Here is what I am dealing with. A rebuilt 351w that has a hesitation just as the throttle is increased. Keep in mind that I have a new fuel pump putting out 6-6.5 psi, new 600 edelbrock carb., edelbrock performer intake, new filter, new distributor with pertronix ignitor and coil (this system replaces the points, condenser, and dwell) note that I replaced the points system while I still had this problem. New wires, plugs and cap. The vaccum adv. is hooked up to the timed side of the carb. Now when I hook up a vaccum gauge to the manifold it says that I have late ignition timing (on the gauge it reads about 16-17) 19-20 would be good. I know the timing is set though and all the wires are in order. When I pull the plugs and look at them they are almost clean. The white part is totally white...clean. The plugs are also gapped at 35. I have checked for vaccum leaks around the intake and carb. by spraying starting fluid around these with the engine running with no difference in rpms. Also have a new timing chain and gears. So here are a few questions of concern......Should I have a four hole spacer plate under the carb. I have no egr. Second, I was told that I should get a rejetting kit for the carb..... but it's new and it should be enough. Right??? Third when I set it in my 70 f100 I had to use an exhaust manifold from a 302. The ports look like they are the same size as the 351w. I dont think it could be a restriction on the exhaust. Could it??? And last of all I did not replace the cam or lifters( the lifters were put back in same position) they seemed to be in good condition.
Your suggestions count!!!!
Thanks, Tony

 

I rebuilt my motor and had a timing issue also. I know I set it properly but the darn thing wouldn't start. I had to mess with the dizzy until it did start. I took it to a shop to have the timing set since it wouldn't start when I set it and to have them tune the carb. I go to pick the truck up and the guy tells me I need a new harmonic balancer. My balancer slipped the ring he said. He set the timing and had the same problem so now I don't feel like an idiot. He set the timing the best he could and adjusted the carb which he said needed a rebuild. Just thought I would share that with you. I guess dampners can slip the outer ring which would throw off the timing marks.

 

Have you tried attaching the vacuum advance to a direct vacuum port off the intake to see if that helps? I had a similar problem with replacing a Holley 4 bareel on a 460 E-250. Seems there was a stumble in the accelerator circuit caused by using the wrong accelerator cam on the new carb. Since your carb is an Edelbrock don't know if the same applies to that carbs accelerator circuit.

John

 

Which Edelbrock carb do you have?? Some of them are set quite lean which could account for the white plugs. You often need to do some tuning with all of the performance carbs, they can't be tuned right for every motor they can be used on.

The accelerator pump might need some tuning also.

 

Try moving the accelerator pump rod to the next hole on the lever to see if it helps.

 

Guess work really stinks and cost money. I read a post on another article and GUESS what I realized I put the wrong flywheel on. The one I put on was off my old 302 and the motor I installed is a 351w. It runs awsome now.....

 

Ah, a bit out of balance eh? Glad you got it figured out