bore question

aight i've seen a couple people on here with 355 cid engines, guessing this is from boring .030 over stock? i'm wondering how much boring out that extra bit really helps. i know it adds displacement, but does it help with anything besides power, like revs or anything? and this is a really general question with a lot of variables but any guesses on how much power it adds to an engine?

It actually slightly lowers the compression. So there is no power increase besides going back to a healthy new motor. Although most people slightly mill down the heads which raises the compression and evens it out.

so what your saying is that if someone takes a used motor and bores it out, than it's pretty much like starting with a new one with lower compression. So there's would be no other reason to bore out a new motor other than to lower compression?

No, unless you want a 383 strocker. The only reason they bore old motors is that theres so much taper in cylinders to get rid of. Plus its easier to set piston/cyliner clearence with the motor with exact bore (less honning involved)
Also 5 extra cid wont make lots of difference.

boring is also used to eliminate any imperfections, warpage, or wear marks on the cylinder walls.

good to know. not planning doing it anytime soon, just trying to learn as much as i can

John, how does it lower the compression? Youre gonna hafta edumacate me on that one sometime. :wink: And Genospyde is right, boring is most often done to re-create a clean, perfectly-round cylinder...the 4-7 ci gained is just a residual bonus, but power gained is negligible. However, I guess every little bit helps lol.

It actually slightly lowers the compression. So there is no power increase besides going back to a healthy new motor. Although most people slightly mill down the heads which raises the compression and evens it out.
I was wrong. I was just reading up on this and over boring actually slightly raises your compression. I always thought due to the adding the cylinder volume with the same length stroke (since there is now more area in the compressed section), there should be less compression but I guess that makes sense since the cylinder size is greater thats doing the compressing. Oh well, I guess you learn something new everyday.

if i was to bore my 3.8 v6, what could i get it bored 2, what results should i expect, and would it be harder to find perforamnce parts for the bigger liter engine.

WHEW!!! Thanky, John. I thought I may have been losing my mind (again). :jump3:
Matt, Im not sure what it could be bored to, but as far as results, Im guessing your main results will be a bored engine and a much thinner wallet. Parts are the same except for your new pistons and rings.

like john said it does raise the compression, and as far as revs... it won't be too noticable but the higher compression and more power will make the engine rev faster... but that's the same across the board, add power, quicker revs (well most of the time)

Well, thats what I was thinking too, til I saw his post. Then I thought maybe theyd done changed the laws of physics and/or math on me without me realizing it. :uhoh:

Well, thats what I was thinking too, til I saw his post. Then I thought maybe theyd done changed the laws of physics and/or math on me without me realizing it. :uhoh:
You know being able to admit when your wrong is a quality alot of people don't have. I explained my thinking behind why I thought what I thought and the amount of compression that is raised by increasing .030 isn't going to be the difference between regular and premuim or even regular and 89. So if this for some reason makes you feel better than me , cause of your comments in a very sarcastic tone. I would appreciate you finding the close window Red/white X on your screen and using it :rolleyes:. Thank you :smile:

Sheesh!!! Settle down John...Im on your side. Noone said anything about who was best. I even thanked you for clarifying yourself above. :wink:
Anyways, youre right about the reasoning behind the increased CR. In order to decrease it, youd increase the combustion chamber size in the heads, like from 64cc to 72cc, etc. :smile: And I know where the "X" is lol.

I am well aware of removing the material from the heads combustion chamber but thanks :). I have ported enough sets of heads in my time to relize what happens if you remove material from that area.

10-4 Just tryin to help. :)

if the preformance increases would almost nothing, then why do people bore out more than .030 over like .060? Does it just raise the compression that much more?

Like Geno mentioned its to take car of wear and imperfections but increased cylinder volume does have a positive effect on performance.

I personally would not bore an average small block unless need be. It increases your risk of overheating since your cylinder wall is thinner, heating up the coolant faster. If you want more displacement, just stroke it....don't get all excited, I'm talking about the motor. :lol: