I recently pulled my old tpi 305 out of my 89 Iroc in favor of a new (to me, has about 10k on it) 350 I got dirt cheap. The 305 ran just fine when pulled. It's just your very basic budget built 350, .030 overbore, world products s/r torquers, LT1 roller cam from a 96 y-body, roller timing chain, roller-tipped rocker arms, around 9.5:1 comp ratio, 22lb injectors from a 86 vette (all injectors ohmed out), BBK AFPR with a new diaphram. New sensors: Knock sensor for a 350, Fan switch, Oil pressure sending unit/switch. I replaced all gaskets except for the head gaskets. Everything else was swapped from the 305. Tps is set to .54 vdc at idle and increases steadly to around 4.5 vdc at full throttle. Fuel pressure is set to 43lbs with vac line disconnected, its around 37-38 lbs at idle with vac line connected. I'm still running it with the factory 305 prom. Base timing is currently set to 8 BTDC with the EST bypass connector unhooked. It idles fine at 700 rpm. It rev's fine in neutral. The issue I'm having is that it bogs down and bucks under heavy load between idle to around 2500 rpms. Once it's reached around 3k rpms it's fine. I've tried adjusting base timing anywhere from 0 BTDC all the way up to 10 BTDC in 2 degree increments but it still does the same thing. I have a new fuel filter for it but havn't put it on yet. It's almost empty fuel wise also. There are no codes present. Tomorrow I plan on putting at least half a tank of super in it and swapping out the fuel filter. My second issue is that the cooling fan doesn't come on. If I unplug the connector and ground it out with the ignition on the fan comes right on. I have another fan switch I plan on trying out tomorrow but is there anything else it can be? Does the CTS/PCM have anything to do with cooling fan function? Sorry for the long post, I'm trying to include all the nessicary information. I'm hoping that my problems are old/low fuel and a defective fan switch.. Can anyone think of anything else I should try or check out? Thanks for taking the time to read through this..

 

did you reburn the prom to the new cam ??

i dont know much about how the cooling fans work, one of my first mods to my car was pulling the factory one and putting a slim line high CFM fan on a manual control

 

I know it was a long post, but no as stated above I'm still running the factory 305 prom. From what I understand it should run decent enough until I can get a custom chip burnt. The LT1 cam isn't an aggressive cam by any stretch of the imagination, I'm only running it because it was free. The engine had some kind of very aggressive sounding flat tappet cam from comp cams in it when I got it. A friend gave me the cam, and I reused all the roller parts from my 305 to convert it to a roller cam. I really doubt the tiny cam has anything to do with the low rpm bog though..
Edit: I think I remember someone telling me the CTS controlled the primary fan function via the pcm, if that is the case could a bad CTS/ bad connection also be causing my bogging/stumbling issue?