Self dissembling harmonic balancer-doh!

[dingocooke]

Ok,

Nice little squirt out this afternoon in my car, end of the bypass after a reasonably quick run (ahem...), and theres a rattle, sounds a bit like a loose flywheel, except maybe not deep enough, so stop to investigate. Turns out the harmonic balancer has self dissembled itself, limped home and left it to cool down.
Just took off the crank pulley and off slid the balance flywheel, absolutely nothing left on either surface to hold it on (assume they're rubber bonded together?)

So heres the question,

Do I need it?
Its a crude thing, obviously not very robust, done 10,000 mainly dry miles in 10 years and has self destructed. The crank rods and pistons are dynamically balanced anyway.

Any thoughts guys?

The engine is a 302 Ford with edelbrock performer rpm kit, and I rev it to about 6500 in the gears (it gets there pretty quick!)

Cheers,

Steve

[Andy302]

I would say YES YOU NEED IT!!!


Perhaps you had best look at an uprated balancer, was yours the original or a replacement? Ive just brought the FMS damper for my motor build and it looks OK. FMS-M-6316-K351 cost about £60 by the time Id imported it with my other stuff.

Im unsure if you would need to get your engine balanced to suit, take further advice!

[JamesP]

You need it...... dont run too far without it.

Have a look at a Fluidamper, no rubber bonding between the hub and outer ring to go wrong. They do a Street version which I've fitted to my 383, uses an internal vaned ring inside the damper and something like a silicon Gel to absorb the harmonic vibrations of the crank.

James

[JamesP]

Originally Posted by Andy Roe

Im unsure if you would need to get your engine balanced to suit, take further advice!

When you remove the original item have a look at the back of it, if theres a weight off center then you have an externally balance crank, the cranck and the balancer should be considered a matched pair when balancing.

If no weight present then the crank is naturally balanced and you can pop on a replacement with no issues.

I'm not sure whether the 302's were internal or externally balanced, I think they are internal and you'll have no problems getting a replacement.

If I remember correctly the internal balance became an issue with the 400's

I'm sure somone here will know and it'll become obvious when you remove the old one.

James

[craigh]

i think the only internally balanced sbf is the boss 302

[rsk289]

You need it. Damper balance is matched to the flywheel. 302s are 28oz or 52oz balance, depends on age. You will need to know which before you replace it, unless you're going to balance the whole lot again.

[dingocooke]

Hi Guys,

Thanks for all the replies.
I've found out today that 302 fords are externally balanced using front bobweight/harmonic unit, and rear flywheel. Apparently Ford went to external balance to reduce the physical size of the small block so it could be fitted in smaller vehicles.
I managed to get an identical 1969 Ford used 3 bolt unit from Stateside Autoparts (on the A5 near Tamworth www.statesideauto.co.uk Tel 01827-717600)
When I showed them the wrecked harmonic, they said they had never ever seen a similar failure since they started in 1973! They had seen searation where people had used a puller on the outer and pulled it off in the workshop. They'd never seen a failure like mine on the move. So I guess I was lucky!!

Thanks again,

Steve:thumb: :thumb: :thumb: :thumb:

[RallySnake]

Steve,

I ran an autocross a few years back and pushed the engine a little too far at one point. It probably hit 8,000 prm. I noticed water leaking from the water pump later and had to stop several times on the drive home to refill. I checked the engine for other problems, too. When I checked the timing, I couldn't get the marks to line up. The harmonic balancer had spun around. At least it didn't come off.

Paul

[dingocooke]

Hi Paul,

Sounds like we both had a lucky escape; the alloy aftermarket pulley stopped the cast iron outer harmonic ring going for a destructive walk around the engine bay (or out of the bonnet/through the wing-ouch!)

Maybe mines been turning for a while, and finally came off, it looked like somebody had machined it off though, not one trace of the bonding rubber on either part!!

Steve

[rsk289]

Look at the Windsor small-block forum - this is not a rare occurence with original, 30-yr-old dampers.