Acceleration issues

Ok, here is the situation: The vehicle pulls strong then sputters a bit at about 3000RPM. After a second or two it decides it wants to pull hard again to 7000RPM. We have played with this thing for a couple weeks now. The vehicle was purchased as an untouched all stock 65 El Camino 283/Powerglide car. We carefully removed everything that wasn't necessary to drive (it's a retro 60's super stocker now) and installed an all new drive train. It does have the stock 10 bolt 3.08 open rear. So we have nothing to compare it to from before.



The engine is a mild 30 over 327. It has stock 4 valve relief pistons, Comp XE262S cam and an otherwise stock bottom end. The heads are port matched double humps with 1.94/1.50 valves and K Motion 1.25" springs with Summit roller rockers. The intake is an old 60's Edelbrock with a 1" spacer between it and a 600 Holley vacuum secondary. The ignition is the cars original Delco distributor with a Pertronix kit and matching coil. The exhaust is a set of Hedman Shortie headers with about 3' of 3" pipe to Summit 16" glass packs. There is then another foot or so of pipe with turn downs.



The transmission is a TH350 with a 2600RPM converter.



Now for the details. We have been able to make it run the best with minimal hesitation with: The carbs secondary spring has the short yellow one and #66 jets. The mechanical advance is a Mr. Gasket set (926G) which is supposed to have the advance in by 2000-2800rpm. We currently only have a way to check timing at initial. We found it to be best at about 10 degrees after. Which is also what the Mr Gasket destructions said to start with when using their advance kit. It did do the hesitation worse with the stock springs and weights.

At idle in gear the engine's vacuum is (I beleave) around 10-12. the powervalve is 65. So that should be about right, correct?

Does anyone have any ideas? We were thinking it sounded like timing. But have so far ran out of ideas.
 
1963 Chevy II SS
1970 C10
1971 Chevelle Malibu
2000 Z71
2005 Passat 4Motion

Sounds like you may have picked up some water or trash in the carb.
What is the fuel pressure at the carb.?  
Professional hi-performance engine builder

Horsepower sells Engines and torque wins races.

I'm not sure what the pressure is. I think it is a factory replacment pump. We pulled the bowls and the floats check good. I don't think there is any water in the tank. The tank was dry when we got to it.  
1963 Chevy II SS
1970 C10
1971 Chevelle Malibu
2000 Z71
2005 Passat 4Motion