hey guys need some advice.

i have a carbed 90's 350 with tbi heads.

Mods are

holley 650 carb vac secondaries
shorty headers
Accell Hei ignition with supercoil/vac advance
Weiand stealth intake

What should my initial timing range be?
The motor is stock no cam/or internal work

I set it to 12* initial and ive noticed i dont have any problems starting the car, but the car does diesel. A friend came over today and advanced the timing to 18* initial. Is that still within range?

He insists my timing was too retarded, but im not so sure.

What initial timing range would you all expect to run with my setup?

Any help appreciated, thanks

 

Give it whatever it wants to be happy. Happy = highest vacuum, fastest idle, with no pinging or hard starting. 18 deg is certainly credible. Eg - mines 15 atm, and with the added vac advance running off manifold vac, this rises to 23.

Try different settings and take it out for a hard run each time, see if/how the power is affected and look for pinging. After, how it runs is what counts, more so than how it idles.

Keep in mind you actually want to be shooting for 35-ish at 3000-ish rpm, and hopefully having the initial timing fall back close enough to whatever leads to the above idle conditions.

 

The dieseling problem is to high an idle speed... Most of the time.... check that..

 

^^^

Means the butterflies are opened too far to maintain your idle speed, in this case because it wants more timing.

 

There is no reason why a stock cammed motor wouldn't idle at 12 deg. There is something else wrong.
Probably a high idle like tree said. Or possibly the ring on the balancer spun causing your timing marks to not read correctly.

 

He never said it wouldn't idle at 12, he was playing with timing to try to correct the dieseling condition (more likely butterflies tho). Good point - verify timing marks.

 

Thanks for the info so far guys,

well ive been running it at 18* degrees since yesterday and i havent had any hard starts issues. Could it be that i was really that far off timing?

The car idled at 12* and started fine. I took it out for a wot run at 18* and i didnt hear any pinging. i also didnt feel much of a difference between 12* and 18* still burned tire for like 300 ft lol

Im thinking about using my vac gauge to set timin to the maximum vac reading, would that be a good idea or would i get inacurate results due to idle speed?

 

No, It will most likely make your total timing to high and cause detonation.
Set the timing at 35 to 36 total and see where idle winds up.

 

29-30 degrees at 2,900 rpm is about ideal for best torque production. Should be at 32 degrees by 4,200, max of about 36 at 4,500. If you get detonation, you need to pull 2 degrees back out. By playing with weights, springs, bushings and stops in the centrifugal advance you can taylor the curve anywhere you want it.

 

This is less timing than what is usually bandied about - is this yet another case of the folklore being wrong?

 

This is straight timing without vacuum advance. This is full power timing, using only the centrifugal advance. You may find more power by going up or down from these numbers but they are a good starting point. Vacuum advance or "cruise" advance will go much higher than this and is intended to increase fuel mileage at lower throttle openings and higher intake vacuum. You will often see as high as 46 degrees with vacuum advance engaged or with computer controlled timing.

The numbers I posted are only relevant if you have either non computer controlled timing, or can access the timing map in your ECM to tune your timing curve. You will have a hard time viewing full throttle timing on your computer controlled ignition. On these, you simply need to set your base timing at a given spec and listen for ping, then when you hear pinging, pull out two degrees.