Proper ignition timing?

[chiggins]

So here's some background info: (I'm not at all experienced here so bear with me) truck has got a frankensteined 307 in it, year unknown but I'm guessing its about a '71. I installed a mild summit truck cam and swapped some heads off of a mid 90's tbi 350. The cam specs are Duration 278/288, Lift .421/.444, and the different heads brought the compression to about 9.8:1 I believe. it has a brand new HEI system and a 600 cfm edelbrock
So with this info in mind, where would someone advise to have the timing set at? turns out when I set it, I put it at about 24 degrees base timing, which I know is too high, but the truck was running fine. Problem is, theres a slight ping at higher rpm's when running just 87 octane fuel, and no noticable ping when running 93. But then dropping it back down to 16 degrees like a typical engine should have it's a total dog. Would setting it to about 20 be a decent idea? do I have to accept the fact that having a near 10:1 compression simply isn't driveable without higher octane?

[aerotest]

It shouldn’t be a dog at 16. Something is wrong. Are you sure you have the right balancer and timing marker on the engine? 16 may not be actually 16.

[chiggins]

That's just based on the timing marker that was already on the block and a cheap nonadjustable timing light. We unfortunately don't have a ticker tape on the harmonic balancer either. I believe the balancer and marker are stock but after seeing the other things previous owners have done to the truck there's really no telling. I'm just wondering if having the higher compression requires a further advance and if having it at about 20 is acceptable. Like I said, the engine ran great on 93 at the 24ish degree setting, but we noticed the ping running 87 after letting off the throttle

[geezer#99]

What rpm are you checking your timing at?

[Getter-Done]

Sounds like you got your low number and high number that is allowed for that engine down to a few degrees.
As long as you are able to check the timing and you are not running this in 1/8 mile Drag race for money
My suggestion would be to fine tune your high or low timing with this kit in the link below.

https://www.summitracing.com/parts/s...ing-_-srese2-_

[aerotest]

That engine shouldn’t require 24 degrees of advance at idle. Cylinder head chamber design is the primary factor there and you don’t have anything out of the norm. Do you have the vacuum advance hooked up?

[davepl]

288 degrees of duration and 307 cubic inches of displacement?

What's your cranking compression, any idea? I'm guessing it not great...

If it were me, I'd put a cam with more like 210 degrees of duration max in that. Then 12 degrees of timing and drive it until they ban it.

Also you don't sound very confident about your compression ratio. Could it be way low and you just don't know it? Lots of cam and no compression is going to require a monster amount of igniton lead to keep it running.

[68 P.O.S.]

Read the following links. They're written by a GM engineer and will tell you more than you probably want to know about timing and vacuum advance. Are those heads you're running Vortecs? Vortecs require a little less timing because of the efficient chamber design.

http://67-72chevytrucks.com/vboard/s...d.php?t=274806
http://www.camaros.org/pdf/timing101.pdf

Edelbrock carbs are finicky with fuel pressure and have a tendency to flood at pressures higher than 6 psi. You're going to need a pressure regulator set to 5 psi to keep it from flooding. Also, Edelbrock carbs tend to carb boil as the engine heats up so you'll need a heat insulator gasket as well.

I agree with Dave, your compression may be too low and you cam may not be the best size either.