Hey all,

first time poster to the forum in hopes that someone will be able to offer some thoughts for me on my custom build out.

what I知 working on is a 92 k1500 ext 4x4 that had a 350 in it. We picked the truck up for my son to be his first vehicle and just did a motor swap as the original motor was in bad shape.

the replacement engine is a 305 roller with a roller cam from a 91 Vette. The problem I知 having is that in order to get it to start I have to dump a little gas in the TBI. It will start up and runs well until it gets warm and idles down at which time it struggles to stay running. At initial start attempts I can see it spurt a small amount of gas from the injectors into the TBI. But not enough in order to get it to fire. The IAC is very load (air intake sound) while warming up and then quotes down once warm. Throttle response is great and I can see it spraying fuel well while warming up/idling.

I have replaced the distributor, rebuilt the fuel pressure regulator, replaced the fuel filter, replaced the oil pressure sending unit, and checked vacuum. It has a new air filter, oil filter, and double roller timing chain. I知 at a loss as to what is causing the issue I知 battling currently. Could running the ecm and injectors from the 350 be the cause?

today I知 planning to unplug the lock sensor and clear the IAC to see if that makes any difference. Only other things I can think to do is replace the ecm, injectors, and fuel pump (which runs and seems to provide adequate fuel during warm up and throttle response).

any input would be helpful. Thanks!

 

I have also replaced the plugs, wires, cap and rotor. The truck would start no problem with the old 350 and idled ok with the old engine as well. The old engine struggled to get up to 50 mph and had a bad leak from the rear main seal. The cat was plugged on it but the truck is currently straight pipes while trying to work through this issue and waiting for the new muffler to arrive. The new short block 305 came out of an unknown 91.