engine's first run

[Clem Z.]

Re: engine's first run

calculate the circumference of the balancer,divide this number by 10,then using a tape measure mark the balancer on the advance side of the TDC line. this will give you 36 degrees. now without the vacuum advance connected rev the engine till the timing mark stops moving,then move the distributor to set the new scribed line even with the "0" mark on the timing tab. removing one spring from the distributor advance will allow you to only have to rev the engine to about 1/2 the RPM to get full advance.

[Clem Z.]

Re: engine's first run

calculate the circumference of the balancer,divide this number by 10,then using a tape measure mark the balancer on the advance side of the TDC line. this will give you 36 degrees. now without the vacuum advance connected rev the engine till the timing mark stops moving,then move the distributor to set the new scribed line even with the "0" mark on the timing tab. removing one spring from the distributor advance will allow you to only have to rev the engine to about 1/2 the RPM to get full advance.

[robert leazenby]

Re: engine's first run

Clem,

After setting the total mechanical advance as you instructed, what affect will connecting the vacuum have. Will I then have too much advance or will it be correct for the given rpm?

My first guess was that I did not have enough advance and what Duke stated makes perfect sense. I knew it was not correct to set timing with vacuum hooked up, but I simply hooked things up during installation and forgot to dis-connect. Lost my focus and wanted to hear the puurrrr.

By the way, it sounded great.

[robert leazenby]

Re: engine's first run

Clem,

After setting the total mechanical advance as you instructed, what affect will connecting the vacuum have. Will I then have too much advance or will it be correct for the given rpm?

My first guess was that I did not have enough advance and what Duke stated makes perfect sense. I knew it was not correct to set timing with vacuum hooked up, but I simply hooked things up during installation and forgot to dis-connect. Lost my focus and wanted to hear the puurrrr.

By the way, it sounded great.

[Clem Z.]

Re: engine's first run

you should be OK,just remember to reinstall the spring and connect up the vacuum advance

[Clem Z.]

Re: engine's first run

you should be OK,just remember to reinstall the spring and connect up the vacuum advance

[Duke W.]

Re: engine's first run

The vacuum advance is there because lean, low density mixtures have a slower flame propagation speed and need more advance. It provides smoother operation at idle and part throttle, reduces EGT and heat rejection to the water jacket , and improves fuel economy.

The "WOT advance curve" is the initial plus centrifugal, which should total about 36 to 38 degrees on a high performance SB. You want to get it all in as soon as possible, but detonation can be a the limiting factor.

The best distributor set up for a high perf. SB (either factory or built by the user) is the late '64 to '65 SHP/FI engines. The centrifugal was 24 degrees and all in by 2350, and the initial was recommended as a range of 10 to 14. If you can run this aggressive a WOT curve you will have the best torque bandwidth, but you might have to cut back on total advance if you have high speed detonation or slow the centrifugal is you have low speed detonation, OR increase fuel octane rating.

These distributors used a vacuum can that started at 4" and maxed out at 16 degrees at 8", and this can should be used on all SHP engines and communciate directly with manifold vacuum.

The distributor in my '63 SHP is set up this way, and when cruising at 2500 revs the advance is 14 + 24 + 16 = 54 degrees, but at WOT it is only 38 becasue there is no contribution from the vacuum advance at WOT.

In testing timing, you should test the intial and total WOT timing. The vacuum can should be tested separately to be sure it is in spec. Usually if it holds vacuum it is okay. Another way to test vacuum is to disconnect it, set the intial at zero at as low a speed as the engine will run, then connect the can as see how far the timing advances. RPM will increase too, so be sure it doesn't increase enough to start the centrifugal. You should test for when the centrifugal starts and make a note of it timing checks and analysis. You also want to be sure that the vacuum can provides full vacuum advance at a vacuum level that is at least a couple of inches less than your idle vacuum, and since the maximum advance on the above referenced can is all in by 8" this will ensure that it's all in with any factory high performance cam, but you should check to see what you have with your setup. With the timing set correctly and the vacuum can connected a SB with the LT-1 cam should pull about 12" at 900 to 1000 RPM.

A lot of guys soup up their engines with cam ,carb, heads, etc., but never give a though to retuning the distributor to match the engine characteristics. Big mistake, as you will never obtain the best and full benefit or your performance modifications unless the distributor is set up properly.

Duke

[Duke W.]

Re: engine's first run

The vacuum advance is there because lean, low density mixtures have a slower flame propagation speed and need more advance. It provides smoother operation at idle and part throttle, reduces EGT and heat rejection to the water jacket , and improves fuel economy.

The "WOT advance curve" is the initial plus centrifugal, which should total about 36 to 38 degrees on a high performance SB. You want to get it all in as soon as possible, but detonation can be a the limiting factor.

The best distributor set up for a high perf. SB (either factory or built by the user) is the late '64 to '65 SHP/FI engines. The centrifugal was 24 degrees and all in by 2350, and the initial was recommended as a range of 10 to 14. If you can run this aggressive a WOT curve you will have the best torque bandwidth, but you might have to cut back on total advance if you have high speed detonation or slow the centrifugal is you have low speed detonation, OR increase fuel octane rating.

These distributors used a vacuum can that started at 4" and maxed out at 16 degrees at 8", and this can should be used on all SHP engines and communciate directly with manifold vacuum.

The distributor in my '63 SHP is set up this way, and when cruising at 2500 revs the advance is 14 + 24 + 16 = 54 degrees, but at WOT it is only 38 becasue there is no contribution from the vacuum advance at WOT.

In testing timing, you should test the intial and total WOT timing. The vacuum can should be tested separately to be sure it is in spec. Usually if it holds vacuum it is okay. Another way to test vacuum is to disconnect it, set the intial at zero at as low a speed as the engine will run, then connect the can as see how far the timing advances. RPM will increase too, so be sure it doesn't increase enough to start the centrifugal. You should test for when the centrifugal starts and make a note of it timing checks and analysis. You also want to be sure that the vacuum can provides full vacuum advance at a vacuum level that is at least a couple of inches less than your idle vacuum, and since the maximum advance on the above referenced can is all in by 8" this will ensure that it's all in with any factory high performance cam, but you should check to see what you have with your setup. With the timing set correctly and the vacuum can connected a SB with the LT-1 cam should pull about 12" at 900 to 1000 RPM.

A lot of guys soup up their engines with cam ,carb, heads, etc., but never give a though to retuning the distributor to match the engine characteristics. Big mistake, as you will never obtain the best and full benefit or your performance modifications unless the distributor is set up properly.

Duke

[robert leazenby]

Re: engine's first run

I have a buddy with a Sun distributor mamachine in his garage. I think I will hit him up this weekend to spec out my centrifugal and vacuum. During the same time I want to shim the distrubutor drive gear. It is pretty sloppy. Any suggestions on clearance. It is the TI distributor.

This is great information that I recevied from you guys and I appreciate it. I recently joined the NCRS mainly due to the help I've recieved from this site.

[robert leazenby]

Re: engine's first run

I have a buddy with a Sun distributor mamachine in his garage. I think I will hit him up this weekend to spec out my centrifugal and vacuum. During the same time I want to shim the distrubutor drive gear. It is pretty sloppy. Any suggestions on clearance. It is the TI distributor.

This is great information that I recevied from you guys and I appreciate it. I recently joined the NCRS mainly due to the help I've recieved from this site.

[Duke W.]

Re: engine's first run

I recommend following the two to eight thou end play spec for point distributors. GM used to sell six and thirty thou shims to meet this spec.

Specing your distributor out on a machine is a good way to go. Then you can set it up properly for your engine configuration.

Duke

[Duke W.]

Re: engine's first run

I recommend following the two to eight thou end play spec for point distributors. GM used to sell six and thirty thou shims to meet this spec.

Specing your distributor out on a machine is a good way to go. Then you can set it up properly for your engine configuration.

Duke

[Chas Kingston]

[Chas Kingston]

[Terry M.]

Distributor shims *TL*

To the best of my knowledge, only the .030 shims are currently available.