Timing

[MedPhys]

If I set my maximum timing at 2500 rpm to 34* (most people say between 36* - 38* for 440)

Will this hurt anything?

How can I tell if I need more without taking the car to the track?

If I bring the timing to 36* at 2500 rpm, and then reduce the timing back to 34*at higher rpm, what effects can I expect from this?

[dodge freak]

The only way I know how you can do that is with a MSD box and its called high speed retard. Some claim you can get a few more rpm's and power by backing the timing off 2-4 degrees at high rpms 6000+ . You are getting in to racing stuff now.

[MedPhys]

I have a holley pro strip annihilator setup, so it is easy for me to retard the timing at high rpm. 

The computer calculates how much time it needs to adjust timing.  If I set the max advance at 34* I have to phase the distributor so the computer will start calculating at 37*.

Dilemma:  Everyone on this site says 36* - 38* of advance, so I would have to phase the distributor so it starts calculating at 41* instead of 37*.  I can increase the advance to 36* from 2500 - 4000 rpm, then the computer makes me reduce it to 35* from 4000 - 6000 rpm, and then reduce to 34* 6500 - 7000 rpm.  I cant advance any further than that in those rpm ranges without rephasing the distributor.

So if 34* is just dandy, then I will leave well enough alone 

I appreciate all of the help. Thanks

[mikepmcs]

 
I want in on this one too.

[firefighter3931]

Dilemma:  Everyone on this site says 36* - 38* of advance, so I would have to phase the distributor so it starts calculating at 41* instead of 37*.  I can increase the advance to 36* from 2500 - 4000 rpm, then the computer makes me reduce it to 35* from 4000 - 6000 rpm, and then reduce to 34* 6500 - 7000 rpm.  I cant advance any further than that in those rpm ranges without rephasing the distributor.

So if 34* is just dandy, then I will leave well enough alone 

I appreciate all of the help. Thanks

The 36-38* is a general rule of thumb that applies to a mild build with open chamber iron heads. That is what most of the members here are using so that guideline works well. A more efficient closed chamber aluminum head casting won't need as much spark lead to make it's best power numbers, from my experience. I witnessed this firsthand when mine was on the dyno.

The timing curve you listed above should be fine, as long as the motor doesn't preignite. At higher engine speeds the motor won't require as much spark lead. I can't imagine that this engine will be spinning up past 6500 rpm anyway, especially if it is a hydraulic cam.

What exactly is the build ? Compression, heads, cam, headers etc...


Ron

[MedPhys]

Engine build

446
10:1 compression
iron heads ported polished, 2.14 intake 1.81 exhaust, crane gold 1.6 rollers
cam (sorry about limited info / no info) 484 lift comp cams, I believe there was a 280 in the listing, bought in 1997, don't remember anything else
1 7/8 tti headers
performer rpm intake, port and gasket matched to heads
speed demon 850 competition
727 with 2500 stall converter
3.91 gears

[firefighter3931]

That looks like a well balanced and thought out combination....congrats.  With that build, the curve you outlined above would be fine. Just keep your eye on those plugs for any signs of detonation. I don't think you'll be spinning it much past 6000 anyway due to the cam profile and hydraulic lifters. It won't make any more power past that point anyway so there's no point in overtaxing your motor.

Ron

[MedPhys]

Thank You, I appreciate the input.  Where would be an good safe rpm for the rev limiter to kick in?  I think I have it set at 6600 rpm right now.  Should I bring it closer to 6k?

[firefighter3931]

Thank You, I appreciate the input.  Where would be an good safe rpm for the rev limiter to kick in?  I think I have it set at 6600 rpm right now.  Should I bring it closer to 6k?

You're welcome. On the rev limiter ; 6000 is where i would set it. Hydraulic lifters are prone to pumpup (unstable valvetrain) at higher rpms which in turn results in valve float. The cam won't make any more power past 6k anyway so i don't see the point in over revving the motor. You'd probably find that the car would ET better using a 6k shiftpoint, rather than noseing it over on the 1st and 2nd gear upshifts.

Ron