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Old 02-16-2011, 06:41 PM
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CR ratio calculators

Anyone got a calculator using the crank to deck calculation? I'm thinking I can use this to my advantage to get my desired CR without having to bowl my heads.

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Old 02-16-2011, 08:08 PM
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Quote:
Originally Posted by Wattsy
Anyone got a calculator using the crank to deck calculation?
What do you mean "crank to deck calculation"? Are you referring to the deck height? I already linked the calculator I use in a thread of yours previously. If for some reason you don't like it, there are many online.

Quote:
I'm thinking I can use this to my advantage to get my desired CR without having to bowl my heads.
Do you mean mill your heads?
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Old 02-16-2011, 09:05 PM
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I don't believe that calculator used that calculation of actually using OE Crank (which is what I'll be using) to deck height. I believe it referred to the piston/deck height.

But yes, when I Mill (deck) my block like I were 0 decking it, except to the specific height to make my compression ratio of what I desired. Those pistons I was looking at from Icon are from OE crank to deck 9.8/119cc heads rated at 10.7 CR. If I had the tolerance to make it 9.9 I want to see what my CR would be, rather than bowling out my heads to the appropriate 122cc (roughly) to do the same thing as I'm going to mill the block either way, this would be one less cost for me on my project at this point in time.
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Old 02-16-2011, 11:41 PM
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With the block only being 9.800" tall, I'm wondering how you figure you are going to cut it to 9.900" tall??

With that said, I'll see if I can get you straightened out a bit. Working with info from your other thread, you are putting a stock crank, stock rod length 427 together, using the Icon #IC988 piston. This piston is 1.765" compression distance, which is the dimension from the centerline of the piston pin to the top of the flat part of the piston(not any part of the dome). The rod is 6.135" long, and the crank stroke is 3.76".

Now, to do a little math. To figure out "stack height"(which is the height of all the parts from the crank centerline to the top of the piston flat) we add 1.765"(compression height) + 6.135"(rod length) +1.88"(1/2 of stroke, since we are working from crank centerline) = 9.780".

So 9.780" is the stack height, and we are going to fit it into a 9.800" tall block(Stock BBC) which leaves us with .020" clearance between the top of the piston flat and the top of the block, this is called "deck height" or "deck clearance".

Now, using a compression ratio calculator and assuming a 119cc head chamber and use of a common .041" thick gasket(common Fel-Pro) we can figure the actual compression ratio of your combination(NEVER trust what a catalog says for compression ratio). I use the calculator at Wallace Racing.

Figured with a 4.280" bore (.030" oversize) and the rest of the needed above dimensions of .020" deck clearance, 38cc dome, 119cc head, and .041" gasket it comes up to 10.3-1 compression. You don't need to do a thing to lower the compression if you are shooting for 10.5-1, in fact you would need to cut the top of the block .010" to get it UP to 10.5-1. Cutting the block .020"(to zero deck) will get it up to 10.8-1.

Remember what I said about never trusting compression ratio ratings from web sites or catalogs, get the dimensions and figure what it will be in your specific combination, because you don't know all the dimension they used to figure their ratio, like head gasket thickness and deck height.

Last edited by ericnova72; 02-16-2011 at 11:56 PM.
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Old 02-17-2011, 07:09 AM
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Thanks again Eric, and I wasn't sure on the deck-crank of the stock block, which is why I was going to play around and see if I had the tolerances to do so, as I'm still waiting on my block and cannot measure it!

But that is the end result I wanted to know, and I appreciate it. Although I am going to have to test the actual cc's of my head because they have been semi-ported already, and look like they have slightly bigger valve seats than what was originally stock (My 2.19 intake valve feels like it's way closer than .13" from seating correctly, although it just be the whole circumference of a circle thing playing tricks on me). I don't know if the combustion chambers are legitimately 118/119 as 1cc can throw off my rating of getting exactly what I want.

As for the catalog rating, I never wanted to trust their rating, but get a general rough idea of what I'm looking at and calculate it out for myself so that way I have nobody else to blame when I blow my engine to pieces starting it up for the first time, I just needed to correct information to do so, thanks!
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Old 02-17-2011, 07:14 AM
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Quote:
Originally Posted by Wattsy
Thanks again Eric, and I wasn't sure on the deck-crank of the stock block...
For your sake and ours, pls. avail yourself of this- http://www.crankshaftcoalition.com/w...e_nomenclature

That way, we know what you're referring to and you wont need to continue to "fabricate" words for things.
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Old 02-17-2011, 07:23 AM
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Which word would I have fabricated? OE Crank CL/Deck? As listed on KB/IC's website, which is what my original question was about? (rhetorical question, please don't respond) Maybe you should find some place else to flame, as I'm really not into the whole thing myself, I'm new trying to find out information. I find it almost humorous that I'm being "bullied" by some Cyber-geek gear-head on an online forum, for trying to figure things out and wanting to learn, as I'm ignorant not stupid.

So for my sake and yours, before I start having flashbacks and harm anyone in the near vicinity of me, for them.. please stop posting anything to my walls so I no longer have to deal with any of your childish "ultimate superior" comments. Thank you.

Justin.

Last edited by Wattsy; 02-17-2011 at 07:35 AM.
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Old 02-17-2011, 08:34 AM
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Quote:
Originally Posted by Wattsy
...trying to figure things out and wanting to learn, as I'm ignorant not stupid.
If that is true, read the info offered in the link. There are universally understood words that are routinely used for these things- you do not have to fabricate new ones.

Quote:
So for my sake and yours, before I start having flashbacks and harm anyone in the near vicinity of me, for them.. please stop posting anything to my walls so I no longer have to deal with any of your childish "ultimate superior" comments.
That is all on you, Wat. Nothing whatsoever to do w/the "sake" of ME. Threats over the internet are about the most impotent thing possible, just so you're aware.

Bottom line:

These "walls" aren't yours to say what can be posted to them. You do not get to pick and choose who responds to your threads. These threads are accessed by anyone doing a search that is similar to the thread's title or content, so if not for you, I will continue to post corrections, etc. for those who will come after you- as I see fit.

Oh, and you're welcome.
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Old 02-17-2011, 09:23 AM
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At 56 I'm sure that you (and especially your wife) know all about impotence. This was not a threat towards you, but towards individuals around me in my response to your ever-so clever messages.

I have provided some information that could possibly help you out, so you don't have to fabricate ways to avoid this situation in the future !

Located here

I'm sure glad these walls aren't limited to what I can post on them. Good thing this is a free country (of which you probably abuse your privileges anyways). Thanks bunches for your input as I put it to good use.


Now you know how you come across, have a nice day as "hotrodders.com" lost a new member due to the standard data individual that enjoys ruining the experiences for everyone and brings them down to their bottom of the barrel level.
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Old 02-17-2011, 09:40 AM
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"standard data individual"?

It's a minor shame you cannot take anything away from all that I have posted except the false assumption that I was being derisive towards you. You DO savvy what the icon: means, right?

BTW, I'm sure the link you provided is very useful/clever/or a "gotcha" of some type, but I know I will not be clicking on it- someone as out of touch w/reality as you seem to be have been known to use viruses, etc. as retribution to perceived threats. I'm not risking it, as I'm sure you'll understand.
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Old 02-17-2011, 09:57 AM
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Compression ratio tools

If you are really serious about compression ratios, here are a few tools you need.

Here is a closer view of the bottom of the burette.


The plates in the first picture are just some pieces of clear plastic, I got in the scrap bin of a local place that fabricates plastic signs. I think they are acrylic, but I am not sure.

I just use some ATF in the burette for a fluid. You can bolt the plates on the cylinder head, for CCing the head, and get some short bolts that match the threads on the head bolts to attach the plate to the cylinder block, to check the volume of the piston dish.
If you have a crown on the piston, that sticks up above the deck, dropping the piston exactly 1 inch will enable you to measure that.
Volume of a cylinder can be found here:
http://www.onlinemathlearning.com/volume-formula.html
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