Timing questions

[pb]

Ok, I just installed the Performer intake and Holley 650cfm carb on the 360. I'm trying to fine tune the setup and was wondering what most of you set the timing to on similiar setups. Right now it is around 8 ATDC. It seems to run fine when warm, but it doesn't run so well when cold. I have to adjust the choke idle, but wanted to get an idea of what timing works for everyone else to start from there.

[jode]

I think the m,ajority run Btdc

[carrotman]

For the 360, the timing marks are listed as A10, 5, TDC, 5, and R10. With the grease on the engine, someone might think the R10 is B10, but the R10 means 10 degrees retarded. The A10 isn't 10 degrees after TDC, but is actually 10 degrees advanced. Depending on your elevation and engine condition, timing between the A10 and 5 should be good.

[88GW]

Carrotman. What year is that cover? I think my cover on my 88 starts at 0, 5, 10, 15, 20 all BTDC.

[joe]

I think in 73 they dropped the retard side of the scale because none of these rigs are timed ATDC anyway.

[carrotman]

An 88? To me that's just off the showroom floor. PB has a 75 and I have a 76 Chief. I just quoted from the 76 TSM. The 76 six cylinder uses the 0-20 BTDC. I guess the Advanced and Retard timing was confusing. I don't know what year they changed. I do know that AMC's like advance. At a Mile High, I can even go some more, but some advance it till it pings going uphill, and then go back a few degrees.

[pb]

Well at lunch, I went home and set it back to 5-10 BTDC (marks above TDC on the scale) and it doesn't run that great now. I think I will have to set it back to the ATDC (The marks at the bottom of the scale...I think I read that was ATDC). In playing with it earlier, it sounds good going beyond the ATDC timing marks. Any problems or issues in going beyond the marks?

[ November 25, 2003, 11:32 AM: Message edited by: pb ]

[joe]

PB, ya missed carrotmans explanation. The "A" in the "A10" part of the scale stands for 'advanced' not 'after' as in the spark is advanced and firing BTDC(before TDC). Your timing should be set at about 8 degress or so BTDC. That's between the A10 and 5 marks on the lower part of the scale. Anything above the TDC mark on the scale the spark is retarded and firing ATDC(after top dead center) and won't run worth crap.

[mandoneer]

the best way I have found to time a motor is by hooking up a vacuum gauge and advancing the spark untill max vacuum is made and then retarding it a little , drive it around a little and see if the motor pings a little and if it does than retard it a little more

[Smooshy]

I run mine at 13-14btdc, 8 btdc is factory I think.

[pb]

joe - thanks for the explanation. Thats what I was trying to get at. I was a little distracted at here at work. Don't they understand the Jeep requires my full attention smile.gif The engine runs below TDC = good, above TDC = bad.

With the performer intake and carb combo, should advance it more? I am at 10btdc right now.

[joe]

Yeah you got it PB. You actually had it right in the first place...the lingo was just messin ya up. ;)
Stock timing specs are obviously for a stock motor but also for a brand new stock motor so you'll have to find the ideal timing on your own for an old and/or non-stock motor. What I've always done is kept advancing the timing till it pings under load and/or rolls over slow when warm and then back it off a bit. I've never done the vacuum gauge timing thing before as mentioned above but it makes sense and will do it my way the next time, record the setting with a timing light and then try the vacuum way and compare notes. Sure sounds like it'd work well. You've been on the right track(and the correct side of the scale) all along now you just need to fine tune it.