I read your tech paper on how to get total timing for optimal performance. I have a 383, not a 350 with a B28 vacuum can on it. Do I mark for 36 total timing and when you say bring it in, do you mean bring your 36 degree mark to the 0 timing tab? Also, you say remove the springs and reconnect the distributor cap. But then you talk about HEI ignition and to use softer springs. Do you do this for regular ignition as well?
Sorry for all the questions and thanks in advance.
Anyone else who may know the answers to these questions please feel free to chime in....

 

"Do I mark for 36 total timing and when you say bring it in, do you mean bring your 36 degree mark to the 0 timing tab?"

With your adjustable timimg light, bring the timing mark to Zero whereby the dial on the timing light will align with 36deg. To get it to 36deg you may have to adjust initial timing by rotating distributor and changing the centrifigul advance springs. Vacuum advance should be disconnected as it has no play with the setup.

"Also, you say remove the springs and reconnect the distributor cap."

Do this on non-hei distributors. This is so you don't have to rev motor to 3000 rpms.

"But then you talk about HEI ignition and to use softer springs."

Do this because apparently taking off the springs on HEI units allows the centrifigul advance go too far which would never happen if the springs were attached.

Hope this helps as I used other papers found on the web on the same topic. One thing I haven't been able to verify, is that with some stock HEI units GM limited the amount of total advance you could ever dial in at about 20 to 26deg, total of inital of 12-15deg and the remainder through lighter springs. Currently I'm battling this issue with my stock HEI and lighter springs. I can not get beyond 20deg total advance with the lightest springs and initial timing set at 12deg. Rumor has it on some other forums that GM did this total advance limitation in the design of the distributor for economy and emission issues.

Good Luck, but you probably have more questions.

 

thevette -
MILO did a good job outlining things in his post above. Let me just re-confirm to make sure you're okay on things:

When "bringing in the 36 degree mark" you can do this in one of two ways depending on if you're using a standard timing light or an adjustable light:

If you have a standard timing light, you need to mark the 36-degree line on your balancer as described in my paper (measure the circumference, divide it by 10, and place a mark this distance clockwise from your existing balancer line as viewed from the front of the engine). This line should align with the "0" mark on your timing tab when the full centrifugal advance (with vacuum hose disconnected) is slammed in.

If you have an adjustable light, there is no need to re-mark the balancer. Set the light adjustment to 36 and simply align the stock timing line with the "0" mark on the tab with the full centrifugal advance slammed in.

Rotate the distributor to achieve the 36 degree total spec.

Removing the springs from the distributor is done because the stock springs do not allow full advance to occur at a safe rpm. I don't like having my face right by the fan with the engine spinning at 4500 rpm... Removing the springs slams the full centrifugal advance in at about 1000 rpm-or-so, making the timing verification fairly safe. If you have a set of soft advance springs that actually allow full advance to occur at 2500 rpm, you can leave the springs in place and check the total advance by simply rev'ing the engine until the advance pegs out. 2500 rpm is still pretty safe.

The HEI distributors cannot be checked for total timing with the springs removed. Removing the springs on an HEI will cause an artifically over-advanced condition that will not ocur with springs installed. HEI systems must have a soft set of springs installed, and the engine must be rev'ed until the advance pegs out. You can then keep the soft springs in place if they produce a fully advanced condition at 2500 rpm-or-so, or you can re-install your stock springs once total timing has been set.

Let me know if you have further questions. Good luck with the tuning!

 

Milo & Lars
Thanks for the replies. That should cover the questions I have to give it a shot, I have non-HEI ignition. I will try it tonight without the springs to get it all in at 36.
Thanks again.