Tuning

[attret00]

Can someone explain how to power tune. It has something to do with the circumference of your harmonic balancer. I just added a curve kit to my '64 327/300 and was told it would function better if power tuned. Something about dividing the harm. bal. into degrees and marking 38 Deg. on the balancer and reving the engine until that mark stops rising on the timing tab. Sorry to be so vague but I'm as confused as you probably are.

 

[WayneC]

I can't tell you exactly how it is done, but here's my best guess:

The basic principle is that a Chevy small block runs best at high RPM if total timing reaches 38 degrees max at about 3500 rpm; that includes your initial distributor advance setting plus vacuum advance plus (mechanical) centrifugal advance. By marking the balancer at 38 degrees, you could verify (in testing runs) that you are hitting that max if you rev the engine until the timing stops advancing, hopefully to occur at around 3500 rpm. If it doesn't, you play with the distributor weights and springs until you get that 38 degrees to happen at about 3500 rpm, which is the purpose of the curve kits... for backyard tuning, about all you can do is experiment with centrifugal spring and weight combinations (using the curve kits) until you've just barely eliminated any detonation under heavy acceleration (ie, by testing on the street or drag strip) all the way up to a full 38 degrees advance at 3500 rpm. Then you set your idle speed, disconnect the vacuum advance hose to read the timing at idle, which now becomes your initial timing setting for that curve kit combination rather than the Chevy book spec.

But even that is only part of the story, since a full "power tune" would probably need to be be done under load on a dynamometer and would include carburetor tweaking as well... the idea is to keep an optimum fuel/air ratio and timing advance all the way up through the rpm range with the engine under acceleration loading.

 

[allcoupedup]

attret00 -
The best thing to do here is pull your distributor and have it "curved". All this means is they take the distributor, put iot on a machine, and set it up (advance characteristics) for optimal performance.

You should probably invest in a dial back timing light so you don;t have to mess around with tape on the balancer. You can then determine your advance curve. The '64 327/300 came from teh factory tuned for power. Remember - emission control was not a concern in '64. If your engine is stock, I'd use the factory settings.

One more thing to consider - unless your springs are too strong, you should always reach maximum timing - the important thing here is the relationship between advance and RPM.

I just rebuilt my distributor and learned many things - I have pictures of everything.

Brian

 

[JohnZ]

The basic principle is that a Chevy small block runs best at high RPM if total timing reaches 38 degrees max at about 3500 rpm; that includes your initial distributor advance setting plus vacuum advance plus (mechanical) centrifugal advance.

The 36-38 degree "total timing" figure is only comprised of initial (static) base timing, plus centrifugal advance; the vacuum advance is disconnected while setting this up, as vacuum advance is zero at wide-open throttle anyway (due to no manifold vacuum under that condition). Set up the "total timing" with the vacuum advance disconnected and plugged, then re-connect it and set your idle mixture and rpm.

 

[attret00]

Help me again. Doesn't the circ. of the balancer play an important part in the setup. I'm trying to figure out if 1/16" equals 1 degree on an 8" balancer or how do I find 38 degrees from the timing mark?

 

[allcoupedup]

If you're using the circumference of the balancer to find 38 degrees then the length of the tape has to be batched to the circumference of the balancer.

Here's where I get confused -- the cam and distributor are turning at 1/2 the rate of the crankshaft so I'm not exactly what 38 degrees means.... 38 crank degrees or distributor degrees.

I just take the timing light set the dial to 38 and align the balancer mark to the tab. Please note this only works if you balancer mark corresponds to TDC.

brian

 

[JohnZ]

Measure the circumference of the balancer, divide that number by ten, and use the result to make a mark on the outer edge of the balancer clockwise (as viewed from the front) from the existing index line on the balancer. When the new mark is aligned with the "0" on the timing tab, you'll be at 36 degrees advance. You can then further subdivide the distance between the index line and your new mark for smaller increments.

A dial-back timing light would make this unnecessary - it's an indispensable tool for mapping an advance curve and trying different combinations of weights and springs; about $70 at Sears or at www.actron.com (they make the Craftsman light for Sears).

 

[attret00]

You guys are great. Soon as I can get in the garage on a day off I'll try this. I will definately get a dial-back timing light. The info I've gotten from you is invaluable.
I hope to be of some help to others someday as you have been to me for the past 6 months.

 

[lars]

att -
Drop me an e-mail request to:
V8FastCars@msn.com
I'll send you a detailed paper on how to do the "power tuning" timing, including a description of measuring the balancer if you don't have an adjustable timing light.

 

[attret00]

Well I got an adjust. timing light and did the set up at 3500 rpm with the new curve kit. Readj. the idle and mix on the rebuilt carb. and she is one sweet running girl now. Thanks to all. Grateful for your help.