Can some one do some math for me??????
#2164533
09/29/16 06:12 PM
09/29/16 06:12 PM
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I'm hoping someone can run some compression ratio numbers for me. I'll supply the data and you do the math. I can't get the numbers to come up with what I think they should be.
Here goes: 4.0705 bore 3.313 stroke .055 gasket with 4.150 bore 67 cc chamber 110 cc 1/2 inch down fill Piston is .044 positive out of the bore
Run the numbers and see what you get.
Thanks in advance.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can some one do some math for me??????
[Re: madscientist]
#2164558
09/29/16 06:33 PM
09/29/16 06:33 PM
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I get 9.95
I thought it should be 10.8 per so.
It's definitely pissing me off.
Thanks for the math.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can some one do some math for me??????
[Re: madscientist]
#2164573
09/29/16 06:50 PM
09/29/16 06:50 PM
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That's one issue I have. The actual downfall is 110 cc's so the flat top piston has valve notches that are about equal to a 3.5 cc dish.
Guess I should have shoved it .060 out of the deck.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can some one do some math for me??????
[Re: CTD5.9]
#2164582
09/29/16 07:02 PM
09/29/16 07:02 PM
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Joined: Jul 2004
Posts: 653 Fredericksburg Va
plycuda
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I got 8.69 in the wallace calculator which feels wrong. I don't know the real math behind calculating so I made some guesses. I went with 3.32 as the valve relief because a 4.0705 x .5 cylinder should be 106.68 CC, the 0.044 into the deck height made me question it. Maybe it should be -0.044? that would come out to about 10.66 I get 8.68 if you do pistons in the hole .044 but out of the hole .044 is 10.65
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Re: Can some one do some math for me??????
[Re: madscientist]
#2164601
09/29/16 07:28 PM
09/29/16 07:28 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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I get 10.68, not accounting for the area above the rings.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Can some one do some math for me??????
[Re: 66er]
#2164687
09/29/16 09:20 PM
09/29/16 09:20 PM
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I get 10.72 without accounting for extra bore size of the gasket, so 10.63-10.68 sounds real close to me. I got 3.32 for the valve relief. 1/2" x 4.0705= 106.68cc. Subtract that from your 110cc and you get 3.32 That 3.32 is what the DISH Is even though the piston is out of the bore. The 1/2 inch down fill is 106.59513 so that makes the piston think it's a dish even though it's positive out of the deck. I'd have to post all my math but I get 9.95 and if that is the case, there was NEVER an actual 10.5:1 340. It's frustrating for sure.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can some one do some math for me??????
[Re: madscientist]
#2164738
09/29/16 10:33 PM
09/29/16 10:33 PM
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We are all using the same numbers with different results.
Unreal.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can some one do some math for me??????
[Re: madscientist]
#2164768
09/29/16 11:07 PM
09/29/16 11:07 PM
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Can you run my numbers they way you are talking about and tell me what you get?
Like I said, I get 9.95:1 and when I get some time tonight I'll post my math to verify. I'm not too concerned with crevice volume at this point.
I guess my other question is what happens at an NHRA event and you have a pull apart your engine after you set a record or something. Does NHRA calculate crevice volume? Do they just drop the piston .500 and do a down fill and calculate the CR?
I have done the down fill for years and for some reason, I'm way off the reservation on this.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Can some one do some math for me??????
[Re: madscientist]
#2164777
09/29/16 11:19 PM
09/29/16 11:19 PM
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Joined: Aug 2003
Posts: 43,285 Bend,OR USA
Cab_Burge
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I Win
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Last edited by Cab_Burge; 09/29/16 11:20 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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