question about boring...dhadley

[Ranger 330V]

I was reading a post earlier about boring. I was wondering why you don't see any performance increase with boring...I know you hear this all the time..."I've been around automotive engines alot"...lol. I know these are different beasts all together. Just wondering the specifics on this and why it is so. What about compression...increasing decreasing? Not trying to do anything but I know you've done it all and can explain this to me. What makes them so different?? Just tyring to pick your brain a bit. Thanks!

 

[flabum]

Re: question about boring...dhadley

Boring any engine won't give you any noticable hP increase unless you go crazy. Compression increase will ( 2 cycle and 4). As with any engine, as you raise compression, you must get better fuel and better oil and in some more extreme cases, more oil. 2 Cycles also benefit greatly with port work.... depending on the motor, opening, raising, polishing and adding ports works wonders. An engine is a bi airpump. The more air you can efficiantly pump, the faster you will go.

 

[F_R]

Re: question about boring...dhadley

Just picking some numbers at random, if an engine is 3.5" bore X 3" stroke, and you bore it .020 oversize, you will increase the displacement about one third cu inch (per cylinder), or approximately 1%. Not enough to notice in real life.

 

[samo_ott]

Re: question about boring...dhadley

I like the big airpump analogy... cause that's exactly what it is... I used to work on old air cooled vw's and in the aftermarket manual they actually stated that if you had a flat you could carry an air hose and screw it in your spark plug hole and fill up your tire... while I could see this working, the pressure would be high and then there's the issue of the gas/air mixture in the tire... but then I reckon it's a lot better than being stranded... but nowadays you get those little 12v pumps for $10 so it's not an issue any more...

 

[jtexas]

Re: question about boring...dhadley

never really thought of dhadley as boring.................

 

[Dhadley]

Re: question about boring...dhadley

My wife says I am (actually she says I'm not -- shows how easily entertained she is).

Yep, even boring .064" over you're not likely to see any gains at the same (stock) rpm with the same port timing & cylinder heads. If you look at the V6 200 / 225 loopers, in 1988 they're .185" bigger bore but have the same output. However you can change heads, turn em up a little and do some porting to easily make 300 hp.

We've actually had guys take apart a good running crossflow just to have it bored .064" over to "make more power". Without messing with port timing it's not going to do much of anything. We always warn them to be prepared to be disappointed -- and they always are. Lots of $$ for nothing.