Timing gurus. Recommended initial and total timing for a warmed ove 273 commando?

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trebor75

trebor75

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Time has come to start tune with the new parts (Ignitor II distributor).

1970 duster
1965 - 273 commando
Cam: Comp Cams Magnum 282S - 282/282 Lift 495/495 (solid) Beehive Springs
Edelbrock D4B intake / Holley 670 Street Avenger
Pertronix Ignitor & Flame Thrower coil
Hooker Headers
2.5" Dual Exhaust / Super 44 Flowmaster
8 3/4 - 3.55 - SureGrip
727 auto / Shift Kit
10" 2000 stall converter
B&M Quicksilver Shifter

It sure seem to like a lot of intitial timing. I have it at 19 right now, the response is really great and peppy. What do you recommend for a total timing, and at what RPM should I have it? I got a spring kit and advance limiters etc with the distributor.

I set initial at 19 yesterday and tuned the carb for best vacum at 800 rpm. I could not set the total myself, need a friend to help me check the tach and rev it up. I did take it for a ride and no pinging at 6500 rpm. It runs great I have to say.

Can someone help me understand total timing? Lets say Im at 40 now, with no pinging, is this ok? Or should I still strive to have it at about 36? Would there be powergains from this? Should I set the curve so it kick in as fast as possible? Say at around 2000 rpm?

Please help me understand to tune for best overall performance for my set up.
 

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100s of posts on this subject. It can get complicated too. Those who have figured it all out say total advance or all in should be 34 degrees at 2500 rpm.
18 degrees base can cause more than the 34 total in many distributers. Sprigs in the centrifugal advance can prevent all in by 2500 rpm. Thus altering the travel in centrifugal advance, changing those springs, all those complications. I didn't mention rotor phasing but I'm sure someone will if you persist.
Those of us who don't race and need every bit of horse power set to get a good run with no ping and drive.
 
RedFish said:
100s of posts on this subject. It can get complicated too. Those who have figured it all out say total advance or all in should be 34 degrees at 2500 rpm.
18 degrees base can cause more than the 34 total in many distributers. Sprigs in the centrifugal advance can prevent all in by 2500 rpm. Thus altering the travel in centrifugal advance, changing those springs, all those complications. I didn't mention rotor phasing but I'm sure someone will if you persist.
Those of us who don't race and need every bit of horse power set to get a good run with no ping and drive.
Click to expand...

Thanks Redfish. When I have a friend to help me out I'll be checking what my total is at this point and change springs if needed.
 
every combo wants something different..the most initial timing you can get in it for the fuel used the better... then limit the total to say 37-8 and test it! them move it up and try down too... good look its tedious work...
 
Sounds like you're on the right track. If it likes 19° initial and doesn't kick back against the starter when you crank then that is good. A rule of thumb is total at 32° and all in by 2000rpm. That's just a guideline. Your total is past 32° but as long as it doesn't ping you're ok. Stock reworked distributors may be limited to 32° total until you plug in the vacuum advance and then it can end up around 50° with no problems. The springs control how fast the advance comes in and the weights and pins limit the total. Let's talk about springs. You may benefit by taking the heavy spring out and replacing it with a lighter spring. The advance will come in faster and it might be even peppier yet.....or it may cause ping because it comes in too fast. You just have to try different combinations. Your engine combo sounds killer. We will need a video when you get it all dialed in. tmm
 
1 person can check total timing, rev the engine until it stops advancing.

To observe when it's all in, then you may need someone else to look at a tach.

Big cam, small engine = more initial. Maybe low to mid 20's.

Total timing is a rotten method to time a street driven car. Get initial set where the engine wants it, then worry about mechanical advance and total timing. Simple test, at idle, turn distributor a little counter clockwise, if engine picks up RPM, it wants the timing at idle. Reset your idle speed, do it again. You may end up with a potentially locked out situation.

Springs usually change the rate at which mechanical advance comes in, rarely does it limit the amount. There is usually a physical limiter in the distributor, slot length, bushings, etc.

If it's not pinging at 40 total , run it. Check the ceramic of the plug for speckling, that's a sign of detonation.
 
Guys, thanks a lot for educating me! I feel I got a better understanding of it all now. Along with my new distributor I got both springs and advance limiters. I will report back, might not have time to work on it more this weekend though.

Toolman: I think you have seen this already, this is with the old edelbrock carb and old distributor, but besides that it's the same setup. I'll see if I can shoot some videos of it when I have dialed it all in.

[ame]http://youtu.be/HxSr8bkjC1s[/ame]
 
trebor75 said:
Time has come to start tune with the new parts (Ignitor II distributor).

It sure seem to like a lot of intitial timing. I have it at 19 right now, the response is really great and peppy. What do you recommend for a total timing, and at what RPM should I have it? I got a spring kit and advance limiters etc with the distributor.

I set initial at 19 yesterday and tuned the carb for best vacum at 800 rpm. I could not set the total myself, need a friend to help me check the tach and rev it up. I did take it for a ride and no pinging at 6500 rpm. It runs great I have to say.

Can someone help me understand total timing? Lets say Im at 40 now, with no pinging, is this ok? Or should I still strive to have it at about 36? Would there be powergains from this? Should I set the curve so it kick in as fast as possible? Say at around 2000 rpm?

Please help me understand to tune for best overall performance for my set up.
Click to expand...

Initial 12-19 is generally a good number. As soon as it kicks back on the starter, back it off a couple of degrees.

Total timming...34-36 degrees, is what you want to shoot for. Leave it at 40 or more, and you just might melt some pistons.

As far as "all in ". With a generally lightweight car, like our A bodies, getting full advance quicker is good. Generally 2000rpm -2500rpm is a good point.

Remember to use the same grade gas you intend to use when tuning.

17 initial
35 total
All in 2500
Would be a great starting point for your street car.
 
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