[wh33lman]

Need some help setting up my timing and idle RPM.

I have a .030 over 1976 455 (462) with 11.5:1 compression, Edelbrock Performer RPM round port heads, Crower 60919 cam, 1.5 HS roller rockers, Doug's headers, Fitech EFI with timing control, MSD Pro-Billet distributor, Pypes 2.5" exhaust, 3000 stall convertor.

Currently I have 14° initial timing set with idle set at 750 rpm. I just picked these numbers randomly to get me going. It idles and runs fine. Even at 650rpm idle it does not seem unhappy

I have looked at other combos, and base timing ranges from 8° to 18°, idle RPM from 500 to 1000.

But is there a preferred method to determine intial timing and idle RPM?

[tooski]

I'd like to know also. The most recommendation I've seen is 12* and 750 rpm in drive. I ended up with 16* and 750. I'm thinking if I try to go down to 12* the engine will stall.

[PDC]

14* base timing and 750 RPMs sounds just fine to me.

[Navy Horn 16]

That's a reasonable timing for base, it will like that. What is your total timing? Most people start at 12 because they have about 24 degrees of centrifugal for 36 total.

If that's what you have, you could be at 38 total...which could to much. You've got a lot of compression.

[PDC]

To confirm, my D.U.I. HEI has 20* all in at 3k, (positive stop at 20* mechanical) so with 14* base, 34* centrifugal is the most my combo ever sees.

[wh33lman]

I am using the Fitech timing controller with a locked out Pro-Billet. Total timing is about 32°

[steve25]

What trans is in the car?

Are you saying it idles clean at 650 in gear?

If you can idle at 650 in or out of gear then what's to complain about if the motor does not ping or knock with that 11.5 comp and whatever octane fuel your running and your timing setting.

Are you racing at the strip in a class where producing every last scrap of HP is needed?

[wh33lman]

No racing yet.
I took the motor from my friends 2800lb tube chassis track car, when he upgraded to a 535 Kauffman.
I replaced his solid lifter race cam with the 60919, and added the FI.
Tranny is a built TH350...but I went through a couple of those until I found a shop to build one properly.
My one and only trip to the track yielded low 13's at 111, with a blistering 2.5 sec. 60 ft.�� on BFG TA's. Next step is to build up the rear end before getting some MT's to put on at the track.

[Formulajones]

I'm not familiar with the Fi-Tech, I use the Holley Sniper, but if they are similar, then you should be able to set your base and total numbers that you want and it will build the curve for you. From there you can tweak anything for better drivability, add in areas, subtract, etc...

14 at idle and 32 total sounds like a great place to start for that combo. I'd play from there and see what it likes, adding more in light throttle areas to simulate the vacuum advance and do some data logging.

Only a trip to a chassis dyno or the dragstrip will tell you where the engine is going to like the total timing at WOT, but 32 is a fairly safe place to start. The nice thing about timing control is it's just a few key strokes away from a quick change and retest. Sounds like a great setup.

Idle is subjective and personal preference. There is no real set number for any combo. Put it where you're happy, as long as the IAC is reset in a range where it controls it properly you can idle it anywhere you want.

[JLMounce]

Originally Posted by Formulajones

I'm not familiar with the Fi-Tech, I use the Holley Sniper, but if they are similar, then you should be able to set your base and total numbers that you want and it will build the curve for you. From there you can tweak anything for better drivability, add in areas, subtract, etc...

14 at idle and 32 total sounds like a great place to start for that combo. I'd play from there and see what it likes, adding more in light throttle areas to simulate the vacuum advance and do some data logging.

Only a trip to a chassis dyno or the dragstrip will tell you where the engine is going to like the total timing at WOT, but 32 is a fairly safe place to start. The nice thing about timing control is it's just a few key strokes away from a quick change and retest. Sounds like a great setup.

Idle is subjective and personal preference. There is no real set number for any combo. Put it where you're happy, as long as the IAC is reset in a range where it controls it properly you can idle it anywhere you want.

Second this.

Your base setup sounds like it's going to actually be pretty close for the combo. If it's running well now, all you can really do is thoroughly test it on the road or a dyno to see where it may want more or less.

On the FiTech you'll have breakpoints for 1100, 3000 and 6000 rpm at several different MAP points. You'll have 45kpa, 45kpa cruise and 95kpa for each of those individual rpm break points.

for your 45kpa settings start with your desired advance at those rpm's plus 10 degrees to simulate a vacuum can with 10 degrees of advance in it. For your you can experiment with the 45kpa setting not related to cruise. This will be your idle timing and you may be able to add more than 10 degrees there.

the 95kpa break points are your wide open throttle values and would be your total timing desired without any additional advance. the 1100 rpm breakpoint is kind of the one that's probably going to give you the hardest time because it doesn't rest evenly between your idle rpm and the 3000rpm break point. This is basically your "off-idle" timing and you may need to experiment on the road to see what the engine likes there.

From those data points the system will build a linear interpolation map between those points that will be based on rpm and MAP reading. It's doing basically what a mechanical distributor with a vacuum advance is doing, just in digital format.

[Cliff R]

The initial question is a bit difficult to answer without a few pages but basically initial timing is limited by cranking pressure on a fully heat soaked engine. There are many things that effect or control how much timing you can put on one of these engines at cranking/idle speed.

With higher compression and smaller cams you will run into difficult hot restarts at some point, so the initial timing will typically be a little less than 14 degrees but not always. In terms of what you end up with less is better in all cases. You'll find that the better job you need choosing the compression and cam for the CID, tighter quench, more efficient combustion chambers, etc, you'll need LESS timing everyplace including initial.

For a high compression 455 with a relatively small cam like the 60919 you may find 14 initial a little high for restarts fully heat soaked on hotter days. My 455 is 11.3 to 1 true static compression with a considerably larger camshaft and I'm not able to run past 10 degrees initial timing or on occasion after driving some distance and attempting a restart in hotter weather it will "buck" the starter just a tad. It will also start harder if I try to use lower octane pump gas in it, telling me that anything past 10 degree initial for this combo isn't going to be happy.

If you are only running 34 degrees total timing and no additional timing at light engine load there is some efficiency being lost. I typically run between 42-48 degrees total on these engines, initial + mechanical + vacuum advance for best overall performance, throttle response and drivability. Those numbers assume higher compression, tight quench and well chosen camshaft. You may find lower compression engines with more quench and larger cams typically want more timing everyplace to be happy......Cliff

[wh33lman]

Currently I am sitting at the default FiTech settings

Idle Advance = 13.9
1100 45kPa = 22.1
3000 45kPa Cruise = 27.8
6000 45kPa = 31.9
WOT 1100 95kPa = 15.4
WOT 3000 95kPa = 29.3
WOT 6000 95kPa = 31.9
So there is a bit of room for adjustment.

As I understand however, the Fitechs have about 20 degrees of advance to play with, so to go higher than 34 I will need to increase the base timing.
No big deal really. You can always retard the initial timing back to a lower value.

Cliff - Sorry about replacing the 800 CFM Q-Jet you built me
But it is always ready to go back in if necessary. I will not sell it.
Retired guys need to tinker you know.

The motor was built a long time ago for a speed shop owner, and no one remembers the actual specs.
I suspect It was one of those. "... let your builder decide" builds.

It has the original Performer RPM EHeads...which were 87cc at that time.
The block was decked and the heads shaved for maximum effort.
The initial compression was 13.5:1 so the Venolia domed pistons were shaved to get it to 11.5:1 for pump gas.
Being that I had to shave the Northwind intake down almost .080" I expect the quench is quite tight. ( but we are out of my level of expertise as far as that goes.)

With the Doug's headers I use a mini hi-torque starter, and my hot starts have been instantaneous.
Heat soak problems do exist with these FiTechs however.
A spacer is a must or it does not spray fuel after sitting for 20min on a hot day when the ECU reaches +165°.
You can do without the spacer, but it takes a few attempts for the circulating fuel to cool it down enough to go.
Squeezing all this under a '81 Turbo hood is a challenge...but it can be done.

I felt the solid race cam was a bit much for the street, considering the LSA , it's higher powerband 3K-6.5K, my 3800+ lbs. vs his 2800 lbs, and my 3:08 gears to his 4:10's and big carb to your Q-Jet.
The motor is coming out this fall for a refresh, so I might be ready to reinstall that cam.

More tinkering !

[dmac]

I agree with Steve25 about setting idle in drive. How it idles in park is much less important. In drive with brakes on gives a little bit of a load on it.

[wh33lman]

Originally Posted by dmac

I agree with Steve25 about setting idle in drive. How it idles in park is much less important. In drive with brakes on gives a little bit of a load on it.

The EFI automatically adjusts the idle and timing when put in gear. However I do have lots of datasets to compare.

[Formulajones]

Originally Posted by wh33lman

The EFI automatically adjusts the idle and timing when put in gear. However I do have lots of datasets to compare.

And that's a neat feature with the EFI, the IAC will automatically shoot for the idle you have set in the parameters, and maintain that timing as well without fluctuations. In gear, out of gear, is all the same. So you can set it where you're comfortable, where the engine seems happiest, and the IAC does the rest.