Can someone download this file and let me know if my calculations in excel are correct for determining compression?

https://drive.google.com/file/d/1gmUWLXWxISqxcCgfYaVuZSWShXtJs4I-/view

 

 

I'm not gonna download the file, I just use this

https://www.summitracing.com/newsand...ion-calculator

 

With that you have to calculate piston deck clearance?

(((Stroke / 2) + rod length) + piston compression distance) - deck height

 

Use -.007


And with any compression calculation you'll need to factor in deck height

 

I put -.007 into my calculator with the values below and it matches what summit calculated for compression and total displacement. For my calculator you enter the values in bold below and it computes the rest.

Enter Cylinder Bore Size 4.125
Enter Piston Stroke length 3.622
Enter Head Gasket Bore Diameter 4.165
Enter Compressed Head Gasket Thickness 0.059
Enter Combustion Chamber Volume in CCs 64.000
Enter Piston Dome Volume IN CCs, For Dished Pistons (Use '+' instead of '-') 12.000
Enter deck height 9.235
Enter rod length 6.125
Enter amount milled off the head (should be "-" number) -0.015
Enter piston compression distance 1.297
Piston Deck Clearance (negative means in the hole) -0.002
Piston compression distance for zero deck 1.299

Modified Combustion Chamber Volume in CCs 61.857
Swept volume cc 793.210
Gasket cc 13.195
Deck Clearance Volume cc 0.438
Total Chamber volume cc 87.490
Compression ratio 10.07
Quench 0.061
Displacement 387.24

 

Wish I would have seen this calculator before I made mine....

http://www.us.mahle.com/en/motorspor...h-information/

LOL my calculations match Mahle's out to 3 decimal places so that's good at least. Only difference is their calculator uses (+) below deck and (-) above deck for deck clearance in cell E9, and for mine it figures (-) below deck and (+) above deck. Just a different way of representing the math. While you aren't going to choose your head gasket thickness until you measure the actual deck height of all 8 installed pistons, it's still nice to get an idea of what the theoretical values are.

Diamond actually takes into account the measurement of the top of 1st ring to top of pistons (FLAT) in their calculation, which many others don't as this difference will only change the compression value ever so slightly. "Top ring down" so to speak. I find the math interesting even though many just tell their engine builder what they want and never worry about these calculations that go into it.

http://www.diamondracing.net/tools/

 

There's about 75 billion "calculators" for compression ratio on the Net.

There's about 750 billion calculators at Best Buy. I can punch in 2+2, and I bet EVERY SINGLE ONE will come up with 4. (which, if you have unusually large values of 2, the answer could even approach 5... BEWARE of the trap of grade school "math", where every "problem" had only ONE "right" answer... how many leaves are on a tree? What separates a tree from a bush? How big is a house? What size does it take to become a "mansion" or a "castle"? and so forth)

They're all "right", to the extent you put in THE RIGHT numbers.

"Calculating" compression ratio out to 3 decimal places is LAUGHABLE. I find it hard to believe that even the N00est n00b would fall for that. Hell, even us EXPERIENCED people have trouble "calculating" it to ONE decimal place before we MEASURE it, and probably won't quote it more precisely than that EVEN AFTER measuring EVERYTHING, because there are SO MANY variables. Everything from rod length, crank consistency (stroke), chamber casting, valve "tulip" or "flat", valve seat wear, block machining tolerances, head dowel pin location accuracy, spark plug insulator volume, ... if you've never been around racing machine work, you have NO CLUE how foggy and fuzzy all that stuff is, until and unless you MEASURE it in YOUR motor. And/or, you PERFECT it. (not AT ALL a small task) Which I'm guessing you don't have the means immediately at hand to do so. ???? 64.000 cc for your chambers, on a factory casting ... bwahahahahahahaha I bet they're anywhere between 63.5 and 65.0, RANDOMLY. (not to make fun of you or insult you, but, ... you figure it out, you're the one looking for help, UNDERSTAND the issues at play here instead of getting sand in your vagina)

The numbers that vary the most are, deck height and chamber volume. Go MEASURE those things in the parts you intend to use. NOT, look up in catalog; NOT, "estimate"; NOT, search with The Google; NOT NOT NOT NOT NOT. The operative concept here is, MEASURE. Which means, pull out yer micrometer, bore gauge, feeler gauges, laser pointer, buret stand, and whatever else, and MEASURE.

Until you do that, everything is just a guess. An "educated" or even "informed" guess maybe; but, AT BEST, just a guess. MEASURE.

 

Yes, I completely agree. It's all theoretical calculations but unless the parts and machine work are measured and tolerances adhered to, it's not worth building it based on off the shelf specs and hoping that it's correct.