Changed rearend and gears, lost E.T./MPH
Swapped out the stock S10 (7.5") rear end with 3.73 gears for a Ford 9" with 4.30 gears and slowed down bad. The truck was running 11.40's @118 mph and is now running 11.90's at @111 mph.
The combo:
11:1 383 flat top shortblock
Patriot 185cc "vortec" heads 2.02/1.60 valves Mild pocket porting
Comp XE294H hydraulic flat tappet cam w/ 125 seat pressure, 310 open pressure springs
Hurricane Single plane intake, Holley 750 (4779-7)
Th350, ATI 8" Treemaster MRT 5000 stall
27 X 10.50 hoosiers
2950# Race weight
The truck is shifted at 6500 and with the 3.73's, it was going through the traps at 5800-6000. Went with the extra gear hoping to get the trap RPM's 6500-6800. Would make a change to 28" tires if run out of gear with the 7K chip.
Since the rear-end swap, the engine doesn't pull nearly as hard as with the 3.73's. Kinda feels like it starving for fuel.
The fuel system is 3/8 line to a Holley blue pump, then stock 3/8 line to regulator. One side of regulator to dual feed line on the carb. That's being upgraded now to 1/2" line from the cell to the pump, 1/2 hardline to the regulator, and 3/8 line out both sides of the regulator--each going to a bowl.
Any other ideas why it could have slowed down so hard?