Been thinking about getting some work done to my head, apart from the usual cams, port and polish is there much more that can be done to a cg?
3 angle valve, larger valves
the GA ones are bigger and have the same size stem, but they,re 3mm shorter iirc karl, and SR etc are fatter stemsSo other than cams there isn't much to do?
Could valves from say a bigger nissan engine, be modified to fit safely?
you going for an N/A screem Karl?
the GA ones are bigger and have the same size stem, but they,re 3mm shorter iirc karl, and SR etc are fatter stems
"another jap car" mate, 1.6mm biggerDo you know which valves ebbdude used? (Can't seem to find his thread on my phone)
Hopefully
Do you know which valves ebbdude used? (Can't seem to find his thread on my phone)
Not trying to put you off though.
and saying im getting rid, gauging interest a lot .dont help the bhp,,,,,,,,,,,,,,,A 1ml head skim will help a good bit.
A 1ml head skim will help a good bit.
and saying im getting rid, gauging interest a lot .dont help the bhp,,,,,,,,,,,,,,,
You could double-up on the spring washers to make the springs more firm, IIRC ebbdude also pointed this out in his blog. But I'm unsure if anyone else has tried and reported back about it. My head has this but it's off the car untested atm.
I'd also go with CR buckets and underbucket shims for a n/a screamer, even if stock cg is fine, I'd do it for peace of mind.
Ebbdude wont post on here again as his threads just get locked for reasons unknown
I'm having a blond moment but when you say CR you're talking about the k12's CR engine right?
Cool late night, early morning doesn't work in favour of my brain
Does it matter which CR engine?
aye 2mm longer stem on the CR,s eh, and my understanding is that you cant actually increase a spring pressure by preload (ie, the springrate stays the same)
hmm, so the increase of pressure from 52kg to 65kg is not down to the extra washer then (maybe down to being near coilbound ?).The spring rate will remain constant yes, (F = kx), but you can increase the closed seat pressure by increasing the static preload, which will have a corresponding offset in force when fully open, assuming one doesn't go coil-bound >.<
Personally, I scrapped the entire OEM valvetrain and started again but with the lift we wanted to run there was little choice and even then things require fairly extensive modification to work.
hmm, so the increase of pressure from 52kg to 65kg is not down to the extra washer then (maybe down to being near coilbound ?).
but the slightly higher static preload while the valve is closed will deter valvebounce a tad maybe ?
erik,s pressure readings daveI don't understand the context of 52kgs v's 65kgs.
but if the springrate always stays the same, then the extra preload will only alter the closed pressure, and the pressure while opening the valve will be the same on both setups.Ah ok.
He will have set the spring to the corresponding installed height in the head, then shimmed it to get the desired spring at the same height to meet his desired spec.
but if the springrate always stays the same, then the extra preload will only alter the closed pressure, and the pressure while opening the valve will be the same on both setups.
ie, if he measured the pressures half open, the dial would read the same on both
same number of coils, same spring, therefore same springrate.Remember one spring has been subjected to additional displacement due to the installed shim. This additional displacement is present throughout the springs entire range of displacement relative to valve lift.
same number of coils, same spring, therefore same springrate.
surely only the valve closed preload has changed ?.
my conclusion is that the fact that the spring is more coilbound with the extra washer in, its registering more poundage ?
my heads have no washers in at all (so i could run the 260deg/10mm lift cams)
nah, the springrate/load stays the same surely ?, like when you alter the preload on coilovers, it does,nt make the suspension any softer or harderWith the increased preload, the spring has effectively been compressed by valve lift + shim thickness relative to it's free height, so has been compressed further than before, thus giving a higher final load when fully open.
nah, the springrate/load stays the same surely ?, like when you alter the preload on coilovers, it does,nt make the suspension any softer or harder
i wonder if the increased overall force between the buckets & cams will squeeze the oil away from the contacting surfaces and cause increased wear?
ah okA decent oil with a good level of ZDDP will help that.
Yeah thats right1 liter pistons do the same
ehh, what are you on about dave ? its the same principle as suspension preloadHa ha very funny. I'm not falling for this prank any longer
ehh, what are you on about dave ? its the same principle as suspension preload
we both agree that the springrate stays the same whatever the preload is.
and the cam lobe just compresses the spring (10mm in my case)
so a 1kg/mm spring will need 10kg to open the valve/compress the spring 10mm wont it ( it does,nt matter how many washers you fit, it will always need 10kg to open the valve, and if you remove the 10kg it will close)
so the only thing you are changing with preload, is the pressure of the valve on its seat when its closed (not the force @ full lift, ie, erik,s dial gauge)
whats that got to do with it dave ?Compress them both by an additional 10mm, (assuming they wont go coilbound), and tell me what the resultant spring loads are.
hmm, so the increase of pressure from 52kg to 65kg is not down to the extra washer then (maybe down to being near coilbound ?).
but the slightly higher static preload while the valve is closed will deter valvebounce a tad maybe ?
and but if the springrate always stays the same, then the extra preload will only alter the closed pressure
which i dont buyYes, valve closed preload has changed due to adding an additional shim and displacing the spring to give additional poundage.
With the increased preload, the spring has effectively been compressed by valve lift + shim thickness relative to it's free height, so has been compressed further than before, thus giving a higher final load when fully open.
and
The spring rate will remain constant yes, (F = kx), but you can increase the closed seat pressure by increasing the static preload, which will have a corresponding offset in force when fully open, assuming one doesn't go coil-bound >.<
yes, and stays at the same 1kg per mm with preload or without preload, just like preload on your suspension wont make it any harder or softer, and will only effect the static height of the carA spring is rated say 1kg per mm "from" its natural unloaded length
ehh, what are you on about dave ? its the same principle as suspension preload
we both agree that the springrate stays the same whatever the preload is.
and the cam lobe just compresses the spring (10mm in my case)
so a 1kg/mm spring will need 10kg to open the valve/compress the spring 10mm wont it ( it does,nt matter how many washers you fit, it will always need 10kg to open the valve, and if you remove the 10kg it will close)
so the only thing you are changing with preload, is the pressure of the valve on its seat when its closed (not the force @ full lift, ie, erik,s dial gauge)