[1971GTO]

Pulled the harmonic balancer off to get to the timing cover......a chunk of the rear hub where it slides over the crank snout was broken away. This stock balancer looks like pot metal.

So, I need a new balancer now too. Do I really need to invest in a steel piece..........is nodular iron a mistake? This is an essentially stock '71 455HO not driven alot. Recomendations please.

Appriciate it!

[Will]

The factory balancers are plenty adequate for stock to street/strip applications. A good aftermarket balancer can't hurt but beware of the cheap Chinese made ones. They usually don't fit the snout properly (too loose) and have been known to explode at high RPMs.

[Schurkey]

If you destroyed a timing chain, you better pull the pan and verify that there aren't a bunch of chunks in the oil pan, perhaps leading to a locked-up oil pump.

The chunks might be nylon teeth from the old cam sprocket; they could also be pieces of valve seals. If either one gets in between the oil pump teeth, it spells trouble.

[gtofreek]

They break usually because they were not torqued tight enough. They need to be torqued at 160 ft. lbs., no less. BHJ offers a very good balancer and they also offer one that is a press fit, which is how a balancer should be in the first place. They won't work properly if they are not very tight to the crankshaft. That is why Pontiac torques them to 160. The only reason Pontiac made them a slip fit was to make repairs easier. In 1947 when these engines were developed, ease of repair was a great concern when people were used to working on flatheads. Pontiac was afraid that if their new OHV engine was hard to work on, noone would buy them. Pressfit with a bolt is really the way to go.

Paul Carter
Koerner Racing Engines
www.koernerracing.com

[DScruggs]

I had this happen years ago to a 428. The Crankshaft keyway was wobbled out. Loose woodruff key, loose balancer and it go boom.

[Half-Inch Stud]

SOUNDS to me the Balancer Bolt was not tight enough.

[1971GTO]

This is all great widom here.....stuff I didn't even think of.

This breakage happened on cold startup, I'll look at the condition of the old chain to see if pulling the oil pan is warranted, THANKS!

Yes, I highly doubt I put 160# on that bolt last time it broke a chain! I felt like I had to back off for fear of stripping..the bolt feels a bit sloppy in the end of the crank, like it's not correct. What do you make of this?

Anyway, I'll probably proceed with an inexpensive OEM type Pioneer balancer from Summit. Is nodular iron alright? I don't feel that I need steel.....heavier too.

Mike.

[engineer]

why not use the stock pontiac one that is still in inventory. no need yet to go to aftermarket. check keyway and use correct woodruff pontiac key, not chevy one that is not tall enough. use pontiac bolt and hardened thick washer to 160 ft lbs. blue lock tite also helps.

[1971GTO]

Yes, good idea. I'll do some checking on that as well. May be able to get one fom the local GM dealer here or..........

[INJUNTOM]

check the snout - the one that i had to do this ate the end of the snout a little before it let go.

[1971GTO]

The outside of the snout looks good. The bolt threading at the end worries me a bit that it may have been stripped.

[Dens71TA]

I would get a factory Pontiac balancer from your local dealer. GM superceded the part number and lowered the price about $85. New part number is 88960256 and list is $39.00. If you can talk your parts guy in giving you wholesale pricing you should be able to get it for around $30.

If your car is a manual trans you can put it in gear and set the parking brake to torque the bolt to 160#. With an automatic it gets a little more tricky. I have a tool made up with a long bar that bolts to the balancer were the pulley is to keep the crankshaft from turning.

[1971GTO]

So if I can hold the motor from turning, it should not be a problem getting the 160 without stripping threads? It is A/T.

I believe i'll try the local dealer for a new GM part then.

Appriciate it!

[Malky]

1971, I'd be worried about stripping threads in the cast crank too if you can wobble the bolt when screwed right in. I would get a new bolt that is as long as possible (without bottoming out in the crank) so you are engaging the good threads at the bottom of the hole.