# Timing - Advance Curve & Vacuum Advance



## PontiacJim (Dec 29, 2012)

Two good video's you can watch that has great info and hands-on explanations.

How To Re-Curve A Distributor, And Why! 24 minute video

How Vacuum Advances Work 12 minute video


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## Lemans guy (Oct 14, 2014)

Good video’s thanks PJ, .......a lot done by feel, he is a pro, but I have found that when you use two very light springs it often brings the centrifugal advance in on top of the base timing at idle. 

#so trying to get all in at 2500 and above idle timing is often not easy. Some cars can take all in at 2500, I have curved Corvettes that way, they like it, but others will ping on acceleration as too much timing is in early.

I think you get better street performance by sticking with Lars formula. And using 10 degrees vac advance from manifold vacumn, that easily gives you great timing on acceleration, without having the Centrifigal so low....

Real light springs can cause that detonation. He likes adjustable vac cans, they can work but I prefer the can limited to 10 Degrees positively by a stop, like Lars sells or a can limited to 10 degrees.

Driving a street performance car without vac advance will be giving up quite a bit, cooling, strong running .....early and at cruise.

But whatever you do check the numbers on your car with a timing light.....And don’t set your springs first nail down that centrifugal first so you know what your base and total will be. Springs I do last,...28 to 3800 RPM will be a strong runner, usually with no pinging or covering over the idle with centrifigal timing.


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## PontiacJim (Dec 29, 2012)

Thought you might like it. I am on board with timing adjustments being more individual. I think 2,500 all-in on the timing is too much and even 36 degrees total is a bit much - neither of which are absolutes for our Pontiac engines. He is more of a Chevy/Ford builder and uses these engines/parts in his demonstration videos. He explains things pretty well and uses examples that you can "see." :thumbsup:


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## 65sohc (Aug 13, 2019)

I cringed when I saw him bolt the rotor back on with all those metal shavings still stuck to the reluctor.


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## GTO44 (Apr 11, 2016)

Im used to working on and tuning modified cars so all books and forumlas go out the window. Cars are tuned by what the motor likes the best. Always pull plugs and see what the motor is really doing. Compression, aluminum heads vs cast iron, weight of the car, rear gearing, auto vs stick, amount of fueling... all factors that will determine the timing curve. I’ve got a ‘77 trans am with a pontiac 400 motor with such low compression i have 44degree’s of total timing and it could probably take a little more.

I will agree the one rule that will always be there is get the timing all in as soon as you can for any particular setup. However, that will be different on every application.


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