ODD Question of the WEEK

[DieselDan]

What is the difference between the 6.2 harmonic balancer (dampner) and the 6.5 balancer? Would they or could they interchange?

The reason for this question goes like this: last fall I did alot of work to the ole Jimmy. I finally got around to replacing the balancer with one I had picked up ages ago. A month or so later, amongst a few other repair issues, I borrowed a Tach 'n Time (Kent Moore diesel timing meter) and tweaked the timing until I finally got about 5* @ 1300 RPM.

Time passes and I'm chasing down other problems (or so I thought). I had a cold start issue which I attributed to an air leak in one of the fuel lines. Well the cold start roughness continues. I got to thinking about my timing after looking at the pump wondering why my timing marks are to the passenger's side of the truck. "Hey, isn't that RETARDED?" So I borrow the Tach n' Time again, only to see my timing hasn't moved. "Maybe I'm reading -5* degrees." More dicking around only to come to the conclusion I'm reading it right but THAT CAN'T BE RIGHT. So I moved the pump to align the marks plus advance. The meter read 12* degrees, truck drives fine. Tomorrow I'll see how it starts.

Now I'm think how the hell could the timing read that far off. I start wondering if the balancer I bought was for a 6.5 rather than a 6.2 After looking at some parts manuals I see two different part numbers: one for 6.2 the other for 6.5's . I also see different timing pointers that mount to the block. Maybe if I can just find a 6.5 timing pointer I can see if that put's me in the ball park.

Here's AGDieseler old thread about timing that's gonna keep me awake tonight.....
http://coloradok5.com/forums/showthread.php?t=112778

 

[DieselDan]

OK Day Two, Test 1: Started the truck this morning and "low & behold!" it starts 100% better. The smoke is almost nil (just enough to let you know it's a diesel ) and the roughness is GONE. It rattles smartly with maybe two sharper knocks, maybe telling me it's still a couple of degrees too much with the HPCA on.

The funny part is I'm not happy. I still don't know where my timing is. I'm a staunch advocate of not doing the "ear & eyeball" method of timing and that's exactly where I'm at right now .


I did do some reading last night. Here's some interesting points taken from the TM 9-2320-289-34 covering the Injection Pump "checking and adjusting the pump timing marks" (when the pump itself is rebuilt):

Utilizing the air-timing fixture: The point where the cam rollers contact the cam ring is the point when injection begins at #1 discharge fitting. Loosen the knurled screw (29) and rotate the air-timing fixture counterclockwise until the cam rollers can be felt marking contact with the cam ring. Repeat step 5 several times t get a definate feel of when the rollers make first contat with the cam ring.

Sight through optical gauge (28) and check for position of existing timing mark o fuel injector pump flange (33). If extisting mark in not in line with timing line on optical gauge perform steps.. .

File off old timing mark. Tap marking scribe adapter (27) to place a new timing mark on fuel injector pump flange

 

[DieselDan]

OK Day two, Test 2: The timing tab on a 6.5 has the probe holder at about 4:00 position VS. my 6.2 timing tab of about 2:00. I would have gone ahead and "borrowed" the timing tab off the 6.5 but it looks to be held on with tamperproof torx screws (I've got a couple of those bits but not here).

Also during my research I came upon this site:
http://www.oliverdiesel.com/tech/timing.htm

What caught my eye, was the reference to using the Number 3 cylinder for the clamp-on probe. My Kent Moore book clearly says to use the Number 1 cylinder. I think I'm having a deja vu

 

[maynardogle]

OK..so you have concluded that you put a 6.5 balancer on your 6.2 engine...and the timing marks are off...but is the 6.5 balancer otherwise correct for your crankshaft? If I understand correctly the balancer is there to compensate for the fact that the crankshaft has an inherent tendency to vibrate when spun and the counterweight on the balancer is suppose to fix that. I suppose it wouldn't matter if 6.2 and 6.5 cranks interchange. Is that the case?

 

[DieselDan]

Well, I haven't concluded anything, it's all still suspect. I was trying to figure out last night if the timing tab was higher (earlier) than the Timer was adjusted for would that give me a reading more advanced or retarded. That gave me a headache. I think it would read more advanced than it was.

If the 6.2 tab is at 2:30 lets say 80* (from horizontal) and the 6.5 tab is at 4:00 lets say 100* that would give me 20* difference. Divided by 2 for half speed of the cam/injection events I end up with 10* (maybe) at the pump.

Right now I have 12* on the Tach n Time and it runs great.

My understanding is the harmonic dampner is designed to absorb the twisting forces in the crank imposed by the firing pulses of the pistons. Assuming the two different dampners do physically interchange; because (IIRC) the 6.2/6.5 rotating assembly is externally balanced are the dampners neutrally balanced? And if not (neutral) are they balanced differently between the 6.2 & 6.5?