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| Sanity Check https://www.slantsix.org/forum/viewtopic.php?t=36152 |
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| Author: | dakight [ Mon Jul 06, 2009 4:07 pm ] |
| Post subject: | Sanity Check |
I took the head to the machine shop today to have the valves, inserts, and general machining done. I asked the machinist about CCing the heads expecting him to just give me a number but he asked what size I wanted the chambers to be. So I have been running through some calculations and here is what I come up with. Bore: 3.460 Stroke: 4.125 piston: 0.00 Gasket: 3.47 / .045 compressed Deck: .100 after future machining, .186 currently CC Vol. 52 CC These numbers give me a CR of 9.5:1. The cam is an Erson "270" so I think that's a reasonable comnpression ratio to shoot for. Comments? |
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| Author: | sandy in BC [ Mon Jul 06, 2009 4:43 pm ] |
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Thats my setup kinda. I like it. Done again I would have 60 cc chambers and mill the deck more. |
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| Author: | dakight [ Mon Jul 06, 2009 6:01 pm ] |
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Quote: Thats my setup kinda. I like it.
I thought of that, but I remembered Doc's advice to not overmill either the deck or the head to preserve the strength of the sealing surfaces.
Done again I would have 60 cc chambers and mill the deck more. |
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| Author: | sandy in BC [ Mon Jul 06, 2009 7:16 pm ] |
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Do you have big valves? |
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| Author: | dakight [ Mon Jul 06, 2009 8:08 pm ] |
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1.70 / 1.44 fron Engnbldr and improved springs with dampening coils. |
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| Author: | sandy in BC [ Mon Jul 06, 2009 8:16 pm ] |
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It is my belief that leaving more meat in the chamber and decking from the block help prevent "shrouding" the valves. No proof...just observing. |
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| Author: | dakight [ Mon Jul 06, 2009 8:21 pm ] |
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That might be, I really don't know. The machinist will provide some relief around the valves and the block has been bored .060 which will also help some. If I ever do another one I might take a different approach but for this one I'm going to be moderately conservative... kinda like my politics. 
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| Author: | sandy in BC [ Mon Jul 06, 2009 8:26 pm ] |
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.....then you must have the Sarah Palin Signature Series valve stem seals! |
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| Author: | dakight [ Mon Jul 06, 2009 8:35 pm ] |
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Naw, they're just the standard black rubber stock type from the Victor gasket set. |
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| Author: | 66aCUDA [ Tue Jul 07, 2009 7:28 am ] |
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Quote: .....then you must have the Sarah Palin Signature Series valve stem seals!
In Pink  David sounds like a good build...but... I would go with the 280/270 you will love it. Frank |
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| Author: | dakight [ Tue Jul 07, 2009 5:03 pm ] |
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I already have the 270; I got it when the group buy was first put together. I've got a couple of good cores so I might experiment with something else down the road. |
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| Author: | terrylittlejohn [ Tue Jul 07, 2009 5:48 pm ] |
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sandy is right, if you do any cutting to increase compression do it on the block, having the combustion chamber as big as you can and the piston as close to zero as you can get it make more power,i done it with my 10.7/1 motor compare to my 11.4/1 motor. |
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| Author: | dakight [ Wed Jul 08, 2009 4:28 pm ] |
| Post subject: | |
Two questions: 1. What is the formula to estimate the amount of chamber volume removed when planing the head? The machinist says about 1 cc per .005. 2. How much can safely be removed from the block? I have heard 0.100 but is that safe? The chambers before cutting the head are at 66cc. At 1cc per .005 I need to take .060 from the head to get the chambers to around 54cc. That means I will have to cut the block .090 at least. I told him to go ahead and take .060 off the head and see where the chambers ended up. I don't feel comfortable taking any more than that from the head. |
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| Author: | Joshie225 [ Wed Jul 08, 2009 6:02 pm ] |
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Remove .0066" off the slant head for each cc. 1cc=.0066". If the cylinder walls and the combustion chamber walls line up then the combustion chamber shape will not change if either the head or block are milled or some of each. Only if the combustion chamber in the head is wider than the cylinder would there be any deshrouding. When I re-built my road race 225 we took .100" off the head and block. I did blow one head gasket, but that was only because I borrowed a torque wrench and ended up not having enough torque. I put the head back on with a new gasket, used my torque wrench and it was fine. |
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| Author: | terrylittlejohn [ Wed Jul 08, 2009 6:56 pm ] |
| Post subject: | |
i had .140 off my block and .075 off the head, gave me a 52cc chamber and 11.4/1 compression, if i were you i would do a cleanup or ture cut on the head cc it and cut all the rest off the block. you can also polish the combustion chamber to get it a little bigger, i got mine up to 58cc by polishing. |
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