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Unread 06-14-2011, 01:30 PM   #1
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1983 CJ7 
Join Date: Apr 2006
Location: NJ
Posts: 46
Timing marks all the same size

I am helping another forum member install an MC2100 carb on his '81 CJ7 with a 258 engine. He was told that the engine is from a 1983, but unlike my '83, the timing marks are all the same size. The only 258 marks I've ever seen are two different size lines. Anyone know how they are numbered? Are they the same as mine?

83 CJ7, Nuttered, MC2100, 4" Rough Country Suspension, 33x12.5 tires
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Unread 06-14-2011, 05:52 PM   #2
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1987 YJ Wrangler 
Join Date: Mar 2008
Location: corpus christi, texas
Posts: 7,055
you fellas are going to have to just try it out like its marked like yours. if it doesn't work out, you are going to have to rough it by ear until you get a good response to help or get down there with a timing chart and mark the pulley your selves
I don't feel like working on anything, at this time.
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Unread 06-14-2011, 07:46 PM   #3
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1981 CJ7 
Join Date: Jul 2009
Location: Bali, Indonesia
Posts: 5,197
They can be all the same size, as on my 1981 and 1984 258ci engines. They have been changed over the years and my manual shows the different size lines.

The marks on the block are FROM THE RIGHT +2deg, 0, -2, -4, -6, -8 etc.

What you set the ignition to and at what engine speed depends on what system you have. If you have the computer it will be much more advanced than a non-computer setup. If the computer, which adjusts your timing for emisisons etc, has been removed your distributor will have limited advance capabilities.

The carburettor choice should not, IMHO, change the ignition timing but like all things Jeep the advance may not work as intended and you may get pinging anyway. I manually rotate the distributor until the pinging just stops under load, this is the ideal setting for that engine. It would obviously be better to sort out the distributor advance / vaccuum porting than the hit or miss approach but it works.

The timing marks allow a good initial setup but to do that you need to see the amount of advance you are setting. If you do not have timing marks you have to find TDC and work back.

I use a Gunson Xenon timing light that allows me to use a dial on the back to alter (advance or retard)the flashes. This appears to make the TDC 0 lines line up and then I can read the actual advance off the back of the gun. This avoids the need to know anything apart from TDC and very useful / pointless depending on your view of such gadgets.
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