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-   -   383 ignition timing recommendations? (http://www.hotrodders.com/forum/383-ignition-timing-recommendations-178128.html)

v8hed 05-19-2010 05:24 PM

383 ignition timing recommendations?
 
Just trying to optimize the timing on my 383... currently running 12* BTDC base timing (vac. disconnected) and 36* BTDC total mechanical. Tried advancing a few degrees and couldn't hear any spark knock, but performance didn't feel improved. Could I make more power with less than 36* BTDC total? My testing technique isn't very scientific... nail it in 1st and 2nd gears and see if/how much tire spin I get between adjustments!

Running RHS ProAction 200cc iron heads, Edelbrock 750 carb, Performer RPM intake.

Thanks.

DoubleVision 05-19-2010 10:07 PM

What`s the compression ratio? What size cam? we have to have more info on the combo before we can recommend the timing curve.

techinspector1 05-20-2010 03:50 AM

Here is a copy and paste from the RHS site....
"Revised combustion chamber design for excellent combustion thermodynamics and enhanced fuel efficiency"

Now, I don't know if this means that the chambers are very fast burn like the Chevrolet L31 design and others currently available, but if they are, then you won't need any more than 34 degrees total initial and centrifugal, with more available from vacuum at cruise. One of the best guides to
determine the initial ignition timing of V8 engines can be
found in the Barry Grant, Inc. catalog or at their website
under the Demon Carburetor Guide. Typically, they recommend 10- to 12-degrees of initial timing when
the duration of the camshaft is less than 220-degrees @ 0.050” of valve lift; 14- to 16-degrees of initial
timing with a camshaft duration of less than 240-degrees @ 0.050”; and 18- to 20-degrees of initial timing
when the camshaft duration is less than 260-degrees @ 0.050” of valve lift.

So, put the initial where it needs to be for the cam timing, then change your centrifugal advance curve to provide a total of 34, all in by 2800. Then add the vacuum.

v8hed 05-20-2010 03:50 AM

Quote:

Originally Posted by DoubleVision
What`s the compression ratio? What size cam? we have to have more info on the combo before we can recommend the timing curve.

Sorry, I know this... don't know why I didn't provide that!

Cam is a Performer RPM (not my choice) and CR is 9.35:1 from what I can gather (why it was built with 64cc heads and -18cc dished pistons, I just don't know).

Anyway, timing recommendations?

techinspector1 05-20-2010 03:54 AM

Quote:

Originally Posted by v8hed
Anyway, timing recommendations?

See post 3. We posted at exactly the same time. What's it, about 11 AM in the U.K.?

v8hed 05-20-2010 04:01 AM

Quote:

Originally Posted by techinspector1
See post 3. We posted at exactly the same time. What's it, about 11 AM in the U.K.?

Great, thanks for that info. I'll set it to 16* initial and 34* total mechanical.

Yep, 11AM here. I could never post anything that made sense at 6AM unless I'd had a few strong coffees first!

techinspector1 05-20-2010 04:07 AM

I'm sitting here watching CNBC, trying to get a handle on the market for Thursday. Man, oh man, those damned stupid Greeks are back out in the street protesting. What part of "BANKRUPT" do those people not understand?

v8hed 05-20-2010 04:50 AM

Quote:

Originally Posted by techinspector1
I'm sitting here watching CNBC, trying to get a handle on the market for Thursday. Man, oh man, those damned stupid Greeks are back out in the street protesting. What part of "BANKRUPT" do those people not understand?

Not that I relish in profiting from other peoples misery, but there are some good stock investment opportunities to be had right now. I'm just glad the UK hasn't joined the Euro as a unit of currency!

SlowGTA 05-20-2010 06:22 AM

1 Attachment(s)
Here is the spark table for my 383 with AFR 195's and a 219/219 roller cam at 9.9:1.
Not exactly the same combo but thought it could give you and idea of what others are running. This was arrived at from a Vortec base timing curve and then data logging runs, it has not been tested on the dyno yet.

One thing that was very clear for this engine was that although it liked alot of advance under light throttle (35), when the load increased, it wanted much less. (as low as 20 deg).

I know this info won't be a direct help as you are mech/vac timing and a carb but thought I'd share anyway to give an idea of what's worked for me.

sooper 05-20-2010 04:56 PM

Quote:

Originally Posted by techinspector1
I'm sitting here watching CNBC, trying to get a handle on the market for Thursday. Man, oh man, those damned stupid Greeks are back out in the street protesting. What part of "BANKRUPT" do those people not understand?

The part where every single person,man woman or child cant have 12 weeks hollidays a year. Sorry had to get that it cause it just kills me

techinspector1 05-20-2010 09:27 PM

Quote:

Originally Posted by sooper
The part where every single person,man woman or child cant have 12 weeks hollidays a year. Sorry had to get that it cause it just kills me

There comes a point where somebody has to work to create wealth to pay the bills. Margaret Thatcher said it best....
“The problem with socialism is that you eventually, run out of other people’s money.”
- Margaret Thatcher

sooper 05-21-2010 03:39 AM

Quote:

Originally Posted by techinspector1
- Margaret Thatcher

Iron Maggy
They didnt know how good they had it

Sorry folks. Now back to your regularily scheduled thread


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