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| Chamber Volume ? https://slantsix.org/forum/viewtopic.php?t=39126 |
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| Author: | Blown 70 [ Tue Feb 23, 2010 1:02 pm ] |
| Post subject: | Chamber Volume ? |
Hello, Building a cylinder head,with oversize valves.Machinist had this question for me. Whats the minimum chamber volume I want to go to ? |
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| Author: | sandy in BC [ Tue Feb 23, 2010 1:12 pm ] |
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What size are they now? What is your target compression ratio? What is your deck height? |
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| Author: | Blown 70 [ Tue Feb 23, 2010 1:26 pm ] |
| Post subject: | |
[quote="sandy in BC"]What size are they now? What is your target compression ratio? What is your deck height?[/quote] What size are they now ? Not sure. Stock head if that helps. Target compression ratio ? Not sure. Want to stay with pump gas. Just a fun little street car. Deck height ? Stock. Plan is to go .100 off the head,with 1.70 & 1.44 valves. This is all new to me so bare with me. |
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| Author: | Joshie225 [ Tue Feb 23, 2010 1:39 pm ] |
| Post subject: | |
You absolutely must measure the combustion chamber volume and the piston to deck clearance. If you want help finding a target compression ratio, then we also need to know your cam specifications. |
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| Author: | 66aCUDA [ Tue Feb 23, 2010 1:52 pm ] |
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Take a lesson and remove the material from the block instead of the head. This will give you more versatility in using the head for other things. MEASURE everything. Frank |
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| Author: | 70valiant [ Tue Feb 23, 2010 2:36 pm ] |
| Post subject: | |
Take the time to cc the head. I didn't and assumed it was stock. I had .100" taken off and ended up with a 39cc chambers and a compression ratio of 9.8:1 which required 98 octane(unleaded plus around here). The bore was .030 over which also bumped the compression up a little. |
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| Author: | Blown 70 [ Tue Feb 23, 2010 3:21 pm ] |
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[quote="Joshua Skinner"]You absolutely must measure the combustion chamber volume and the piston to deck clearance. If you want help finding a target compression ratio, then we also need to know your cam specifications.[/quote] Cam is the Erson 280/270 Pistons are in the hole 5/32". Probably not the correct way to measure,but thats how far down they are. Probably shooting for 9.5:1 ? Maybe a little less. The pistons are .40 over Dont plan on touching the block. |
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| Author: | Reed [ Tue Feb 23, 2010 4:00 pm ] |
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The problem is that stock slant six combustion chamber volumes varied quite a bit. Two heads with the same casting number can have greatly different combustion chamber volume, and two chambers in the same head can also have different volume. There is no way around the fact that you MUST measure the volume of the chambers (all of them) in the head you want to work with. It is very easy to do and the tools cost under $10 to do it. |
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| Author: | Joshie225 [ Tue Feb 23, 2010 5:07 pm ] |
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Reed has it right on the chamber volume. You can measure the piston deck clearance with feeler gauges and a straight edge. I had .080" taken off both the block and head to get my .040" overbored 225 up to 9.8:1. That's getting into radical head milling if you're not going to touch the block. Your head and block will be different than mine. The question is how much. |
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