Just curious if anybody knows the final displacement if we were to bore our 6.5s .30 over? Would that add a considerable amount of hp & tq? You could then run a different CR. Just curious. OK, now everybody go ahead and tell me how stupid I am.

You are so stupid,:D

just because you asked for it.

leave it to one of those guys from massachusetts to say that!! hey, that's me too. must still be too early for me to think straight ):h

Your compression ratio is going to be even higher than the sky high 21.3 that it already is.

How does that country song go?

Bore me another one,
I'm finished with the other one,
I'm kissin' my engine good bye.

country guys sing about the weirdest things

You are so stupid,:D

just because you asked for it.

Thanks, I needed that.

So it can't be done, not worth it...?

Your compression ratio is going to be even higher than the sky high 21.3 that it already is.

How does that country song go?

Bore me another one,
I'm finished with the other one,
I'm kissin' my engine good bye.

AW I wouldn't give up my day job if I were you, at least not just yet,

I don't think they are saying is ain't possible just may not be worth it, I guess.
CR could be controled by using 17:1 pistons

YEEEHA 1000 post finally

YEEEHA 1000 post finally

Congrats:lol:

Just checking. I plan on droppin' a 12V cummins in her once this one goes, but just allowing ya'll to help me think.

if you know the bore and stroke you could just do the math. are those dimensions in the FAQ section? :confuzeld

b x s

3.9676" x 3.818"

Congrats on 1000 and being moderator, Bow.

Cubic inches would be 383.4 with a .030 over piston.
(bore*bore) / 4 * pi * # of cylinders * stroke

A 6.5L is 396 ci stock.

I was looking at the 6.2L page earlier. 6.5L is 4.06" x 3.82"
396 ci+ .030" over (2.88 ci) = 399 ci

Loose math, I think will be
462 CID
7.5 L displacement

CR, still workin' on that one. You did say .3 right, not .03?

LOL, no its .03 three hundredths, .3 (3 tenths) would be a little much ;)

- - - - bore x stroke |piston area|cylinder disp| engine disp
6.2stock- 3.98 X 3.80 | 12.44 | 47.27 | 378.2 cid | 6.19L
6.5stock- 4.06 X 3.82 | 12.95 | 49.47 | 395.7 cid | 6.48L
10 over - 4.07 X 3.82 | 13.00 | 49.66 | 397.3 cid | 6.51L
20 over - 4.08 X 3.82 | 13.07 | 49.94 | 399.5 cid | 6.55L
30 over - 4.09 x 3.82 | 13.14 | 50.19 | 401.5 cid | 6.58L
40 over - 4.10 x 3.82 | 13.20 | 50.43 | 403.5 cid | 6.61L
duramax- 4.06 X 3.89 | 12.95 | 50.38 | 403.0 cid | 6.60L

So, if you go 40 over, you'll get a hair advantage over the DMax, well, displacement wise anyway ;)

TDG,

Thank you! It's about time someone took this post serious enough to answer the original question!

Just curious if anybody knows the final displacement if we were to bore our 6.5s .30 over?

Hey, I was tryin'. . . see . . . I answered his question, just not what he wanted :o:

country guys sing about the weirdest things

Play it backwards, you get your engine back!

Now, let's do it with IPs too!

OK. here is a wrench for the works. On an 18:1 engine that essentially has either the piston shaved or the wrist pin offset how does this affect these figures? I am NOT a math person... so for those who tried, you're braver than I!

No math needed. Piston height (Shaved piston or offset pin hole ) has no bearing on Cubic inch displacement. CID stays the same.

Changing Compression ratio does not affect displacement.
Those numbers are good for 21.3:1 18:1 whatever.
Dropping CR will lower Volumetric efficiency of the engine, so you will need more boost to compensate, but thats normally what your would be aiming for anyway.

Wow, did you guys get that? We posted at the same time and AGREED on something!

Man chevydiesel, you are makin' me sing for my dinner now. . . I promise, no more country music . . .

*IF* my math lines up correctly. . . On a stock 6.5 @ 21.3 CR, and then figuring backward to 18:1 CR, your stroke would change a whoppin' .03" (there's that number again) Stroke would now be 3.85 giving you a 399 CID displacement.

If you are really, really wanting to see the math, I'll just scan the page of my chicken scratch, post the image, and see if someone can deciefer it. I don't think I can myself now.

We all were working on this at the same time. . . gee I guess I lose.

Do I get a conselation (sp) prize? I know I'm not gettin' any music awards here.

Whatever you take off the top, you lose it on the bottom too.
Stroke is determined by the crankshaft, not the piston.

Changing Compression ratio does not affect displacement..

Wow, did you guys get that? We posted at the same time and AGREED on something!

Sorry don't agree.

De-stroking the engine will change displacement and compression.
Piston pin height will not change displacement.

The distance from top of crank stroke to bottom is your piston stroke, so if you don't change the crank, you don't change the stroke.

Oh, and the only way to 'de-stroke' the engine, is to change crankshafts, and no where on this thread has anyone mentioned that.

Offsetting pins and cutting on the piston (which was mentioned by they way) will change compression ratio not displacement.

Ummm...no it won't, the only way to change displacement is to change piston diameter, IE oversize, or change the crankshaft.

Difference from top of crank stroke to bottom is your piston stroke, so if you don't change the crank, you don't change the stroke.

Oh, and the only way to 'de-stroke' the engine, is to change crankshafts. Offsetting pins and cutting on the piston will change compression ratio not displacement.

Well, you could build up the inside of the crank and then offset grind to achieve a shorter stroke....but, I would think that a crank already made would be a cheaper alternative....
And, you're exactly right TDG....when it comes to displacement, there is nothing in the formula that has to do with the piston other than the diameter of it.

Sorry don't agree.

De-stroking the engine will change displacement and compression.
Piston pin height will not change displacement.
I didn't see destroke come it to play until this posting
SO changing compression ratio in this matter will not be destroking an engine, just lowering the CR and there fore not change the engine Cubes.

And you can also destroke the engine by changing the rod length, but that wasn't mentioned here either

And you can also destroke the engine by changing the rod length, but that wasn't mentioned here either

Rod length will not alter crankshaft stroke. Rod length could alter compression.

Crank can be offset ground to destroke engine, requires no welding, just smaller I.D. rod bearings.

What is the rod-ratio on a 6.5?

Volume of a cylinder is length times included area of the cylinder diameter.

V = L x A(pi Rsquared)

Displacement of a piston in a cylinder is stroke times surface area of the piston - S x A.

Altering the stroke alters the displacement - S x A.

Altering the piston heighth in the cylinder alters the position in the cylinder, but if the stroke remains the same, the mechanical displacement is the same - S x A.

The 4" stroke is still 4", but while the overall cylinder volume between the head and the piston surface has increased, the volume displaced by the piston has not - S x A.

Lower compression ratio is resulted.

Compression ratio for unaltered bore and stroke can be altered by -

shave piston crown - lower
dish piston crown - lower
alter wrist-pin location- raise or lower
dome piston - raise
rod length - raise or lower
alter combustion chamber area in head - usually lower
shave heads - raise

last four usually only for gassers

Compression ratio does not change with Boost - only the final pressure changes.