Last year I rebuilt my hei dist with a rebuilt kit. It came with three sets of springs. I put the stiffest ones on becuase I was just trying to get the stock motor going. Now that my engine has been rebuilt I was wondering what springs I should use. The three springs are

------1---2---3---4--5---6--7---8 RPM in 1000
Cop-13-19-24-26-26-26-26-26
Sil---03-11-15-17-20-21-22-22
Nat--00-10-12-14-15-18-19-20
Crankshaft degrees

So does this mean I need to set my car at 8 degrees and use the copper springs to get 34 degrees at 4000 rpm? I'm at a bit of a loss.
Also it came with an adjustable vacuum cannister preset at 16 degrees. What would adjusting the vacuum advance get you? Sorry for the basic questions. I just thought I might be able to eek a few more HP out of the motor and got a bit confused.



[Modified by TTop Tony, 5:57 PM 6/13/2002]

 

You've been revving the engine to 8000RPM in the driveway? Stop doing that!

Disconnect and plug your vacuum advance.
Install the lightest springs you've got in the mechanical advance.
Run the engine up to the point that the mechanical advance is fully advanced.
Go a few hundrad RPM above that to be sure the advance is full open.
Check your timing. It should be 34 to 36 degrees.
If it is not, reduce the engine to idle. Look at your timing setting.
If you had 28 degrees full open and 8 degrees at idle, you need to add 6 to 8 degrees to get to 34 to 36 so add that number to your idle timing and adjust your idle timing to 14 to 16 in this example.
Tighten the dist. down and run the engine up to verify your adjustments.
You want to get 36 degrees of full advance before 3000 RPM. At the same time the advance needs to be retracted to idle smooth. Change springs to obtain the best overall feel. The springs do NOT have to match from side to side. You may find that you need one light and one medium spring to get the best of both ends of the advance curve.
When you've made all the adjustments, install the vavuum advance hose and drive at speeds from 40 to 70 cruising. You do not want to hear any pinging. If you do hear any, or if the engine feels real weak with slight throttle adjustments you need to reduce the vacuum advance if you have an adjustable vacuum advance or back off on the full advance setting.
Good luck with it.

 

The springs don't determine the total adavance, only how soon it arrives. Your peak power will be affected by how much total you have, not by how fast or slow it arrives. Bringing the advance in sooner will enhance low end torque but too soon can cause drivability problems, pinging, and damage. What works best for your particular combination will probably require some "trial and error" testing. I usually find it easier and faster to start with the lightest springs first, test drive, and adust if needed. If the lightest springs are a problem (surging, pinging, etc.), go to a heavier combination depending on the severity of the problem. The springs can be "mixed `n matched" and you might get your best results using a light spring and a medium spring or a heavy and light. In any case, your best peak power will usually be made at a certain total advance and I highly recommend starting there and adjusting the "curve" to match.

 

OK trial and error I get it. I have an adjustable timing light I'll give that a shot. I guess the chart they gave with the springs was confusing me. I was trying to derive some mathmatical computation from it. Oh well I needed something to do this weekend.


[Modified by TTop Tony, 6:58 AM 6/14/2002]

 

I don't know but it looks like with the COP springs at 3000 RPM your mech advance will be 24 and at 4000 RPM it will at 26 and stay that way all the way up to 8000 RPM.

According to LARS you want 36 at 2500 but you have to watch your total timing (vac + mech). So as the other guys mentioned you can try to mix your springs to get mech advance to 36 and if you leave your vac set at 16 that would be 52 total.

 

Well this is the first project that went without a hitch. I put the copper springs on and set the timing to 10degrees. It got to 36 around 3200 but thats the best I could do. There was a noticable change midway through the rpm band and I feel a definite kick when the secondaries chime in. No pinging or knocking that I could detect. Thanks all.