Ignition timing set at zero degrees?

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May 31, 2010 | 02:10 PM

AT-82Collectors

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From: Cumming GA

Ignition timing set at zero degrees?

I recently had a ZZ4 engine in my '82. I checked the timing this morning and to my surprise the timing was set at zero degrees @ 650rpm. Going back to the site where I bought the engine:

http://paceperformance.com/index.asp...&ProdID=194446

I found this in the specs:

Distributor - Part # 93440806 GM HEI Large Cap style with internal Ignition Coil.

Advance Curve:

Mechanical Vacuum

1100 RPM-0.0 3.00 (in.hg.) 0.0 Timing Should be Set @ 32 Total @ 4000 RPM

1600 RPM-12.0 7.50 9in.hg.) 20.0 With Vacuum Advance Disconected.Vacuum

2400 RPM-16.0

Am I reading this correctly that the base timing should be set at 0 degrees?

Thanks,
Andy

May 31, 2010 | 04:02 PM

'75

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From: McHenry Illinois

It's a little confusing, what is your timing at 4000 rpm? 32 deg of centrifigul advance seems like too much.

Last edited by '75; May 31, 2010 at 04:07 PM.

May 31, 2010 | 04:08 PM

'75

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From: McHenry Illinois

It may be that your base should be 16* and an additional 16* in by 2400 rpm.

May 31, 2010 | 05:00 PM

AT-82Collectors

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From: Cumming GA

Thanks '75

I can check the timing at 4000 tomorrow, family BBQ today. Zero degrees just sounds wrong to me unless there is something I do not know about this distributer. Also the engine does not seem to come alive until 1800 rpm or higher. Perhaps this is the reason why.

Andy

May 31, 2010 | 08:00 PM

lars

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From: At my Bar drinking and wrenching in Lafayette Colorado

Quote:

Originally Posted by AT-82Collectors

I recently had a ZZ4 engine in my '82. I checked the timing this morning and to my surprise the timing was set at zero degrees @ 650rpm. I found this in the specs:

Mechanical Vacuum

1100 RPM-0.0 3.00 (in.hg.) 0.0 Timing Should be Set @ 32 Total @ 4000 RPM

1600 RPM-12.0 7.50 9in.hg.) 20.0 With Vacuum Advance Disconected.Vacuum

2400 RPM-16.0

Am I reading this correctly that the base timing should be set at 0 degrees?

Thanks,
Andy

No, the timing should not be set at 0 degrees. They are telling you that the mechanical advance at any rpm below 1100 is 0 degrees, and that your total advance should be 32. Set your total advance to 32 and let your initial timing fall where it may - they are not giving you an initial timing spec because it is irrelevant once total timing is set to 32. Small block engines with good heads will typically run at 32 total. Small blocks with stock iron heads tend to run best at 36, and big-bore engines like timing as much as 40 total, depending on head design. The other numbers they've given you are curve versus rpm numbers, which are also irrelevant once you set your total to 32.

Lars

May 31, 2010 | 08:13 PM

AT-82Collectors

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From: Cumming GA

That makes sense, thank you Lars!

Andy

Jun 1, 2010 | 06:58 PM

AT-82Collectors

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From: Cumming GA

Just as a follow up, setting the timing at 32 degrees @ 4000 rpm has the engine doing much better that when it was installed with no rattles or knocks. I think the shop assumed zero degrees when they read the documentation I supplied with the engine.

The base timing turned out to be 11 degrees BTDC at 650 rpm after setting it correctly in case someone else runs into this.

This forum Rocks!

Thanks again
Andy

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