I just completed swapping the 305 in my '89 Silverado P/U to a 350 everything was swapped over and it starts and runs fine but has some part throttle hesitation. Any ideas where to start? I was hoping some of you guys had a recipe for this swap I could learn from to get me back on the road. More fuel pressure? stock 350chip? bigger injectors? all of these? Thanks

 

Starting with at least a 25% increase in FP will help immensely. Theoretically, you need a 31.7% higher FP change to make up for the displacement change alone. (take the % displacement change and square it, or [350/305]^2=31.7%)

So, find out what pressure you are running at now, and bump it about 25% to start and go from there. Or, run about 13.5psi and go from there. (About 11psi is OEM nominal, I believe...)

 

Aaahhh sounds like a good place to start, know where I can get some info on adjusting fp on trucks? I don't even see a regulator. Thanks alot.

 

My chiltons book doesn't even have a fuel regulator listed as part of the fuel system that I see....There is one isn't there like on TPI? Or is there another way to bump up the pressure? Is there a easy way to increase it like putting a quarter in there like on tpi?

 

Assuming you swapped the TBI unit off the 305, they don't have an adjustable FPR.

You can either go aftermarket or do the ultimate TBI mods listed on this site.

 

The FPR is located in the injector pod at the rear of the throttle body.

 

Okay just read the Tech article and plan to do that soon.
Should I be worrying about a chip now? Has anyone done this and gotten by with just upping the FP? Thanks guys.

 

Just try the FP adjustment and go from there. Do one thing at a time.

 

I'll do that in a couple of days and check back. Thanks for the help.

 

Check out www.turbocity.com - I believe they have adjustable fuel pressure regulators for TBI units. Upping the fuel pressure 2 or 3 lbs. should help richen things up a bit. They also sell matched injectors - can get injectors that will flow better than the 305's. Might be good to get a new chip for it also.

Scott

 

Okay I'm planning to bump up the FP on Wednesday. In the mean time I made a cable and used WinALDL to check in on the ECM. My BlM's are over 128 almost all the time except at idle,so more fuel seems to be the answer but will that mess up my idle even more? Since it's a little rich there already? Thanks.

 

Oh and my knock counts stay at either 9 or 10 is that right?
BlM's are 144-145 crusing at 65mph
but it still has the rich flag checked most of the time
and "DRP occured"? anyone? Thanks.

 

You definatly need more fuel. A 144 BLM is running really lean. Don't worry about the idle since you aren't doing custom eproms yet. This is why a custom eprom is so important. It'll give you that smooth idle, great gas milage, and the best performance.
Your knock counts are fine. As long as the number doesn't keep going up you're fine. Crank the fuel pressure up and reset your min idle after doing so. More fuel and the engine will want to idle higher so you need to adjust accordingly. This is also where a custom eprom would be very useful.

 

thanks