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Original Message
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| I disagree........ |
| By kevin - 12/28/2002 7:17:04 PM; IP 209.240.198.60 |
| thats not a fair comparison. If you use 144 gram CJ intake valves, they wont go that high without floating. This will lead to nice things happening to the rest of the valvetrain. I was able to achieve over 8,000 RPM's with the heavy valves by using 165#'s seat pressure with a vibration free valvetrain on a solid cam. Its not easy, but it can be done. A rev kit would be the way to go for more R's with a roller body, whether solid or hydraulic, and if you need to spin it high, you need the rest of the components that make power up there in the danger zone. On BBC engines, there was a rev kit by Isky (rev caps) that used a single large capped spring over the rest of the spring and retainer to preload the rocker, pushrod, and those way too heavy roller bodies (we need to design some for the FE). The roller tip rode right on top of the tool steel cap. This way, the valve is not over stressed by having more than it needed, and those 2.3" intakes were HEAVY (pre titanium days). This was the only successful way to get them to go 8k plus in tractor pulls with a 6-71 (the biggest supercharger at the time). Blown engines need an additional 30% valve spring pressure due to the positive pressure in the manifold instead of negative for naturally aspirated ones. Most people forget about the importance of the pushrod. It is always under dire conditions, and stores a lot of energy. It looks like a diving board when its under compression and extension. I'd run 1/2 diameter ones if I could. Like Smokey used to say "poppet valves were outdated when invented". But we have to live with them. Cut down the titanium valves that are 7mm stemmed for the SBC SB2 engine. They are larger than Fords, and much longer, allowing you to have a taller spring stack, and a bigger selection of springs. That way, you can run a rev kit, and use low spring pressures that allow much longer seat life, and those heavy hyd rollers. |
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