What is the differance from a 305 tpi and a 350 tpi? I know the injectors are different, but anything else?

 

Couple of the Sensors and the Chip. Everything else is the same.

 

knock sensor,PROM injectors are the only differences.

 

they look identical, thats why be careful when buying a tpi car thats suppose to be a 350 tpi...

 

I don't even know if it's possible to visually distinguish the two engines..

I know the block has casting numbers.. but I'm not sure if the TPI unit itself has any kind of identification?

-LJ

 

I just bought a a tpi setup that came off a 305 and I want to use it on a 350. Just wanted to make sure the runners and ports are the same size. Is the TB. the same size? Hopefully all I have to do is change the injectors. I'm switching from 305 tbi to a 350 tpi in my 88 iroc. The chips different of corse but I can still use the same ECM. A few other little things I have to do to.

 

Yes everything is physically the same size.

 

305 & 350 TPI setup are the same. except for the Injectors (22#)
the Chip and 1 or 2 sensors. I would check the ECM P/n to see if its the same.

 

I know this is gonna sound dumb but when I changed out my stater motor in my 305(?) the parts counter guy asked me if my bird was a 305 or a 350...I told him I didnt know (motor swap was done BEFORE i bought the vehicle) so I told him to send both starters down to my garage. The parts guy I talked to I feel is pretty educated when it comes to getting parts for me.....when I have problems getting the RIGHT part for a car I can usually count on him to send me what I need. Anyway...just wanted some feedback from you guys.....

 

Same starter. I also work at a auto parts store.

 

The ESC module is different as well. Nobody mentioned it, and I'm not sure if it matters, but it is different.

So... PROM, ESC, injectors and knock sensor.

 

I couldn't use a 350 sarter due to clearance w/ my exhaust and I'm useing the t-5 bell housing which only came w/ a 305.

 

I just had a long winded response and then I watched my computer crash before I could click submit.

Cliff's notes: I think the issue is 5 speed vs. automatic, and since 5 speeds only came with 305s, you get an association. I'm willing to bet that GM has the same part number for LB9 autos and L98s. It's also just as possible that they have a lighter-duty starter for the LB9, but if so, they are interchangable. My 305 starter did just fine starting my 10:1 355.

 

the sensors and the injectors alongwith the ecm are the only differnce, so u will have no problem puttin it on a 350, my best friwend just did it but w/o replacin the injectors,

 

I forgot about the auto., man. trans.

 

i didnt replace the injectors and everything was fine

 

my buddy went from 305 TPI to a 355 TPI with out changing the injects.he ran alittle lean but it ran great other than that.

 

If you don't bump your fuel pressure, you're going to be too lean with 19lb injectors unless you reprogram the chip. If you do that, you may run into a situation where you're exceeding the safe duty cycle of the injectors. This can reduce overall reliability, and with the wide production tolerances that the 19lb stock injectors are known for, I don't know if I'd want to chance it.

If you bump fuel pressure to help compensate, you run the risk of the problem I mentioned above in regards to the 19lb injectors flaking out above a certain pressure.

Plenty of people have used the 305 injectors with no problems, and with a mild (read: very mild) 350 you'll probably never exceed the capabilities of the injectors, but if you ever plan to start modding the car, you might find yourself in trouble. It's just some food for thought.

 

isnt there a difference in the balancers between 305 and 350, 305 being externally balanced?

 

A 305 isn't externally balanced. It's internally balanced, just like all other smallblocks except for the 400. That's why the flywheel/flex plate is interchangable.

There probably is a difference in balancers though, because the 305 will exhibit different harmonics than a 350.