VCCA Home Forums TECHNICAL - 1945 AND NEWER 1971-1979 396 ignition timing

A friend of mine has a 396 in a street rod. The problem we have is that none of the specification books down under that I can find list it therefore I dont know what ignition timing it should be set at.
I have set it by ear and checked with light at 10 degrees but would prefer to know the correct timing light setting for future reference.
Thank you in advance
Tony

My books show that the 1967 thru 1969 Chevrolet 396 has a timing of 4 degrees BTDC. Hope this helps!

4° BTDC is the factory setting, but may not be the optimal setting for performance, especially for a street rod where you might be using different carb(s), cam, etc. The Engineers usually pick a timing point that winds up being a "one size fits all" setting, but might not be the best for your particular motor or needs.

I would set the initial timing at 4° BTDC (with no vacuum advance)to start with and then advance it 2° and take it for a run and see if you hear any spark knocking under load. If not, advance it 2° at a time (no pun intended) until it starts knocking under acceleration and then back it off 1° or 2° from there. That will be your intial timing, which may vary due to ambient temperature, gas octane rating, etc.

Besides initial timing, you'll also want to check the total advance, vacuum & mechanical (centrifugal) advance (the "curve"), to see where it starts to advance (RPM), when it advances fully and how much it advances (degrees). You might want to take the distributor to someone that has a machine to check the distributor curve which would save a lot of time and guess work.

-Bob

I thank you all for your replies. By what you say I probably have it too far then at 10 degrees but it is running nicely at that around the block (1/4 mile total). So I will retard it slightly and when we can give it a good run do some more guesswork while we are at it.
As I am not practiced in big blocks with blowers discretion better (and cheaper) part of valor to check on specs before doing damage especially when it is not my motor.

Tonyw: If it's not pinging under acceleration at 10° BTDC, don't worry about it. I've got my 401 Buick at 14° BTDC and it runs very strongly. You want it advanced as much as possible, until it pings, for best performance.

-Bob

Being in town and unregistered we cannot give it a good run let alone open the throttle at this stage. The short run we have given it there was no ping or rattle upto about 40 kph (idle).
It needs to be inspected by a specialist engineer that is registered with tha appropriate bodies before registration and the closest is 200k (120mile) away. We can drive it there but we also dont want it to have a expensive spell on the way.

CAN ANYONE HELP ME WITH A VINTAGE INTAKE QUESTION?

I guess it depends what the question is-give us a try