Quote:
Originally Posted by dynomatt
Bazza,
FWIW, the advice I got (from a guy who worked with Cosworth motors for many years) is you'll be wanting to chase the lift...I can't remember exactly but stock coil bind is around 9mm...even with different grade springs, you might be able to get that higher but to what end?
Solid buckets, shim under (not over) is really the way to go I think for reliable high revs. I realise people have had hydraulic buckets higher but is it worth it when valvetrain weight starts to become a factor.
Interesting on the drag motor...glad you dug that up. 310 duration is decent...must have idled like a ***** and had a very narrow peak curve.
The other thing worth considering is if you're doing a turbo build...a lot of the cam theory goes out the window in my experience.
M
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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.
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.
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
