Q&A / Tech

Monday Mailbag: Talking Timing for Small Block Chevy V8s

 

Got questions?

We’ve got the answers—Mondays when the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re answering questions about timing for small block Chevy engines.

W.H . • Temple, TX
Q: Which way do you turn the distributor on a small block Chevy to advance the timing? We’re having a family debateI say one way, and my boys say the opposite! Also, I believe advancing the timing on a carbureted engine (without a choke) will help it start easier on cold mornings. The boys disagree saying the spark should be retarded. And, if the engine backfires through the carb under acceleration (only when cold), is the timing excessively advanced or retarded? Finally, I think you should be able to install a distributor 180 degrees out of sync, and my sons don’t believe the engine will start, let alone run this way. How would you even know if it was installed 180 degrees out of sync?

A: Chevy distributors rotate clockwise, so you’d want to turn the distributor counterclockwise to advance the timing. Advancing timing to aid in cold starting will only help if the timing was retarded to begin with. Retarding the timing can help the starter turn a hot engine but that’s about it, so excessive timing one way or the other is not the answer.

Generally, advanced timing (up to the point of detonation) will make the engine run cooler. A vacuum advance that’s connected to the manifold vacuum rather than the ported vacuum can also reduce the engine’s operating temperature at idle. Not utilizing the vacuum advance can make an engine run excessively hot at any throttle position other than wide open.

When a cold engine backfires through the carburetor, it’s most likely an indication that your air/fuel mixture is too lean, not excessive timing.

If the the distributor is installed 180 degrees out of sync, the spark will occur during the exhaust stroke, so the engine won’t start, plus it’ll backfire out of the exhaust and possibly out of the carburetor as the intake valves open. If the rotor points to the #1 cylinder post, and the cam-gear alignment mark is at 6 o’clock, the distributor is 180 degrees out of sync with the crank. When the distributor is properly installed, the cam-gear alignment mark will be at 12 o’clock when the rotor points at the #1 cylinder post (you can use any of the eight posts for #1the distributor won’t know the difference.)

 

 

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4 Comments

  1. Good info but not completely true. I have experienced and engine with timing 180 out. It will run. Just not like it should. I bought a truck with a 305 and after fighting with it trying to figure out why it ran like crap I figured out they had it timed 180 out lol.

    • I also have a 305 chevy silveradodoing same thing backfiring and then not wanting to turn on havevto hold gas to keep on could it also be 180

  2. Zeppo Jaworski says:

    Why do we have to read stuff like this. It is completely accurate to say neither the letter writer nor the guy who left the comment about an engine running when it was 180 degrees out should be working on engines.

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