Hey,



can someone confirm if 12a Twin dizzy stationary gears are different compared to standard 12a stat gears. Did a build a while back and ran into some end play issues, as i used new standard 12a stat gears on an unknown to me at the time, 12a twindizzy block. Basically I got no endplay at all, as soon as i torqued up the stat gear bolts, the torrenting bearing underneath locked up the thrust plate...after inspection i realized that 12a twin dizzy stat gears have a thinner gear than standard 12a..The overall height appears the same, but the gear is thinner, hence it proved that they are differnt and cannot be replaced with standard 12a ones. I ended up having to push new bearings into the original 12a Twin Dizzy stat gears...



This got me thinking, is it the front and end irons that cause this incompatibility? or is it the e-shaft?



can anyone shed some light on this? or has anyone else came accross this.



Cheers.

 

i thought that they had had some stat gear failures and updated them, so i thought they were compatable?

 

I'm going to measure the height difference, if any, from '73 to '74+ in the front plate at the stationary gear recess. If there is a difference I'll have to machine a later stat gear down; the type with a roll pin which can be pressed out of the way. Plus it's good to use the '76-'85 tall gear type for strength or less likelyhood of cracking with those heavy old rotors.



I suspect the height is the same but we'll see.

 

The pieces are interchangeable. The early gear teeth are shorter and were not hardened. Later gears have longer teeth, but the same engagement depth, so some of the gear tooth length is not used, but is stronger as far as cracking between the teeth goes.



None of this affects end play. In fact you could check end play with the front stationary gear and thrust assembly and the crank. Nothing need be attached to the front iron. Only the spacer length affects end play.



However,



On a very early engine it is possible that the irons have been ground several times, as there is no nitriding. The engine may be a bit short, and if that is the case, the rear stationary gear may sit too deep on the crank, and touch the throw holding the crank forward and eliminating any end play. Also the crank radius may be scrubing on the end of the main bearing. A spacer under the front and rear stationary gears cures this problem. Just a paper gasket will work fine. Bush beer cartons work best.



Lynn E. Hanover



Bad iron repair by Chuck Dunlap

 

i like that iron repair!