Sheared Distributor Gear

[93Foxbody331]

I sheared my distributor gear and have been looking for answers. Upon searching threads alot of people place blame on HV pumps, alignment, gear type etc. Its a 331 with HV pump Msd distributor (Steel Gear). Never had a problem with same cam and distributor in 302 block. I talked to MSD and the guy said i broke the gear in wrong. Engine builder said to use straight 30 weight to break in engine so i did. MSD says i should have used straight 5 weight. Whats your thoughts or experience on this? Thanks

 

[Rick 91GT]

Did you check the depth of the gear...ive had them wrong out of the box. Never had an issue with 30w break in

 

[93Foxbody331]

No I didn't check depth. cam and distributor were in original 302 block together with no issues. When i blew a piston i ordered a 331 short block and swapped the parts over. Ever since swap was done the car sputtered with exhaust popping when it would get warm. It ran fine and strong until it got warm. I could let car cool down for 20 min and it would drive again until heat built up. then the gear shear happened. Not sure if this is a coincidence because i do now know the history of this distributor because it was on the car when i bought it.

 

[vristang]

Pic of the gear?

MSD really wants their gears to be 'broken in' with 5w oil?
Crazy.

 

[vristang]

What part number was the gear?

 

[93Foxbody331]

Its MSD. Its the steal gear

 

[93Foxbody331]

Its MSD. Its the steal gear on a pro billit

 

[montegoman351]

Make sure your oil pump still turns, had that happen on a stock 351c, the oil pump locked up going 70 down the interstate...not fun

 

[93Foxbody331]

Ya pump still turns. I have a stock distributor currently in car and she idles fine. Dont want to drive her just yet though. The engine builder told me to use 10w40 oil. Is this too thick causing excessive resistance in pump or is this a normal weight to run?

 

[montegoman351]

Definitely check alignment on the gear, how long did it take to shear? If the pump is fine, it maybe a faulty gear, I have never heard of breaking in a distributor gear, I know you're supposed to put some lube on the gear before stabbing the distributor. The cam/distributor could have walked.

 

[93Foxbody331]

the wear marks on gear appeared normal. camshaft endplay checked normal during build so i dont think cam walked. however distributor shaft was excessive. MSD told me shaft play should only be .025-.035. Mine was easily double that so im hoping that this caused erratic timing when car was warm and the gear shear. Not sure if thats wishfull thinking though, that would be to cheap of a repair.

 

[junkyardwarrior]

One of the things I like to do is to drill a 1/16" hole in the galley plug that is directly behind the distributor gear. Almost eliminates dist. gear WEAR. However, if there is a separate problem, say, misalignment or improper depth, it'll destroy it no matter if it runs continually in a bath of oil or not. Also watch the oil pump shaft. I've seen more than one that is too long which can cause issues of the same sort.