383 magnum stock timing?

[MoparMotel]

Hi,

With the help from you guys on what I read on here and also a few friends answering questions, I am teaching myself to be able to work on and tune my car myself. After much thought on a new carb I sent the original Carter 4401 to Jeff at Old Carb Doc in North Carolina to be restored/ rebuilt. I am very eager to be able to tune the car myself and be able to check timing and give the car a tune up if needed.

I sent the carb off last week so it will probably be a few weeks before I get it back. Right now it is sitting with a lift plate over the intake to make sure nothing gets inside the intake.

To tune the carb I went out and bought a new vacuum gauge and I do have a timing light. Last time I checked the timing at idle it was at 15 degrees. Total advance I have not checked because I am not sure exactly how (I think full advance comes in at 2000-2500rpm from what I read?). Car is running a stock distributor with a pertronix ignitor kit instead of points.

Does 15 degrees at idle sound about right or should it be higher/lower?

Car is a '68 383 Magnum rebuilt to factory specs except cam below and a 727 auto

Brand      COMP Cams
Manufacturer's Part Number      21-306-4
Part Type      Camshafts
Product Line      COMP Cams Magnum Hydraulic Camshafts
Summit Racing Part Number      CCA-21-306-4
Cam Style      Hydraulic flat tappet
Basic Operating RPM Range      1,800-5,500
Intake Duration at 050 inch Lift      224
Exhaust Duration at 050 inch Lift      224
Duration at 050 inch Lift      224 int./224 exh.
Advertised Intake Duration      270
Advertised Exhaust Duration      270
Advertised Duration      270 int./270 exh.
Intake Valve Lift with Factory Rocker Arm Ratio      0.470 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio      0.470 in.
Valve Lift with Factory Rocker Arm Ratio      0.470 int./0.470 exh. lift
Lobe Separation (degrees)      110
Camshaft Gear Attachment      1-bolt
Intake Valve Lash      0.000 in.
Exhaust Valve Lash      0.000 in.
Computer-Controlled Compatible      No
Grind Number      CRB 270H-10



Thank you!

[MoparMotel]

Also....As much as I'd like to tune it myself, there is a local shop here in town that will dyno tune the car for $400 if you think that would be my best bet.

[MoparMotel]

After doing some more reading it seems that i should be right around 36 degrees at total advance...Now with a stock distributor with pertronix when should full advance be all in, 2000, 2500, or 3000rpm? I've seen all three numbers. Also I've seen some guys say they run 12 initial, and some that say there motor likes 18-19 of initial timing. With mine being at 15 I'm guessing this is a happy medium? Reason I was thinking of adjusting initial was because the car is a dog off the line, but after 2800-3000rpm really takes off.

[Chryco Psycho]

having the timing near 36* total is more important than idle , the engine spends most of its time & all of it in the powerband at total timing , if the total timing is in too early you may get pinging so slowing the curve with heavier springs may help . A looser torque converter will get you into the powerband faster & help the car accelerate quicker .

[MoparMotel]

having the timing near 36* total is more important than idle , the engine spends most of its time & all of it in the powerband at total timing , if the total timing is in too early you may get pinging so slowing the curve with heavier springs may help . A looser torque converter will get you into the powerband faster & help the car accelerate quicker .

Thank you for the info, this is definitely a learning experience for me. So if I'm understanding it correctly I'm going to hook timing light to #1 cylinder and disconnect vacuum line and put the light on it just as if I'm checking initial, only rev the engine up to 2000 or 2500 to see what advance I have and when it comes on?

Or do I leave the vacuum advance hooked up to see when it comes on?

My timing light is pretty old I might pick up a nice snap on one.

[Chryco Psycho]

if you put a line on the damper 2 3/8 clockwise from the zero line that is 36*
generally I run either with the vacuum advance disconnected at all times or using an allen wrench dial it of so it can only move maybe a couple of degrees , set the timing at 36* at 3000 rpm & see what you get at idle .

[mhinders]

My 67 model 383 is standard except for Eddy RPM, radical Comp-cam, Holley 750, Hooker headers. Unfortunately the camspec is unknown at this moment, but I'm running 7-10 in of vacuum, and powerless  engine at low rpms.
- Have to have my initial timing at 24 degrees to avoid the engine stalling when I put it in gear. Yes, it's a pain. I have limited the mechanical advance to 12 degrees, vacuum advance is impossible to use and disconnected. So at speed I have 36 degrees ignition advance.

The problem is fairly low static compression paired with a radical cam giving very low dynamic compression, resulting in powerless low rpms.
My temporary solution will be to advance my cam a few degrees to allow it to build more cylinder pressure.

[MoparMotel]

Thanks guys, As soon as I get the carb back I'll try that. I'm sure it's a mixture of the old carb needing a rebuild and my torque converter which feels very tight/ hardly any stall at all, but I've seen 383's hit the gas and they just light up the tires, Including my old 69 Superbee 383 I sold a few years ago. This car... you can hold the brake and floor it and it will not even begin to break them loose.

[MoparMotel]

Also what is a good brand of timing light to purchase? A friend of mine had a Snap On one that had the degree of timing right on the gun on a screen it was neat.

[firefighter3931]

With that cam and 383 cubes i'd be looking to have 18-20* at idle and 36-38* total all in by 2500 rpm. 


Ron

[MoparMotel]

With that cam and 383 cubes i'd be looking to have 18-20* at idle and 36-38* total all in by 2500 rpm. 


Ron

Thank you Ron I'll give that a try 

[MoparMotel]

Definitely learning a lot about how to tune this thing myself  

I'm sure you guys know a lot more than I about these cars and engines, but if anyone else is interested this video helped me out a lot:

When I get the carb back I am going to set it at 18* initial and see where that puts my total advance at.... Then figure out if I need to re-curve the distributor with different springs or not.

Only thing I still don't understand is "Welding the slots" in the dist? I thought you just have to change the springs inside to a lighter/heavier one?

http://youtu.be/UYGU7mTwsZc