View Full Version : Question about the TBI 305/350.

06-16-08, 11:15 PM
Why do the TBI 305 and 350's always crank over for an extended amount of time before they fire up? If you compare a L05 and LT1, the LT1 will fire up in a second, and you've gotta crank the TBI version over for a few seconds to get it to start up... Is it because the TBI versions will use much less fuel pressure?

06-17-08, 04:38 PM
Holy crap I just discovered this forum. Now I have two Cadillac Forums to check on.


The reason is pretty much because of the way the fuel system works. Unlike a carb you can't prime the manifold by simply pressing the gas pedal. The injectors, which sit over the throttle body, don't fire until the engine turns and it takes a few revolutions for the fuel to reach the cylinders, especially in a cold engine where the fuel is not going to atomize - it pools. However, I find TBI cars to be very quick firing when warm, easily as fast as an LT1, maybe a little faster. LT1s have port fuel injection and the fuel sprays right onto the back of the intake valves.

On your next cold start try feeding a little bit of throttle (experiment on the amount). Mine starts faster this way but I actually prefer the extended cranking in the winter because it gives the oil pump a chance pressurize the engine (well, a head start) before it actually develops any torque and thus pressure on the bearings.

06-17-08, 07:29 PM
Ah, sweet. Thanks for the info. :thumbsup: