Well just got done putting in my zz4 cam here like 2 days ago and today im trying 2 put the harmonic balancer back on. Get the lil kit from autozone and nothing screws into the crank. So im like thats odd and I try 2 screw in the original bolt that holds the crank pulley on and goes in through the center of the harmonic balancer, and it also does not screw in. Im thinking I may have damaged the threads when useing the harmonic balancer puller. Now im not going to replace the crank or any of that so I would like to know what I can do to fix it or if I need that bolt on there at all. Could I just hammer the damper on and then use the 3 bolts to attach the pulley? Doesnt seem safe so I donno. Biggest screw up so far real pain in the *** its a 305 TBI any help would be much appriciated.

 

The stock thread is a standard SAE size but an odd one- 7/16" x 20 (or 24, can't remember). You may be able to find a tap/thread chase in that size but you won't find it at the local hardware store.

Maybe someone else can help out here.

 

Yup, 7/16"-20, which is the standard "fine" thread in that size.

You can probably tap it back out, if you're careful.

Next time you use a balancer puller, stick some kind of a bolt in there, and let the tool push on the bolt head instead of sodomizing the threads.

 

Ya I think only the front parts messed up and it just wont screw in but will go fine after that. So id just wanna try 2 tap it the same size so get a 7/16" - 20 tap and its all good right ... hopefullly?

 

Man, you're going to the wrong hardware store. I can get almost any UNC, UNF, NPT, and metric tap at my favorite hardware store. I did have trouble with the M4.5-.25 tap for the TPS screws, but I found another source locally.

Anyway, the thread is a 7/16-20, and you should be able to find a tap easily. Get a plug tap instead of a bottoming tap, since the extra long lead-in will make it easier to pick up the original threads.

If you find that the thread is completely vertically fornicated, not all is lost. Ed Cole outsmarted all of us by using that somewhat less-than-standard bolt size. Without even drilling, you can easily retap the crank snout to a 1/2-20 thread (standard UNF tap) and drill the clearance hole in the balancer hub to 1/2" to match. Get a Grade 8 1/2-20 HWH cap screw the same length, and have at it. Don't ask how I know...

 

Ive removed and put on 3 harmonic balancers and the threads always get damaged some. I just use the bolt to reinstall the balancer.

Buddy heli coiled threads into his crank LOL. We ended up pulling that motor and installing a new GM motor anyways tho.

 

aite thats what imma do thx a lot guys pray 4 me :hail:


damn i feel like a dumby

 

dont trip dude..ull be alright.

 

If somebody could take the 2 mins to look at the sears website and tell me which is the cheapest tap kit I need id be extremeley greatful sorry guys im helpless lol and have no idea which one I should buy.

 

Not good advice! Un less you want to tap an even bigger hole than Vader has suggested...Rent an installer, or make one per Vaders instructions!

I just ran into this myself. I was getting my motor ready for install. Putting the crank pully on, when I noticed the balancer bolt was loose. I tried to tighten it ..nothing. I thought OH ****! The threads at the end of the bolt were fubar! A new, slightly longer bolt, solved thee problem.