Recently found out the engine in my 95z is bored 30 over.don't think it's a383 because it's not that strong.whats the difference other than the crank of course

 

28 cu in and more low end grunt. There's endless information on it available on the web and even on this site.

 

Are the rods different...length wise...

 

Not necessarily. Some builders choose to stay with the 5.7" rod and others prefer 6.0".

 

Sure 28 CID more but usually much higher compression which has a profound effect...

 

You can build it to have any compression you want.

 

People have built 383s that made less power than stock engines, by blindly adding displacement without any clue what was good or what made power. You add displacement but do it with cheap parts and cheap machining and you can make less than stock power.

There was a kid around for awhile that had a 383 Impala that made 220rwhp with headers which is what the stock b-body engine made through manifolds on stock 87 octane tuning.

Then at the other end of the spectrum there are those who top 400rwhp or even 420+rwhp without changing the rotating assembly atall still a 350 naturally aspirated.

 

Of course you can, that's what the "usually" meant.

 

I've ridden in well built 383's and 355's. Imho the 383 had much more torque throughout the low and midrange. I think they're about even on top end but I have seen some pretty sick 383's that revved too 8500-9k with ease. Impossible to tell the difference without disassembling the motor . Obviously there is no replacement for displacement but like dwayne said there are stock shortblocks making over 400rwhp

 

Compression is adjusted when you build it, so why would it "usually" have more compression unless you wanted it to? You could say that people "usually" build their 355s with more compression, or their Honda 4 bangers. And it depends on the cam as well as the pistons, heads, gaskets, etc. what compression you end up with - and don't forget how dynamic compression figures into it - it's not just static. You don't use all the same parts and just get more static compression, and therefore more power, from the longter stroke. Is that what you're trying to say?

 

I was just suggesting that people go to higher static compression when building 383's. I understand static v dynamic but was making a general statement, not a specific build....

 

Plenty of rebuilt LT1s 355 or 383 end up with stock or lower compression because clueless people use clueless machineshops. Have actually seen NA LT1 with a mild "performance" rebuild by a reputable shop with compression somewhere down around 9.5:1

 

Surprised no one mentioned it, but the additional cubes come from the the increased stroke from the new crank. 3.75 rather than 3.48. This makes the motor very torquey in the lower rpm ranges, making for a great street motor

 

Over stated. A properly done 355 can easily have more lowend than you can use on the street.