Thread: 402 & edelbrock carb

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We have a Chevy 402 bored .030 over, Keith Black 10.5-1 pistons, comp roller cam and rockers. The heads have been reworked. Edelbrock air gap intake and Edelbrock model 1813 800 CFM carb. We have a dead spot in the transition from idle to acceleration. The dead spot happens at the take off from a dead start under normal acceleration. After we get past the dead spot, the engine performs great.
We have changed the rods and jets using the guide that came with the carb. We have changed the springs using the strongest to the weakest and still have the dead spot. The rods move at idle to acceleration like they should. We have moved the accelerator pump to all three positions. We have adjusted the fuel pressure to 5.5 lbs. Changed to a larger squirter. We have moved the timing advanced and retarding, still have the dead spot. We have installed a hotter thermostat and currently running a 180 thermostat. The automatic choke has been moved to every setting. We are running 93 octane gas.

how big is the cam .what rear gear is in the car . how big of stall in the trans . how fast is the curve in the dist. were is the timing at when s it stop total and RPM . how much timing at idle. did you try more timming on squirter and bigger squirter. when the engine was built was the cam degreed. was TDC found and checked with damper and set to timming pointer ?

The cam is 242 int. 248 ex @.050 LSA 112 Comp 11-456-8. The rear gear is 3.73. Stock 350 hydro converter. The engine was dyno'd and the timing is set @ 40 degrees at 3000 rpm. The cam was degreed at TDC on #1 and set 0 to damper. The engine dyno'd @ 483 HP and 482 torgue. We have moved the timing advanced and retard and little change on the dead spot.

What type of distributor? Should be about the point in acceleration where the vacuum advance is approaching it's max, and maybe the mechanical advance isn't quite coming on soon enough... Initial timing and timing with and without vacuum, as well as the mechanical advance rate might be your stumble. The total timing might be a bit high, but if it's not rattling or falling over with 40 degrees cranked in then it should be ok, too. Have you tried the vacuum advance hose on a fitting above, then a fitting below the throttle blades????

Welcome to CHR!

To follow up with Dave's suggestion - looking at the front of the carb, the vacuum port on the left is timed and vacuum comes on after idle. the port on the right is manifold vacuum, i.e., present at idle. I'd recommend the one on the right. Also - as simple as it may sound, perhaps there is a vacuum leak somewhere as it certainly sounds like a vacuum issue. Try a little squirt of card cleaner around the base of the carb and if there is any difference in the idle speed you have a leak. Also go along the intake manifold where it meets the heads. The manifold bolts are notorious for coming loose and can cause vacuum leaks.

Good luck and keep us informed of what you find.

Again, Welcome to CHR,
Glenn

Originally Posted by oldman43

The cam is 242 int. 248 ex @.050 LSA 112 Comp 11-456-8. The rear gear is 3.73. Stock 350 hydro converter. The engine was dyno'd and the timing is set @ 40 degrees at 3000 rpm. The cam was degreed at TDC on #1 and set 0 to damper. The engine dyno'd @ 483 HP and 482 torgue. We have moved the timing advanced and retard and little change on the dead spot.

you need a 2600.to 3000 stall to get this cam to work your going to have a dead spot the @ 050 is very big for a stock stall.DID some over look this were is the intake center line at ? at on a 112 it would help alot if it was on 108 this cam stops pulling at 6000 and max QT should be about 2500to2700 building a 402 now at the shop about he same cam but on 110 and i would never think of using a stock stall with that small of CID