i was just wondering if someone could inform me exactly what the difference is between the 305 anf the 350 engines in our cars. is it the bore or the stroke? i'm pretty sure that its the same block. the reason that i am asking this is that i am planning to rebuild my 305 tbi this summer and i wanted to know if it would be good to make it a 350. i've thought about going to a 383 but i am on a budget and can't afford a whole new rotating assembly.

thanks for any help anyone can give me

 

It is the bore. 3.736" vs 4.000". Their stroke is the same 3.48", although the cranks themselves are different, because of balancing.

THerefore the block is different. That's why you can identify them by their block casting numbers. You can't turn a 305 block into a 350 engine.

 

you can make as much or more than a stock 350 as far as power..but if you go get a good 350 block and build it, you'll actually save $$ and you'll be alot happier good luck

 

The one thing that the 305 has going for it is that everything you bolt on to it can be swapped over to any small block. The blocks themselves are different animals. You won't see any large overbores on a 305 because you can't do it like you can on a 350.

 

You can bore a 305 and 350 to the same oversize. The difference is the bore diameter to start with. The max bore for a 305 is 3.795" and a 350 is 4.060". That is .060" over. The rest of the block is Identical so it is a myth that the 350 block is stronger than a 305. Mine has 4 bolt main caps from the factory and High nickel content.

 

You cannot safely bore a 305 .060 over. The water jackets are much closer to the cylinder walls than in a 350. .030 is about as safe as you can go.

 

Talk to some reputable machinist as the .060" over number is what you can safely bore them too. If a piston was available to do so most could be bored to .080". In fact my machinist checks them with a sonic checker. Most of the time he finds the 305 to have more material left when bored .060" than a 350 does at .030". Think what you want but it is a fact most 305s have thicker cylinder walls than 350s do. Weigh a bare 350 block and 305 block and you will find that most of the 305 blocks weigh ATLEAST 10 lbs heavier. It can also be seen in the fact that the 305 has lower heat rejection to the coolant than the 350 does. This is due to the thicker walls and helped in emissions reductions. You'll can sit here and argue with me all day, but I have researched the facts and as I stated the 305 is a thicker casting. It is a fact whether you believe it or not. This may not be true with the late model roller cam blocks though. I know that this is true in the Canadian built 1982-1984 LE9 truck/van motors and the HO 305s, casting numbers 14010979 and 14010203 respectively.

 

I think this is where the differences lie in the roller blocks. I have read numerous horror stories of .060 over 305's that busted and had water come pouring into the bore because the walls couldn't take the cylinder pressure and collapsed. Maybe this isn't true for a non roller 305.

 

thanks all of u for the info, i didn't realize that there was that much of a difference, but i have another question, would it be possible to take a 350 block from an l98 and just drop it into my car but use my tbi and factory computer still?(because of money issues), i figure i'd have to get some tuning done but would this be possible?, i would also most likely upgrade the cam and maybe even port and polish the heads.

 

Yes it would be possible but you will need a new prom and a few other things to get it all to work. That is the true beauty with all small blocks is their interchangability of parts. Everything you do to your 305 can be transfered over to your 350 or bigger small block. There are exceptions but that is not the point right now. Check out the TBI board for specifics.