With 30 over pistons and otherwise stock bottom end, I had 9.8:1 with 39cc chambers.
I miss my Valiant
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| Author: | drgonzo [ Thu Sep 16, 2010 8:09 pm ] |
| Post subject: | Smallest effective cumbustion chamber Size? |
How low can we go? How small a chamber can be achieved with just flat milling the head? Looking into just pulling my head and getting as much compression gain there as i can. |
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| Author: | hellion_locdogg [ Thu Sep 16, 2010 8:35 pm ] |
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The best way is to figure out how much you want and go from there. You can mill the head and the block for a combo far beyond what you'd ever want. As seen on here most stock heads run 56-58 cc and blocks about .185 or so. Roughly speaking .006 per cc. I think a 45cc chamber is what is most often recommended. ,Cliff |
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| Author: | hellion_locdogg [ Thu Sep 16, 2010 9:07 pm ] |
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Try to find some reading on squish and quench. Smaller cc + less quench = detonation. This needs to be balanced betweeen the head and the block from what I understand. ,Cliff |
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| Author: | Joshie225 [ Thu Sep 16, 2010 9:39 pm ] |
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Quote: Try to find some reading on squish and quench. Smaller cc + less quench = detonation. This needs to be balanced betweeen the head and the block from what I understand.
What? Short of domed pistons or welded combustion chambers it's near impossible to achieve quench with a 225. We have open combustion chambers and most live with that, but a few have made substantial changes to achieve quench. Simply milling the head won't do it. ,Cliff Dart270 has angle milled at least one /6 head severely. Intake and manifold sides cut .110"/.210" to get 33cc combustion chambers. One of his posts: http://slantsix.org/forum/viewtopic.php ... gle#284991 There is no set milling recommendation. Measure so you know where you are and see if you can get where you need to be by cutting the head or if more drastic measures are needed. |
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| Author: | hellion_locdogg [ Thu Sep 16, 2010 9:50 pm ] |
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I did say "from what I understand", never claimed to be an expert. I stand corrected then. Does this mean he has dramaticly dished pistons to keep his cr within reason then or just valve relieved? ,Cliff |
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| Author: | Joshie225 [ Thu Sep 16, 2010 10:25 pm ] |
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I'm pretty sure Lou's engine with the angle milled head has stock replacement flat top pistons. The compression ratio isn't insane, but it's got a pretty serious cam which drops the dynamic compression ratio. |
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| Author: | drgonzo [ Fri Sep 17, 2010 4:58 am ] |
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I know I can't decide how much to mill until I pull the head and measure my deck height. Assuming it's in the .160-.170" range, could I conceivable get to 10:1 CR with head milling only? Brad |
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| Author: | Dart270 [ Fri Sep 17, 2010 5:33 am ] |
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10:1 is easy with milling the head. My '64 motor (60k miles and counting on rebuild, with rering about 10k ago), has just under 11:1 with the angle mill Josh posted and stock 3.460" cast rebuild pistons - 0.175" deck ht. You can mill something like 0.120" off the head for 10:1, but you'll have to measure as mentioned above. Lou |
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| Author: | drgonzo [ Fri Sep 17, 2010 6:00 am ] |
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Thanks Lou |
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| Author: | Dart270 [ Fri Sep 17, 2010 7:49 am ] |
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You want about 35-40 cc head chamber depending on gasket and deck ht for 10:1. Lou |
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| Author: | 70valiant [ Fri Sep 17, 2010 12:51 pm ] |
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With 30 over pistons and otherwise stock bottom end, I had 9.8:1 with 39cc chambers. I miss my Valiant
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