Performance Harmonic Balancer Explosion

[coupe72001]

I got my car back on the road for the festive season and it went well for several days.

Does anyone remember me splitting my stock harmonic balancer in two last year? To avoid that misery I again I invested in a Professional Products Powerforce Plus SFI racing spec Harmonic Balancer, and had it shipped over from the USA, and bolted it to the front end of my L28 late last year. In less than 2,000 kms I did this to it.

It has actually split in two, and the outer section spins freely around the inner section.

Who'd have thought?

[V8skylineMAN]

i would say, at a guess, that your engine is out of balance. maybe an odd piston, or a poorly balanced or mismatched reciprocating set.

ive had some fairly angry L series eninges in my time, and have only ever used stock balancers. never ever broke one.

There is some underlying problem there.

cheers

Jason

[coupe72001]

Hey Jason,

The stock balancer split on the smokey old L26 that came out of the wrecked rally car that I bought in 2006; could have been a myriad of unknown problems there. However the performance balancer that I just broke in the pic was on my recently built L28. I had the crank/flywheel/balancer assembly machined and balanced and the bores honed and pistons machined to match deck height by Motor Improvements (engine builders in Vic)... but I never considered that I might have a mismatched set of pistons.

Now I don't know what to think. I didn't recycle the pistons or crank from my L26... Could it be that I was just unlucky twice?

[Silent Shadow]

id be on the phone to Motor Improvements if i were in your shoes.

the last time i heard of a harmonic balancer 'letting go' was because something was dropped on it and it was damaged (only very slightly).

i do hope your problem is the best case scenario

[coupe72001]

I swear I didn't drop it! I'd be to embarrassed to post if I did. Pics have been sent to Motor Sports Auto, the supplier, and forwarded to Professional Products, the manufacturer. It's a first as far as anyone knows! We'll see what they make of it, and what they want to do about it.

I should have been an engineer, destructive testing seems to be my forte.

[coupe72001]

I have replaced the busted pulley with a light-weight billet aluminium number out of the states. The car has since developed an interesting new trick. It does some amazing low-rider style bunny hops when I try to pull away from low revs.

While this might be the latest installment in my never-ending untunable SU carby idiocy, a mate has suggested that driving with a damaged harmonic balancer can put unholy forces on the crank and bend it. Anyone ever done this? What happens when you try to drive with a bent crank?

[Al]

I dare say, at the very least, it damages bearings and then time for a new rebuild.

[stagefumer11]

I have replaced the busted pulley with a light-weight billet aluminium number out of the states. The car has since developed an interesting new trick. It does some amazing low-rider style bunny hops when I try to pull away from low revs.

While this might be the latest installment in my never-ending untunable SU carby idiocy, a mate has suggested that driving with a damaged harmonic balancer can put unholy forces on the crank and bend it. Anyone ever done this? What happens when you try to drive with a bent crank?

Rarely will the crank bend.. The L serries cranks are internaly balanced. The harmonic balancer does what the name says. Harmonics. Pretty sure your crank will be fine. You might find with the aluminum Balancer has changed the mass on the crank and you now notice the Su carb problem

[coupe72001]

Thanks for the replies. Fingers crossed that the crank is all good. The problem occured in 42 degree heat, so mass change/temperature may well have caused more carby madness.

I recently tried dynoing the car and couldn't. At certain rev ranges the car ran so rich it went of the measureable scale. I hate the SU's and as soon as I have the cash I'll source triples from the states. Most of the problems with how the car runs have been carby related. I've spent about $2,000 trying to get them right and are not even close. Can't wait to bin them and try something different.

[noddle]

Thanks for the replies. Fingers crossed that the crank is all good. The problem occured in 42 degree heat, so mass change/temperature may well have caused more carby madness.

I recently tried dynoing the car and couldn't. At certain rev ranges the car ran so rich it went of the measureable scale. I hate the SU's and as soon as I have the cash I'll source triples from the states. Most of the problems with how the car runs have been carby related. I've spent about $2,000 trying to get them right and are not even close. Can't wait to bin them and try something different.

For 2K, you could off had a sweet EFI system.

Nigel

[coupe72001]

Tell me about it... oh well, the benefit of hindsight.

[passin ewe]

I'm with you on that one Drew. I also had SU's ( shitty upstarts). 3 x I had to take them back to a guy who was supposed to be a SU guru. I'd drive it for 15 min and the plugs would foul. My webers on the other hand are beauuuutiful and I'm not afraid to have a go at tuning them either." Go the webers". Sorry to hear your having these ongoing dramas, if it makes you feel any better I also wasted about $1300 on my SU set up. Sold them for $250 with manifold, good ridence. Ricky

Don't mean to offend those of you who do have good set ups, I'm sure there's plenty of good ones.

[coupe72001]

From what I hear 240z dome-top carbies are more than tunable in the right hands, but 260z or 2" English SU are a real pig, and most carby guys either don't know how to tune them properly, or aren't interested in even trying.

[BensDR30]

My 240Z round-tops weren't a problem to keep in reasonable tune - I generally gave the idle & mixtures a tweak at each service. Having said that, I was determined to run EFI, and 18 months after buying the car, I had aftermarket EFI & a TO4 doing the deed...