Setting up curve on a distributor.

[skokie]

How do you setup the curve on a distributor?

Thanks

[GMC Jim]

I feel the only truly accurate method for setting the proper curve is with a distributor machine... Check for a shop that specializes in this type of service....

[70c10]

Thats what I have always heard also. It's only like $25 but I'm not sure if they supply new springs and weights . I guess they would have to.

[JimKshortstep4x4]

I use one of the old distributor machines for recurving distributors. It is set up for HEI or points type distributors. The total advance that I prefer is 34-36 degrees in by 2500 rpm. With an initial advance of 10-12 degrees, the distributor is then curved to advance 22-24 degrees.

Summit has kits for either the point distributor or the HEI distributor, (other suppliers have them, also). Sometimes filing of the mechanism is needed to get the advance but it is usually a minor amount.

One of the the benefits of testing your distributor on a machine is that you can check the distributor over the entire rpm range and be confident that it will work well once installed.

Here is a pic of my machine.

Jim

[GMC Jim]

There are a great number of specs regarding the proper curves as per the engine manufacturers. For example:- 1971 Chev Truck Manual; 402 engine; (degrees centrifugal advance @ Engine RPM) :: 0 @ 930; 2 @ 1200; 16 @ 2400 and 30 @ 4400. 350 engine w/ auto trans specs are :: 0 @ 865; 2 @ 1335; 11 @ 2400 and 18 @ 4200. About 10 years ago; I took an HEI distributor obtained from a wrecking yard ; to a shop that specialized in distributor re-curve and re-build.. They curved the distributor to meet the factory recommened setting for the 402 engine. This unit was installed along with a new vacuum advance mechanism and the initial timing of 8 degrees @ 600 RPM was set up.. Also installed new spark plug wires designed for the hotter spark produced by HEI units. Installed new set of AC-R44TS spark plugs gapped @ .045. The setup has given trouble free service since the install.

[GMC Jim]

Another reference guide published by GM is the GM/AC/Delco manual, 1971-80 tune up specs.This manual stated that total advance ( centrifugal & vacuum) should be 28 to 35 degrees @ 2000 engine RPM... for the 1971 402 engine. Specs for the 350 auto trans engine is 20 to 27 @ 2000 engine RPM..... Using an adjustable advance timing lite; is relativley easy to check the timing @ 2000 RPM by setting the timing light to the specified advance degrees and reading the results.

[ddsmith]

Every engine even in the same family has it's own individual character. There is no one size fits all approach that will be right. Check out the FAQ section. I know a long time ago I passed on some information from Jacobs Electronics about setting up a distributor curve. Others may disagree about this approach but the truth of the matter is that there is a big difference between static and dynamic situations. The distributor machine does not replicate actual engine conditions. Good luck on your set up.