Vintage Mustang Forums banner

1 - 20 of 25 Posts

·
Registered
Joined
·
68 Posts
Discussion Starter #1
Ok, my 67 has a 289 with an edelbrock 600, headers, a petronix ignition and an msd 6a box. The firing order is 1-3-7-2-6-5-4-8, which I understand to be consistent with a 351, so the cam is not original. I had a shop fix the freeze plugs in it and when it came back the rotor was pointed to number 6 cylinder at TDC. I did the trick of sticking my thumb in the cylinder hole while rotating the harmonic balancer to verify that I was on the compression stroke when it hit TDC according to the balancer. I then used a piston stop to verify that the timing mark for TDC on my balancer was accurate, which it was. I restabbed the distributor so that the rotor was pointed at the number one cylinder hole on the distributer at 10 degrees before TDC. New plugs gapped at .035. She started up with some coaxing but ran rough with below 15 mercury on the vacuum gauge. Will barely stay idling and seems to be missing. I have adjusted the timing multiple times with rpm gauge and vacuum gauge adjusting until the vacuum and rpm readings stop going up and backing off slightly. I then drive it and retard the timing until I stop hearing any pinging and retard the timing another couple of degrees. Every time I do this I get to a timing of about 22 or 23 degrees btdc, and the vacuum gauge has a reading of 18, which I believe is right, but the 22 or 23 degrees BTDC makes no sense to me. She seems to run really well at this timing setting, but I am worried about how advanced it is and don't want to damage the engine. I take it out for test drives and it does not ping as best I can tell. The jets on the edelbrok are at about 1.5 turns out. I have checked the vacuum lines on the carbeurator and the vacuum advance is hooked up to the passenger side line, PVC line is hooked up to the middle and the full vacuum line is plugged as it should be. Anybody have any thoughts on this one? I would love to be confident that the timing is set correctly or figure out a way to fix it such that 10 btdc works which I know is slightly advance from the 6 btdc that is in the shop manual for a 2 barrel. Thanks for any advice you can give.
 

·
Premium Member
Joined
·
7,400 Posts
Ok, two questions......
1. What was the stats prior to having the freeze plugs fail, if that's what put in the shop, in the first place?
2. How are you checking the timing after your test run? Be specific.
 

·
Registered
Joined
·
68 Posts
Discussion Starter #3
Ok, two questions......
1. What was the stats prior to having the freeze plugs fail, if that's what put in the shop, in the first place?
2. How are you checking the timing after your test run? Be specific.
I believe the timing was about 12 before it went into the shop, but I am not a hundred percent sure. I check the timing by pulling the vacuum hose from the dizzy and plugging it. Thereafter, I use a timing light with the inductive pickup being on spark plug wire number one. I look at where the pointer is pointed compared to the white lines I put on the balancer at TDC, 6, 10, 20 and 30 btdc. It reads just a little after 20--looks like about 22 or 23.
 

·
Premium Member
Joined
·
7,400 Posts
I believe the timing was about 12 before it went into the shop, but I am not a hundred percent sure. I check the timing by pulling the vacuum hose from the dizzy and plugging it. Thereafter, I use a timing light with the inductive pickup being on spark plug wire number one. I look at where the pointer is pointed compared to the white lines I put on the balancer at TDC, 6, 10, 20 and 30 btdc. It reads just a little after 20--looks like about 22 or 23.
Ok, how old is the balancer? Any reason to suspect the outer ring moved? Your timing check process is "spot on", as long as, your idle is in the 700-800 range.
 

·
Registered
Joined
·
68 Posts
Discussion Starter #5
Idle was at 800. The balancer looks to be old. I did use a piston stop to check to see if TDC was still accurate and it appeared to be.
 

·
Registered
Joined
·
37,647 Posts
There's nothing wrong with that amount of advance at idle provided it doesn't ping. Heck, on cars running vacuum advance off the manifold at high rpm deceleration you could expect to see 50*+ if you could check it.
 

·
Premium Member
Joined
·
7,400 Posts
There is something to "64....."'s comment. I too, have heard some digital timing lights don't play nice with CD boxes and require an old analog light. In my case, when my Actron digital went on the blink (no pun intended), I grabbed my old Penske analog and I didn't see any difference. I run 14-16º and this was originally set with a digital. I run a Jacobs CD system. So, I guess it depends on the timing light and the system?
 

·
Registered
Joined
·
845 Posts
There's nothing wrong with that amount of advance at idle provided it doesn't ping. Heck, on cars running vacuum advance off the manifold at high rpm deceleration you could expect to see 50*+ if you could check it.
He might be showing 50+ deg. with full mechanical advance. Seems like a lot not to have detonation, kind of why I suspect an erroneous reading.
 

·
Premium Member
Joined
·
7,400 Posts
...I've seen those high numbers too (Vac connected, high initial and built-in mechanical) just not at 800 Rs with the Vac line plugged. Looking at facts as provided, you have 12º initial, before the freeze plugs are installed, you have this crazy 22-23º and a healthy Vac reading of 18 hg., upon return. Something's amiss? Could it be a broken advance spring?
 

·
Registered
Joined
·
845 Posts
...I've seen those high numbers too (Vac connected, high initial and built-in mechanical) just not at 800 Rs with the Vac line plugged. Looking at facts as provided, you have 12º initial, before the freeze plugs are installed, you have this crazy 22-23º and a healthy Vac reading of 18 hg., upon return. Something's amiss? Could it be a broken advance spring?
I would guess that 22 deg. at the crank with mechanical advance applied at an idle would be no different than 22 deg. without mechanical and still be considered initial advance. It would limit the total advance and change the curve though.
 

·
Registered
Joined
·
320 Posts
My daily driver 302 is running at 20 initial, I can even go higher if I reduce my mechanical advance. If it starts easy and runs good with 22 initial with no pinging, I say you are okay, no need to lower it. I put a DS2 so I have retard during cranking.
 

·
Premium Member
Joined
·
7,400 Posts
I would guess that 22 deg. at the crank with mechanical advance applied at an idle would be no different than 22 deg. without mechanical and still be considered initial advance. It would limit the total advance and change the curve though.
Question is, why?
 

·
Premium Member
Joined
·
7,400 Posts
Not sure what you mean.
Barman10 stated the last he checked his initial was 12º, if you've kept up with his replies. Now, he's seeing an initial of 22-23º. What's going on? His engine Vac at this point is good at 18 hg. When he reduces the initial to 12º engine and the engine doesn't respond as well and the Vac drops. I was thinking one of two possibilities, given his timing light is accurate and hasn't become defective since last he set it at 12º.
1. Did the balancer outer ring slip?
2. Did a distributor spring break or somehow slip off the post?

Obviously, unless there is more to the history than what has been conveyed.....
 

·
Registered
Joined
·
845 Posts
Barman10 stated the last he checked his initial was 12º, if you've kept up with his replies. Now, he's seeing an initial of 22-23º. What's going on? His engine Vac at this point is good at 18 hg. When he reduces the initial to 12º engine and the engine doesn't respond as well and the Vac drops. I was thinking one of two possibilities, given his timing light is accurate and hasn't become defective since last he set it at 12º.
1. Did the balancer outer ring slip?
2. Did a distributor spring break or somehow slip off the post?

Obviously, unless there is more to the history than what has been conveyed.....
Sure, I've kept up.
His answer to previous timing was
I believe the timing was about 12 before it went into the shop, but I am not a hundred percent sure.
As far as the harmonic balancer
I did the trick of sticking my thumb in the cylinder hole while rotating the harmonic balancer to verify that I was on the compression stroke when it hit TDC according to the balancer. I then used a piston stop to verify that the timing mark for TDC on my balancer was accurate, which it was.
I'm just saying that initial, mechanical and vacuum advance is all just changing the relationship between the breaker plate and lobes. An engine can't differentiate now the advance is applied, 12 deg, is 12deg. If an engine runs best at say 12 deg. btdc and if you remove a spring and initial advance becomes 22 deg. you would have to retard the advance to get the optimal 12 deg. it wouldn't suddenly prefer more advance.
I was just relaying an fyi about an MSD compatible timing light and my take that when you figured in the total advance with mechanical added that it would seem high at probably 50+deg.
One thing this thread has made me wonder about, does a retarded cam require more advance, such as installing the timing gears a tooth off, skipped tooth or by way of keyed crankshaft gear. I suppose it's just a Google search away.
 

·
Registered
Joined
·
68 Posts
Discussion Starter #17
I believe you can get an erroneous reading if you aren't using an MSD compatible timing light.
Thanks for this. Did a little research on Google and there is a lot of discussion about this possibility. I am using a simple timing light, but I think I will get an old sears craftsman light which is supposed to work with MSD to see if my timing reading is accurate.
 

·
Registered
Joined
·
68 Posts
Discussion Starter #18
There's nothing wrong with that amount of advance at idle provided it doesn't ping. Heck, on cars running vacuum advance off the manifold at high rpm deceleration you could expect to see 50*+ if you could check it.
Well maybe I let well enough alone, run it for awhile and check to see what the spark plugs look like. I do listen pretty carefully for the pinging, and do not hear any.
 

·
Registered
Joined
·
68 Posts
Discussion Starter #19
...I've seen those high numbers too (Vac connected, high initial and built-in mechanical) just not at 800 Rs with the Vac line plugged. Looking at facts as provided, you have 12º initial, before the freeze plugs are installed, you have this crazy 22-23º and a healthy Vac reading of 18 hg., upon return. Something's amiss? Could it be a broken advance spring?
The two springs in the distributor for mechanical advance are intact. I wonder if the distributor is just stabbed in the wrong place.
 

·
Registered
Joined
·
68 Posts
Discussion Starter #20
...I've seen those high numbers too (Vac connected, high initial and built-in mechanical) just not at 800 Rs with the Vac line plugged. Looking at facts as provided, you have 12º initial, before the freeze plugs are installed, you have this crazy 22-23º and a healthy Vac reading of 18 hg., upon return. Something's amiss? Could it be a broken advance spring?
It does leave me scratching my head. I am considering taking it to a shop to have them look at it once this covid stuff calms down.
 
1 - 20 of 25 Posts
Top