Thread: Edelbrock 750 vs. Speed Demon 750 and timing.

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Ok for those of you who want to know - the result are in are astounding:

After replacing all my roller lifters, after a stuck accelerator incident after I has my MSD with rev limiter out for repairs. I then found a broken intake valve spring, the inner spring was in about 4 pieces and the valve seal was trashed. Replaced the valve spring and seal (piece of cake - got to use my cylinder air-up tool and moroso valve-spring compressor).

Since I had to wait for the spring to come in from Speed Unlimited, I took the distributor to some good ol' boys who have a distributor machine, who told me they could put 28 degrees of timing on my distributor, all in at 3000rpm, with a jump out curve.

Cost $30 - best $30 I ever spent to get something adjusted.

I put my 357 Chevy back together - set the crank on 7 degrees BTDC and rotated the distributor until the flash on my timing light went off, checked it twice by twisting the distributor back and forth to make sure it was dead on. Locked it down at 7 degrees BTDC. At 3000rpm that gives me 35 degrees of advance. I can adjust + or - 7 degrees with the MSD variable timing module. I adjusted it to a total of 36.

Took out my Jeep to an unused road, this road has a slight incline, clocked at 0-60 with the following run times as the engine warmed up, 5.1, 4.9, 4.7, qne finally 4.6 seconds. These reading are from a Nordskogg, programmable speedo that has been calibrated on a maked mile. I am running 33"x12.5" Firestone Destination tires, and 3.55:1 gears. My Jeep weighs 4300lbs with the hartop, full steel doors, and back seat in.

I would say this is a marked improvement over the Edelbrock Performer 750cfm carb. The Speed Demon by far has more punch than the Edelbrock ever did. I lightened the spring in the secondary actuator, and adjusted the accellerator pump cam for a bigger squirt.

I just took it back out tonight and can consistantly get 0-60 in 5.1 seconds with a cool engine (not yet up to operating speed).

I will play with timing and maybe invest in an MSD detonation sensor.

BTW - I let of at 95mph and managed to do 14.2 in the quarter mile. 95 is too fast for a for a vehicle with only an 8' wheelbase.

I am pretty certain I am cranking out 430 hp with numbers like this.

Next mod will be dual exhaust instead of a "Y" pipe.

nah 95 mph aint to fast for an 8' vehicle. just look at fuel altered's with 88-102 inch wheelbases running what 7's and 8's yes the old ones were shorter and thats the ones im talking about


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"keep the shiny side up and try not to bicycle it!"

I'm wondering what a "a jump out curve" is?


Looks like you did some well thought out tests.
Can't find my dragstrip calculator, but the 1/4 mile times sound about right.

I'd bet that your Jeep (CJ5?) weighs less than 4300#.
I've found that truck and farm scales aren't too accurate at the low end of their scale.

Am I reading it right that you repaired the broken spring etc. and then replaced the Edelbrock carb with the Demon?
If so, seems like the Edelbrock didn't get a fair trial.

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.

BTW - it's a 1989 Jeep Wrangler Islander with full hardtop and steel doors on it right now.

It's curb weight is 4300 lbs. I can drop an easy 600 lbs by taking off the hard top, taking off the steel doors, and taking out the back seat. Probably closer to losing 700 lbs. I could drop another 60 lbs taking the 33" spare off the back of it too.

Losing all that should easily give me 12s in the 1/4 and consistantly under 5 second zero to sixty.

My son has a 49 Willys CJ3A with a small block 302 in it, that we are restoring right now. It weighs under 2000 lbs and burns a set of 31" BFGs until you let off the gas.

You can see my Jeep at www.gpzilla.com