank was of 30 grams,,,so I threw the SCAT POS cast crank in the trash, literally, and bought a 4340 forged crank..

All I am saying is, rule out the tranny first, it will take some time, but I have been where you are now

 

Larry, was the forged also SCAT? I was thinking of going with a forged SCAT.

 

Hi Ray, the problem cam was a SCAT 5140,,, I bought an Eagle 4340 with Eagle H-beam rods, and Wiseco forged pistons.

Be safe!

 

well I hope it s not the crankshaft. I dont have yet the budget to rebuild the engine

and the shipping to romania for every heavy part will cost me a lot of money

 

I am not inferring that it is a cam problem, but more likely, something with the tranny, or input shaft etc,,, just a guess, but if you take a couple of hours to rule out the tranny, then any other problem is mush less costly.

 

I think I would check these points over again.

Firing order.
Dist rotor in place and tight? Cap on good? Set the timing? At idle does it even sound right? If not can you turn the dist by hand and get the engine to smooth out?

Then I would check the harmonic balancer and then I would pull the TQ converter back.

I know what an out of balance engine feels like. I also know what firing order out of whack is like. they are different, and you can hear it in the exhaust. Out if balance engine will just get worse with RPM's. Screwed up firing order can be driven, but it has no ***** and just feels like something is very wrong and sounds like hell.