Thread: VERY small SBC Harmonic balancer/pulley troubles

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Sorry, I didn't know where else to put this-

I have Chevy Vortec roller lifter 4.3 V6 in my Model T. It's basically a SBC with the back 2 cylinders slicked off, from what I have been able to gather.
My problem is this-
I changed over to the short water pump and pulleys, and twice now, when I put the lower pulley on, and snug it down, it seems to jerk the balancer out of true, so it wobbles...It bends the pulley (yes, they are the cheap chrome units from Speedway) When I take the old pulley off, and start the engine momentarily, the balancer runs straight and true. I put the new pulley on, and it starts wobbling...I know the center bolt, and the big flat washer go on the outside, and gets snugged down pretty good... but what about the 3 outer bolts? Do I just snug them a little, and use Loctite to hold them in place? Do I need a shim/spacer of some sort that I'm missing behind the pulley? I know the bolts are okay, they barely protrude through the balancer when tight. Do I not use lock washers on the outside of those 3 bolts?
This will be my 3rd pulley attempt, and I'm getting sorta burned out on buying new ones. I'd like to do it right the 3rd time, and be done with it...

Thanks,

Dave

kaferdave@charter.net

Hey Dave –

Well there’s some bad news and some good news. First the bad news – your stock harmonic balancer (really a “harmonic dampener” as the 4.3 V6 is internally balanced) will not accommodate aftermarket pulleys. The stock unit has a lip around the edge that will prevent a true alignment. (See the pictures below). Even though the bolt pattern is the same as a V-8 and everything will “tighten up”, the lip will cause this mis-alignment you’re experiencing.

The good news is that there are some aftermarket dampeners that will work well with your application, specifically, a unit from Pioneer (PN 872021) a 6.125-inch, unit that fits perfectly. In that the 4.3 is an internally balanced engine like a 350 you’ll be fine with this unit. They’re available for about $150. Check out this link to Summit:

http://www.summitracing.com/parts/PIO-872021/

I’m glad to see you using this engine. It’s a great unit and often overlooked because it’s a “six banger”. The bore centers are 4.400”, the deck height is 9.025” which is identical to a 350. The 1985 and newer 4.3 has the same bore and stroke as a 350 V-8 (4.000” x 3.480”), and uses the same pistons, cam and main bearings, valve train components, timing cover, oil pump, and water pump. Connecting rods are 5.700 inches like a 350, but the journal size is 2.250” rather than the 350’s 2.100” so they are not interchangeable.

The 4.3 can be lethal when built correctly.

Regards,
Glenn

Thanks, that's kinda what i was afraid of.
How about using a stock V6 lower pulley, is that an option? I had to head over to the local wrecking yard anyway...

That should work for you. Just make sure all the pulleys line up and you'll be okay.

Good Luck,
Glenn

Pulley alignment can always be a sticky issue. Hope you can find a solution or some assistance. Let me know if you need help, always willing to lend advice.

Now, of course, I pulled the pulley off, and the dampner is wiggling....It didn't used to do that, with the pulley off, it ran straight and true... now, it doesn't.
Crap... another 150 bucks I was hoping I didn't have to spend.
Thanks for your help, Glenn...it appears that I need a puller of some sort, to get that thing off...

That would be correct - you can probably rent one at your local NAPA store.. Or maybe another hot rod guy near by has a harmonic damper puller??

Borrowed a puller from a friend, MAN that thing was on there !! It was all my old Ingersoll-Rand 1/2 inch tire gun could do to get that thing loose!

It looks just like the top one Glenn posted, and the part # is 10224885, which seems to be the balancer for 1996 and later Chevy trucks.. The bright side is it came off with no carnage, although I'll be damned if I can see anything wrong with it...and when I ran the engine with it on, I did have the center bolt pretty darned tight.
Now for another (probably stupid) question- I don't have a lot of money, it's taken me 5 years to get this far, but I do have access to drills and grinders and lathes, etc...could I make a spacer, that fits inside the lip of the pulley, with the 3 small holes and the large center hole? I can make one of those a heck of a lot cheaper, than I can afford 150 bucks for one of the fancy racer specials... and I've found the replacement balancer for under 40 bucks.. so i could get away for under 50 bucks, which would make my poor, understanding, long-suffering wife a lot happier, too, and we all know if mama ain't happy....

If you can find a 6.125 inch damper at a wrecking yard with a flat front you should be okay. A lot of 305's used the small one and they should be very readily available for about 10 bucks at a wrecking yard. Take your old one and if you can match size (diameter) you should be okay. The key is to have a flat face.

As to the spacer, you could try it but balance would be real important. If it's not perfect, the vibration could be significant.

i have done what you are trying .. iv`e a 4.3 in my pinto .. i will look at what i had to do to make mine work and post about it ..

Thanks, Hoss429... if I have to, I guess I can buy the 152.00 one, but if I can apply some "Yankee Ingenuinty" to the problem, that would be even better.

Originally Posted by Louey

ps: If he has one like above, I might be tempted to make a metal shim to level things out, and use the 152.00 on something else. jmo

i`m certain thats what i did .. i`ll know when i get home

Well, I can get the aftermarket (Dorman) brand for 37 bucks, and I'm sure I can drill and balance a piece of aluminum to fit inside... and that sound like the cheapest, most cost-effective way out...Although i don't see anything wrong with the one I pulled off, it was wiggling, even with the center bolt in the crank snout impact-gunned on.. so I guess it's warped itself, or the rubber has started to come loose.. I've seen what happens when one of those things lets go, and it wasn't pretty...aluminum radiator, plastic timing chain cover, water pump, and probably the crank snout, but I didn't stick around long enough to fully assess the carnage...

Not to get too far afield, the correct term for this component on all stock Chevy small blocks (with the exception of the SB 400) is “harmonic damper” or to be perfectly correct, “crankshaft harmonic damper”. The term often used is harmonic balancer, which suggests the unit “balances” the engine. Except as noted above (SB 400) this statement is misleading as the crankshaft assembly is internally balanced. A harmonic dampers purpose is to address torsional vibration.

Torsional vibration occurs in the crankshaft of all internal combustion engines. This is a result of an immediate and drastic reversal of load on the piston, wrist pin, connecting rod and crankshaft during compression, followed by the ignition of the compressed fuel and air in the combustion chamber. Subsequent relaxation of the load following combustion causes deflection or flexing of the crankshaft (up to 2 degrees). The crankshaft literally “snaps” back in the opposite direction! This sets up an oscillating vibration which continues until dissipated by internal friction or damping. It is possible for these oscillations to come into phase with each other and create potentially damaging torsional “peaks” in the crankshaft. Unless the magnitude of these torsional “waves” is controlled, damage most certainly will occur to engine components, specifically; wear of the timing chain and gears, pitting or cupping of the camshaft and lifters, broken valve springs and, scuffing of your crankshaft bearings. In extreme cases, left unchecked, torsional vibrations can cause loosening of bolts (flex plate or flywheel) or even a broken crankshaft. The damper is not a balancer. Its job is to control torsional vibrations on internally balanced (neutral) engines. And yes, as stated above, it provides a mounting surface for pulleys.

So – when you hear someone call it a "balancer", you can politely remind them that it's a harmonic damper, not a "balancer". They’ll probably look and you and say, “yeah sure – whatever.” But you will know that you’re correct!

Whew - that felt good.

Regards All,
Glenn

Oh -I nearly forgot - Dave, if you certain you can, " drill and balance a piece of aluminum to fit inside" I'd say go for it! I laud your approach!

Take a few pictures of the process so we can follow along. This is what hot roddin' is all about!

Regards,
Glenn