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Old 04-27-2011, 06:20 PM
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cucumber1949 cucumber1949 is offline
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TechInspector1, thank you for the excellent analysis.

First of all, these are indeed flat-top pistons Ė no dish, just the 4 reliefs. What I didnít know was the correct relief volume when I used the CR calculator and I made an incorrect assumption and went too high. Using your figures, I come very close to your SCR, which confirms weíre on the same page here. Thank you again for helping to avoid a mistake.

Secondly, I also confirmed that 9.9 SCR (Wow!) with the 64cc head and concur it is too much for what I want to do with a street cam. I donít want to venture into the aluminum heads in this app either although the machine shop keeps trying to talk me into an Edel E-Street head Ė with a 60cc chamber Ė he didnít think the engine should be Ďordianaryí LOL!

So, in the RHS world it looks like the Pro-Torker 76cc head is a good choice in this app. I would think that continuing to use a thin head gasket (somewhere in the .020 area) would maintain about the same SCR I have now and allow adequate quench as well. I would still lean towards the smaller valves to facilitate the low end of the rpm range. High rpm ops are rare and not a factor, and anyway these small valves I currently have in the 487 heads are so gunked up that new heads and valves of any size could easily outflow what I have now, and Iím happy with the performance as it sits!

So, with bare heads, Iím still looking for recommendations on what parts to finish out these heads with.

Tech, I see youíve recommended a valve kit, guide plates, studs etc for a similar setup in this thread - http://www.hotrodders.com/forum/hor...que-196916.html. Taking a closer look at those, these parts look compatible for what Iím trying to do but would appreciate your comment.

DoubleVision Ė thanks for the recommendation on the cam. The cam that is in the car now does not show any wear that is excessive or indicative of an impending lobe failure. I really just donít know what it is and I havenít degreed it Ė I just know it is a mild cam based on the idle and vacuum Iím seeing now. My current thinking is if I was considering a new flat tappet cam, Iíd probably just leave the existing cam in it as it is adequate. Although Iím not looking for a performance gain from the cam, the benefit I see in a new (roller) cam is that I would finally know what cam is in the engine, and flat tappet break-in and wear issues go away. That to me is worth a few more dollars especially when Iím not far away from changing it out on the way to having the heads off.

GenY Ė thank you for the advice. Yeah, roller cams and lifters are pricey. I see the Howards cams Iím looking at goes for about $240 and their lifters are about $310 from Summit and they could probably sourced for a few dollars less. Itís still a significant bump over flat tappet prices but Iím feeling this is an area where I could justify it. Iíll take a detailed look at the specs on the Elgin cam if I can confirm the lifter spider retrofit.
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