jumping timing mark - Vintage Mustang Forums
Vintage Mustang Forum
HomeForumGalleryClassifiedsAbout UsAdvertiseContact Us
» Auto Insurance
» Featured Product
Go Back   Vintage Mustang Forums > General Discussion > Vintage Mustang Forum
Vintage-Mustang.com is the premier Ford Mustang Forum on the internet. Registered Users do not see the above ads.
Reply
 
Thread Tools
Old 05-07-2008, 05:09 PM   #1 (permalink)
Senior Member
 
Join Date: Dec 2004
Location: North Carolina
Posts: 135
Default

Here is the situation/setup. 1965 289, edelbrock performer cam/intake/carb setup. Petronix in a relatively new distributor.

When I time the car at idle (dist vacuum advance disconnected) it seems to be best around 12 btdc or a bit more. The timing mark does hop around a bit at idle.

When I rev it up it up to around 3000 I am getting over 40 deg advance and the mark does hop around quite a bit.

I am getting no pinging/detonation and the car runs well. My questions are:
1. Has the balancer just moved over time? (doesn't explain the hopping of the timing mark).
2. Timing chain issue? I replace the cam two years ago and the chain seemed fine. I haven't put 500 miles on it since then.
3. Anything with the Petronix?
4. Wacked out timing light?

thanks
mustang289 is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 05-07-2008, 05:24 PM   #2 (permalink)
Senior Member
 
AzPete's Avatar
 
Join Date: Apr 2005
Location: Panama City...or not...
Posts: 5,462
Default

If you have the stock balancer, it could have moved a bit. I have seen them about 1/4 turn off. Best check it manually. Jumping around when running is a kind of the nature on an engine. My '66 would jump a bit even with the Pertronics. Any change of the air/fuel could make the timing bounce a bit.
__________________
http://i25.photobucket.com/albums/c7...100_9745-1.jpghttp://i25.photobucket.com/albums/c7...arina001-1.jpg
AzPete
USAF (Ret)
'07 GT Vert (The family car)
'66 Coupe (For fun)
Previously owned: Blue '66 Coupe, Red '66 Coupe, red '68 Coupe, Black '87 GT HO, Red '00 GT Vert
AzPete is offline   Reply With Quote Quick reply to this message
Old 05-07-2008, 06:20 PM   #3 (permalink)
Senior Member
 
mikemstang66's Avatar
 
Join Date: Aug 2006
Location: palmdale
Posts: 4,563
Default

sounds like you should take a peek at your timing chain to me
__________________
1966 convert
mikemstang66 is offline   Reply With Quote Quick reply to this message
Old 05-07-2008, 07:34 PM   #4 (permalink)
Supporting Member
Senior Member
 
Midlife's Avatar
 
Join Date: Jul 2000
Location: Panama City, FL
Posts: 18,978
Default

I don't think you have a problem at all. AT 3000 rpm sitting in the driveway, you're mostly using vacuum advance, which gives you a much higher timing reading than under load (mostly mechanical advance). Jumping around of timing can be a function of a small vacuum leak or variations in rpms.

Seems completely normal to me.
__________________
http://midlife66.com/miscfiles/traylersmiley2.gifhttp://midlife66.com/miscfiles/hotshots.jpg
http://midlife66.com/miscfiles/hotshots.jpg[

'Electrical Guru: Let me Check Your Shorts! Ooops...that didn't turn out right.

MCA Historian
Midlife is offline   Reply With Quote Quick reply to this message
Old 05-07-2008, 07:34 PM   #5 (permalink)
Senior Member
 
09Frank65's Avatar
 
Join Date: Sep 2001
Location: Warrington, PA
Posts: 5,889
Default

Quote:
Originally Posted by mustang289
Here is the situation/setup. 1965 289, edelbrock performer cam/intake/carb setup. Petronix in a relatively new distributor.

When I time the car at idle (dist vacuum advance disconnected) it seems to be best around 12 btdc or a bit more. The timing mark does hop around a bit at idle.

[color:red]OK[/color]

When I rev it up it up to around 3000 I am getting over 40 deg advance and the mark does hop around quite a bit.

[color:red]40 degree advance or 40 degrees total advance? Are you reading 40* BTDC or running out to 52* The former would be about normal and the latter excessive.[/color]
I am getting no pinging/detonation and the car runs well. My questions are:
1. Has the balancer just moved over time? (doesn't explain the hopping of the timing mark).
[color:red]No - if this were the case you would not be able to set the initial timing.[/color]
2. Timing chain issue? I replace the cam two years ago and the chain seemed fine. I haven't put 500 miles on it since then.
[color:red]No again. Your timing chain has nothing to do with ignition timing, only valve timing.[/color]
3. Anything with the Petronix?[color:red]Nope[/color]
4. Wacked out timing light?[color:red]Nope[/color]

thanks
Truth be told, it seems pretty normal to me provided yo are reading 40* BTDC at 3000 RPM. If you are pulling in 40* of advance with the distributor I think you should get it re-curved.
__________________


1965 Mustang Coupe

www.not2fst.com
09Frank65 is online now   Reply With Quote Quick reply to this message
Old 05-07-2008, 08:00 PM   #6 (permalink)
Senior Member
 
johnpro's Avatar
 
Join Date: Jul 2000
Location: Roseville, California
Posts: 25,242
Default

I'll go against the grain here. First, if you have a vacuum advance, it should be plugged when timing an engine, removing it from the equation.

A properly running engine should not have a bouncing timing mark. Even with the .544 lift and 226°/226° duration cam (advertised duration of 288°/288°) in my 408, the timing mark doesn't vary enough to be discernible by a timing light and human eye.

If the engine RPMs are remaining constant, I would venture that there's a problem with the timing light. If the RPMs are bouncing enough to change timing at idle, you need to start finding the problem. The cam you have is not very radical. You should be able to get a rock steady idle with your combo.

If your're pulling a total of more than 36° of total timing (initial timing + mechanical advance), you need to a) checking the accuracy of the balancer then b) recurve the distributor or reduce your initial timing to get back to the 36° or less of timing. Just because you can't hear the pinging doesn't mean it's not. And if there is some predetonation going on, it's reeking havoc on your engine.
__________________
VMF Jedi Knight who's spirit will be with us forever.
johnpro is offline   Reply With Quote Quick reply to this message
Old 05-07-2008, 08:08 PM   #7 (permalink)
Senior Member
 
BornInAFord's Avatar
 
Join Date: Jun 2003
Location: Winston-Salem, NC 27040
Posts: 2,061
Default

+1 on the timing light. As far as bouncing timing, it may be the timing pickup for the light. Although you put it around plug wire #1, you may be picking up scatter from other spark plug wires. Move the pickup further down #1 towards the spark plug and away from the other wires to double check. Easy fix if that's the problem.

Oh, and if you have an adjustable light, double check that you know your setting. I once timed my engine to +12, but had accidently preset it at +16. It idled great, but pinged badly.
Daniel
__________________
Currently enjoying my grandfather-in-law's 1966 A-code coupe. I am the second owner.
BornInAFord is offline   Reply With Quote Quick reply to this message
Old 05-07-2008, 09:57 PM   #8 (permalink)
Senior Member
 
ultrastang's Avatar
 
Join Date: Sep 2006
Location: Arkansas
Posts: 757
Default

In 1991, my daily driver (from 1990-1997) was a '66 fastback. I was checking the timing one day and the timing marks would appear, then disappear, then re-appear?

It developed a knocking sound that would come and go. I looked at the (stock) harmonic balancer but the outer ring didn't seem to have spun on the inner portion.

I decided to remove the entire balancer to check it out thoroughly. When I slid the balancer off, the problem was obvious --the keyway on the balancer had a split in the casting running the full length of the key slot.

This allowed the inner bore of the balancer to expand, which would let the balancer spin on the crank shaft out of phase with the crank, then it would spin back into place on the crank key.

I replaced the balancer but made the mistake of not replacing the key. It wasn't very long until the 2nd balancer spun too, since the first time it happened, it rounded the edge of the key off.

I got a 3rd blanacer and a new Woodruf key (#23 key) and that fixed the wandering timing marks problem on my engine.

Don't know if this is your engine's problem, but might not hurt to check the balancer out just to be on the safe side.

__________________
My current vehicles:
1968 Mustang notchback
1990 Mustang GT
2003 Mach 1
1969 F-100 short bed Ranger pickup

Producer of Mk VII and SN-95 Rear Disc Brake Conversion Brackets Since 2002.
http://www.ultrastang.com
ultrastang is offline   Reply With Quote Quick reply to this message
Old 05-08-2008, 04:18 PM   #9 (permalink)
Senior Member
 
buening's Avatar
 
Join Date: Sep 2000
Location: Stinky Town, IL
Posts: 8,572
Default

Quote:
Originally Posted by BornInAFord
+1 on the timing light. As far as bouncing timing, it may be the timing pickup for the light. Although you put it around plug wire #1, you may be picking up scatter from other spark plug wires. Move the pickup further down #1 towards the spark plug and away from the other wires to double check. Easy fix if that's the problem.

Oh, and if you have an adjustable light, double check that you know your setting. I once timed my engine to +12, but had accidently preset it at +16. It idled great, but pinged badly.
Daniel

I'm going to agree with Daniael as I have experienced this myself.

My thread: http://forums.vintage-mustang.com/sh...rch/1/#1406018
__________________
70 Mach 1 - 351w/T-56
70 SportsRoof - 302/C4
05 F150 FX4
06 BMW 530xi

T56 Conversion
DIY Ron Morris-like Motor Mounts
DIY Engine Crossmember
DIY Camber Eccentric Eliminator Plates
buening is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Vintage Mustang Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are Off


Powered by vBadvanced CMPS v3.2.2

All times are GMT -4. The time now is 08:30 PM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.3.2 ©2009, Crawlability, Inc.