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Originally Posted by bazza
Indeed. Big lift would be nice. However when you start increasing lift and upgrading springs you turn the head into a full race head. Which means very high maintenance, increased risk of breaking valves, hammering seats and guides etc and this is something my mate and I didn't want to do or have to R&D. We want reliable track motors with mimimal maintanence which means keeping it close to stock design as possible.
As for hydraulic buckets they're absolutely fine for my purpose. They'll do 6500-7000 rpm all day long:
http://www.youtube.com/watch?v=qssbthwIb4s
The only rule I stick with hydraulics is to use a SOFT RPM limiter only. A hard rpm limiter going off can pump the buckets up and you can lose compression in all cylinders for a few seconds.. BAD.
Solids would be nice but given the "PITA" factor and the cost I'd only recommend them for a NA engine like Jack's or what Tony is planning on building.
P.S. My mate wanted the heads and cams profiled to ensure we didn't make any mistakes - I believe his brand new billets arrive today  |
Gee Bazza, I can see that you are determined to go your way, so I won't deter you.
, but there are a few things that need to be straightened out.
The EZ30R runs 10mm lift on solids, this is common on a lot of production engines, not really a race motor.
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So we're going to run 8-9.5 mm lift with massive duration - LAN already has shown these to work and Kelford show in there charts that this can easily be done. Something else to note is you don't actually need more lift than that - the stock heads flow huge amounts to that lift however above that lift the heads don't really increase in flow (based on our flow figures) - HOWEVER this flow still supports 400 maybe even 500 kw ATW. So as you can see there aren't really any positives for us running lots of lift for the planned 300-400 kw atw. Above that yes.
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I can see that you don't understand the benefits of big lift.
You say that the flow bench shows that 9mm is really the maximum lift for flow. That is when the area of the open valve matches or exceeds the valve throat area, and the throat dia is limiting the flow. What the flow bench does not show is how much, when, and for how long.
If you use 9mm, you are getting the maximum flow at maximum opening point, for maybe 10/15* but each side of that it is not maximum. it is either opening or closing, and port flow is at less than max.
This is a diagram of two 240* profiles, one at 9mm and one at 12 mm
You can see that the line at 9mm shows the max port flow, which the 9mm lift cam just reaches, for 10/15*. The 12mm lift cam reached the 9mm max port flow early, and it maintains max port flow right through max lift, till the valve has closed down to the 9mm lift point, almost 90* of max port flowing air into the cylinder. This is the benifit of using the higher lift.
You also say " massive duration ", massive duration is for massive rpms, but you are only reving to 7000, the standard duration will cover that speed without any loss of torque spread.
Harvey.