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tmdog
10-12-2003, 02:48 PM
I have a Thunderbolt IV ignition. Intend to replace distributor gear. I heard the gears are made from steel to nylon. What kind is best suited for replacement? Where can I buy it? Any help is appreciated. JIM

MOP
10-12-2003, 02:56 PM
Does the original gear show wear? If not keep it, but if it shows of wear I would go with the nylon. The cam gear is worn to a matching pattern a new hard steel gear will accelerate wear. In the long run replacing a nylon gear is far better than replacing a cam shaft. My 2-1/2 cents!

tmdog
10-12-2003, 03:28 PM
MOP- There seems to be some slop in the gear when inserted in cam. When checking total timing at 32 to 34k there is some variation in the timing mark. Cam has 15 hrs. on it. I'd rather replace the gear than cam. I know what you are talking about. Where can I buy this dist. gear?

MOP
10-12-2003, 04:19 PM
Even at the dealer the price is pretty cheap and most of the time factory is best. The slop my not be all in the gear but in the advance mechanism and shaft, may be wise to re-bush and also replace springs. That stuff gets tired after awhile. I have seen some wild variations in timing with sloppy stuff.

tmdog
10-12-2003, 05:15 PM
No springs in this dist. Has electronic advance. Module is 22 degree built in. Classic is 88 and I bet dist. was never overhauled. You gave good advice MOP, I thank you for it. JIM

tmdog
10-12-2003, 06:11 PM
May sound like a post between two members but this a open forum. I' like to hear other suggestions for this problem or where to purchase parts.

BUIZILLA
10-12-2003, 07:15 PM
TM, the distributor gear is NOT nylon... if you went with another cam at some point, you need to run a bronze gear. Available from many hi-po shops. Pat close attention to the roll pin for correct fit on the gear and shaft. Then go to your Chevy dealer and buy a distributor shaft shim kit. Set the clearance to .008/.012 with the new shims on the new gear. I have seen some stock units clearanced at .035 or more. Set the base timing to 12* at hot idle @ 800 rpm in neutral. If it still bounces more than 1* or 2* when checking for total advance at 3000 rpm, it's the timing chain slop at that point..

J

tmdog
10-13-2003, 04:32 PM
Timing chain should be ok. since the chain and gears were replaced when new cam installed.Good advice on shim and gear clearance. I really never gave the clearance factor much thought. Thank goodness this board has some good people. JIM

MOP
10-13-2003, 04:56 PM
Jim shows you how old I am getting, called my parts guy to see if nylon gears were still avilable. Got a big giggle out of him, he said your slipping and getting old, said the only nylon gear he had on his shelf was one left over Chrysler. Got off the wrenche mid 80's, a few things have changed!