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Re: What compression would you run with a 499 stroker?
[Re: challengermike]
#1123610
11/29/11 12:39 AM
11/29/11 12:39 AM
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Joined: Dec 2010
Posts: 392
Mississippi
lahatte
enthusiast
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enthusiast
Joined: Dec 2010
Posts: 392
Mississippi
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71 degrees after BDC is late for a closing, which would reduce the DCR. The cams I've looked at typically have an intake closing between about 63-67 degress ABDC.
Last edited by lahatte; 11/29/11 12:40 AM.
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Re: What compression would you run with a 499 stroker?
[Re: MR_P_BODY]
#1123613
11/29/11 01:29 AM
11/29/11 01:29 AM
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Joined: Aug 2003
Posts: 1,062
Amherst,NY
challengermike
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 1,062
Amherst,NY
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Quote:
I must be doing something wrong at the wallace one.Its coming up with a 7.21 for the DCR,does that sound correct?i did use the 71 abdc
Heres a pic of all the specs when i built the engine with the 906 heads.
Look at the effective stroke... its 3.04
Why is the effective stroke 3.04? is that because the cam opens to early and closes late? Im sorry, i dont understand all this info.
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Re: What compression would you run with a 499 stroker?
[Re: challengermike]
#1123614
11/29/11 01:38 AM
11/29/11 01:38 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
I must be doing something wrong at the wallace one.Its coming up with a 7.21 for the DCR,does that sound correct?i did use the 71 abdc
Heres a pic of all the specs when i built the engine with the 906 heads.
Look at the effective stroke... its 3.04
Why is the effective stroke 3.04? is that because the cam opens to early and closes late? Im sorry, i dont understand all this info.
Effective stroke is when you start to make compression
(when the intake closes)
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Re: What compression would you run with a 499 stroker?
[Re: challengermike]
#1123619
11/29/11 09:16 PM
11/29/11 09:16 PM
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Joined: Feb 2005
Posts: 4,324
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,324
Prospect, PA
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Quote:
Quote:
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There are several different DCR calculators that use different closing points
 Dont use KB's CR calculator for anything but SCR. I think for DCR (dur at .006) is accurate rather than KB's (dur at .050"). Wallace racing I think has good calculators
I must be doing something wrong at the wallace one.Its coming up with a 7.21 for the DCR,does that sound correct?i did use the 71 abdc
Heres a pic of all the specs when i built the engine with the 906 heads.
If you use the Wallace Calculator, and the actual valve closing point, the resultant DCR will be lower than what is deemed by many as the acceptable DCR for pump gas, i.e. the Wallace calculator gives lower numbers than other DCR calculators. Said differently, if you get a DCR of 8.5 using actual closing point on the Wallace Calculator, you will have serious detonation. This is why I said what I did earlier, there are several claculators that all used different closing points, and wont give you the same results.
What is the cranking cylinder pressure of your current motor, and what is you confidance in the 9.75 CR being accurate? Did you measure or validate the numbers used in the 9.75 CR calc.?
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Re: What compression would you run with a 499 stroker?
[Re: lahatte]
#1123620
11/29/11 09:31 PM
11/29/11 09:31 PM
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Joined: Oct 2005
Posts: 4,968
WI
Dcuda69
master
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master
Joined: Oct 2005
Posts: 4,968
WI
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Quote:
Dcuda69, I'm curious what cam are you using? Do you happen to know the closing angle after TDC (at .006) on the intake valve?
Sorry, don't have the specs. in front of me. It's Comp xr280r solid roller. 242/248@.050 .570/.576 lift IIRC. Idles beautiful at 850rpm with 12" vacuum. Pulls hard and like I said,runs fine on pump swill. My little 245 street tires don't have a chance!   
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Re: What compression would you run with a 499 stroker?
[Re: BSB67]
#1123621
11/29/11 10:14 PM
11/29/11 10:14 PM
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Joined: Aug 2003
Posts: 1,062
Amherst,NY
challengermike
OP
super stock
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OP
super stock
Joined: Aug 2003
Posts: 1,062
Amherst,NY
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Quote:
Quote:
Quote:
Quote:
There are several different DCR calculators that use different closing points
Dont use KB's CR calculator for anything but SCR. I think for DCR (dur at .006) is accurate rather than KB's (dur at .050"). Wallace racing I think has good calculators
I must be doing something wrong at the wallace one.Its coming up with a 7.21 for the DCR,does that sound correct?i did use the 71 abdc
Heres a pic of all the specs when i built the engine with the 906 heads.
If you use the Wallace Calculator, and the actual valve closing point, the resultant DCR will be lower than what is deemed by many as the acceptable DCR for pump gas, i.e. the Wallace calculator gives lower numbers than other DCR calculators. Said differently, if you get a DCR of 8.5 using actual closing point on the Wallace Calculator, you will have serious detonation. This is why I said what I did earlier, there are several claculators that all used different closing points, and wont give you the same results.
What is the cranking cylinder pressure of your current motor, and what is you confidance in the 9.75 CR being accurate? Did you measure or validate the numbers used in the 9.75 CR calc.?
I dont know the cranking pressure,the engine isnt in a car right now.I do trust the 9.75 comp rating,it was done by a performance shop near me when i had them do all my machine work on my engine.I have used a couple calculators on quite a few sites since last night and they all come up about the same 9.75 to 9.77,I think i might just put the same head gaskets on and keep the comp the same for now.Im just worried im going to end up needing to run some race gas or the timing real low.I just sold a 86 buick t type because the price of race gas kept me from going to the track as much as i would like to.It was $80 to $100 everytime i went to the track(including entery fee)
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Re: What compression would you run with a 499 stroker?
[Re: challengermike]
#1123622
11/29/11 10:37 PM
11/29/11 10:37 PM
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Joined: Feb 2005
Posts: 4,324
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,324
Prospect, PA
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Quote:
Quote:
Quote:
Quote:
Quote:
There are several different DCR calculators that use different closing points
Dont use KB's CR calculator for anything but SCR. I think for DCR (dur at .006) is accurate rather than KB's (dur at .050"). Wallace racing I think has good calculators
I must be doing something wrong at the wallace one.Its coming up with a 7.21 for the DCR,does that sound correct?i did use the 71 abdc
Heres a pic of all the specs when i built the engine with the 906 heads.
If you use the Wallace Calculator, and the actual valve closing point, the resultant DCR will be lower than what is deemed by many as the acceptable DCR for pump gas, i.e. the Wallace calculator gives lower numbers than other DCR calculators. Said differently, if you get a DCR of 8.5 using actual closing point on the Wallace Calculator, you will have serious detonation. This is why I said what I did earlier, there are several claculators that all used different closing points, and wont give you the same results.
What is the cranking cylinder pressure of your current motor, and what is you confidance in the 9.75 CR being accurate? Did you measure or validate the numbers used in the 9.75 CR calc.?
I have used a couple calculators on quite a few sites since last night and they all come up about the same 9.75 to 9.77,
Yes, I was asking about validating the measurements (head cc, dish ccs, comp. distance), not the calculation. If you had the cranking pressure, you could work the numbers backwards to estimate an acceptable CR for the aluminum heads.
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Re: What compression would you run with a 499 stroker?
[Re: lahatte]
#1123624
11/29/11 11:06 PM
11/29/11 11:06 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Ah, well then, I already had 6.76 for the rod length when I did the calculation earlier, so that's why I also got the 3.04 dynamic stroke length.
Actually that was what I got also with the 6.76...
the 3.08 was a error
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