Initial Timing tuning help!!!
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Initial Timing tuning help!!!
Okay, I am thoroughly confused at this point.
I have a new 400 in there with a Holley 670 carb (for now). It runs but not very well. When I shot the initial timing with the vac adv plugged it read 40 BTDC! When I adjusted it down to 15 BTDC it started chattering and running much hotter. I felt the heat off the engine go WAY UP.
I have an MSD distributor currently set for 25 mechanical all in at 3000rpms. Now, I'm using a flaming river timing light and I read that these MSD units can be hard to get an accurate read on, could that be a problem? The cam is a hyd roller with .50 lift and like 220 duration, plus 1.6 rockers.
The car runs great at idle but has no power and with lots of hesitation when the rpms go up.
Thanks in advance...
--Jack
I have a new 400 in there with a Holley 670 carb (for now). It runs but not very well. When I shot the initial timing with the vac adv plugged it read 40 BTDC! When I adjusted it down to 15 BTDC it started chattering and running much hotter. I felt the heat off the engine go WAY UP.
I have an MSD distributor currently set for 25 mechanical all in at 3000rpms. Now, I'm using a flaming river timing light and I read that these MSD units can be hard to get an accurate read on, could that be a problem? The cam is a hyd roller with .50 lift and like 220 duration, plus 1.6 rockers.
The car runs great at idle but has no power and with lots of hesitation when the rpms go up.
Thanks in advance...
--Jack
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: Initial Timing tuning help!!! (Corz)
:lol: Could be... but I've been 180 out before and things weren't so pleasant! I dropped the distributor in with the engine set to TDC when I got from the builder. The value covers were also off & verified TDC by the #1 rockers being equal.
Drifting
Joined: Oct 2000
Posts: 1,825
Likes: 56
From: Shawano WI
Re: Initial Timing tuning help!!! (Jack71)
The motor won't run if it is 180° off.
To me, the easiest way to find your problem is to power time the motor. To do that, first unplug the vacuum advance (and plug the vacuum source). Then bring the motor up to about 4000 RPM and set the timing at 34°. Let the motor come back to an idle and see what the timing is. It should be somewhere between 4° and 12°. If it is higher than that then you have a spring/weight/weight base binding problem.
If your timing is between 4° and 12° then you have something else wrong and you have eliminated the timing. Be sure to hook the vacuum advance back up before driving.
[Modified by Pete79L82, 5:04 PM 2/22/2004]
To me, the easiest way to find your problem is to power time the motor. To do that, first unplug the vacuum advance (and plug the vacuum source). Then bring the motor up to about 4000 RPM and set the timing at 34°. Let the motor come back to an idle and see what the timing is. It should be somewhere between 4° and 12°. If it is higher than that then you have a spring/weight/weight base binding problem.
If your timing is between 4° and 12° then you have something else wrong and you have eliminated the timing. Be sure to hook the vacuum advance back up before driving.
[Modified by Pete79L82, 5:04 PM 2/22/2004]
Pro
Joined: Sep 2002
Posts: 690
Likes: 1
From: near Memphis TN
Re: Initial Timing tuning help!!! (Jack71)
You should check initial timing with vacuum advance UNPLUGGED. 25 total mechanical doesn't sound like enough, s/b about 36 or so for a small block. My best guess to a solution to your dilema - bring initial up to 15 with vacuum advance unplugged, make sure total is at about 36 at 2800-3000, connect vacuum advance to ported connection.
That's one big cam you have, that brings all sorts of vacuum, idle questions into play that may impact the above advice. You may need more than 15 initial just to get it to idle without stalling.
That's one big cam you have, that brings all sorts of vacuum, idle questions into play that may impact the above advice. You may need more than 15 initial just to get it to idle without stalling.
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: Initial Timing tuning help!!! (SpyderD)
You should check initial timing with vacuum advance UNPLUGGED. .
25 total mechanical doesn't sound like enough, s/b about 36 or so for a small block.
My best guess to a solution to your dilema - bring initial up to 15 with vacuum advance unplugged, make sure total is at about 36 at 2800-3000, connect vacuum advance to ported connection.
That's one big cam you have, that brings all sorts of vacuum, idle questions into play that may impact the above advice. You may need more than 15 initial just to get it to idle without stalling.
That's one big cam you have, that brings all sorts of vacuum, idle questions into play that may impact the above advice. You may need more than 15 initial just to get it to idle without stalling.
Pro
Joined: Sep 2002
Posts: 690
Likes: 1
From: near Memphis TN
Re: Initial Timing tuning help!!! (Jack71)
Oops, sorry Jack, you seem to have covered all the bases and I misread some of your post. I still think the large cam may be an issue although you appear to have strong vacuum.
Could the timing marks be off?
Well, if nothing else, I can bump this back to the top.
Could the timing marks be off?
Well, if nothing else, I can bump this back to the top.
Melting Slicks
Joined: Jun 2002
Posts: 2,842
Likes: 99
From: Orrtanna Pa.
Re: Initial Timing tuning help!!! (Jack71)
I had a picnic setting up my 406 too.With a lumpy cam,a new carb and no baseline to start with I feel your pain.First be sure to attach your pickup as close to the number one spark plug as you can,and seperate the plug wires so as to eliminate any false triggering on your timing light.With the vacuum advance disconnected and plugged,rev the engine to 3500 or so and set the timing to 36 degrees.This will be the distributers 20 degrees plus an initial of around 15-16.With this setting,idle down,plug back in the vacuum advance and play with the idle mix adjustment screws for the best idle.I found with my cam I could not get a decent idle with the vacuum advance disconnected,and though major experimenting during my distributer recurve,a manifold vacuum source worked much better than a ported source for the distributer.
All this assumes the mark on your balancer is correct.I verified mine with the heads off,so I was 100% sure of my timing.I also used timing tape on the balancer during the recurve,so I'm also sure of my 36 degree reference.
Good luck! :cheers:
All this assumes the mark on your balancer is correct.I verified mine with the heads off,so I was 100% sure of my timing.I also used timing tape on the balancer during the recurve,so I'm also sure of my 36 degree reference.
Good luck! :cheers:
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Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Re: Initial Timing tuning help!!! (The Money Pit)
This 40 degree initial reading really has me baffled though. Tomorrow I'll check inside the dist. to see if a weight or spring cam loose. Maybe I'm getting all of the mechanical at idle too. Ugh...
