Timing for a stock 69 302 - Team Camaro Tech
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post #1 of 6 (permalink) Old Aug 3rd, 03, 12:45 PM Thread Starter
 
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Any ideas on the best timing settings these days for a stock '69 302 setup (480 dist., DZ 4053 carb, 186 heads with 11.0:1 C.R., 472 intake, 30-30 cam, A.I.R. pump system, etc.) running 96 octane, so it will idle properly at 900 RPM and have no detonation and have good power at wide open throttle at freeway speeds?

The manual indicates initial advance:
4 BTDC @ 900

centrifugal advance:
0 @ 1250
22 @ 2200
32 @ 4400

vacuum advance:
0 @ 8" Hg
15 @ 15" Hg

and point dwell:
28-32

I think that some of those numbers are proabably a bit outdated at this point. My gut feeling is that the inital advance should be at least 10 BTDC.

Any thoughts and experiences on what setting at various RPMs work well would be appreicated.
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post #2 of 6 (permalink) Old Aug 3rd, 03, 01:48 PM
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Mark
 
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You would need to pull some of the centrifugal advance out of the distributor. If you reduce the travel inside the autocam plate by about 1/3, you are in the ballpark. It has 32 degrees in it from the factory but you want more like 22. The centrifugal curve needs to start around 1200 RPM or so and be all in by around 3000. It should not be "idling on the curve" [img]smile.gif[/img] Mix and match advance springs starting very light and moving to heavyer ones until the WOT ping goes away. Keep the GM weights as they are preferred over speed shop cheapies. In order to do these modifications, you might want to use the guts from another distributor core in your correct housing. Save the original pieces for the museum. I would!

38 degrees as a sum of initial plus all the centrifugal is about right but if it pings at WOT, you need to back off to 36 or so. Let the initial fall where it may but I bet 12-16 would work well. This is realy dependant on how much advance you take out of the centrifugal.

Use manifold vacuum to the canister and be sure to use a VC-1810 can from NAPA. Looks stock and costs less than $10. It was originaly used on pre-emission SHP 327 fuelie Vettes and it works very well hooked up to the manifold with big cams and low idle vacuum.

If you keep the vacuum advance hooked up to the ported tap on the carb you could keep the stock canister if you wish. It will run cooler/smoother at idle if you do change the can and hookup location though.

-Mark.
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post #3 of 6 (permalink) Old Aug 16th, 03, 10:45 AM Thread Starter
 
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Thanks for the info. The initial advance is now set to 14 degrees and the centrifugal advance is 22 for a total of 36 at wide open throttle, and total advance at cruise is 50.

The engine idles perfectly and there is no detonation at cruise or at wide open throttle. It runs great.

The only problem is now that the initial timing is advanced so far, when the engine is hot, it is hard to crank. It does start because it doesn't take much to fire, but it seems like the starter motor is really under a lot of stress. It cranked fine when hot with 4 degress initial advance.

Any suggestions? Should I back off the initial timing advance, say, by 4 degrees, and increase the centrifugal by 4?
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post #4 of 6 (permalink) Old Aug 16th, 03, 07:29 PM
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Denis
 
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Do you have headers on the car? Perhaps a shield for the starter or a new starter might be in order. Also make sure choke is fully open.

Timing seems to be right on the money.
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post #5 of 6 (permalink) Old Aug 16th, 03, 09:35 PM
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Mark
 
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If you want to reduce the initial for easy cranking, you can add a few degrees to the centrifugal and take a few out of the initial by widening up the autocam advance slot slightly. I have mine set for 16 initial and she starts up fine(as long as she cranks)

If you can get that NAPA advance canister I mentioned earlier and hook it up to the intake vacuum it would give you much more advance at idle using less initial. You have the best of both worlds that way. Lower initial for cranking and higher initial once she fires up. That will realy help smooth out the idle and reduce temperatures while idling with that setup. You will need to re-set the carb mixture screws and idle speed screw when you do this as the RPM's will realy pick up once you hook up the canister to the vacuum signal.

You can't use the factory can hooked up that way as it will cause the idle to fluctuate. The factory can does not pull "in" all the way at the roughly 9" of idle vacuum so the timing will bounce around as the vacuum bounces around . The NAPA can will be fully "in" at the low idle vacuum produced by the "30-30" cam so the RPM's will hold steady. This is how I have mine set up.

P.S. - If you are using stock style stamped steel rockers, you need to set the valves at .026" cold. The .030" spec was based on "theoretical" 1.5 ratio rockers but the factory pieces will check out at about 1.33 ratio so the original spec has been wrong for close to 40 years . This is where all that valvetrain "noise" is coming from. It's your valves beating down on the seats at full lift ramp velocity and causing valve recession.

If you would like the long version of the valve setting technique and explanation, just ask. I have it saved to my hard drive in case it comes up. [img]smile.gif[/img]

-Mark.

[ 08-17-2003, 12:50 AM: Message edited by: stingr69 ]
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post #6 of 6 (permalink) Old Aug 17th, 03, 04:30 PM
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Denis
 
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Mark gives good advice...
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