SanDiegoPaul

Looking for numbers from similar engines to compare mine with. I'm running Cast Iron heads with this cam: http://dab7.cranecams.com/SpecCard/D....asp?PN=113942 and (DUH!) looking for more power. :blueangel: Compression ratio is pert near 10:1 currently.

Running 91 octane (at $2.20/gal :nono: ) the engine does not ping. I have it set up with 32 degrees total advance at 3,000 RPM and the base timing, for whatever that's worth is set to 8 degrees.

Now, this is an EGR motor and I think that with the EGR cooling the cylinders down, I may be able to get away with more advance than some others with cast iron heads. Any takers on this?

Thanks!

SanDiegoPaul

ttt :yesnod:

VETDRMS

Well, there's one way to find out...go up in 1-2 increments, take it out and run it, if you can hear any ping, just let off. A few instances aren't going to rocket your motor. Find an empty stretch of road and time some 0-60 runs with each setup. If you can get on the dyno, that would be even better. :cheers:

Vetterodder

I agree with VETDRMS, trial is the only way to know for sure what is best for your particular combination. Unless you're runniing fast burn style heads, I'd expect that your optimum timng would be closer to 36º total.

Cali,68,L-79

I take it you already took care of the fuel pump issue? Sorry no cruise this weekend Vettes STILL at the painters. :mad

brimcc

What is 36 degrees when you set the timing the old way with vacuum off and at idle, is it 8 degrees?

Vetterodder

Brimcc, total timing is the combination of initial + centrifugal, with vacuum advance disconnected. For example, if your distributor allows 24º advance as rpm increases and you set initial at 12º, your total will be 36º. With the vacuum advance connected and deployed, you would likely see 50º or more. Because not all distributors add the same amount of advance, there is no set "ideal" initial setting that will get you to the desire total. If your distributor allows 20º centrifugal, then it would take 16º initial to get 36º total. Keep in mind that 36º is not necessarilly optimum for all engines but is often recommended because is usually close to optimum for most and is a good starting point to work from.

I prefer to determine my initial by setting total timing first and then see where initial happens to be. If you have a dial back timing light you can set it at 36º (or whatever total you want) and, with the vacuum advance disconnected, rev the engine until the timing marks no longer move. If you're using a standard timing light, measure the circumference of your balancer, divide that figure by 10, and place a mark on the balancer that distance from it's 0º mark. That mark will be at 36º. Some stock distributors don't achieve full advance until well past 4,000 rpm so don't be shy about reving it up until you're sure that it's through advancing. Removing the advance springs from the distributor will, in most cases, allow total advance at or near idle rpm. I don't recommend that method though because I've encountered several cases where the springs themselves have limited total advance. If the spring travel is limiting full advance, you could set it at 36º but wind up with something less after the springs were reinstalled. Turn the distributor until the the 0º marks are aligned and you will be at total.

For future reference, recheck timing at idle. That figure will be your initial and hopefully it's not excessive. Too much initial can cause kick back from your starter or even mimic a weak battery and not turn over at all. If your distributor doesn't provide enough centrifugal to get you to the desired total without using excessive initial, it can be modified to do so.

SanDiegoPaul

I take it you already took care of the fuel pump issue? Sorry no cruise this weekend

Yea took care of fuel delivery last week. No more breaking up over 4,000 but the prob is that it didn't increase the HP on the Dyno. :mad So that's where I 'm at.

lars

SDPaul -
I think you're short of peak power and best throttle response at 32 & 8. If I were you, I'd get it bumped right up to 36 total, giving you 12 initial. Generally, as long as this doesn't ping, it will give you the best starting point for optimum performance and best throttle feel.