[fashaof4]

i've read some of the threads in the engine forum and most have made sense but i have a question:
i have an edelbrock carb and there are two ports for vacuum advance. the cd that comes with the carb tells me to use the left port (which doesn't suck until you throttle up). the other port sucks all the time. i need to start from scratch and have someone tell me where to set the initial timing, which port to plug my vacuum advance into and where i should be at 3000 range. i had a q-jet before using the maniofold vacuum port (sucked all the time) and never had pinging. once i put this edelbrock on, i've had to keep screwing with it.....HELP!!!

 

[dpvoiceguy]

I've got an Edlebrock Performer 1405 (600 cfm) on my 355. As per all of the instructions from the "experts" on this site (whom I trust implicitly!) you want your vac advance connected to manifold vacuum (full time), not ported vacuum.
Next you need to look at your cam and whether or not it is a stock profile. Anything in the "perfomance" category will want 14-16 deg. initial timing. (This assumes you know how to check your initial timing...do you?) Beyond that you can shoot for approx. 34-36 degrees "total" timing which includes your 14-16 initial plus the mechanical advance offered by the distributor at or around the 3000 rpm mark you make reference to. (Once again this assumes you are confident in your ability to check the mechanical advance).

 

[fashaof4]

first of all, i only have a very mild cam in it. with that being said, tell me if i'm correct.
i should un-hook my adavnce vacuum and plug the carb, set my timing to approx. 6-8*, hook my vacuum hose back up to the RIGHT side of the carb (constant vacuum), check my timing again and it should advance to around the 22-24* range. then at 3000 rpm my timing should be no more than 36*
sound right?

 

[Mike]

NO ,your total timing ,which you show as "3000 rpm my timing should be no more than 36*" is without the vacuum advance connected.
After you get it set to 36°'s ,then hook the vacuum advance back up.

 

[Tom Mobley]

6-8 is way too short for a performance engine. those are like old stock numbers from the 70's early smog era. you should be running twice that much even with a near stock cam.

 

[fashaof4]

sorry for all the questions guys, i want to do this the right way, the FIRST time. unhook vacuum, set timing to say 8-10*, run it up to about 3k rpm with vacuum UNHOOKED and i should be at no more than 36*?.........THEN hook the vacuum back up?
please explain initial timing also.i want to make sure i understand the terminology
thank you, dave

 

[Tom Mobley]

initial is where it starts, what you see with the timing light at slow idle with the vacuum advance disconnected.

 

[Jerry70]

Also, make sure that your total is actually all in by 3,000 before you set it there. Many factory curves didn't reach total until 4k-5k rpm. After setting total reconnect the vacuum advance. With it hooked up you should see about 50º once all your timing (vacuum and mechanical) is in.

 

[gnicholson]

on a mild or stock engine you do not need the vacuum hooked up to manifold vacuum. on some more radical engines with low idle vacuum the extra timing from a manifold source helps idle quality .also , because the extra timing raises idle rpm the the idle speed screw can be backed off putting the throttle blade lower on the transfer slot which keeps the idle mixture from being too rich. sometimes thetiming can be erattic if the idle is set where the ported passage is just starting to be uncovered.however, on a milder engine the throttle opening to produce the correct idle rpm is less. the instructions are telling you to use ported vacuum because that puts the throttle at idle in the correct position compared to the idle discharge port/ transfer slot for the majority of applications that carb will see. also a mild engine doesnt need as much initial timing. is the car pinging now? what dist, vacuum adv. are you running?

 

[fashaof4]

o.k. one more question:
i set my initial at 8* with vacuum unhooked. hooked up the vacuum and set the dial on my timing light to 35*. my timing mark was at 0-2* on the balancer. is this accurate?
if so, it starts a little hard but runs better. still a slight pinging when throttled up but NO MORE POPPING at higher RPM's. if not, what is my next step? i feel i'm close but no cigar yet....

 

[fashaof4]

i have a stock summit HEI distributor with the every day vacuum advance. it's pretty much ALL stock except for what summit called a "tow package" mild crane cam, edelbrock performer intake and a 1407 (750) cfm carb.

 

[gnicholson]

you need to find out what your total is. if theres a good shop in your area with a sun dist machine i would go that route. barring that the easiest thing to do is to get a dial back timing light unless your balancer is marked up to 36 deg.un hook the vacuum adv and with the light rev your engine slowly until it quits advancing . adjust the nob until the timing reads 0 and read on your light what the advance is. adjust the dist to read 36 deg. now check the timing at idle . slow the idle until the timing quits retarding. the timing should be about 12-16 degrees. if the initial timing is much different than this the advance slots in the dist shaft may need to be modified but i bet it will be ok. next check your rate of advance and change your springs and or wieghts to get maximum advance at about 3200 rpm. if the car pings on hard accel you may have to reduce timing or advance rate. if it pings at light throttle you need to work with the vacuum advance cannister