Okay so i finally went out and got a digital timing light last night and a vac gauge and decided to set my timing up properly (had problems before, long story on another thread). i set the timing so it reads 10 initial w/ the vac line disconnected and plugged, and 32 with the vac line connected, i also adjusted the mixture using the vacuum gauge so it was at peak press ~20.5inhg. Now where do i go from here, i'd like to be able to tune my engine correctly to get the most power out of it, not looking to mod this engine yet just mark the most with what i have, i know that it still has more power waiting to come out. It seems to lag a little on the low/mid range and doesn't really launch very hard or spin the tires up as well as it should. should i leave the timing alone, or experiment with adding a deg or two at a time and checking results?? i'd like to get more indepth with the timing and learn all i can about tuning this engine, again i am still learning though so plain english explianations help out a lot, thankyou :bowtie: :bowtie: :bowtie:


oh yea car is a 72 4speed 350ci with rv cam, holly street avenger carb preformer intake, and preformer nitrous 75 shot (but i want to tune it for non-nitrous, then when i go to the track or know i will be using the bottle i'll fix the timing before i use it)

Set total time to 34-36* with vac advance unhooked.

If your timing light is a dail back or advanced type to check total time you...

Rev engine up to 3000 rpm and hold it there.. Shoot light at damper, and push your timing lights button/knob till the damper's hash mark alines with your 0/TDC mark on tab... Read the number on your gun.. Turn dist untill you get it reading 34-36*

If it's a stock dist. you will probbly have to rev engine up high to get full advance . I would est in the 3600 rpm range.

To get more throttle responce and power out of the engine you might want to get a dist. recurve kit and install 1 light spring and 1 med spring in place of your GM heavy springs and check to see at what RPM full advance is in at..

You want to get full advance at around 2800-3200 rpm.

Most GM HEI dist gives around 20* of mech. advance so to get 34-36* total your initial timing will need to be in the 14-16* range

Check to see if your Vac advance is on the timed port or the vac port of the carb. You want it on the vac port (Lowest point on the carb) made a huge difference in mine. Also what rear gears are you running? Elvira had a 2:73 peg leg, it sounded mean as hell but I could walk faster that it would launch.

Went to a Eaton 3:73 posi - I still grin ear to ear.

okay so, initial timig set at 16* with the vac line plugged rev up the engine and goes to 36* however it is all in by ~1100 rpm, WTF????

also what should my idle speed be set at right now i've got it at about 850

anyone??

if the vacuum line is HOOKED up it should act like you are describing. If the vacuum line is UNHOOKED and you are all in at 1100 RPM's then there is a serious problem with your distributor.

Make sure the vac line is disconnected from the carb, and plug the bung on the side of the carb so it is blocked off. Otherwise it screws up your idle mixture because of the extra air leaking into the carb below the throttle blades.