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Re: Economy 440 Build Suggestions
[Re: CYACOP]
#468948
09/17/09 01:42 PM
09/17/09 01:42 PM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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new one: "decompressed pistons"
 I'm so sorry . Low compression pistons, dog dish pistons, blower pistons, smog pistons.........any of these suit you?
Yes, all the same thing. If you order a complete engine kit make sure the pistons are NOT the ones with the 1.912" compression height. There's no point in putting those in a motor, you'd be better off re-ringing a tired 440 than wasting your money with those. The one summit may be waiting on are likely their 'not as bad' 1.991" compression height pistons. At least with those you get a somewhat usable CR. My choice if you want something on a budget would be KB237's or even trw 2355's.
I did some checking and see the KB237's will give me a 10:1 compression ratio at 88cc heads. To get a 9.5 to 1 ratio It was suggested use the KB184's which I cannot find, orders since June not filled yet, back orders The TRW's 2355's at 9.4 to 1 are also not available until who know's when. So I continue my search.
Decided to get away fron rebuild kits and get the pistons for now but that seems to have it's own issues. 
I want to shoot for a 9.5 to 1 comp ratio.
Just get the KB237s, with a 90cc head (wich most 906/452s are around 91-92 stock) says the comp. will be 9.7.1, this is with the piston around .010" in the hole & a .039" gasket, i've run these pistons before, with an untouched block, they accually sit around .016".017" below deck, mine ran fine on pump premium, Competition Products has them in stock for 329.99, don't know what Summit/Jegs wants for them, i checked on the TRW 2255s, they didn't stock them.
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Re: Economy 440 Build Suggestions
[Re: CYACOP]
#468949
09/17/09 03:45 PM
09/17/09 03:45 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
I did some checking and see the KB237's will give me a 10:1 compression ratio at 88cc heads. To get a 9.5 to 1 ratio It was suggested use the KB184's which I cannot find, orders since June not filled yet, back orders The TRW's 2355's at 9.4 to 1 are also not available until who know's when. So I continue my search.
Decided to get away fron rebuild kits and get the pistons for now but that seems to have it's own issues.
I want to shoot for a 9.5 to 1 comp ratio.
if you actually do the math, those pistons, to a blueprint height block will sit .015" in the hole. with a 4.35" bore, 3.75 stroke, a gasket 4.5" diameter, .039" compressed, with the 5cc valve pockets and .015" in the hole, and neglecting crevice volume, for an 84cc head (closed chambered eddies) you get 9.9:1 comp, 88cc (open chambered eddies) 9.55:1, and the typical OEM open chambers (90-92cc) 9.25-9.4:1 compression. change the head gasket to a steel shim (.018-.021" thick, 4.38-4.45 bore for the MP or Mr. gaskets'), compression goes up by ~.4. reducing my 4.5" diameter, .039" head gasket to a 4.35" diameter, .039" gasket raises compression by .05
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Re: Economy 440 Build Suggestions
[Re: Robbins]
#468951
09/17/09 06:24 PM
09/17/09 06:24 PM
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Joined: Feb 2005
Posts: 3,958
SW Fla.
CYACOP
OP
master
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OP
master
Joined: Feb 2005
Posts: 3,958
SW Fla.
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To get a 9.5 to 1 ratio It was suggested use the KB184's which I cannot find, orders since June not filled yet, back orders The TRW's 2355's at 9.4 to 1 are also not available until who know's when. So I continue my search.
Decided to get away fron rebuild kits and get the pistons for now but that seems to have it's own issues.
I want to shoot for a 9.5 to 1 comp ratio.
This info below is for the KB184 piston
ENTER YOUR DATA CALCULATED DATA
Cylinder Head Volume (cc) 78
Piston Head Volume (cc) -2
Gasket Thickness (in.) .044
Gasket Bore (in.) 4.5
Cylinder Bore Diameter (in.) 4.35
Deck Clearance (in.) .08
Stroke (in.) 3.75
STATIC COMPRESSION RATIO 09.40
OPTIONAL DATA Rod Length (in.) 6.758
Adjusted Stroke (in.) 3.255
Intake Closing Point (degrees) ABDC @ 0.050 lift plus 15 degrees 49
DYNAMIC EFFECTIVE COMPRESSION RATIO 08.29
This is what I ran with 915's.
Looks like the dynamic calcs are much lower than expected. Looking at the chart I have it says the 80cc heads result in a 9.7 CR your static number is even lower, then you add in the dynamic variablles and end up with about an 8.3 CR. It seems to be a fine line but I really didnt want to have to run premium gas but upon closer inspection the KB237's are looking to be the better choice. Actual results may vary. 
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Re: Economy 440 Build Suggestions
[Re: CYACOP]
#468952
09/17/09 11:02 PM
09/17/09 11:02 PM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Quote:
Looks like the dynamic calcs are much lower than expected. Looking at the chart I have it says the 80cc heads result in a 9.7 CR your static number is even lower, then you add in the dynamic variablles and end up with about an 8.3 CR. It seems to be a fine line but I really didnt want to have to run premium gas but upon closer inspection the KB237's are looking to be the better choice. Actual results may vary.
Don't waste your time with those charts. The charts the piston manufacturers put out make all kinds of assumptions and always give back an overly high CR. Just use an online calculator and plug in the real numbers and get an accurate reading.
For a piston installon a real-wold block and a typical .039" gasket, 90cc production heads, etc, compression is not as high as they make it out to be. Granted it is high enough for iron heads and pump gas, but should be doable. I still think that the KB237's or TRW2355's are the ticket for you, if you can find them in stock.
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Re: Economy 440 Build Suggestions
[Re: DaytonaTurbo]
#468955
09/18/09 09:37 AM
09/18/09 09:37 AM
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Joined: Feb 2005
Posts: 3,958
SW Fla.
CYACOP
OP
master
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OP
master
Joined: Feb 2005
Posts: 3,958
SW Fla.
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Quote:
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Looks like the dynamic calcs are much lower than expected. Looking at the chart I have it says the 80cc heads result in a 9.7 CR your static number is even lower, then you add in the dynamic variablles and end up with about an 8.3 CR. It seems to be a fine line but I really didnt want to have to run premium gas but upon closer inspection the KB237's are looking to be the better choice. Actual results may vary.
Don't waste your time with those charts. The charts the piston manufacturers put out make all kinds of assumptions and always give back an overly high CR. Just use an online calculator and plug in the real numbers and get an accurate reading.
For a piston installon a real-wold block and a typical .039" gasket, 90cc production heads, etc, compression is not as high as they make it out to be. Granted it is high enough for iron heads and pump gas, but should be doable. I still think that the KB237's or TRW2355's are the ticket for you, if you can find them in stock.
I did the online calculator and see what you mean. Resulted in a 9.5 CR. Looks like I'll go with the KB237's. I spoke with the machine shop and early next week he will underbore the worst cylinder to be sure .030 will clean things up then I will order the pistons next week. Thanks for all the help, I'm sure I will be back for more. 
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Re: Economy 440 Build Suggestions
[Re: CYACOP]
#468956
09/18/09 11:26 AM
09/18/09 11:26 AM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 12,675
Columbia, CT
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Also keep in mind, a dynamic compression depends on teh cam, and you dont want a dynamic with open chamber heads any higher than 8.3:1. To put it in perspective I use 8.5:1 as a max dynamic with aluminum and closed chambers to run pump high test.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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