Dyno Simulators and ignition timing

Just to pass some time i was playing with the DynoSim5 program. According to program my pump gas 511 is making 680hp/640tq. Sounds reasonable to me, but it shows the Ignition Timing requirement to be 28*@1500rpm and 40*@6500rpm. That sound right? I have always been under the assumption that you make more power taking timing out at upper rpm? Anyone know what these combos really require for timing at upper rpm? Currently locked at 34*, but i still have that issue with the msd dist. taking out 3-4* timing with rpm.

Sounds like that program is based on Chevy V8 engine results
None of the Mopar V8 engines I've work on made from 1952 to 1990, no NASCAR race motors though, liked more than 36 degrees total on gasoline, none of them At the track or on the dyno

My daily used 318 liked 2 degrees of timing being pulled right after peak torque.
It extended the curve just a little bit further.

I went through the trouble of setting up a rpm
retard in high gear.. on my junk it made ZERO
difference so after 1 season I pulled it off..
my timing was best around 34*.. my last SB
liked 40* on the dyno.. I used 36* on the street
due to fuel(I run moose piss pump crap.. still do
unless I'm going to the track)

All good info, thanks guys. I'v been contemplating getting a new Ice Ignition box with matching distributor and wires. Their box has many ignition curves mapped into them. Thought i might be able to take advantage of that. Guess not. I'll keep it locked out at 34* for now. Thanks again.

There is no engine simulation software that you or I can afford that I'd use to predict my ignition timing requirements.

Dave, I found similar with Dynomation 5. I've e-mailed Larry about that, and the fact the shape of the curve didn't match what I've seen. As far as the timing goes, I beleive its just based on the generic head categories. I'll look through the his replies to see if there was anything more informative.

I think Cab is right - its based largely on Chevy motors. It's hard for me to beleive that the crank to rod ratio and the combustion chambers don't effect best timing curve. Shrinker thought it did, and I give him more credence on such things than the simulation program.

Mr. P - that's interesting about the 40* on the dyno. When Hot Rod tested a 340 on Edelbrock's dyno in 1969, they claimed to be using 39*.

Yur right. Just too many generics in that program. I'll stay with 34* locked out to be safe for now.

How married are you to that MSD distributor? Could be in the dist. or could be slew rate (switching time of all the electronics adding up). Can you borrow a mopar performance 'tach drive' distributor from anyone?

The plugs will tell you the correct timing.

Unless the Chevy has a late model head they take 42 total most of the time. And big block stuff was about 40.

Every BBM took 39-40.

I'd be surprised if 34 is best power for you. The only way to know is to test.

Its in the distributor for sure. Had a Firecore before the MSD and timing was rock solid no matter the rpm. Had to send it back because of the rotor tip melting off. Had same timing issue with an MSD in a small block. Put a crank trigger in it and issue went away.

ok, i'll test it at the track or a chassis dyno later this summer.

Is the dist moving up and down and rotating

no, i fixed that last year with a shaft collar. there's something not compatible with Ice and MSD. Crank trigger or different distributor is the only fix i know.

Was thinking of your locked timing issue while posting about the MP distributors on FABO.
Skim toward the bottom if you're interested
https://www.forabodiesonly.com/mopar/threads/p4120701-small-block-mech-tach-drive.404838/

Thanks. Looks like 35* is the magic number. Being that mine loses 3 or maybe 4* with rpm, set at 34* would be 30 or 31* down track. Being locked helps with the large cam as well, but i would like to see the required timing mapped some how on a big block and mapped every 500rpm. curious how much power loss there would be with timing locked at say 35* instead of giving it what it wants at every rpm increase.

If you're willing to play with a curve on that distributor, maybe using the heaviest pair of springs and modifying the weights for a short advance. I'm thinking every 1000 rpm that can be delayed before 'all in' will be 1000 rpm it doesn't show retard on the top.

https://www.tapatalk.com/groups/racingfu...-less-t765.html

Can you afford the time experimenting??

Absolutely nothing odd about running 40 degrees of timing for best results. Known of a few combinations over the years( smallblocks) that was the case. One was a stroker B1BA headed motor that immediately comes to mind.
Few years back i had a ross flattop 416 Hensley built i had eddies on top of. Sold the whole top end. Ran that combo several years, liked 34 degrees best( and i tried it everywhere)
Put W5 heads on that shortblock, TTi W 5 headers, a modified Victor W2 i bought from Brett, and plopped all that stuff on the untouched 416.
Had the timing all over the place on that motor, and the car flat ran a tenth better at 40 degrees than it did at 36, 34 or 32.... the other places i ran it..... late that same year i broke that cast crank 416 shortblock.
Built a new roller x block 422 with CP domes. Dropped the W5 topend on that, and it was happiest at 32.......... slower everywhere else

34 or 35 is probably the correct number or very close to it for your combination. It isn't all that easy to figure out the "perfect" timing. It is a little easier on the dyno than it is at the track but you can sneak up on it at the track if you have enough time.

My new EFI system allows me to adjust the timing of each cylinder. That opens a whole new can of worms......

Thats what i'm talkin about. Mapping timing for every 500 rpm increase til max power. Isn't that what the OEMs are now doing and for each individual cylinder as well. Not sure anyone has done this on a Big Block mopar though. I'm happy just locking out for now, but just wonder how much power is lost thru the rpm range with fixed timing.

IF you gain it would be very little being you
have a locked dist.. if you had a vac adv dist
it would be adding timing on light throttle
and it can get up into the 50* range

Don't know what i'm gonna do yet. My MSD doesn't have a vac can, but i am looking a getting a different distributor. think i'll just leave it alone locked out for now. Thanks Mike

The Chrysler tach drive will get you pretty close to that. Whether it shows as a flat line or a slight rise intiming will depend on two things. One, adjustment of the secondary spring perch. The other, speed of the ECU's electronics and other factors that may slow the firing time.
That SB unit that I showed the plot for was tested on a SUN 404 with an amplifier box. That box is pretty slow. Still flatlined.

Thanks for that linc. Looks like chrysler knows what needed and i just need to lock timing at 35* without losing any timing thru rpm increase.