ok, let's suppose i'm not a complete moron, ok? when setting the timing, stock is easy. match the pointy thing to the corresponding color notch. now, i'm eyeballing in the yaw settings.... my question is: when setting 24BTDC (at 4k rpm) isn't the stock trailing mark at 20 BTDC? i'm trying to make sure i'm moving the dizzy in the right direction. if looking straight down at the stock pulley, what side (drivers or psngrs) of the timing mark is ATDC and what side BTDC? i started thinking too much about it and had a complete and total brain fart, so i figured i'd ask before i hosed my engine. so far, where it's set, it seems to have more low power, but after around 5k rpm it makes a weird kinda garbley, rattleing sorta noise. hard to explain, but i'm guessing its a misfire. and also.... if you do the ddlififssddfs (yeah, iknow, sp.) what would you set the timing at?

 

The trailing timing mark is 20deg ATDC.

When looking at the pulley from above, the mark towards the exhaust side of the engine is the trailing mark (and thus the ATDC side of the pulley) and the mark towards the spark plug side is the leading mark (0*) (and thus the BTDC side).

Instead of screwing around with expensive pulleys, or spending all that time taking the pulley of, making measurements, etc. I carefully took a set of calipers (actually, needle-nose Vise-Grips ) and measured off the distance between the two marks. Then went forward, towards the plug side of the engine, and used a white crayon to mark off where 20*BTDC is. This is meatball surgery but if you're careful and double-check everything a few times you'll get it close enough.

I also had to mark where 20*A and 0* were because there were so hard to see. Now I had 20*A, 0*, and 20*B marked off, takes about 5 minutes tops. Downside is the crayon washes/rubs away after a few days so you have to do this before you set the timing. No biggie, timing is usually a set-and-forget thing because we don't have to worry about timing chain stretch.

Basically, ignore what Paul says about timing - most people find that it causes detonation at worst, or high RPM power loss at best. 20*L/10*T seems to work best, which is great because then you just set leading to your new mark and trailing to halfway in between it and the middle mark.

The reason you set timing at high revs is so you set it once mechanical advance is "all in". Just watch the pulley with the timing light and rev the engine until it stops advancing. (This is another way to find out which way is advance and which way is retard)

 

exactly what i needed to hear! thankyou peejay! it seemed so easy when i started, but i kept looking, and thinking, and looking, and thinking...... i basically thought myself to stupidity.

 

Thanks peejay! You've put into words what I've suspected for a little while now. Ignore Paul. Well, for ignition anyway. Boy, am I glad I didn't put Autolite plugs in my engine. Oh yeah, I used PLASTIC calipers!!!!!!!! :p

For fidlfistiddifisis, follow peejay's advice.

If you happen to have a '74 or '77 engine, you'll have Trailing pulley marks at 10*A ('74-'76) or 15*A ('77-'78?).

Are all '79+ pulleys marked at 20*A? I ask because my funked up 13B has parts from multiple years. The front pulley and intermediate housing are wrong for a '74 (they didn't have gas nitriding back then).

 

HEY NOW... I run cut down Autolite plugs, for the leading. I used 3923 plugs because "they were there" and they did make the car faster. Maybe it's because I am running the MSD in direct-fire... maybe the MSD prefers the cut-down single strap plugs and vice-versa? Who knows, it works!

As for the timing Q's for non-'79-85 12As... I'd imagine that the pulley marks are wherever stock timing at idle is supposed to be... RX-7 12As happen to be set at 0*L/-20*T, so that's where the marks are.

 

Piston ignition with piston plugs. That makes sense.

I botched the list a little I think. The L/T split for '76 is 15*. I'll get down and dirty some time and measure it, but so far, it looks like 15*.

My 13B has a 12A pulley.

 

well, i fiddled around with the timing yesterday, i used a dab of paint to mark the pulley and calipers(albeit plastic ones) for measurements. no meatball surgery here took it back on the road and... HOOO HAAAA! works great! shifting and all 'round power feel much better. it was bogging between shifts, and being all funky at high rpm.... now, xlent all the way around. now if only i could narrow in on these darn carb settings! and dfdddflubberstuttertsstisis is in the works too. hey, just cuz i cant type it doesnt mean i dont want it in the car

 

BAD!!!! That noise is detonation, stop doing it!!!

Go out and check your plugs right now, specifically your trailing ones. Chances are one of them is broken.

This is so true, I had nothing but problems with the Yaw timing. I broke 3 spark plugs, luckily no ceramic went into the engine.

IMHO, the best timing setting is the Racing Beat recommendation, 2 BTC leading and 19 ATC trailing at idle (with vacuum advance disconnected). Feels the best of any setting I've tried.

 

I don't like trying to set timing at idle. I can idle anywhere from 600 to 1000 on a regular basis. I only set my timing at 4k RPM.

I have one of those 20* advancing dizzys. I might try a dizzy with 25* of advance and see what happens.

Isn't a 10* split better than nearly 20?

 

I don't like the way it feels with a 10 degree split. For me, it seems to give better lower end but shitty top end. You don't feel the secondaries come on as much. It just doesn't feel healthy. Also, the emissions seem a lot worse, and my car stinks.

Since I pretty much drive my car like I stole it, I don't care too much about low end. Also, after I broke a few plugs I'm staying the hell away from that timing. And I'd rather my car didn't smell like a truck, at least if it doesn't have to.

The 10 degree split feels 'different', but not faster. I guarantee you my acceleration times would not be too different in either case.

Again I like the Racing Beat settings, but everyone has their own opinion.

Jeff, I'm guessing you don't have a 79-85 12A? Because on the earlier rotaries, a 10 degree split is specified. But for those of us with RX-7s, I'd stay away from it.

 

Jeff, just set your idle to the factory recommend 750, and then adjust your timing. Do them both at the same time. It's as easy as that.

For those that are reading this, adjusting your timing different than stock really doesn't give much more power. It's more the way it feels. It is definitely not worth ******* around with strange settings for 2 more horsepower.

IMHO, if you have a high flow exhaust, just advance it 2 degrees from stock (RB settings) at idle at leave it like that. I don't consider 1-2 horsepower on the low end to be worth the risk of breaking plugs and losing yourt motor.

 

checked the plugs... boy were they fugly! i think i'm running a bit(a lot) rich. but none were broken. cleaned em up w/ a dremel wire brush and now its great. i've been screwing with the timing cuz it was set on stock, i've got headers, exhaust, and a dellorto 48 sidedraft. there's a wee bit more than 2hp to be had. but seeing as this is easy to change, i'll try silver's settings too. i dont think the yaw settings were necessarily wrong. i think they were the right settings for THAT car with whatever mods he's running. he also says all engines are different so feel free to play around with the timing. and it gives me something to do other than remove my exhaust to track down that squeaking/rattling.

 

My friend used to have a dellorto on his 13B and boy did it ever run rich!

 

yeah, it was on my old SE, that thing was godawful fast... even w/ a crap exhaust sys. now its on a 12A and i cant seem to figure out the right jetting. guess i need to get an A/F meter now.... cool... another gauge to look at