Sorry.. lots of questions here.. 
I was talking to a friend who knows a lot about engines about a 1 second hesitation I have under hard acceleration. I was talking to him about how I have tried all kinds of accelerator pump cams and discharged nozzles and didn't notice a change either way. Its a vac secondary holley 600 cfm carb and it does it just as bad with the stiffest secondary spring as it does with the lightest so I don't think its the secondaries falling open. My friend suggested to plug my vac adv on my distributor since my engine been slightly modified and he said he never liked vac adv and always ran mechanical. Anyways that got me thinking about things and have some questions.
My friend is leaning towards a ignition advance/timing issue.. I told him I wasn't so sure about it that but it got me thinking anyways. He said switching to mechanical fixed it on his.
I'm referring to a stock 69 302 vac adv distributor with the pertronix-1 points conversion, it has a crane energizer 260 cam, performer rpm heads and intake with headers.
1)
Can someone explain how the total advance is calculated and how to physically measure it? My understanding is total timing = initial plus mechanical plus vac adv.
Do I just shine the timing light down there and see how far it goes? Then make note of the RPM at which it stops advancing? Since its vac adv, can this be done without a load (in neutral)?
2)
I know centrifugal will advance and the rate the engine speed increases. What keep the vac adv from throwing in too much timing too soon? I had someone tell me that the mechanical adv will ultimately limit the vacuum adv.
Also, does the vacuum advance add to the total amount of timing or does it supplement the centrifugal? In other words, will my total timing be the same, however it just would take longer to advance since the vacuum isnt there to help it out? Or will I get a decrease in the total timing if I plug the vac adv?
3)
What is the benefit between having a vac adv? I've seen people suggest using only a mechanical for more power/racing and read that a vac adv is better for street. Why is this? I thought the vac adv was to improve throttle response?
4)
I'm thinking about plugging it temporarily just to see what it does. If i do, should I increase my initial timing?
If I remember correctly from about a year ago when I had my distributor out.. I saw 2 parts of the distributor...not sure what you would call them.. but I believe they both had 13 stamped into them. From what I read these are the pieces that control the total advance.. 1 for the mechanical and 1 for the vacuum. Is this right? so with a 10* initial, 13 is added by mechanical and another 13 by the vacuum for a total of 36*?
I was talking to a friend who knows a lot about engines about a 1 second hesitation I have under hard acceleration. I was talking to him about how I have tried all kinds of accelerator pump cams and discharged nozzles and didn't notice a change either way. Its a vac secondary holley 600 cfm carb and it does it just as bad with the stiffest secondary spring as it does with the lightest so I don't think its the secondaries falling open. My friend suggested to plug my vac adv on my distributor since my engine been slightly modified and he said he never liked vac adv and always ran mechanical. Anyways that got me thinking about things and have some questions.
My friend is leaning towards a ignition advance/timing issue.. I told him I wasn't so sure about it that but it got me thinking anyways. He said switching to mechanical fixed it on his.
I'm referring to a stock 69 302 vac adv distributor with the pertronix-1 points conversion, it has a crane energizer 260 cam, performer rpm heads and intake with headers.
1)
Can someone explain how the total advance is calculated and how to physically measure it? My understanding is total timing = initial plus mechanical plus vac adv.
Do I just shine the timing light down there and see how far it goes? Then make note of the RPM at which it stops advancing? Since its vac adv, can this be done without a load (in neutral)?
2)
I know centrifugal will advance and the rate the engine speed increases. What keep the vac adv from throwing in too much timing too soon? I had someone tell me that the mechanical adv will ultimately limit the vacuum adv.
Also, does the vacuum advance add to the total amount of timing or does it supplement the centrifugal? In other words, will my total timing be the same, however it just would take longer to advance since the vacuum isnt there to help it out? Or will I get a decrease in the total timing if I plug the vac adv?
3)
What is the benefit between having a vac adv? I've seen people suggest using only a mechanical for more power/racing and read that a vac adv is better for street. Why is this? I thought the vac adv was to improve throttle response?
4)
I'm thinking about plugging it temporarily just to see what it does. If i do, should I increase my initial timing?
If I remember correctly from about a year ago when I had my distributor out.. I saw 2 parts of the distributor...not sure what you would call them.. but I believe they both had 13 stamped into them. From what I read these are the pieces that control the total advance.. 1 for the mechanical and 1 for the vacuum. Is this right? so with a 10* initial, 13 is added by mechanical and another 13 by the vacuum for a total of 36*?
