I recently purchased a 1970 40 with a SBC that is in serious need of a tune up. Unfortunately all the PO could tell me about the engine was that it was a 327 and that it was rebuilt about ten years ago- he had no idea what it came out of or even it was still in stock configuration. At this point I have no idea where to set the timing, and was hoping that someone could give me a procedure for figuring out the correct timing on this thing.
Determining correct timing for a SBC (1 Viewer)
- Thread starter belaw
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inkpot
SILVER Star
Howdy! Start around 8 degrees advanced, with the vacuum line removed from the dizzy and block it. Check for a stamped number on the front of the heads to find the origin of the motor. John
1 degree for ever 1000 feet above above sea level or something like that.
i just turn mine until it idles good and doent backfire when i rev it high and let it go back to idle,
if you have a good ear you can tell when you hit the sweet spot yes start around 7 or 8 ish and go from there. replace your plugs and wires too
i just turn mine until it idles good and doent backfire when i rev it high and let it go back to idle,
if you have a good ear you can tell when you hit the sweet spot yes start around 7 or 8 ish and go from there. replace your plugs and wires too
I agree with timeing by ear much better with worn engine.
- Thread starter
- #6
Well that explains a lot. I'm in South Louisiana, just a few feet above sea level, and my truck came from the Colorado high country. I've already re-jetted the carb, but it's still running rough as a corn cob.
I think timing by ear may be the way for me to go since I don't know much about the specs or wear on this engine.
Thanks for all the input, guys.
You can advance the timing until the engine speeds up and smooths out, reset the idle and take it for a test drive. Get the rig rolling in 1st gear, shift into 3rd and floor it. If it pings retard the timing a little. Repeat until there is no pinging.
Also, while you're under the hood, I'd check that the firing order is correct. You'd be suprised at how often plug wires get crossed during assembly and tune ups. Firing order should be 1-8-4-3-6-5-7-2 for a small block Chevy.
Also, while you're under the hood, I'd check that the firing order is correct. You'd be suprised at how often plug wires get crossed during assembly and tune ups. Firing order should be 1-8-4-3-6-5-7-2 for a small block Chevy.
That depends. Altitude allows for timing to be set a little higher so if it was set correctly in CO it should be pinging now that you're at sea-level. Running "rough" as you describe does not sound like the timing is high.
