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Unread 04-02-2002, 11:11 AM   #1
CJ8DV8
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ignition timing question

Hi Gang-

I have a timing problem and am getting conflicting info. Perhaps someone can help.

Here goes: The pollution label on the radiator support says to set the timing at 6 degrees Before TDC ( +/- 2 degrees) at 1600 rpm, with the distributor vacuum disconnected and hose plugged and the vacuum solenoid assembly electrically disconnected.

OK, so I try this.

First off, at 1600 rpm the motor is screaming. Why is this the rpm spec for timing and is this even right?

Second, when I race the engine up to 1600 rpm and shine my timing light at the marks, It is way off base. Something like +16 degrees BTDC. What gives?

When I try to follow the label word for word and set the timing to the 6 degrees, the motor stumbles and runs real rough at idle and just seems like this is not the correct setting.

One more thing: My Haynes manual says the spec is +12 degrees btdc but no rpm is specified. It did say to disconnect and plug the vacuum advance and hose but made no mention of disconnecting the vacuum solenoid assembly. It also says that if there is a label on the radiator support, to follow the spec's on the label. Actually, Haynes settings work better than what's on the Jeep label.

I have an appointment at my service center tomorrow, but I'd hate to spend a couple hundred bucks for something I could do in an hour.

Please help.

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Unread 04-02-2002, 12:37 PM   #2
Bulletproofcj7
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The reason it stalls out may be due to a poorly adjusted carb. try adjusting that to keep it running then check your timing.or...
You can just tune it by ear, provided everything is in good working order,i.e. new plugs, good wires etc. run the motor at normal operating temp disconnect and plug the vacume advance, adjust the distributer to get the highest possible idle.dont forget to hook the advance back up. if after that it starts hard when it is hot you may need to retard it a little.
crude but it works.
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Unread 04-02-2002, 12:53 PM   #3
V8wrangler_idaho
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the 12 degrees sounds more correct to me. I have done a lot of work on a lot of diffrent motors and none of them have been set to anything less then 12 degerss top dead center. the timeing on that motor isant really that improtant to get it right on what the specs say it might run better even more advanced. The more advenced you have on the motor the hotter it runs. which means better gas mileage and more power. But you have to be carefull not to have it run to hot or you could burn up your valves. What i ususally do is set the timming forward and then try to start the motor if it starts right up advance it more and more and more untell it dosen;t start very easy. Take a reading at that point see what the advance is. from that number say if it was 23 degrees take it back about 2-4 degrees and run the motor at that settings for awhile. drive it around a bit and take a spark plug reading. see if its the plugs are a nice tan color. If they are white take it back a few more degrees. It can be kinda time consumming but by doing it that way you can find the apsolute best timeing for your motor. With my 5.0 motor with the aluminum heads I ran mine at 36 degrees advance. and it was perfect. Just every so often do a plug reading make sure its not running to hot.
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Unread 04-02-2002, 02:30 PM   #4
johny1i
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I don't know who came up with that 6-degree spec, but that does sound ridiculously low. My sticker says 9 (+/-2) also, but I run mine at 11-degrees (1600 RPM, disconnected and plugged vacuum advance and disconnected solenoid connection like you said) and it runs great. I do have to run 89 octane gas to keep it from pinging because of that extra advance, but other than that, no problems. BTW, I've never been any good at tuning a carb by ear, but it's simple with a vacuum gauge (I could never discern whether it was the leaning out or the drop in vacuum causing the idle to slow down). With a vacuum gauge, just start with the screws at about 3 full turns out, then start easing them in--one at a time--until the vacuum starts to drop suddenly (the vacuum guage shouldn't move much--if at all--up until that point). When it starts to drop off quickly, unscrew the mixture screw about 1/4 of a turn (this is where opinions vary). For reference, mine are unscrewed exactly 3 full turns from being bottomed out, but I know some guys have them as little as 2-1/4 turns out. Mine runs so good, though, I hate to lean it out any further. Hope this helps you somewhat!
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Unread 04-02-2002, 03:37 PM   #5
CJ8DV8
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Thanks-

I had a feeling that the 6 degrees spec was off.

Here's my story... I owned this Jeep about 5 years ago, fixed it up and then sold it. It was running great at the time- new carb and everything - bone stock, no mods.

I just recently bought it back. It's still stock but has ANOTHER new carb, exhaust leaks, vacuum leaks and rust, rust, and more rust - also known as the Fred Flintstone floorboards and the rustproof plywood bed upgrade. It had several years use as a beach buggy (salt water).

Anyway, The vacuum leaks were fixed and the exhaust was replaced. Also, new cap, rotor, plugs. New tub/body maybe later in the year. Now it's time to fix the idling problem, but at anything above an idle it runs great.

I think I'm still going to take it to the repair shop for a couple reasons. First, the owner of the shop is a great guy and wouldn't try to rob me. Plus, I'll pick his brain about the timing and idle problem for future reference. Also, the Jeep needs a state inspection. I figure if he gets some cash for repairs he may not notice that small crack in my taillight lens if you know what I mean.

Thanks for the input, guys. It just goes to show that you can't always believe everything you read - even if it is on a Jeep emissions/tune-up spec label!
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Unread 04-02-2002, 05:39 PM   #6
4wheeler4CJ
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I have to agree with V8wrangler_idaho, he is right on with his "timing procedure". Forget the book or sticker, and do it by ear. You'll get the feel, seriously. I had a Clifford Performance Modified 258, that I had to run at about 19 degrees at an idle! At the time,i couldn't belive it, but when I called Clifford himself, he told me that sounded right, and I never had a problem for 5 years (sold the motor last year, and it's probably still running strong!)
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Unread 04-04-2002, 10:20 PM   #7
jeepdaddy2000
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Just a quick FYI. almost all stock motors from Detroit up to the mid 70's ran the timing from 5 to 8 degrees BTDC. this was done with the vac. adv. disconnected and the idle at about 550 to 700 RPM's.While this info might not apply to your situation,it is a fair rule of thumb for early motors.
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Unread 04-05-2002, 05:04 PM   #8
CJ8DV8
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UPDATE-

Here's what happened:

The shop had it for two days, suspecting that the carb (BBD)was causing my idling problem. They adjusted it best they could, they said.

It passed inspection and got a window sticker.

Picked it up this morning and it was hard starting. Drove it to work and it wanted to stall at every stop I made. Not good. Before it would only run rough at a stop light. Now, it doesn't want to run at all when stopped and in gear (auto trans).

Only charged me $30 for adjusting my carb and timing. BTW, the timing is now set at 6 degrees BTDC.

What do they say? "One step forward, two steps back."?

Anyway, I found a good site on the web regarding my exact problem, including the "vacuum timing" method. I'm sure you've seen it:

<a href="http://home.sprynet.com/~dale02/home.htm" target="_blank">http://home.sprynet.com/~dale02/home.htm</a>

I printed out a couple pages and cleaned up my garage.

Guess what I'm doing this weekend...?
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Unread 04-06-2002, 05:14 AM   #9
4wheeler4CJ
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Same thing about 50% of us Jeepers are probably doing this weekend, working on them! LOL <img border="0" title="" alt="[Wink]" src="wink.gif" />
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