Whats the best fuel pressure to run on the LT1's? I did a fuel pressure test and the numbers were a little low so i'm going to bump them back up.

 

ttt

 

The best fuel pressure is 43 which is stock. How low was your fuel pressure and how you test it, if it's low for no reason then it could be a problem in the fuel system.

 

When I tested it, it was at 33psi at idle. I tested it by hooking up the gauge to the schrater vavle. Honestly I don't know why it is low. The owner before put on an AFPR so i'm wondering if he messed it up. The reason I checked is because my car was hitting a flat spot on the top end of the track (hence my 101 trap speed). A friend hooked his scanner up to the car and noticed that it was running a little lean on the top end. So I checked the fuel pressure and it was lower than spec.

 

You need to test it under several different conditions.

Hook the gauge up to the Schrader valve. Start the engine, let it idle, and pull the vacuum compensation line off the fuel pressure regulator. Plug the vacuum line so it doesn't idle rough. With no vaccum line, the correct fuel pressure is 43.5psi, but the factory spec is anything between 41-47psi.

Then reconnect the vacuum line. The fuel pressure should drop proportional to intake manifold vacuum, which can be as much as 8-10psi with a stock cam.

Then tape the gauge to the outside of the windshield, and take for a drive, and observe the pressure at peak HP/full load rpm. Should stay within 1 or 2psi of the reading you got with "no vacuum".

 

Thanks Injuneer, I will do that tonight.