what do you guys run for intial timing on your carb cars my stock cam 350 is at 12 im wondering if i could go to 14 with benefit. Right now when i adjust my idle mixture screws the best i can get is likt 16" of vacuum on the gauge it says not enough timing. Let me know what you think right now it runs a 14.3 at 94 back when it was tpi it traped at 96 with a 14.5.

 

Timing is specific to each engine. What works best in one engine may not be the best for another engine. No matter what other adjustments you do, where your engine likes it's timing will never change.

Base timing is just a starting point which also helps when starting the engine. A good timing curve will be at full advance before 3000 rpm. Adjusting the base timing without adjusting the mechanical advance will change the total timing. The best proper total timing needs to be known first.

Once you know the best total timing for your engine, changing the base timing will mean needing to change the mechanical timing to keep the same total timing.

With an older large cap HEI, this is done with the weights, springs and cams. The weights and cams determine how much mechanical advance is in the distributor. The springs control the ignition curve.

With the newer computer controlled small cap distributors, all that timing is controlled by the computer and the knock sensor.

I run my MSD distributor locked out to 37*. I don't know if this is the best timing for my engine but it runs fine so I leave it. There is no timing curve. The engine starts at 37* but I also have a timing retard that retards the timing up to 20* to aid in starting. When my engine is under power, it's above 3000 rpm so I don't need a timing curve.

Vacuum advance is for part throttle operation only. At an idle or WOT, there is no vacuum advance. In a race car it's a variable you don't need.

The old trick of advancing the timing until the engine pings under load then back it off a few degrees is highly inaccurate and is nowhere close to the proper best total timing.

You can find the best timing on the dragstrip. Bump up the timing 2* at a time and keep track of the mph. When the MPH drops off, go back to the last setting and leave it there. If your base timing is now too high, the distributor needs to be recurved for a lower base timing while keeping that total timing.

A more accurate way to find the best timing is on a dyno. An engine dyno is best but not everyone can pull their engine to put it on a dyno.

Now you can play with tire pressure, jetting, plug gaps, valve lash etc and none of it will affect where the engine likes it's timing.

Your headers are too big for your engine. You would make more power with 1-5/8" tubes. Bump your fuel pressure to 6 psi and keep it under 7 psi. A 750 carb will make more power.

 

thanks for the advice im going to take it up to the track friday and give it two more degrees of timing and im going to try to bump it up to 6 psi fuel pressure 1 psi really going to help? How can my 1 3/4 headers hurt me but a big 750 carb help me when i have stock heads and cam 350?

edit: Don't quote an entire message

 

A 650 carb is small for a 350 unless it's an economy street driver. 1-3/4" headers are good for 500+ hp while 1-5/8" will build more low end torque which is what you'll feel the most. I ran 1-5/8" long tube headers on a 383 stroker into the 11's.

You've got too many mis-matched parts.

 

i see what kind of tire psi should i run i ran 35 last time and should i do a burn out or drive around on street tires?

 

Drive around on street tires. They just drag the water up to the line for you. If you want alittle heat in them, then drive around and back up to the edge of the box and get them alittle wet and spin them up real quick and let off. Street tires don't benefit from lots of heat as do slicks.