Re: Installed Tach Drive Dist now car wont idle in gear hot
[Re: bigsbigelow]
#1254248
06/20/12 10:40 AM
06/20/12 10:40 AM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Assume the tach drive distributor does not have vacuum advance, in which case you just don't have enough advance at idle for the cam you are using. I bet your other dist. had the vacuum can hooked up to manifold vacuum. Only solution is to shorten up the curve in the dist. ( so you can run the same total advance ) and run more advance at idle. Tach drive itself shouldn't have anything to do with it.
Fastest 300
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Re: Installed Tach Drive Dist now car wont idle in gear hot
[Re: Crizila]
#1254249
06/20/12 10:54 AM
06/20/12 10:54 AM
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Joined: Aug 2007
Posts: 1,564
St. Clair Shores, Michigan
bigsbigelow
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pro stock
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OP
pro stock
Joined: Aug 2007
Posts: 1,564
St. Clair Shores, Michigan
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The vacuum advance was hooked up to ported vac with the MP vacuum dist. The tach drive is the MP aluminum body "race" unit so no vacuum advance. The vacuum advance dist had 14 degrees at 1000 rpm and the tach drive has 28 at 1000 rpm. Both dist I set the total timing to 32. The engine idles awesome cold in park or drive. Currently, the tach drive has a cap and rotor of unknown vintage.
P.S. Sorry I did not specify the type of distributor I have in the first post.
Last edited by bigsbigelow; 06/20/12 10:55 AM.
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Re: Installed Tach Drive Dist now car wont idle in gear hot
[Re: bigsbigelow]
#1254250
06/20/12 11:36 AM
06/20/12 11:36 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Master
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Posts: 52,972
Romeo MI
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Since you say it idles fine when cold that tells me its fat when warmed up... assuming it doesnt have a choke and a fast idle cam on the carb... check the cap and rotor first to make sure its getting a nice spark and check to see if the phasing is correct 
Last edited by MR_P_BODY; 06/20/12 11:38 AM.
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Re: Installed Tach Drive Dist now car wont idle in gear hot
[Re: bigsbigelow]
#1254251
06/20/12 11:54 AM
06/20/12 11:54 AM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Quote:
The vacuum advance was hooked up to ported vac with the MP vacuum dist. The tach drive is the MP aluminum body "race" unit so no vacuum advance. The vacuum advance dist had 14 degrees at 1000 rpm and the tach drive has 28 at 1000 rpm. Both dist I set the total timing to 32. The engine idles awesome cold in park or drive. Currently, the tach drive has a cap and rotor of unknown vintage.
P.S. Sorry I did not specify the type of distributor I have in the first post.
From that info I would say 28 degrees is too much advance at 1000 rpm. Depending on the cam you are running, I would shoot for 14 - 18 degrees advance at idle. The more overlap you are running ( LSA in the 108 range ) the more advance you will have to run. In the 110 112 LSA range, advance at idle in the 14 degree or less range. Forget the total for now and just set the initial for best idle - in gear - with a vacuum gauge. Once you are good there, you will need to adjust the dist. curve length ( in degrees) so your total falls in where you want it - 32 degrees I think you said. Example: If your motor likes 17 degrees of timing at idle and it likes 32 degrees total, 32 minus 17 = 15 degrees of timing advance at the crank ( 7 1/2 degrees in the distributor ). Once you have the amount of advance set in your dist, then you need to set the curve rate with the springs. You probably want it all in around 22-2500 engine rpm. BTW, an easy way to set the amount of advance in your dist is with a cheap plastic protractor. Cut off the straight section and just use the curved degreed part. Tape it to the side of your dist. and make a simple pointer with a piece of wire off a rotor hold down screw. Hold the dist shaft and rotate the rotor to see how many degrees advance you have ( again, dist. degrees. - it will be double that at the crank ). Weld up the slot or file it longer to get the amount of advance you are looking for. Hope you can follow this  .
Fastest 300
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Re: Install MP Tach Drive Dist now car wont idle hot
[Re: Crizila]
#1254254
06/22/12 02:03 PM
06/22/12 02:03 PM
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Joined: Aug 2007
Posts: 1,564
St. Clair Shores, Michigan
bigsbigelow
OP
pro stock
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OP
pro stock
Joined: Aug 2007
Posts: 1,564
St. Clair Shores, Michigan
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Quote:
Quote:
What do you think about swapping the pick-up from the vacuum distributor into the tach drive?
The pick-up is just a trigger for the ignition box. Swaping them won't solve your problem.
So is fouled plugs a symptom of the timing being too far advanced? (I have never heard of it)
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Re: Install MP Tach Drive Dist now car wont idle hot
[Re: bigsbigelow]
#1254255
06/22/12 04:19 PM
06/22/12 04:19 PM
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Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
Performance Only
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top fuel
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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have you checked the reluctor gap yet? if you set your initial timing with the new dist to be the same as your old one the engine should idle the same. i think you already know the tach drive dist will need to be recurved for your application.
machine shop owner and engine builder
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