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Tuning question #1271552
07/21/12 03:12 PM
07/21/12 03:12 PM
Joined: Jan 2007
Posts: 531
Charlotte, NC
Kowal Offline OP
mopar
Kowal  Offline OP
mopar

Joined: Jan 2007
Posts: 531
Charlotte, NC
I am working with a buddy on his heavily customized early eighties Jeep. Decent cam, Holley carb, MSD everything, headers, bIg stall convertor, big rear end, etc..

Anyway, idle performance was very poor, stalling all the time, very rough idle, even a high idle speed didn't help it. After playing with the carb (floats, mixture) I bumped the timing up a bit. Was 18 initial and now probably in the low twenties. Did it by feel and ear as well as with a Full Advance timing light. Really, really, improved the Jeep, but now at around fifty or so, at steady speed, it "bucks" a bit. Detonation? That was my thought and I can back off on timing, but I wanted to see what others thought.

It has vacuum advance hooked up. The Jeep bucked more with the advance disconnected than connected. Hence my confusion.


'69 Hemi Charger 500, ‘70 U code Challenger R/T
(These and a bunch others at www.dkowal426.com)

P.J. O'Rouke: "The old car ran perfectly, right up until it didn't."
Re: Tuning question [Re: Kowal] #1271553
07/21/12 07:21 PM
07/21/12 07:21 PM
Joined: Jul 2003
Posts: 1,212
Canton, Ohio
Crazy68Dart Offline
pro stock
Crazy68Dart  Offline
pro stock

Joined: Jul 2003
Posts: 1,212
Canton, Ohio
How much vacuum is it pulling at idle and cruise and is it steady or bouncing all over the place?


383, Hemi 4-Speed, AlterKtion, D60
Re: Tuning question [Re: Kowal] #1271554
07/21/12 08:21 PM
07/21/12 08:21 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
R
RapidRobert Offline
Circle Track
RapidRobert  Offline
Circle Track
R

Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
Quote:

The Jeep bucked more with the advance disconnected than connected.


Check rotor phasing. Drill a 1/2" hole in the top flat of the dist cap 2/3 of the way between the center terminal & the #1 terminal & shine your timing light straight down on the rotor at the offending RPM & see if the rotor blade is close to the #1 cap terminal then disconnect the vac adv & check again


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