Thread: how much more horse power do you get when you bore a engine.060

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Originally Posted by sparky2263

You also get a slight compression increase. I think .060 will give .2-.3 increase.

I routinely bore mine the max. I know good and damn well I won't be doing it again.

WHT WONT YOU DO IT AGAIN?

Originally Posted by DONNY43

WHT WONT YOU DO IT AGAIN?

Because I take proper care of my engines.

I have a solution to and a big increase in horsepower for $10 bucks a piston when you build a motor . We dyno'd a Ford stroker and picked uo a bunch of new horses by coating the piston tops with our product .

Originally Posted by 76GMC1500

With good blocks getting harder to find every day, it makes me so mad when someone bores a perfectly good block .060 over. If you even scratch a cylinder wall, the block is trashed. When I built my engine, I bought a standard bore block and went .020 over. I can rebuild it again at .040 over and again at .060 over. I should get a lot of life out of this block. If I went .030 over on the first bore, I would only have one more rebuild in it.

I HAD TO BORE MY BLOCK .060 I HAD TO MUCH DAMAGE!

none.

i will take none but i would like to have some

Simply increasing the volume of the cylinder .030, .040 or even .060" will get you no more horsepower. Yes you increase the size of the engine marginally but the incresed volume is offset by the loss of compression. Example, a 350 chebbie bored .030" over nets a 10 cubic inch increase, assuming 1 hp per cubic inch or a 350 hp 350 you have reduced the compression ratio by 3% so if you had a 10:1 C/R you now have a 9.7 C/R.

Obviously you can offset the loss in C/R and use those 10 cubes more effectively by increasing lift or duration of the cam and get 1 hp per cube and net 360+ hp without much trouble but simply increasing the bore size will not increase your horsepower output.

Yeah, it's kind of funny, because boring an engine oversized has become sort of a status symbol. You hear us car guys all the time saying " I've got a 30 over 350 in there" or something similar, as if that makes it so much more powerful than just a regular 350. I do it too, but in reality I'll bet if you put an engine on a dyno, tore it down an bored it 30 over you would see a very small increase if any.

Kind of strange when you think about it.


Don

yes it is but when your pistons are 4.530 or 4.625 i think thats is the mark and the good thing is the block get lighter . i like to bore holes that is some thing i like to do the most is boring out blocks and putting in sleeves:

Originally Posted by 1cobra1

incresed volume is offset by the loss of compression.

Incorrect. If stroke and combustion chamber volume remains the same, compression increases. If my engine makes 1 hp per cube, and I increase the size by 10 cubes, I pick up 10 hp. Not including the resulting increase in compression.

Yea whatever, don't ask questions like this when it's hot and I've been drinking. It is true the fastest way to bigger power is bigger displacement, displacement isn't the deciding factor.

Look at Chebbies in the early 1970's. 396 engine in 1969 made 300 hp standard and as much as 450 hp in LS-7 trim. The same engine in late 1970 ws bored out .015" to 402 and lost 60 hp. It didn't lose 60 hp because it was bored out it lost 60 hp despite being bored out because the compression ratio and subsequently the volumetric efficiency was decreased.

Boring an engine is principally a method of extending the usable service life of an engine block it has a side benefit of allowing for, not creating more air flow. Air flow is the key to power. The smooth uninterrupted flow of air into and out of the combustion chamber and how much volume you can compress into and out of that chamber will dictate how much power your engine will make.

Intake, cylinder head design, valve size, cam lift and duration all play a part. Compression ratio plays a big part. No single part can be over looked if you want to get the most from your engine.

not to be a smart a$$ a 396 to a402 is + .030 over . we would bore out a 396 to .030 and bore to fit a used set of 402 pistons . i had a .
030 over big block and then bore it to 468 all the same stuff cam heads oil pan intake every thing. but piston bore pistons the pistons trw ls7 type and if you ask my friend he will tell you the 468 was faster? he was my road dog any time i had the car out he went for the ride. the 468 did run much better but i have a hard time with thinking .030 more would help that much but i built it the same way and not one thing was change but the pistons????

Originally Posted by DennyW

I see some no's up there on the voting. I would like to know why you would not get any more horse power if you bore the engine. Please explain it to me ?

I dunno. Maybe they're thinking cylinder deflection or heat from the thin walls will offset the marginal gains in HP?? It has been tested and proven by Reher-Morrison that aluminum blocks don't make as much hp/torque as the same build in iron blocks b/c of deflection.

The Motown 454 makes a lot more hp than the Motown 427 with the same components by only changing the bore from 4.125 to 4.250.

well the heads do work better with a bigger bore and like i said if the block is good and can take a over bore i think .100 is where you can see it so get out your the block rock

[QUOTE=DennyW]

"The old rule is still accurate. The only thing better than lots of cubic inches is more cubic inches".

Denny is right on the money. All things being equal, 351 ci will outpull 350 ci. We're not talking Chevy's vs. Ford's here, rather the same block. With everything else being exactly the same, bigger is better. You're not going to feel it seat of the pants, but a dyno will show it. If this wasn't true, people wouldn't be wasting money building 383's and small blocks over 400 for racing amd no one would touch big blocks. The line we use to use was "There's no substitute for cubic inches."

Oldman2

I may be old, but I'll be older tomorrow