[C2] 63 FI Odd Timing Issue
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 5,401
Likes: 986
From: Itasca IL
63 FI Odd Timing Issue
I had my FI restored (runs amazing) and I rebuilt my original distributor. Everything is working fine, but my vacuum canister is almost touching the plenum when I have the timing set. I have ~20 degrees of centrifugal advance, that starts around 900 and is all in by 2400. With 12 degrees initial, that's a really conservative setup. I can get to about 14 initial then I am touching the plenum. The distributor has a 722 cam in it, no bushing on the limit pin currently, and the wires are in the normal orientation and match the AIM. The distributor gear is installed correctly. If I advance one tooth, I can't get below 22 initial where the vac can is then touching the coil instead. I have never had this problem on any carbed cars, always plenty of adjustment room either way. I notice from looking at pictures online, basically every 63 FI car has the vac cannister hard against the coil. Anyone have some insights to share?
Instructor
Joined: Jul 1999
Posts: 235
Likes: 20
From: Albuquerque NM
FI timing...
I had my FI restored (runs amazing) and I rebuilt my original distributor. Everything is working fine, but my vacuum canister is almost touching the plenum when I have the timing set. I have ~20 degrees of centrifugal advance, that starts around 900 and is all in by 2400. With 12 degrees initial, that's a really conservative setup. I can get to about 14 initial then I am touching the plenum. The distributor has a 722 cam in it, no bushing on the limit pin currently, and the wires are in the normal orientation and match the AIM. The distributor gear is installed correctly. If I advance one tooth, I can't get below 22 initial where the vac can is then touching the coil instead. I have never had this problem on any carbed cars, always plenty of adjustment room either way. I notice from looking at pictures online, basically every 63 FI car has the vac cannister hard against the coil. Anyone have some insights to share?
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 5,401
Likes: 986
From: Itasca IL
Sounds like you need to remove your dist. knock out the pin holding the driven gear at the bottom of the dist. With the pin out, hold the top of the roter and rotate the driven gear 180 degrees. This will give you the room to adjust your advance as needed. For a more complete description of why you are doing this look up an old post from Duke. Bill
Last edited by SupremeDeluxe; Aug 7, 2022 at 09:59 AM.
Safety Car
Joined: May 2014
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In many cases when a replacement camshaft is used the distributor gear has to be turned like Bill say's above. Doing this should get your vacuum advance in the middle of it's travel points and get you the 14* BTDC . Further to the coil bracket is better because it lines the tach cable better.
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 5,401
Likes: 986
From: Itasca IL
In many cases when a replacement camshaft is used the distributor gear has to be turned like Bill say's above. Doing this should get your vacuum advance in the middle of it's travel points and get you the 14* BTDC . Further to the coil bracket is better because it lines the tach cable better.
Safety Car
Joined: May 2014
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The camshaft could possibly be a stock grind but if it's not a GM camshaft the issue above holds true in many cases. Don't sweat it, remove the distributor and rotate the gear 180* and install again. I think (from memory and previous post on this subject) the timing will change approx 14* so it should work out fine.
Instructor
Joined: Jul 1999
Posts: 235
Likes: 20
From: Albuquerque NM
Over the years (don't ask how many!) I have seen several pure stock SB engine distributers with the dimple on the drive gear drilled on the wrong side. I have seen this most frequently on a SB high performance engine with an aluminum intake. Good luck and let us know if this works. Bill
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 5,401
Likes: 986
From: Itasca IL
I will absolutely swap the gear. I can tell that will fix it already. You are right, the delta should be 14 deg by moving a tooth. 13 teeth = 27.69 degrees per tooth of distributor angle, approx 14 degrees of crank angle.
I thought for a moment I had a bad damper or the wrong damper, but I validated it's right this morning (but still probably needs to be rebuilt anyway, the rubber is extruded pretty far out the back side and rubbing the timing cover.
I get only a couple hours every few weeks to work on this, so it will be at least next weekend before I can work on it again.
If I can get 16 initial, I will be at 36 total even with the 722 cam and 36 weights. That will be just fine on 100 octane leaded.
I thought for a moment I had a bad damper or the wrong damper, but I validated it's right this morning (but still probably needs to be rebuilt anyway, the rubber is extruded pretty far out the back side and rubbing the timing cover.
I get only a couple hours every few weeks to work on this, so it will be at least next weekend before I can work on it again.
If I can get 16 initial, I will be at 36 total even with the 722 cam and 36 weights. That will be just fine on 100 octane leaded.
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I will absolutely swap the gear. I can tell that will fix it already. You are right, the delta should be 14 deg by moving a tooth. 13 teeth = 27.69 degrees per tooth of distributor angle, approx 14 degrees of crank angle.
I thought for a moment I had a bad damper or the wrong damper, but I validated it's right this morning (but still probably needs to be rebuilt anyway, the rubber is extruded pretty far out the back side and rubbing the timing cover.
I get only a couple hours every few weeks to work on this, so it will be at least next weekend before I can work on it again.
If I can get 16 initial, I will be at 36 total even with the 722 cam and 36 weights. That will be just fine on 100 octane leaded.
I thought for a moment I had a bad damper or the wrong damper, but I validated it's right this morning (but still probably needs to be rebuilt anyway, the rubber is extruded pretty far out the back side and rubbing the timing cover.
I get only a couple hours every few weeks to work on this, so it will be at least next weekend before I can work on it again.
If I can get 16 initial, I will be at 36 total even with the 722 cam and 36 weights. That will be just fine on 100 octane leaded.
Thread Starter
Le Mans Master
Joined: Mar 1999
Posts: 5,401
Likes: 986
From: Itasca IL
Yep, 16* initial and approx 22* centrifugal will work good. it's possible someone may have been in that distributor in a previous life, the 724 weight base is usually what is factory but you never know how it was assembled. The weights should be #37 and the auto cam may be stamped with the # 54. That's what was in my 300hp distributor and I think all the centrifugal curves (all engines) were the same in 1963.
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I think I would leave the limit bushing and just set the initial timing at 14-16*, that should get you a nice running engine. If you have a dial back light, remove the weight base springs and power time the engine at 36*. Removing the springs lets the weights move out without free reving the engine, just fast idle should do. You can also mark the damper at 36* ( just move it 10* at a time until you get to 36-38* and mark it then you can use a regular timing light to power time the engine, total WOT advance.
Keep your hands away from fast moving parts or it won't matter what advance curve you have. :-) That's why I have removed the springs, a fast idle will have the springs completely out so you don't need to rev high.
Do some research on the high performance timing marks, I remember reading years ago over at the NCRS TDB something about the marks being off just a little bit.
If your FI coupe has a ported vacuum signal the the V/A you will be better off with less centrifugal advance and more initial timing so it may be better with 16-18* initial (provided it doesn't crank hard) and approx 20-22* centrifugal advance. Use the new brass bushing, make sure it fits tight and if you have the original #201 vacuum advance see how the engine runs with it.
Keep your hands away from fast moving parts or it won't matter what advance curve you have. :-) That's why I have removed the springs, a fast idle will have the springs completely out so you don't need to rev high.
Do some research on the high performance timing marks, I remember reading years ago over at the NCRS TDB something about the marks being off just a little bit.
If your FI coupe has a ported vacuum signal the the V/A you will be better off with less centrifugal advance and more initial timing so it may be better with 16-18* initial (provided it doesn't crank hard) and approx 20-22* centrifugal advance. Use the new brass bushing, make sure it fits tight and if you have the original #201 vacuum advance see how the engine runs with it.
Last edited by tbarb; Aug 10, 2022 at 04:07 PM.