I am in the process of having the head for ruster setup now by Mike Jeffrey.
Question is What is a Good Target Compression ratio for these cam Specs?
Thank you!
Greg
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| Author: | Greg Ondayko [ Mon Jan 11, 2010 3:06 pm ] |
| Post subject: | Calling Cam and Compression Guru's |
I am in the process of having the head for ruster setup now by Mike Jeffrey. Question is What is a Good Target Compression ratio for these cam Specs? Thank you! Greg |
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| Author: | Shaker223 [ Mon Jan 11, 2010 3:17 pm ] |
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Since it will be race only, I'd shoot for 11:1 or better with that much duration. |
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| Author: | Doc [ Mon Jan 11, 2010 3:43 pm ] |
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I do not go over 11.5 on engines that I run with availible "off-the shelf" composition type head gaskets. (Fel-Pro) You can go a bit higher if you use a steel shim type headgasket and do careful surface prep. DD |
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| Author: | Joshie225 [ Mon Jan 11, 2010 3:58 pm ] |
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11.5:1+ for the much overlap. I'm with Doc on this. I'd be thinking really hard about a copper gasket and o-rings. |
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| Author: | theomahamoparguy [ Mon Jan 11, 2010 10:10 pm ] |
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Yes, between 11:1 and 11.5:1 wuold probably get you about 8:1 - 8.4:1 in dynamic effective compression ratio with that intake closing of 74 degrees. It would probably be at the limit for pump gas. I guess the only question then would be the sealing issues as mentioned earlier. Just my .02. (mid 8's on dynamic compression is very good, if you wanted more octane tolerance, you could run a bit less compression and still be at mid to high 7's dynamic, it would still be very responsive). Above this 8.5:1 on the dynamic, you would be adding race fuel to the mix unless the combustion-chamber design was very good and/or you have some type of swirl port config or maybe alot of "squish" in the chamber. Of course, BOOST throws all of this out the window. (turbo etc.) |
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| Author: | Dart270 [ Tue Jan 12, 2010 7:00 am ] |
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I will be running an almost identical cam in the new Project V motor (260 @ 0.050" on INT/EXH and 0.530", 106 LSA - old "American Cams" regrind). I have it set up for 11:1. What make is that cam? FYI, the Permaseal AUS/NZ head gaskets are good to 12:1+ with an O-ring on the block side, according to Tilley. He said 11:1 should be no trouble with just the gasket. Lou |
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| Author: | wvenable [ Tue Jan 12, 2010 7:37 am ] |
| Post subject: | |
Schneider cam I think. |
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| Author: | Al T [ Tue Jan 12, 2010 8:40 am ] |
| Post subject: | Playing around with Dynamic Compression |
Greg try putting you values into this calculator. http://www.rbracing-rsr.com/comprAdvHD.htm. For example, if you have stock internal geometry, SCR of around 11 and the Ivalve closes at 57 ABDC (0.050"), your DCR will be around 9.07:1. Have fun. Cheers! Al T |
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| Author: | Greg Ondayko [ Tue Jan 12, 2010 4:26 pm ] |
| Post subject: | Thank you. |
This Engine Will be race only - 112 Octane Only - Thanks for all the replies. Mike jeffrey said that the Fel-Pro Gasket Without boost or Spray should not be an issue with This engine. I do have 2 copper Gaskets on the shelf should I need them at a later date. The Cam is a Schneider. Lots of good info here! Thank you! Greg |
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| Author: | Polara1974 [ Wed Jan 13, 2010 5:09 am ] |
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I was wondering the very same question about my new slant buildup. I have the MP276 cam, but since I got it without the cam card I do not have the numbers for @.050. The cam is 276/276 , rockers 1,6 .523/.523 lift , 64 overlap, lobe separation 106, degree intake lobe 104 The engine will use long 7,3 rods, being that the other mayor change. What do you think my SCR should be? No race fuel for my engine. |
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| Author: | Dart270 [ Wed Jan 13, 2010 6:21 am ] |
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Polara, I would run that cam with SCR = 10:1 on 92 octane gas, or if you will run race gas, then you can go higher - 11:1 or so. I ran that cam for several years in my daily driver with 10.5:1 on pump gas. It did ping from time to time, but never hurt the motor (still running strong with 140k on it, about to get turbo'ed with smaller cam and comp). I would have run 10.0:1 if I did it again. Lou |
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| Author: | Polara1974 [ Wed Jan 13, 2010 8:12 am ] |
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Thanks Luo, that was what I have in mind. Also here we do get 97 / 98 octane at the pump, so maybe I can push it a little harder ... My other concern about high SCR is running too hot all the time ... I'll have to check this as well ... Thanks! |
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| Author: | Dart270 [ Wed Jan 13, 2010 8:21 am ] |
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I did not have a heat problem with mine, even with stock radiator, and was living in Los Angeles, CA for much of the time I used that cam. Lou |
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