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Old 12-13-2007, 09:27 AM
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Chevy 383 Stroker timing

I just built a 383 stroker for my truck. Engine fired right up, and runs great. I just want to see if anyone has any suggestions for optimal ignition timing on one of these bad boys. Here's the specs.
Hydraulic flat tappet cam and lifters
Duration at 0.006" Lift: Intake: 308 Exhaust: 318
Duration at 0.050" Lift: Intake: 234 Exhaust: 244
Lift at Cam: Intake: 0.325" Exhaust: 0.340"
Lift at Valve: Intake: 0.488" Exhaust: 0.510"
Timing at 0.050" lift: Open Close
Intake: 10 BTDC 44 ABDC
Exhaust: 59 BBDC 5 ATDC
Centerlines: Lobe Separation - 112 Intake Centerline - 107
Stock Ratio Roller Rockers 1.5
Edelbrock Aluminum Heads
64cc 170cc 2.02"/1.60"
Di****op forged aluminum pistons
Eagle rotating assembly
Edelbrock aluminum RPM air-gap intake manifold.
Stock style HEI coil-in-cap modified distributor.
Still has a rochester quadrajet carb on it, but it runs great with that
Right now it's running at 28 degrees BTDC static with the vacuum disconnected at 1000 RPMS.
It seems to like that, but it seems like an aweful lot of timing for what I'm used to. I'm a little nervous about that, but if I retard it much more, it tends to get really-really hot! If I advance it any more, it labors pretty good at Idle. Does anyone have a way to calculate an good base timing with those specs? I'd really appreciate it. Thanks to all, and happy gearheading!

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Old 12-13-2007, 10:42 AM
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Quote:
Originally Posted by Hotrodder78
Stock style HEI coil-in-cap modified distributor.
Still has a rochester quadrajet carb on it, but it runs great with that
Right now it's running at 28 degrees BTDC static with the vacuum disconnected at 1000 RPMS.
The stock GM HEI distributor has 20 degrees of built in mechanical advance.

Your 28 degrees BTDC at 1000 RPM more than likely has got the initial and some mechanical advance together because of the RPM.

With the engine fully warmed up and the choke fully open, dis-connect and plug the vacuum advance hose from the distributor. Bring the engine RPM up to 2500-3000 RPM. Assuming that the centrifugal advance weights and springs have reached the maximum mechanical advance at the above RPM range (this can be adjusted by lighter or heavier combination of springs), set the timing at 32-38 degrees. Do not exceed 40 degrees. What you are looking for is the maximum amount of timing with no pinging. At this point you can check the idle timing and just leave it at whatever shows up. Remember that because the idle RPM is above 800 that some mechanical advance will be added to the actual initial timing. Re-connect the vacuum advance hose. If connected to the full vacuum source the idle will go up as well as the timing. Leave the timing as is and lower the idle RPM to whatever you like. Even with your combo you should be able to get the idle in the 650-750 RPM range if the carb is adjusted correctly.
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Old 03-15-2009, 08:09 PM
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i have the same problem, but my hesitates and backfires at the correct 12 degrees timing.
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Old 03-15-2009, 11:02 PM
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did you change your damper and/or timing pointer ?? . If so, maybe your reading is off. Weights should not be active at 1k. I wouldnt think you would need no more than 18 initial with your combo.
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Old 03-15-2009, 11:15 PM
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the engine is set perfect as far as tdc , tdc on crank is 0 on the timing tape which is 0 on the timing tab.
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