I see a lot of people turning their 350s into 355s.....how do you do it and how much HP is to be gained from it?

 

Its the CI you get when your bore a stock 350 block .030 over. It doesn't gain anything by itself, its for people who have rebuilt their motor.

 

5hp at the most.

 

the advantage of a 355 is a nice smooth cylider bore wall for good ring seal.

the power comes form internal components, forged etc...and what kind of heads/cam you top it all with

 

355 is more for compression changers and rebuilders. A friend of mine had a 94 z28 that he did it to. He had all the exact same mods as I did except he replaced a few more internals than I did. Like the pistions. Same heads and intake and port/flow same cam specs. He put 378 rwhp and 352rwtq, I made 381 rwhp and 349 rwtq. So you can see that the 355 is not much of an advantage on a 350.
If you want to see real results go to a 392+ Then you will make some real numbers. Good luck with your results.

 

How many dollars do you want to invest, and what are looking for.

 

I was always told from a 350-355 there is a 2-3% power increase. So say you had 400 HP with a 350, with a 355 youd make "around" 408-412HP all things being equal.

Like mentioned earlier its done mostly to clean up the bores and for a chance to but in forged internals to handle lots of spray or boost.

 

My 355 is basically putting out out the same hp as it was when it was a stock short block. It started smoking so I rebuilt it with stock compression etc. but went with 6.0 rods & kb pistons & saw no improvement on track times. 355's are, as stated above,for people who had to rebuild or people how dicide to go forged to hold crazy amounts of power whether it be produced by good heads cam etc, or a power adder. Not near as much power can be found in a .030 overbore & compression change as in the top half of an engine. 355's aren't worth it IMHO when your stock bottom half is in good condition & your after no more than 375/400 rwhp(I have no clue what your goals are).