stabbing distr. & timing questions

[BRAD ARTHUR]

Posted: Sun Jan 16, 2005 1:08 pm Post subject: setting timing

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I'VE READ ALL KINDS OF THREADS ON TIMING ,BUT HERES SOME MORE QUESTIONS.
FIRST OFF IAM RUNNING A 1405 EDEL. CARB, EDEL. CAM,EDEL. INTAKE, STOCK EXH MANIFOLDS, Z&M HEI, ALL THIS ON A 304. WITH ABOUT 1500 MILES ON A OVERHAUL.
I VE BEEN GETTING IT TO RUN GOOD BUT NOT ITS BEST. WHILE TUNNING IT IN STILL IVE BOUNCED BETWEEN CARB TUNNING AND SETTING, TIMING INITIAL ,MECH VACCUM.
IVE READ THESE MOTORS RUN WELL FROM 3*-15*INT.,W/34*-38*TOTAL. ADVANCE. MY QUESTION WHEN SETTING TIMING AND INSTALLING A DISTRIBUTORROTATE ENG IN THE DIRECTION IT RUNS TILL #1 IS AT TDC ON COMPRESSION STROKE. TIMING MARK ON HARMONIC BALANCER SHOULD BE AT TDC, THEN INSTAL DISTRIBUTOR W/ ROTOR POINTING AT#1 .
1(WHEN LEADING EDGE OF ROTOR CONTACTS EDGE OF #1 OR CENTER OF ROTOR TO CENTER )OF#1?) WILL IT RUN @TDC, THEN ADJ TIMING.
2WILL IT MAKE A DIFFERENCE IF YOU ARE OFF 1 TOOTH OR WILL YOU BE ABLE TO ADJUST THAT WITH RATATING THE HOUSING?
3 IS THERE A WAY TO VERIFY YOU ARE ON THE EXACT RIGHT TOOTH FOR THE DIST.
I AM USING A DIALED TIMING LIGHT , BEFORE I HAD THIS I USED A STANDARD LIGHT. AND WAS @ 55* TOTAL ADVANCE 12 INT. AND IT RAN GOOD WITH NO PINGING. WHEN I BACK OF TO 36 TOTAL RUNS GOOD BUT NOT LIKE IT SHOULD.
IAM TRYING TO OPTIMIZE PERFORMANCE AND PLAYING WITH MECHANICAL SPRINGS AND TOTAL TIMING , BUT THINK IAM OFF A TOOTH OR SOMETHIG CAUSING IT TO RUN BEST @55 *TOTAL.
I ALSO CHANGED ACCEL PUMP NOZZLE FROM #28-#43.
I GET A SLIGHT HESATATION ,FROM IDLE TO TAKE OFF IN GEAR ALMOST A HICK UP OR STUMBLE ,BUT GOES AWAY WHEN LET OFF.

right now it runs best @36* initial advance, doesn't seem right, back it down to 36* total advance@3000rpm's and loose power ???????

i rotated the disrt. 2 teeth c.w. and restabbed the distr. still runs best at high initial timing, i've also been playing with the springs &wieghts of the mechanical. my wieght bushings were wore on the bottom lip- compared to the new bushings in the adv. kit.

any base #'s of initial, mechanical, or vaccum. would help. or why 36* initial adv. is running the best. how many turns out for the vaccum adv. screw?

I ALSO THOUGHT OF RUNNING A CTO SWITCH FOR THE VAC. ADV. IS IT WORTH IT? WHICH ONE?

[3jeepsdeep]

wow - lots of questions. I cant help much with the aftermarket dizz y questions, but in general...

1) work one adjustment at a time an measure / document the results. Optimize, then move to the next.

2) yeah, takes lots of trial and error, goin' back to earlier adjustments -- but take 1 step at a time anr RECORD the results (somewhere).

3) if the Dizzy is 1 tooth off, sure, you can make-up the adjustment by rotating the shaft / housing provided that you have enuff clearance to rotate it to the correct position (vac advance housing room to move between engine fan & block)and the oil pump slot lines up ok. Best position ..? well, ideally you coul dtry to land it where you have adequate room to adjust either way without interference (it really doesn't matter, otherwise) or look at position depicted in a service manual.

4)you CAN NOT make up for a timing chain that jumps a tooth, however (you can change the ign timing by adjusting, but not the valve timing).

6deg BTC seems typical for 'base' timing setting, I would think that anything > 25 degrees additional vac advance is excessive. This does not include whatever mech advance is added on top of that -- not sure about typical mech advance (never messed with stock spring / weight curves). Take this one step at a time - base timing, vac advance, mech advance, acc pump, etc. Time consuming, but the only way to do this and understand the efect of the adjustments you are making unless you are following some one else's 'cookbook' (in this case, be sure to note all your original settings).

hope this helps
df

[ January 17, 2005, 08:08 PM: Message edited by: 3jeepsdeep ]

[BRAD ARTHUR]

hey thanks for the info i'll try some more trail &error.

[nograin]

First,
Kill the capital letters unless for some reason you can't help it. It's considered equivelent of shouting, and is also harder to read. Many people will simply ignore a post in all caps.

Second, A little starting guidance that might help. Go to the Edelbrock website and find out what initial timing they recommend with that cam. If they don't have a recommendation, then go to Barry Grant's website. Under Demon Carburators they have a table (maybe under tech) with recommended initial timing. To use it, you'll need to know the duration(s) at .050 for your cam. It doesn't matter that you're not using a Demon carb, you're just looking for a ball park starting number.

Most hot motors like additional initial advance over stock as you'll see in the chart. Get yourself a good idle at as low of an rpm as you can. Then remove the vacuum advance line from the dizzy and plug it with a golf T. CHeck your total mechanical advance. Make your wide open throttle test runs (you an reinstall the hose if you want). Any ping at all and back out. You will have to reduce your advance. Record how much advance you have to take out. You can then have a shop reduce the amount of mechanical advance if you want later using that info. Once wide open throttle is OK, you can test the vac advance. Make accelerations at part throttle, up hill even better. Any ping, you need less vac advance. If that doesn't solve it - then it may be that the carb isn't curved quite rich enough. Edelbrock can help you through that.

[ January 18, 2005, 05:41 AM: Message edited by: nograin ]

[BRAD ARTHUR]

hey thanks! a lot of different info you gave me, no one else has mentioned. i 'll follow up on your suggestions and let you know.

didn't mean to be capitalized.
thanks for the help!