445, 444, or 436??

I think I may have slipped a cog in my brain... I was checking cylinder bores with a snap gauge a few minutes ago and grabbed the Haynes manual to see if they were still in the ballpark. I noted that bore and stroke are square (4.11" x 4.11"). I decided to see for myself whether our 7.3L engines are closer to 444 cu.in. or 445 cu.in., so I did the math... Pi x Radius squared, gives area.. So, half of 4.11" is 2.055". Now square that- (2.055" x 2.055") = 4.223025", right? Pi is 3.14159, and the bore's radius squared is 4.223025, right? So then, 3.14159 x 4.223025" = 13.267" area, right so far? The stroke is 4.11", so 4.11" x 13.267" = 54.527 cu. in. per cylinder, right? We have 8 of those, so 54.527 x 8 = 436.216... Every time. I know I have to be doing something wrong, but the calculation is a simple one and it's defying me. Anybody see anything obvious where I'm screwing up??

Do the calculations in METRIC and see what you get ROFL...

What about the precups? Do they factor in?

smolkin said:

What about the precups? Do they factor in?

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Negative Ghost Rider....only pistons swept volume to calculate the displacement.

However they do come into the equation when you are calculating out a compression ratio. Compression ratio is the pistons swept volume ...yet again, compared to the remaining volume in one cylinder so then and only then do the precups come into play.

Hope this helps clarify things some for you.

Al

Not that it matters in this instance, but the easy "formula" I use to calculate displacement is: BORE X BORE X STROKE X # of cylinders X .7854 (constant)
I believe I got it from HOT ROD magazine about 30 years ago.

riotwarrior said:

Do the calculations in METRIC and see what you get ROFL...

Click to expand...

Oh, OK then..

Pi (3.14159) x radius squared (5.2195cm x 5.2195cm), or 27.24318cm = 85.5869sq. cm. So far so good? Bore area (85.5869 sq. cm) x stroke (10.439cm) = 893.4416cc per cylinder x 8 cylinders = 7,147.533cc, or 7.14L.... Hmmmm, Lets convert 7.147L to cu. in.... Wow! 436.137 cu. in.! Amazing! It comes out to the same thing! ROFLMAO ALSO...

If you actually know the answer, then heckling the questioner is in poor taste, but pretty much to be expected. However, if you don't know the answer, then it's just poor taste.

wh1056 said:

Not that it matters in this instance, but the easy "formula" I use to calculate displacement is: BORE X BORE X STROKE X # of cylinders X .7854 (constant)
I believe I got it from HOT ROD magazine about 30 years ago.

Click to expand...

Interesting, I don't think I've seen that one before.. Lets try it then- 4.11 x 4.11 x 4.11 x 8 x .7854 = 436.22078. Close enough for government work...

Are those the 6.9 specs?

Stoke is wrong.

http://www.dieselhub.com/idi/7.3L-idi.html

You forgot about the 0.040 the pistons go above the bore

Stroke is 4.18"

laserjock said:

Are those the 6.9 specs?

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No, those are 7.3 specs, they're just wrong.. Straight out of Haynes.

Your math is correct and I don't feel someone was teasing you about doing the math in metric. The problem is the stroke figure is wrong. So is the Haynes manual you got it from. Sad to say the Haynes manual is not the best example of what these idi engines are. BTW I have the same Haynes manual and have for many years had 2 of the International CGES435-1 engine service manual. Its a far better shop manual telling everything you need to know about these engines. It covers connecting rod twist to piston fit to so much other great info. The 7.3 bore is 4.11 and the stroke is 4.18.

OLDBULL8 said:

You forgot about the 0.040 the pistons go above the bore

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That .040" travels with the stroke so it doesn't count, nice try- you made me think about it for a second!

icanfixall said:

Your math is correct and I don't feel someone was teasing you about doing the math in metric. The problem is the stroke figure is wrong. So is the Haynes manual you got it from. Sad to say the Haynes manual is not the best example of what these idi engines are. BTW I have the same Haynes manual and have for many years had 2 of the International CGES435-1 engine service manual. Its a far better shop manual telling everything you need to know about these engines. It covers connecting rod twist to piston fit to so much other great info. The 7.3 bore is 4.11 and the stroke is 4.18.

Click to expand...

Yes sir, I see that now.. Gotta admit that I'm pretty disappointed with Haynes. It makes me wonder what else may be in error. You wouldn't be interested in selling the more dog eared & dirty of those CGES435-1's, would you??