99A Checking Timing.

[Phil Gillespie]

So have a 99a Engine I have been playing with. Presently set up to run on engine stand. Had made up a timing pointer and fitted when I had heads off to check. Its fitted with a crab type distributor.
So couple of questions on checking timing.
Moving side adjuster plate clockwise advances timing, right?
General ball park for advance brake all the way out then 3 turns in?
To check timing is it necessary to disconnect vaccum advance line from inlet manifold to distributor?
Appreciate assistance given here as always.
Phil NZ

 

[KiWinUS]

Phil did you put a 26* mark on lower pulley or just TDC. I always put a 26* mark as I know that’s what I like max advance to be as a starting point.

 

[TerryOH]

The vacuum brake slows mechanical advance, yes all the way out by hand then two or three turns in. Advance and retard is the flat plate on the side of the distributor with the stamped hash marks.

 

[Bill OH]

I also have a pointer and a mark on the crank pulley marked at TDC. The initial timing is 4* which is about 1/4 inch on the circumference of the pulley. For 26* it will be about 1.25 before TDC. You can figure this out by 7” crank pulley x 3.1416 divided by 360 degrees by 26 will give you the distance in advance of TDC. I have computed this and 4* is about 1/4 inch. The adjustment screw on the side of the distributor, move the breaker plate (up) against the rotation of the distributor and that advances the firing point on the crank pulley.
For the vaccum brake I back it full out and lock down the nut on the adjustment screw.

I had a 221 in high school that would do 74 mph and no more. Backed the vacuum brake out to full off and it went to 84 mph. And that was back in the early 50’s.

Greetings to you - Wife and I have been to New Zealand, including Christ Church. - great place.

 

[Bored&Stroked]

I always have the vacuum brake at least touching/dragging just a bit - helps to control timing flutter due to the mechanical advance mechanisms flopping around.

 

[Phil Gillespie]

Phil did you put a 26* mark on lower pulley or just TDC. I always put a 26* mark as I know that’s what I like max advance to be as a starting point.

Tony, Just put TDC as am using a timing light with the dial back feature to read off total timing advance.
Phil NZ

 

[Phil Gillespie]

I always have the vacuum brake at least touching/dragging just a bit - helps to control timing flutter due to the mechanical advance mechanisms flopping around.

Yep agreed to have some drag to eliminate that flutter as mentioned.
But when checking it is done with the vacuum line from manifold to distributor in play. Must be this way as if disconnected vacuum brake would not be operating?
Phil NZ

 

[Phil Gillespie]

I also have a pointer and a mark on the crank pulley marked at TDC. The initial timing is 4* which is about 1/4 inch on the circumference of the pulley. For 26* it will be about 1.25 before TDC. You can figure this out by 7” crank pulley x 3.1416 divided by 360 degrees by 26 will give you the distance in advance of TDC. I have computed this and 4* is about 1/4 inch. The adjustment screw on the side of the distributor, move the breaker plate (up) against the rotation of the distributor and that advances the firing point on the crank pulley.
For the vaccum brake I back it full out and lock down the nut on the adjustment screw.

I had a 221 in high school that would do 74 mph and no more. Backed the vacuum brake out to full off and it went to 84 mph. And that was back in the early 50’s.

Greetings to you - Wife and I have been to New Zealand, including Christ Church. - great place.

Thanks so much for your input and advice. Forgot to mention I am using a timing light with the dial back function to be able to read off timing advance direct.
Also using a vacuum gauge from inlet manifold where wiper line normally hooks up. Combine the timing along with getting best vacuum reading.

Thanks for your endorsement of our little country down under. Pleased you enjoyed your visit. Down here in the Sount Island we like to think of it as The Mainland better quality of life than North Island.
Phil NZ

 

[flatjack9]

I always have the vacuum brake at least touching/dragging just a bit - helps to control timing flutter due to the mechanical advance mechanisms flopping around.

Most of our driving is at light loads, so relatively high vacuum. So the vacuum brake is away from the plate. How will it eliminate any "flutter"?

 

[Phil Gillespie]

Thoughts on setting timing for best vacuum? This is what I tend to go for.
Phil NZ

 

[Flathead Fever]

I make a pointer and mark the pulley with a file at TDC, 4, 10 and I don't worry about total advance. You have to find the diameter of the pulley and then figure out what distance equals one-degree on the pulley. If you have the TDC mark on the pulley you can then measure from it to make the others mark you want on the pulley. As long as you have a TDC mark you don't need any other marks with an adjustable timing light.

With the head off and the #1 piston at TDC temporarily mark the pulley and pointer. Do not rotate the engine backwards to line it up, if you pass TDC go around again and carefully stop at TDC and make your mark. Rotate the engine a full turn in the opposite direction and stop at TDC and make another mark. True TDC will be in-between the two marks. Make your permanent mark there. That comes for the instruction in a vintage Isky catalog. If you do this, you will find there will be a small space between the two marks. You can't mark the pulley with TDC any more accurate than this.

If you know the direction a distributer rotates, just remember if you move the breaker plate in the opposite direction of distributer rotation you will be advancing the timing, the points will open earlier. Same with rotating a late model distributer. A Flathead Ford is the only V8 engine I know of where the furthest forward cylinder is not #1. Every other V8 I ever worked on the furthest forward cylinder was always #1. If you assumed that on a flathead, you would be wrong.

 

[Phil Gillespie]

I make a pointer and mark the pulley with a file at TDC, 4, 10 and I don't worry about total advance. You have to find the diameter of the pulley and then figure out what distance equals one-degree on the pulley. If you have the TDC mark on the pulley you can then measure from it to make the others mark you want on the pulley. As long as you have a TDC mark you don't need any other marks with an adjustable timing light.

With the head off and the #1 piston at TDC temporarily mark the pulley and pointer. Do not rotate the engine backwards to line it up, if you pass TDC go around again and carefully stop at TDC and make your mark. Rotate the engine a full turn in the opposite direction and stop at TDC and make another mark. True TDC will be in-between the two marks. Make your permanent mark there. That comes for the instruction in a vintage Isky catalog. If you do this, you will find there will be a small space between the two marks. You can't mark the pulley with TDC any more accurate than this.

If you know the direction a distributer rotates, just remember if you move the breaker plate in the opposite direction of distributer rotation you will be advancing the timing, the points will open earlier. Same with rotating a late model distributer. A Flathead Ford is the only V8 engine I know of where the furthest forward cylinder is not #1. Every other V8 I ever worked on the furthest forward cylinder was always #1. If you assumed that on a flathead, you would be wrong.

Thats the exact method I did use to find TDC. As above. And hence the only mark required with the adjustable timing light.
Phil NZ

 

[Bored&Stroked]

Most of our driving is at light loads, so relatively high vacuum. So the vacuum brake is away from the plate. How will it eliminate any "flutter"?

Obviously when the piston is being pulled back, there is nothing dragging on the mechanical advance rotation plate, but when you're under load it isn't a bad idea to have the timing as steady as possible - so a bit of rubbing isn't a bad idea.

It is probably more of an issue when you're on/off the throttle in more of a racing situation. On my distributor machine I tend to see a steadier strobe with just a bit of pressure.

To each his own . . .

 

[Bored&Stroked]

To add to 'Flathead Fevers' post: If you want really accurate TDC markings, use the "dead stop" method - instead of a dial indicator. With the head off, I just take a short 7/16" coarse bolt and a big heavy washer and bolt it down so the washer extends into the bore. Then rotate the engine one direction until you hit the stop (put a temp mark on the pulley), then rotate it backwards until you hit the stop again (put a temp mark on the pulley) - TDC will be right in the middle of those two stop markings.

When a crankshaft is at the full top or bottom of the stroke, there are a couple degrees of rotation where the dial indicator almost doesn't move (at least much). This makes it hard to know exactly where TDC is. A dead stop takes this issue of peak stroke dwell out of the mix.

 

[cadillac512]

To add to 'Flathead Fevers' post: If you want really accurate TDC markings, use the "dead stop" method - instead of a dial indicator. With the head off, I just take a short 7/16" coarse bolt and a big heavy washer and bolt it down so the washer extends into the bore. Then rotate the engine one direction until you hit the stop (put a temp mark on the pulley), then rotate it backwards until you hit the stop again (put a temp mark on the pulley) - TDC will be right in the middle of those two stop markings.

When a crankshaft is at the full top or bottom of the stroke, there are a couple degrees of rotation where the dial indicator almost doesn't move (at least much). This makes it hard to know exactly where TDC is. A dead stop takes this issue of peak stroke dwell out of the mix.

^^^^^^^ This is the absolute accurate way^^^^^^^^


Terry