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Unread 04-17-2002, 03:34 PM   #1
CJ8DV8
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Join Date: Mar 2002
Location: LI, NY
Posts: 35
Timing Advance Question

Hi Gang-

Question:

When I time my engine, at idle up to about 1000 rpm, the timing is set to 6 degrees btdc. I've asked several people but have mixed answers. Most say this is too retarded (in more ways than one) and should be set to about 12 degrees.

BUT...

When I rev up to above 1,000 rpm and above, the timing jumps to about 12 - 15 degrees btdc. This is what most people agree with.

What's the deal with the timing jumping like that? The emission sticker says that the timing should be set at 6 degrees at 1500 rpm, but this is the rpm range when the timing advances.

BTW, all computer and emission stuff is intact. I also follow the the timing instructions on the emission label (disconnect the distributer vacuum advance line and plug vacuum hose, etc)

Anyone else have this timing advance situation? Is this normal?

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Unread 04-17-2002, 03:55 PM   #2
OldJeepguy
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1979 CJ7 
 
Join Date: Dec 2001
Location: Santee, CA.
Posts: 753
</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Originally posted by CJ8DV8:
<strong>Hi Gang-

Question:

When I time my engine, at idle up to about 1000 rpm, the timing is set to 6 degrees btdc. I've asked several people but have mixed answers. Most say this is too retarded (in more ways than one) and should be set to about 12 degrees.

BUT...

When I rev up to above 1,000 rpm and above, the timing jumps to about 12 - 15 degrees btdc. This is what most people agree with.

What's the deal with the timing jumping like that? The emission sticker says that the timing should be set at 6 degrees at 1500 rpm, but this is the rpm range when the timing advances.

BTW, all computer and emission stuff is intact. I also follow the the timing instructions on the emission label (disconnect the distributer vacuum advance line and plug vacuum hose, etc)

Anyone else have this timing advance situation? Is this normal?</strong></font><hr /></blockquote><font size="2" face="Verdana, Arial">Your timing will advance with the engine RPM to keep the spark arrival at the correct time. Most engines will have a total timing advance of at least 32 degrees at full speed. If your initial timing is set too high (10 to 15 degrees is too high for a stock engine) your total advance will stand a good chance of being too much and can cause really bad things to your engine - holes in pistons come to mind...
I usually set my 304 V8 to about 7 to 8 degrees initial advance and it seems to work well there.
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Unread 04-17-2002, 05:06 PM   #3
johny1i
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Join Date: Mar 2002
Location: Crestview, Florida
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Mine is pretty consistent with oldjeepguy, 9-10 degrees at 1600 rpm, but I also use 89 octane gas to help make sure that it doesn't ping. A question for oldjeep--have you ever experimented with running your vacuum advance from a ported (carb) source versus the stock manifold vacuum source? I know some guys make this modification, and I wondered if it has any advantages.
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Unread 04-18-2002, 12:31 PM   #4
4wheeler4CJ
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Check your manual, but you usually set your timing with your vacuum advance hose off the distributor and plugged, and the idle set to about 500 RPM. Timing should be between 5 & 8 degrees BTDC. That's it. Once the vacuum is hooked up and working properly, your engine will advance to what it needs to and run fine.

The initial setting, however, is crucial. I had a 258 that I modified with a mild cam, and my initial setting had to be 16 degrees BTDC at idle for the engine to run right. Depends on your motor, whether it is stock or modified.
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