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| Max static compression on 92-93 octane? https://slantsix.org/forum/viewtopic.php?t=41892 |
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| Author: | drgonzo [ Tue Sep 14, 2010 8:51 am ] |
| Post subject: | Max static compression on 92-93 octane? |
Gathering parts for my 225 build. So far I have Clifford 6-2-1 headers, Clifford hyper pak intake, 450 Holley, ford 9 inch with 3.50:1 gears. Stock converter for now....high stall later. So, help me with static compression vs cam timing for this engine. I guess what i am asking is what is a good cam and C.R. for this set up and run it on pump premium. thanks, Brad |
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| Author: | Joshie225 [ Tue Sep 14, 2010 9:09 am ] |
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What you're really asking about is dynamic compression ratio. I would suggest you go read this article on the KB Pistons web site. http://www.kb-silvolite.com/article.php ... ad&A_id=36 That will give you good info on selecting a compression ratio and cam with the appropriate intake closing point. Be aware that a 225 with a big cam will run best with the intake centerline around 100-102 degrees ATDC. So adjust the intake closing point when using the dynamic compression ratio calculator also found on the KB Pistons web site. That stock torque converter is really going to limit the cam duration you can run and still have a car that's fun to drive. I highly recommend a low compression ratio and mild cam with a stock converter. If you can't afford a $4-500 torque converter you really can not afford to get the compression ratio and cam duration up where you start making serious power. |
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| Author: | Doc [ Tue Sep 14, 2010 9:18 am ] |
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Target 8 to 1 DCR (Dynamic Compression Ratio) for a pump gas street engine. Review this calculator and start "playing with the numbers" http://www.kb-silvolite.com/calc.php?action=comp I will give you a head start: Combustion chamber in cc's , use 56 to 58 (Check yours for actual cc's) Head gasket thickness, .045 for composit, .020 for steel shim Head gasket bore size, 3.5 (special gaskets can be larger) Bore 3.4XX Stroke is 4.125 Connecting rod length for a 225 is 6.700 The big question is always: What is the closing point of the intake valve at .050 lift? (Plus 15 degrees per the calculator's instructions) This is that "relationship" question you are talking about and this is a number that has to be checked with a degree wheel and varified... each cam and combo is different. As a "baseline", the RDP Erson designs we did for "street performance" come in around 48 to 52 ABDC @ .050 + 15, Intake closing point. With this info, a touch over 9 to 1 static CR gets you the "magic" 8 to 1 DCR number. DD |
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| Author: | drgonzo [ Tue Sep 14, 2010 10:19 am ] |
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Josh. Here is my situation. I can afford a $4-500 converter but not at the same time i get the cam and do head work, etc. I doing this on a budget and it does not HAVE to be my daily driver. But since the round trip to work is a paltry 4 miles. I can over look a fair amount of incivility...lol. Right now I am just collecting parts and trying to get my combination planned out before I go farther. Thanks for all the numbers doc, sure saves me some research time! |
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| Author: | sandy in BC [ Tue Sep 14, 2010 7:51 pm ] |
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Buy the convertor first. 9.5:1 Erson 280/270 and gears/5 speed(gears/convertor) ....you can run 89 most days Do the math...you wont be sorry. |
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