need help w/ my 383

97051 bigblock said
well the intake is a weiand dual plane and it has a mech. sec. 650 dp I just had it on the dyno and everything is set perfect ,sorry i can not remember the timing or the cam size i know its the one size small than the 480 lift comp cam, it runs good but there seems like i should have alot more asskickin power I was thinking about a 509 purple shaft to put into it,i've also herd that MSD ignition makes a big difference but i'am dont want to waste the money if its not going to help...

If you replace the carb, try a vacuum secondary carb. They are much easier to tune. It's difficult to tune a double pumper for off the line, they usually bog when the throttles are opened too fast and the accelerator pumps and squirters are not perfectly tuned in. Vacuum secondaries are much more forgiving.

The 509 MP cam will be more sluggish at low RPM's than the cam that you currently have in it.

I would verify the ignition timing and distributor curve before trying to replace the parts. Try setting your total timing advance between 34° to 38° and see where it runs best in 2° intervals. Only make one change at a time so you can see what effect the change had on your performance. If it makes it better keep it, if not change back to the "older" setting. What vacuum are you getting at idle and at what rpm does it idle at?

Then try replacing the carb with a vacuum secondary one and get it tuned in. If you go with a Holley, put the lighter yellow spring in the vacuum secondaries to get the secondaries opening up quicker. Make sure that you properly adjust the accelerator pump clearance.

I have run Wiand dual planes on small blocks and they seem to run good. I would change the carb before changing the manifold or cam. If you overcarburate, you hurt the whole rpm band. If you undercarburate, you only hurt the top end rpm. A vacuum secondary carb will be more forgiving to overcarburation by only opening as much as the engine demands.

I would work on the tune up and then the carburetor. I think the cam and manifold are not causing the problem.