Jump out curve is is an exponentially increasing curve with a sharp advance at the beginning, that gets more gradual toward the end of the curve. It gives more advance quicker in the beginning of the curve, good for lots of fuel, out of the hole, especially good for engines with lots of low end torque for getting off the line.

Many shops say split the timing - 18 on the crank and 18 on the distributor. putting 28 on the distributor makes the engine real easy to crank over, jump out curve is real nice when you only have single digit advance at idle.


I ran the Edelbrock for a couple years. I came into a Speed Demon 750 from a good buddy who had it on his 340 Mopar because I talked him into it. He opted to go back to his 650 because he thought he was getting too much fuel for his Edelbrock performer heads. His problem is crappy dished pistons.

As for the spring, I broke the spring and screwed up a set of lifters when my engine over-revved above 7000 rpm. My accelerator stuck (have since fixed that). I had my failed MSD-6AL out for repairs, and no over-rev protection. Edelbrock told me their hydraulic lifters are only good for about up to 7000 rpm. After that valving damage can occur. You want to spin fast - put in solids. I had too much tied up in the valve train to change it all out, so I bought another set of roller hydraulic lifters. The spring I had to special order from Crane through Speed Unlimited, to replace the broken one, since the springs are part of a Crane Camponents kit. They are shimmed to the correct spring height, tension etc... so got to make sure I get the exact replacement spring. Every detail for a performance engine is important.

One problem that usually occurs is the cam thrust bushing dropping down behind the cam gear on a Chevy when the cam walks forward. That bushing is generally only .060. A little gap makes it drop right down behind the gear. The fix is to install a Torrington bearing onto the back of the cam gear and make sure the button to timing cover clearance is snug. To install the Torrington, the cam gear must be machined to allow for the extra thickness of the Torrington. This machining process is costly because the gears are made of hardened steel. Guy charged me $100 to cut a grove in the back of my cam gear for this purpose. I realized this problem when I tore my engine down to replace a set of Keith Black Hypereutectic pistons that came apart, and found the cam thrust bearing had dropped onto the cam.