cams .lift and duration

[Celica RA45]

ok we all know how,and what does what .but how far is to much lift for a small 4 cyl motor with 16 valve and cams direct on bucket
reason is i have been playing around with new cams that has over 14mm of lift ,,both have 575 thou lift and both will fit onto a 34mm bucket
i also can still use some vvti ,well hoping at the moment

q with this lift will the valve springs break down quicker than say if i was using 520 thou etc .still thinking out side the circle here but if i can use vvti on both and have this lift
the springs in question coil bind at 750 thou lift and with what i have worked out will be 70 lbs on the seat and are single spring /.. i have also weighed every thing from valves to spring and retainer ,bucket shim etc
with this head hoping to make red at 9500 rpm or if power drops earlier so be it i also have 4 different versions of this but only 4 use vvti

[oldcorollas]

yes they will break quicker. more compression, more force, more heat generated etc.

will they break? that is the real question, but higher lift is more "likely" to break...

will you have odd spring harmonics around those rpm with that lift?

[Celica RA45]

hi stewy the valve springs are conical and have been tested and will use titatium retainer 70on the seat and 200 on the nose there abouts and i have had the cam tested to see how bad it is any way
also this will be a na motor not turbo and will be using E85 and a comp of 14.5 to 1
im just trying to see if any body has gone this far in cam lift and have a motor last
25years ago you were lucky for cams to go to 450 thou and now 540 is the mark im only going another 35 so to speak higher

[oldcorollas]

well, many V8's have larger lift than that (up to 18mm, 0.71"!!), but not quite the revs.
kind of different kettle of fish tho, as their springs are exposed and yours are under a bucket... so they can utilise oil cooling etc.. (and they target 3000km for engine life..)

i guess the answer is.. yes break quicker, but you may still be well within the "acceptable life" range of the springs lift. can the spring maker help?

[oldeskewltoy]

can the spring maker help?

+1

If cams normally lift to .535 now... then springs should have no problem to that point.... So, I'd repeat what oldcorollas said.........

[mattysshop]

have you looked into how springs are made for honda engines?? some of thier common aftermarket cams are around .525 lift, i've seen all motor race cam specs for .570 on the K20A motors... BUT they are not bucket/shim arrangment

[Billzilla]

No point in lifting the valve any more than where the flow really starts to drop off. On your engine I'd guess that'd be at about 40% of the valve diameter.

[Celica RA45]

flow starts to drop off from 600 thou and is linear to 650 thou also this head has bigger valves than std both inlet and exhaust and has been cleaned up etc and flowed ,will out flow the s honda head and also the k series as well

[abently]

flow starts to drop off from 600 thou and is linear to 650 thou also this head has bigger valves than std both inlet and exhaust and has been cleaned up etc and flowed ,will out flow the s honda head and also the k series as well

Then 575 thou of lift is a non issue. In fact you could go even higher.

What will damage the valve train and cost power, is harmonics. As long as that is minimal, then you and your engine will be loving life at 9000rpm.

Some high end cam places can model this, but I'm unsure on the cost.

Look into beehive springs, they are designed to minimise this issue.

[Joshstix]

The lift will definately be an issue. Whether it is enough of an issue to cause problems or not is hard to say. The more you lift the valve the more you twist the wire in the spring therefore the more heat is put into the spring and the more likely to fatigue the material.

I would expect a decent service life out of what you're looking at using but it's worthwhile looking at what the guys running big revs with big valve lifts for extended periods of time are doing. Take a look at the setup in Nascar engines, they all pretty much run oil sprays to cool the valve springs to keep them in one peice at big revs. How you can get decent cooling for the spring in a bucket based system I'm not too sure.

[abently]

Actually post up the question on Speedtalk, they will be able to give you some very good answers from personal experience.

I had a quick look the other day and the harmonic issue seemed to boil down a bit to the distance from coil bind and then determining exactly what is causing the harmonic, to isolate and remove it.

They discussed a bit the use of ovate spring wire and should have links to Prof Blair's work on the topic.