Mild Built 340 Timing/tuning help?

PyePerformance said

Hello all!

I am new to the forums, but have been reading advice here for a couple years now. Time to finally post.

Me and my friends have built my father's '70 Swinger 340 engine, and now it is finally time for me to start tuning it. I am still fairly new to tuning older vehicles, although I have been studying and learning tons(quite a bit from you folks!) over the past few months. It runs well, I just need some advice on intitial/total timing(and timing curve) before I move onto tweaking the carb. Here's the engine:

340 .040" over
TRW pistons
Comp xtreme energy hydraulic flat tappet 224 @ 050
Eddy aluminum performer RPM heads
Eddy performer RPM Air gap aluminum intake
Mallory Unilite Distributor (mechanical advance, no vac)
Holley 800cfm DP
C/R is somewhere in the mid 9's:1 if I had to guess.
NGK BKr6e gapped @.035"
We run Sunoco 110 leaded.

I understand each engine is unique, but would anybody be able to possibly give me a "ballpark" answer to these questions?

1. Total timing. I have heard around 34-36* is recommended. Would that roughly apply to this mild built engine as well?
2. Mallory dist. springs -- what spring combo(timing curve) would be a good place to start?
   
3. What is the best way to determine initial adv?

Bonus points for a really dumb question. I have never personally heard engine ping, and I have read many times to pull as much advance as possible without pinging. What exactly is the noise I should be listening for, and would it only be under acceleration?

Anyways, thanks in advance, and forgive my stupidity! :D
- Steve

Click to expand...

Let us start with ping, sounds like rattling marbles in a jar. Definately you want to steer clear of this. The 390 FE Ford even with the lower compression 2V engine would rattle about twice when stepping on it off a light. That is OK as it was not sustained. That rattling while driving will destroy the engine real quick.
Now what is the cause? Combustion in the cylinder under normal conditions is the burn of the air/fuel in the cylinder. This starts at the spark plug and progresses across the combustion chamber. Two things can cause ping or knock, both detrimental. One is preignition caused by a glowing hot spot in the cylinder from sharp edges or carbon. This lights the fuel early causing the cylinder pressure to rise quickly while the piston is still traveling up the bore. As the pressure rises the temperature in the cylinder rises quickly until the air/fuel reaches the temperature to auto ignite. This is like a diesel but the remaining air/fuel explodes like a hand grenade. This burns holes in the side of the piston crown, breaks pistons and hammers rod bearings out.
Too much ignition advance does similar in that that combustion pressure rise occurs too soon and ignites the remaining air/fuel. Proper ignition advance has the pressure rise maximum occur about 10° ATDC. By then the piston is starting to move down the bore. Static compression is part of affecting facturs. Dynamic compression is a bigger factor. A/F ratio and load which is a contributor to mixture density also affect the speed of combustion.
Concerning the Al heads and AirGap manifold; you do not have much heat transfer to the air/fuel mixture coming out of the carburetor. I hope by this time you have broken in your cam with breakin oil and have changed to an oil with 1,000ppm to 1,200ppm ZDDP to protect the cam. If you hook up your timing light, start the engine and point the light down the carb. You should just see the venturis. Slowly rev the engine and you will start to see droplets of fuel coming out of the carb into the booster venturis. With a dial back timing light you can see how the droplets break up as they drop further. With the AirGap style manifolds, they benefit from annular discharge boosters or "shear boosters". Holley has a few boosters they use. Straight boosters, downleg boosters and annular. The annular have a series of holes around the inside of the booster venturi which tends to break the fuel up into smaller droplets before entering the manifold. You will get better performance and economy with them. You can search shear boosters. Patented and available from the patent holder to install in your Holley.