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Another bad distributor gear story

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bcsideshow View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bcsideshow Quote  Post ReplyReply Direct Link To This Post Topic: Another bad distributor gear story
    Posted: Oct/01/2015 at 2:37pm
I thought I would post some info on a recent wiped out distributor gear I have. It was in a mildly built ScRambler with a 69 390 I recently bought. I put a few hundred miles on it. I am not sure how many mile were put on prior to me but fairly fresh and no other issues. A few weeks ago I checked the timing and noticed it was at TDC when I thought I set it 10 degrees advanced initial. I thought I made a mistake or damper slipped. Then out for lunch one day it backfired twice and died. No spark. The only oddity prior to this was oil pressure was always higher than my other 390. Hot idle on SC was 40 and hot crusied at 60. My AMX is 15-20 hot idle and 40 hot cruise. Confirmed I had an OEM timing cover. I believe OEM timing gears. Confirmed cam gear was properly clearanced for oil path. Looked like an OEM gear on cam driving dizzy. MSD ignition and did not look like an oem gear. Went back and forth on whether to use a Bulltear matched set or oem. Decided on OEM and thanks to BIGBADGREEN (Earl) installed a set from him. I also swapped the front cover just because I had a spare. I reused the oil pump and gears although had a few scores in them as did the cover. Stock oil pump gasket at .012" new. Checked clearances on oil pump and all within TSM spec.s. Checked fit of dizzy with pump off the car and on. Primed the oil pump and saw oil dripping from gears. Flushed the pan, reassembled, and now running again. Our local machine shop who has AMC engines regularly said the most common cause is cam gear not clearanced properly for oil path and mismatched gears. I think my issue was the MSD gear not matched to what was on the car. Oil pressure is still the same..
MSD has a real nice write up for this issue: http://www.msdignition.com/page.aspx?id=6442452163
Here are a few pics:
1969 SCRambler "B"
1970 AMX 390 Auto
1968 AMX 390 Auto
1970 Rebel Machine Project
1969 AMX 390 4SPD Project
1969 AMX 390 Auto Project
1969 Javelin 390 project
1997 Cherokee lifted
1998 TJ Lifted
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mr. z Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2015 at 3:52pm
Thanx for the heads up on the article put up by MSD.  I am currently running a Mallory Unilite dizzy, but the cam and distributor gear are matched. My 390 is much like your's pressure wise, hot idle at about 30-35 hot cruise at 55. My two previous 390s that I've had never ran this high, however at that time(much younger and dumber in the '70s and '80s) we swapped cams without any thought to distributor gear clash, and in in shop schools back then, at least in my area, it was never mentioned.

Good luck and keep us posted how this goes...
1974 AMX Javelin,P code 4-speed,original 360,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2015 at 5:44pm
Remove the cam bolt and gear (what's left of it) and inspect the oil path from the front cam journal, through the timing gear and through the fuel pump eccentric. Somewhere there's probably either a misalignment of the galley to the distributor gear or a blockage.

-Steve-
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Post Options Post Options   Thanks (0) Thanks(0)   Quote a401classic Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2015 at 7:20pm
the pump eccentric looks a bit chewed as well. :(
'64 Rambler Classic 770 2DR

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2015 at 9:46pm
Have an MSD list (new, but sat around for years) and ran it with a good OEM timing cover and a good OEM cam gear. I also modded the cover with the oil relief slot to eliminate the hydraulic lock and oil pump drag, you could easily spin it with a hand drill for full oil pressure. No problems with the oil supply to the gear.

After dyno time only pulled it to look. The gear had the most bizarre wear starting on it, slots cut in the base of the teeth but not on every tooth. My opinion is the gear was NFG. Probably a very early MSD dist. - it had been through at least 2 owners before me but never installed. If there is a better newer gear this would not have had it.

Made 2 changes, installed a good used (some wear) OEM gear and increased the endplay on the dist. a tiny bit. I don't like the MSD for endplay - I think it is too tight stock.

Since then it's been fine. Not a lot of miles yet, maybe 1000, and a few trips to the track. Had it out to look a few times and seems OK to the eye. Will look again when I put it away for the winter.

My opinion is the biggest problem is the aftermarket gears themselves.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/02/2015 at 6:45am
Originally posted by Ken_Parkman Ken_Parkman wrote:



My opinion is the biggest problem is the aftermarket gears themselves.




Yup. The early release of MSD Pro Billet distributors had soft gears. I bought one of the first produced. A couple of months after I got it the place I bought it from phoned me to tell me of the distributor gear problem. I removed the distributor and it was about 1/3 chewed up.

MSD sent out replacement gears.

-Steve-
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bcsideshow Quote  Post ReplyReply Direct Link To This Post Posted: Oct/02/2015 at 7:33pm
From what i can tell the msd distibutor i have has very few miles before me on it but is a minimum of 6 years old and more likely 7+.

Ken, Steve, what time frame are you thinking your distibutors were from?

Thanks for the input!
1969 SCRambler "B"
1970 AMX 390 Auto
1968 AMX 390 Auto
1970 Rebel Machine Project
1969 AMX 390 4SPD Project
1969 AMX 390 Auto Project
1969 Javelin 390 project
1997 Cherokee lifted
1998 TJ Lifted
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/02/2015 at 7:47pm
Originally posted by bcsideshow bcsideshow wrote:

From what i can tell the msd distibutor i have has very few miles before me on it but is a minimum of 6 years old and more likely 7+.

Ken, Steve, what time frame are you thinking your distibutors were from?

Thanks for the input!


Got mine just as they became available, probably 20 years ago. I remember buying it from WSC classicone.com (I think is now defunct) that was run by the guy who worked with MSD to bring them to market, think his name was Ron Waters.

-Steve-

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Oct/02/2015 at 10:19pm
Dunno how old, but old. I know the previous owner had it for many years, and he bought it new from another guy who had it probably for years as well. I expect it is also a very early one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Oct/04/2015 at 12:10am
Had exactly the same issue, but it took out a muffler when it "backfired"! Violent backfire and then nothing. I also had the timing adjust itself from 10 degrees to tdc. If anyone has a sudden timing adjustment toward the retarded end of the scale, that is likely a warning sign. I replaced both gears with a set of OEM but not matched gears, and checked the oiling passages through the camshaft/eccentric etc. No further problems. I am not convinced that the gears must be matched to each other, but I am a fan of OEM. As mentioned by Mr. Z, that matched gear theory seems to have come to be in more recent times. People used to change dizzies all the time and no one really thought much of it. 

Chris 

PS: I also get 15-20 psi warm idle and around 40-45 at cruise, hot with 15/40 oil. 
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