How to tell difference between 305 tpi and 350tpi? I'm been looking around for used 350's. Is there any external difference between the 2 that i can tell if it's truely a 350?

Casting numbers on the block. They are located on the back of the block on on the driver's side. Some blocks (not sure from TPI) actually say 305 or 350 on the back too.
Other then that, I'm not sure. I know with a carbed small block, their is no other difference.. but now you are dealing with fuel injection so it might have some other signs.

the only dofference is the injectors.. also the corvettes fuel lines are on the other side of a camaro or firebird. pre 89 has a cold start valve that you do not want to use. 90 up have a map sensor and are speed density. early units are maf

are you talking about the engine or the tpi unit?

I'm talking about the engine. This engine I'm chatting with the guy says it already out of car. I'll have to look for above casting as stated above. But always wondered if one was in a car what should I look for to tell the difference. Is there a casting book i can pick up to help decipher differences?

All 305 TPI engines came from the factory with 19 lb injectors. All 350 TPI engines came from the factory with 22 lb injectors.

externally 305's and 350's look the same. There isn't a "looks bigger/looks smaller" on the blocks. Visually the only thing you have to go by is the casting numbers. If the engine is still in the 3rd gen, then you can check the vin number. If the 8th digit (IIRC) is a "F" its a 305 if its "8" its a 350. Someone might be able to verify that for me...

If it is 87 or newer block it will say 5.0L or 5.7L on the driver side where it mounts up to the transmission.

And since Fbodys didnt get the 350 until 87, this works all of the time for 3rd gens

Mine is an '88 vin 8 it's a 350. They put 5.7L on the rear bumper, but that don't guaranty that's what's under the hood.

If the VIN says "F" and you have a 350, it was put in there...and vice versa. The VIN is from factory correct of what motor it has unless someone changed it along the years. Basically agreeing with the above post...can't go by stickers and other easy to tamper with external badging :-p

I actually had a car with the VIN showing a 350 and pulled the motor because it had a knock...spun main bearing...and it had "5.0" cast in the rear of the block by the distributor hole. Needless to say I was upset, but goes to show you, it can go both ways...up or down.

Exactly the reason why i want to know what i'm buying. Yrs ago I bought a 2nd gen camaro with a "350" in it come to find out it was a 267 V8. If you guys are saying the 350tpi motor is stamped as such(350) on the back I'll look there thanks.

It will say 5.7L or 5.0L, not 350

This trend is still in effect even with GEN III/IV engines