Small block points question
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Instructor
Joined: Sep 2002
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From: Marysville WA
Small block points question
I'm getting ready to start a fresh 327. I brought up #1 piston to TDC. The rotor and cap clips are pointing correctly as shown in my 66 motor manual and the distributor is down all the way on the block. Usually that is all I check except for proper spark plug wire location. Because the body is off I can see pretty well what is going on with the points and I see that the point opening wiper is right in the middle between cam lobes. The swing of the dist. for timing is not very much before it hits the coil or the intake and it doesn't seem to have enough adjustment to break the points. In a perfect world, what should I be seeing in there as far as the location of the cam wiper?
Thanks for any tips, Bill
Thanks for any tips, Bill
Le Mans Master
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There is insurmountable data and points of interest in the archives on this very topic. I would try a search function, using Distributor, Points, Timing, Etc for search topics.
First thing to ensure is that the stake dimple on the distributor drive gear is pointing in the same direction as the rotor firing tab. There is no written literature addressing this issue, as far as the old shop manuals are concearned, but the dist. drive gear orientation is critical to obtain the degree of “swing” necessary to get the correct timing with the correct cap and wire orientation.
Back to the question at hand, to get a good initial timing set, find TDC and then rotate the engine to (for academic purposes say) 8* BTDC. Then align the number 1 cap tower to the rotor firing tab, do this by placing the cap on the dist. and moving the dist. to get the alignment. I mark the dist base, then use that to orientate the number 1 tower. Then check to see what the points are doing.
Mark
First thing to ensure is that the stake dimple on the distributor drive gear is pointing in the same direction as the rotor firing tab. There is no written literature addressing this issue, as far as the old shop manuals are concearned, but the dist. drive gear orientation is critical to obtain the degree of “swing” necessary to get the correct timing with the correct cap and wire orientation.
Back to the question at hand, to get a good initial timing set, find TDC and then rotate the engine to (for academic purposes say) 8* BTDC. Then align the number 1 cap tower to the rotor firing tab, do this by placing the cap on the dist. and moving the dist. to get the alignment. I mark the dist base, then use that to orientate the number 1 tower. Then check to see what the points are doing.
Mark
Last edited by ghostrider20; Sep 6, 2005 at 01:22 AM.
Thread Starter
Instructor
Joined: Sep 2002
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From: Marysville WA
Thanks Mark, I will check the orentation of the dimple. I had the dist. completely apart so who knows........Also I will try for the search. I haven't been too successful with that in the past.
Melting Slicks
Joined: Apr 2005
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Mark,
What is the stake dimple? Where is it? What does it look like?
I have an MSD distributor with a tach drive, can I set this unit up the same as the stock distributor?
I ned to get the vac can in the right place between the iginition shielding and intake manifold.Thanks,
Al
What is the stake dimple? Where is it? What does it look like?
I have an MSD distributor with a tach drive, can I set this unit up the same as the stock distributor?
I ned to get the vac can in the right place between the iginition shielding and intake manifold.Thanks,
Al
Le Mans Master
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The dimple, is located on the helical drive gear, (the drive gear on the bottom of the dist).
This dimple is on the machined surface just below the gear teeth. Around the same area as the set pin. Duke did the math and gear count some time ago and explained why this was necessary.
I am not sure if an MSD dist has the dimple or not.
Mark
This dimple is on the machined surface just below the gear teeth. Around the same area as the set pin. Duke did the math and gear count some time ago and explained why this was necessary.
I am not sure if an MSD dist has the dimple or not.
Mark
Safety Car
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From: St. Joseph Mo
orono64:
After you make sure your dimple and rotor tip are lined up you can set static timing very easily by:
1. Turn crank untill you have balancer mark aligned with desired advance mark on timing tab. Make certain of compression stroke.
2. Install a spare plug wire with spark plug in desired #1 terminal. let the plug lay on intake manifold where you can observe gap.
3. With key switch on, rotate dist housing clockwise well past your #1 terminal. Pop cap to verify and replace cap.
4. Rotate dist housing counter clockwise untill you get a spark at test plug.
5. Repeat 3 & 4 untill you are comfortable of housing position when spark occurs and snug down clamp.
Works on any spark ignition engine. Transistor distributers have to be rotated rather quickly, but it works on them also.
After you make sure your dimple and rotor tip are lined up you can set static timing very easily by:
1. Turn crank untill you have balancer mark aligned with desired advance mark on timing tab. Make certain of compression stroke.
2. Install a spare plug wire with spark plug in desired #1 terminal. let the plug lay on intake manifold where you can observe gap.
3. With key switch on, rotate dist housing clockwise well past your #1 terminal. Pop cap to verify and replace cap.
4. Rotate dist housing counter clockwise untill you get a spark at test plug.
5. Repeat 3 & 4 untill you are comfortable of housing position when spark occurs and snug down clamp.
Works on any spark ignition engine. Transistor distributers have to be rotated rather quickly, but it works on them also.
Le Mans Master
Joined: Jan 2002
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Quote
"Thanks Mark, I will check the orentation of the dimple. I had the dist. completely apart so who knows........Also I will try for the search. I haven't been too successful with that in the past."
Type in the key word in the search box.
Next check the box marked "Archives" at the bottom.
Then Click "C1-C2 section"
You can also search by user name.
Mark
"Thanks Mark, I will check the orentation of the dimple. I had the dist. completely apart so who knows........Also I will try for the search. I haven't been too successful with that in the past."
Type in the key word in the search box.
Next check the box marked "Archives" at the bottom.
Then Click "C1-C2 section"
You can also search by user name.
Mark
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Thread Starter
Instructor
Joined: Sep 2002
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From: Marysville WA
Great info all,
I pulled the dist. to find the dimple in the correct position. so now the question remains.....Timintg mark on 0...rotor directly below the wire to #1 cyl. at the middle of the adjustment swing of the dist. in a perfect world, where should the cam lobe be at this point in relation to the point opening wiper?
I pulled the dist. to find the dimple in the correct position. so now the question remains.....Timintg mark on 0...rotor directly below the wire to #1 cyl. at the middle of the adjustment swing of the dist. in a perfect world, where should the cam lobe be at this point in relation to the point opening wiper?
Team Owner
Joined: Mar 2003
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From: Greenville, Indiana
Originally Posted by orono64
Great info all,
I pulled the dist. to find the dimple in the correct position. so now the question remains.....Timintg mark on 0...rotor directly below the wire to #1 cyl. at the middle of the adjustment swing of the dist. in a perfect world, where should the cam lobe be at this point in relation to the point opening wiper?
I pulled the dist. to find the dimple in the correct position. so now the question remains.....Timintg mark on 0...rotor directly below the wire to #1 cyl. at the middle of the adjustment swing of the dist. in a perfect world, where should the cam lobe be at this point in relation to the point opening wiper?
To specifically answer your question, with the crank timing set on "0" or TDC, the cam lobe on the distributor should not be touching the rubbing block on the points. The coil fires just as the points open. I'd bet you don't want initial timing on "0".
If you're confused, I would suggest you roll the crank around to whatever timing mark your engine requires and then move the distributor to where the points just start to break open, You'll be plenty close enough to get it started.
Last edited by MikeM; Sep 7, 2005 at 09:04 AM.
Thread Starter
Instructor
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From: Marysville WA
Originally Posted by MikeM
To specifically answer your question, with the crank timing set on "0" or TDC, the cam lobe on the distributor should not be touching the rubbing block on the points. The coil fires just as the points open. I'd bet you don't want initial timing on "0".
If you're confused, I would suggest you roll the crank around to whatever timing mark your engine requires and then move the distributor to where the points just start to break open, You'll be plenty close enough to get it started.
If you're confused, I would suggest you roll the crank around to whatever timing mark your engine requires and then move the distributor to where the points just start to break open, You'll be plenty close enough to get it started.
Thanks, the problem I'm seeing is that at 6 degrees advance I'm not getting (I think) enough dist. swing to break the points. Tonight I'm doing the suggested static timing just to see how far off I really am.
Thanks to everyone for your advice.
Team Owner
Joined: Oct 2000
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From: Washington Michigan
Set the balancer index line at your 6* initial timing mark on the timing tab, put a test light across the points, turn the distributor clockwise (as viewed from the top) until the light goes on, then turn it counter-clockwise (slowly) until the light JUST goes out (firing position), and tighten the clamp bolt. Then check it with a timing light - it will be within a degree of where you want it.
If the vacuum can is way off (against the intake or coil) at this point, re-stab the distributor - you're off by one tooth (27* of distributor housing location).
If the vacuum can is way off (against the intake or coil) at this point, re-stab the distributor - you're off by one tooth (27* of distributor housing location).
Last edited by JohnZ; Sep 7, 2005 at 11:46 AM.
Race Director
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If you don't have a test light or ohmeter to determine when the points open, just rotate the dist. housing until you can just see the points begin to open then tweak it back a hair. Using this method I get within 2 degrees of the timing tab value that I set the balancer notch at.
Duke
Duke
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Instructor
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From: Marysville WA
Thanks JohnZ and Duke et al. I think I have enough info now to start my own clinic 
Normally I wouldn't be so picky about this but I had a bad experience starting up my last one and burned two cams in the break in. This was due to a couple valve springs not being fully seated in their counterbore. This time I'm checking everything twice.
Thanks again, Bill
Normally I wouldn't be so picky about this but I had a bad experience starting up my last one and burned two cams in the break in. This was due to a couple valve springs not being fully seated in their counterbore. This time I'm checking everything twice.Thanks again, Bill
Melting Slicks
Joined: Apr 2005
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John,
Why does the dimple have to be in line with the rotor?
I you dont have a dimple what difference does it make?
The aftermarket units like MSD do not line up.
If you install the distributor correctly facing #1 at TDC, what importance does the dimple represent?
Al
Why does the dimple have to be in line with the rotor?
I you dont have a dimple what difference does it make?
The aftermarket units like MSD do not line up.
If you install the distributor correctly facing #1 at TDC, what importance does the dimple represent?
Al
Team Owner
Joined: Oct 2000
Posts: 38,897
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From: Washington Michigan
The Delco Corvette distributor drawings are VERY specific about having the dimple aligned with the rotor tip; the fact that the Corvette distributor is enclosed in the ignition shielding and there is a narrow window of vacuum advance can positioning available between the can hitting the #8 intake runner at one extreme and hitting the coil and plug wire support bracket at the other extreme makes it essential to get the distributor installed correctly. If the distributor is installed one tooth off, the housing will be mis-oriented by 26 degrees, and if the dimple is 180* out relative to the rotor, that will add another 13* of mis-orientation. Doesn't matter that much on non-shielded passenger cars with low-runner cast iron intakes and coils mounted on the driver's side of the intake, but it matters a lot on Corvettes with distributor shielding, coils mounted on the spark plug support bracket, and aluminum intakes with high runner profiles.
Burning Brakes
Joined: Aug 2001
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From: Frederick Md
Originally Posted by babbah
John,
Why does the dimple have to be in line with the rotor?
I you dont have a dimple what difference does it make?
The aftermarket units like MSD do not line up.
If you install the distributor correctly facing #1 at TDC, what importance does the dimple represent?
Al
Why does the dimple have to be in line with the rotor?
I you dont have a dimple what difference does it make?
The aftermarket units like MSD do not line up.
If you install the distributor correctly facing #1 at TDC, what importance does the dimple represent?
Al
What would one do if your gear is junk and you need a new one? They don't have the dimple and I asked this qustion of a number of companies that make the gears, they had no idea what I was talking about.
I've done a lot of reading on early cars and have yet to see anything about this, I wish someone would say "go to this document and you will find the answer" or better yet post it some place.