I'm shuddering...

[Mac]

...to think I should have had the rotating assy. balanced when I rebuilt the 305 I put in my pickup.
It's got a vibration between 1000 and 2000 RPMs. Idle is smooth and steady and it smooths out above 2 Gs.

The specs:
305 roller out of a 92 auto trans TBI Camaro (never opened before)
New rings, bearings, timing set, valve springs, oil pump
Used LT1 cam, Edel 500, Performer dual plane, block huggers into 2.25" down pipes Y'd into single 3" pipe and straight thru muff.

TDC was checked by dial gauge during the build and the OE harmonic balancer's mark was right on the money so it was reused. I don't think it "slipped" since the vib was evident from first start up.

The pistons never came off the rods. They were all numbered and went back in their orig. bores. The new flywheel (since I run a T5) is ext balanced, generic aftermarket from Jegs and the clutch set is generic aftermkt. from Northern Autoparts.

Tomorrow I'll take the belts off and verify that it's not an accessory like the fan out of balance but I'm leaning toward flywheel / clutch as the culprits. Can they be balanced using another crank? Maybe with my harmonic balancer?

[kb426]

Need more info. Does this happen in neutral or driving in gear? Is there a chance one of the motor mounts is damaged? Does it have the original balancer and flywheel?

[UGLY OLDS]

I would think that they could be balanced to "0" ( neutral) balance on a crank that is also "neutral" balance ... Same thing with the P/Plate .. They are normally made to a "neutral" balance when built ... Other wise you would be required to rebalance the engine when replacing the pressure plate ....  Not likely...Got a good machine shop nearby


Bob ........

[wayne petty]

a HUGE TRICK... or TIP...


got a friend with a wheel balancing machine.

stick the old flywheel on it...  set the offset and the rim width to zero...   spin it up..

same set up... check the replacement.. ?

if they are ZERO.. it will be ZERO...

bubble type balancers also work...  but are fewer and farther between nowadays..


flywheels and dampers when out of balance is needed are measured in OZ inches...   how many ounces at 12 inches from the center of rotation..




the 92 camaro TBI 305 uses a flywheel with a weight..

did who ever installed the flywheel on the crank... align the 7th non tapped hole with the non tapped hole in the flexplate???

http://contentinfo.autozone.com/znetcs/product-info/en/US/pnr/FRA-160HD/image/4/

lastly... do you have a small cap hei distributer??

can you take the cap and rotor off and examine the exposed section of magnet under the first layer of reluctor..  there is a gap around the shaft where you can see it..

if the magnet is cracked.. it can create ghost patterns in the wave form and really mess with the electronic spark timing control...  sometimes its enough to throw in some random spark with it not in electronic spark control...

are the spark plug wires separated properly??? especially the #5 and #7 spark plug wires.. as they are 90 degrees apart in the firing order..  if the wires are too close.. the magnetic field created by the spark traveling thru the #5 wire will INDUCE a spark in the #7 wire 90 degrees early when the valves are closed and the piston is part way up on the compression stroke.. this causes some of the air fuel mixture to burn off.. but as the piston reaches the top.. there is not enough fuel when the proper spark happens and that combustion is lean..  it will make a harmonic imbalance as you describe..  just before it completely destroys the motor..

a terrible twist on the saying.. what is the sound of one hand clapping...

What is the sound of one piston detonating..  

i don't know if any of this is going to help...

you might also want to OHM your spark plug wires...

set your digital volt meter to 200K OHMs... 200,000

read the wires directly...  wires should display on the meter less than their length in inches...

a 24" wire will read less than 24 on the display.. usually around 10 to 15K ohms ..

a 18" wire will read less than 18.. usually around 8 to 12K

just a thought... i have found way too many with the ends pulled off inside the boots...  or the carbon burned completely out..