Timed, runs good, but....
Thread Starter
Instructor
Joined: Jul 2011
Posts: 246
Likes: 15
From: Pell City AL
Timed, runs good, but....
The engine was setup with the timing locked out at 33 degrees. After 2000 miles it started running rough so I decided to replace the distributor so I could tune it in.
The recommended starting point for this engine with a big cam was 20 initial and the black bushing which gave 38 total. In order to get the best performance I had to go 10 initial, the red bushing for 34 total and the light silver springs for all in at 2600.
Does this sound right? Is this because the distributor doesn't have a vacuum or maybe I am off a tooth with the distributor?
The only issue is at 2500-3000 RPMs it runs rough and vibrates. Seems to fade out over 3K. Not sure if that is engine or drivetrain.
383, compcam XE284H, Bowtie heads .205, MSD 6AL Ignition, MSD Pro-Billet 85551 distro, AED Holley 650 (set idle jets for max vacuum of 9.5Hg.
Thanks in advance for any advice,
The recommended starting point for this engine with a big cam was 20 initial and the black bushing which gave 38 total. In order to get the best performance I had to go 10 initial, the red bushing for 34 total and the light silver springs for all in at 2600.
Does this sound right? Is this because the distributor doesn't have a vacuum or maybe I am off a tooth with the distributor?
The only issue is at 2500-3000 RPMs it runs rough and vibrates. Seems to fade out over 3K. Not sure if that is engine or drivetrain.
383, compcam XE284H, Bowtie heads .205, MSD 6AL Ignition, MSD Pro-Billet 85551 distro, AED Holley 650 (set idle jets for max vacuum of 9.5Hg.
Thanks in advance for any advice,
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
The recommended starting point for this engine with a big cam was 20 initial and the black bushing which gave 38 total. In order to get the best performance I had to go 10 initial, the red bushing for 34 total and the light silver springs for all in at 2600.
Does this sound right? Is this because the distributor doesn't have a vacuum or maybe I am off a tooth with the distributor?
The only issue is at 2500-3000 RPMs it runs rough and vibrates. Seems to fade out over 3K. Not sure if that is engine or drivetrain.
Does this sound right? Is this because the distributor doesn't have a vacuum or maybe I am off a tooth with the distributor?
The only issue is at 2500-3000 RPMs it runs rough and vibrates. Seems to fade out over 3K. Not sure if that is engine or drivetrain.
Being "off a tooth" has no effect on timing - it only affects the cosmetic installed orientation of the distributor.
Timing won't cause a vibration issue or a roughness issue.
Lars
Thread Starter
Instructor
Joined: Jul 2011
Posts: 246
Likes: 15
From: Pell City AL
Actually I started with the light silver and blue spring and the timing was coming all in at 2900 so I changed it to both silver springs thinking I needed more advance at 2600 to get rid of the vibration. Didn't help.
Thanks for replying Lars. The majority of my timing knowledge comes from your posts and the email you sent me. It was another post by you and Holley's recommendation that made me concerned about having to set the initial timing at 10 degrees.
As far as having the distributor gear off a tooth, I don't think I explained it well or I have a misconception. When the engine was at TDC I lined up the rotor with the plug #1, however, because of the way the shaft rotates dropping in I am thinking I have the rotor just before plug #1 causing to much advance. In turn I am having to excessively retard the timing to make up for it.
I will address the vibration outside of this thread.
Open to suggestions!
Thanks for replying Lars. The majority of my timing knowledge comes from your posts and the email you sent me. It was another post by you and Holley's recommendation that made me concerned about having to set the initial timing at 10 degrees.
As far as having the distributor gear off a tooth, I don't think I explained it well or I have a misconception. When the engine was at TDC I lined up the rotor with the plug #1, however, because of the way the shaft rotates dropping in I am thinking I have the rotor just before plug #1 causing to much advance. In turn I am having to excessively retard the timing to make up for it.
I will address the vibration outside of this thread.
Open to suggestions!
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
