By Rocky Rotella

When we hear someone speaking about their recurved distributor we take for granted that the advance curve has been professionally calibrated and that the specs are known. And while in some instances that might actually be the case, oftentimes the owner just purchases an off-the-shelf advance curve kit from the local parts store or their favorite mail order supplier and installs it into their distributor.Depending how poorly the original curve was, performance may or may not increase but regardless, the generic kits are far from optimal.

We recently completed testing of nearly every aftermarket advance curve kit commercially available. Having spun every spring combination from each respective kit using an Allen Syncrograph distributor tester and either a points-type or HEI distributor as required, we can accurately state that aftermarket advance curve kits are not worth installing in your vintage distributor. While the points-type kits are far more accurate than the HEI kits, neither kit’s weights appear to be hardened like the factory pieces and the advance curve from the HEI centerplates are horrible. The springs are marginal and the light tension pieces are worthless not allowing the weights to fully retract.

Our suggestion is to reuse the GM weights and centerplate combined with the aftermarket kit’s medium and heavy weight springs. It is suggested to check and recheck the advance curve often, as some kit’s springs are prone to loosing tension quickly. The only way to be sure what your distributor is doing is to check the advance curve on a distributor machine but since so few of us have them available, that is not always an immediate option. Follow along as we take a hard look at the advance curve kits widely available today. You may find that you are already using one in your own distributor and might now know that it isn’t doing what you thought all along!

All numbers shown are at crankshaft values.

Moroso 72310 .255” diameter bushing, weights provide maximum mechanical advance of 34 degrees without bushing. Medium and heavy springs appear to be very good. Gold/Gold 400-2600 Silver/Silver 800-5000 Black/Black 1000-6500 Gold/Silver 600-3600 Gold/Black 1000-6000 Black/Silver 1000-6000

Accel 31042 .267” diameter bushing, weights provide mechanical maximum advance of 30 degrees without bushing. Black/Black 500-3200 Gold/Gold 700-3200 Silver/Silver 700-3200 Black/Silver 550-3200 Black/Gold 600-3200 Gold/Silver 600-3200

Mr. Gasket 925A .267” diameter bushing, poor weight design limiting mechanical advance to 8 degrees without bushing. Black/Black 1800-2400 Silver/Silver 1600-2000 Gold/Gold 2200-2800 Black/Gold 2200-2600 Gold/Silver 2000-2400 Black/Silver 1800-2200

Moroso 72300 Weights and centerplate are identical to Mr. Gasket 929G kit. Medium and heavy springs are good quality Gold/Gold 25 degrees 600-2800 (jumps) Gold/Silver 22 degrees 950-4000 Black/Gold 23 degrees 1600-6000 (jumps) Black/Black 23 degrees 1400-6500 Silver/Silver 24 degrees 800-4500 (jumps) Silver/Black 22 degrees 1400-6000

Accel 31041 Same weights as Spectre kit, centerplate slightly different. Red/Red 22 degrees 900-3000 (jumps) White/White 18 degrees 1200-5000 Blue/Blue 20 degrees 1200-7000 White/Blue 20 degrees 1400-6000 Red/Blue 20 degrees 1400-6000 (jumps) Red/White 18 degrees 1600-6000 (jumps)

Spectre 5754 Gold/Gold 24 degrees 600-5000 (jumps) Gold/Silver 20 degrees 1400-7500 Gold/Black 19 degrees 1500-7000 Black/Black 19 degrees 1500-7500 Black/Silver 19 degrees 1500-7500 Silver/Silver 19 degrees 1500-8000

Mr. Gasket 929G Black/Black 21 degrees 1500-6000 (jumps) Black/Silver 16 degrees 2000-6000 (jumps) Black/Gold 20 degrees 2000-6000 (jumps) Gold/Gold 18 degrees 2000-6000 Gold/Silver 15 degrees 2400-7000 Silver/Silver 15 degrees 2600-7500