[bistledink]

What's the deal with this Boreing and/or Stroking I hear so much about? It doesn't add to the cid does it?

 

[Harley]

Adding "cid" is uselly why it's done.

------------------
Harley
69 461 El Camino Nitrous Model, 69 Chevelle coupe
70 El Camino,71 SS Camaro
79 Corvette
Kerrville,Tx.

 

[Clark]

bistledink
The engines "Bore" is the inside diameter of a cylinder. One way to increase the displacement and thus horsepower is to make this Bore bigger. The block is positioned on what is essencialy a large lathe and the inside diameter of the cylinders are cut out to a larger diameter. After a rebore you must use larger pistons to fill the larger hole. Small block Chevy's cant usually be overbored by more than .040, sometimes you can go out .060. During a routine engine overhaul the engine will usually be overbored to remove any previous damage. .030 is a standard overbore. (ie, a cylinder with a 4 inch bore becomes 4.030) This increases a small block Chevy's displacment by about 5 cubic inches.

The engines "Stroke" is the distance the piston moves in the bore. If you can make the piston sink into the bore hole further you will increase the displacement and again its power. To change an engines Stroke you must change or modify the crank shaft, pistons and possibly the rods.

Many Chevy lovers have turned thier 350 into a 383 by putting a 400 crankshaft into a 350 and overboreing the cylinders .030. Special pistons are also required (plus other stuff gets changed) The 400 crank has a longer stroke and thus increases the displacment.

Chevy made it easy for us to do this because they produced the small chevy with alot of different bore/stroke combinations and alot of the parts are easily interchangable.

Hope this helps

Clark

 

[bistledink]

Thanks Clark, that pretty much answers all of my questions!

 

[DJRisberg]

Another bonus of a longer stroke, besides greater displacement, is basically increasing the leverage of the crank...Kinda like when you take off a rusty bolt, it takes less effort to remove that bolt with a longer wrench (why cheater bars work ect.) In an engine, what that amounts to is greater torque at lower rpms. As with everything there's a tradeoff, in the form of higher piston speed at any given RPM = higher friction, and greater centrifugal stress on the crank at any given RPM = broken crank at high revs...

In general terms, if you want a low/mid range high torque engine go for a big stoke. If you want a high revver, keep your stroke within limits of say a 350 cid stroke. If you want both...prepare to pay for forged billet stuff in your short block.



------------------
68 El Camino...Slow, Much Work Required
98 Z28...Fast, No Work Required
Goodfellow AFB, San Angelo, TX -- Where? That's what I said..

 

[bistledink]

Thanks DJ, now it's just a matter of restoring my interior before i can bore or stroke my engine. Oh, by the way, I used to live in San Angelo, just outside of Goodfellow. Do they still have that big smiley face on the water tower?

 

[DJRisberg]

No...I think some of the neighbors felt they were being watch...Now it has a 17 TRW patch...All business these days. I'm in the middle of an interior resto myself...waiting for parts that have been on backorder for over a month...can't put the glass back in until the headliner comes...well I'll whine somewhere else - good luck!

------------------
68 El Camino...Slow, Much Work Required
98 Z28...Fast, No Work Required
Goodfellow AFB, San Angelo, TX -- Where? That's what I said..