O.K. Here's what I'm running : 85 TPI 305 LB9, 50,000 actual ,48 mm t-body with TPIS air foil, ported plenum, runners matched, gutted air boxes, K&N's, cold / forced air, MAF screens & fins removed , recently cleaned & flowed injectors, AFPR @ 48 lbs, throttle body coolant by-pass ,170* t-stadt, cooling fan on toggle switch, Bosch 4's, TPIS wires, stock TPI exhaust manifolds, gutted cat ,2 3/4 in mandrel pipe back to Dynomax Ultraflow welded #17227, stockchip, base timing 12*, 92 octane, 3:42 posi, 700R4 with Corvette servo. It was at 44 lbs stock , I think its stronger/more responsive at 48 lbs. What fuel pressure does anyone out there like with your set-up and why? Also, I'm thinking of a 52mm t-body,what size do any of you prefer?

 

What does that 305TPI LB9 do in the 1/4 mile.

 

your talking when everything is hooked up right.........

i tried to push mine higher and i'm still running way to rich at 38 psi idle and around 43-44 wot.

i'm running all the same types of mods you would expect that most raise there pressure up too. i think it's different for each car.

 

iroc_craigg, 15.7 with NO off the line traction last year. I'm not proud of that time, I literally was having trouble keeping from fish-tailing out of the box. At the time, I KNOW I could have done better with a lighter foot/ more traction off the tree. As it was, I had to gently squeeze into the throttle. I was only able to go 3 runs, would have loved to gone many more. I don't want this to sound like a cop-out, its just the way it was. This was prior to the vette servo, AFPR, cleaned & flowed injectors, ported plenum, gutted cat, Dynomax welded, TPIS wires, and new Delco cap & rotor. I expect with traction out of the hole, I'd see at least high 14's.

Now, anybody have anything to say about their fuel pressure or their throttle body size preference for a set-up similiar to this, or any set-up of their liking? I have toyed with different AFPR settings, always made with the vacuum line disconnected and plugged, of course. By changing it up or down, and going by the tried and true "butt-dyno" method, it seems good at 48, but who knows, maybe 42 would be better. I do know that from what research I've done that slightly higher fuel pressure will give better atomization and a better burn, while not exceeding 50 lbs and possibly over-taxing the hard to replace in-tank fuel pump. Most G.M. 305 and 350 engines came stock beginning in 88 with fuel pressure set from 46-48 lbs. Prior to this, they were anywhere between 34 to 43 lbs from the factory. From what I've read, G.M did this to improve atomization, thus performance, due to a better burn. Emissions would not be a concern, since the O2 sensor reads the exhaust, and keeps the mix at the correct14.7-1 ratio, except at WOT, where it in effect goes into "open loop" and goes full everything (mixture, max allowable timing short of detonation, etc).

I'm also toying with the idea of a 52mm t-body and / or a MSD box. Any comments from anyone good or bad? Thanks.

 

Bump...............

 

52mm on a 305 is a waste of money, it doesn't need it. The best way to set the pressure is at the track, set it were the car runs best. Go by trap speed, not ET.

 

1991 RS 305

Quote:
15.7 with NO off the line traction last year. I'm not proud of that time, I literally was having trouble keeping from fish-tailing out of the box. At the time, I KNOW I could have done better with a lighter foot/ more traction off the tree. As it was, I had to gently squeeze into the throttle.


I really think the best thing to do would be to sell the car to your best friend Scott for about $3,000 and just be done with all the problems.
Scott (just razzin ya dude)

 

My 91Z 350 car runs best at 50 psi, I have headers and camshaft also. And my original pump lasted 10 years at that pressure so I dont want to hear from anyone how it will shorten pump life. It might shorten pump life if you run it at 50 psi, but 10 years is enough pump life for me

 

Mine works best at the stock 42 PSI. If I run more then 42 PSI it starts to run rich at high RPM.