Observation:
About a year has passed since I added an ext crankcase vac system.
I had problems with hot starts (Eng temp below 180*F when hot).
Thought it was the starter, but the Summit high torque starter has similar symtoms of high application load. I interlocked all other electrical acc equipment off selection for diverting maximum current to starter circuit.

Car runs strong. The ext Vac pump has helped much w/ increase in perf.

Theory:
So, my next thought is the external Vac pump system (1/3 atm vac) has reseated the piston rings improving compression. (I have not run a leak_dwn test yet).

Other mods:
I also resized the bypass valve springs holding more boost(~14psi).
Drive setup is 7.6" to 3.4"pd. (4.44:1 gear head)
Checked all ext drive fo excessive prevailing torque (looks OK).
Checked all wiring to starter (OK).

App... 97ss 383-D1 MM6.

Comments/ Thoughts welcome.
Thanx.
B.

 

Which setup did you use?

-Dustin-

 

GZMS VP103 crank driven pump. Custom mount to Rt side Mtr-compartment rail.
Fabbed my own vac reg set @ (1/3 atm)
Designed/ fabbed a centrifugal air receiver w/ ext oil re-circ to lube pump vanes for street use.
Crank drive machine by myself.
Moved rad forward & down to provide pump and drive clearance.
My own design except for GZmotorsports pump and some plumbing components.
http://s306.photobucket.com/albums/nn244/mzgp5x/

 

What picture are we supposed to be looking at in that link?

What pulley sizes or ratio are you using for it? How much vacuum are you seeing?

 

http://s306.photobucket.com/albums/n...p%204th%20gen/

1/3 atm, 10"Hg, 5psi vac.

 

Nice do you drive your car on the street or is it a track only car, can you provide a list of parts, prices and part numbers?

 

Street driven. Not much track use due to expense, and, don't have friends. The pump from gzmotorsports.com. A VP103 unit (not offered any more, but replaced with a VP104n). Cost of pump is $380.
Pulley $60+35_crank. Belt $25_Napa. Hose $35 Enco. Fittings $85. I made most of the parts myself from stock purchased from Enco Mfg.

I also made the pump receiver from 3 1/2" exhaust pipe experimenting (sorry no pics). Fits in the bumper up front. The Gzms oil receiver was to large and a poor fit in the 4th gen F_body motor-compartment (MC). Did not work well with the oil re-circ mod. I think works better (centrifugal design).

Also, made the vac regulator. The Gzms Reg units did not fit well in F_body MC pre LS motor. Reg is designed for 1/3 atm (opens @ 5psi vac). I used Gzms design stats for the design.

For the street, you need the oil re-circ to lube the pump vanes. Working for 2 years now. Pushing 12 to 14 psi will cause alot of blow-by and pressure down_low. Bad for seals (rear & front). Lots of leaks. Now, no leaks @ all. Sorry for long rant. B.

 

Have you checked for voltage drop across the battery cable, or taken a resistance reading of said cable?