sbc total timing questions

[Grandprixpaul]

Have a sbc 350 timing is set at 14 and med springs in hei,as the builder told me nkw im trying ti fine tune it ,its getting alot better but total timing seams to be comming in just a little over 2 grand and i was told should be 3500 how do i get there or is it fine as long as its all there before 3500 ?

 

[khan0165]

are you using an advance timing light to see timing past the 20 or so degrees a factory timing mark has? Or do you have one of those cool aftermarket balancers with the timing marks? do you have vacuum advanced hooked up?

I have medium weight springs on my Accel factory replacement HEI distributor, total timing comes in around 3700rpm. I have set at 34 at 3700rpm where it stops advancing.

take off your cap and rotor, push the distributor weights throw their full range of motion... make sure they're not binding or jamming somewhere.

 

[pontiacgp]

for those of you who want to control the vacuum advance you might want to take a look at the MSD e-curve. You can set it up to have any curve you want with 2 dials and it had an onboard rev limiter you set by turning another dial. It takes all the guesswork out and it's always consistent..

this program is only a few $$ and you can use to set the e-curve

http://www.youtube.com/watch?v=6lq82b0EcXo

 

[khan0165]

yeah, listen to PontiacGP... those e-curve dizzy's are awesome!

it's gonna take alot of time and experimenting to set the tune you want... And before you get to fine tuning, you'll need to figure out the basics like vac advance, where the motor detonates and where it doesn't, carb tuning, how consistant your carb is, etc...

the e-curve is a great alternative if you have the funds and want a no-headache tune...

 

[pontiacgp]

khan, the price I paid for a slightly used e-curve is now the price of a new one. Summit has them for a little over 300. They are really worth their price

 

[Grandprixpaul]

Would like to buy it but im going to school right now,so i can turn the vacuum advance down to strech out the advance and maybe the springs .i know ive read that different weights can change the springs you use to so ,im headed to the garage to mess around .thanks guys.

 

[khan0165]

yes, it's about the combination of the springs and the weights=
generally speaking...
- stiffer springs with lighter weights will give a longer timing curve (slower to reach total timing)
- looser springs with heavier weights will give a shorter timing curve (quicker to reach total timing)

a stock to mild cam'd motor will like slower curve. They can handle the advance in higher rpms without detonation, and the longer curve gives a broader flatter torque curve thru a larger rpm range

a motor with a rowdy cam likes the extra advance at lower rpms to cover some of the cam overlap. Advance at early rpms helps give back some of the torque they've lost with so much cam duration. And if compression is high, they don't like advance in the higher rpms.