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Anyone got some tips as to what is going on here.

Cam tech 270- 9.5mm cams no vct

Shimmed to

.010" intake

.012" exhaust

+\- .001"

Pretty confident of the clearances, have checked twice. Cams don't appear to be hitting anything. Can't see any marks on Pistons (checked with bore scope). Listened with stethoscope and it sounds valve train related...

Running performance springs.

Stock cams were quiet. Same springs just changed clearance

Edited by Huzqld
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I'm no cam expert (and no idea how to diag by the sound of it), but how did you decide on the clearances and are those hot or cold readings?

http://www.sau.com.au/forums/topic/397382-rb25det-neo-r34-gt-t-valve-clearances-solid-lifters/

Workshop manual in the above thread says 0.31mm intake and 0.51mm exhaust when cold.

0.31mm = 0.012" which is close to your figure.

0.51mm = 0.020" so your exhaust side has about half the clearance it should have

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Have asked camtech. They Aren't really sure what's going on. Obviously more investigating to do.

But always Good to see if anyone else has had issues similar

Came up with those clearances as that's what it says on the cam card they are cold readings.

You are right though the factory cams do run with bigger clearance and that is what I had the stock cams set to and the engine was quiet as.

Edited by Huzqld
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Not running vct in mine anymore.

Triple checked the clearances and it is as per cam card.

Retarded the intake and advanced the exhaust just to see if the noise changed (doing this should effectively give more piston to valve clearance?)

No change in noise.

Will keep investigating.

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The VCT assembly will still need some form of lubrication even if you're not using it. I remember reading some issues a while back about someone swapping heads and didn't keep the VCT oil feed and then had cam bearing issues. But if you are using the stock head and have just unplugged the actuator electronics then it will be fine. Didn't realise the cam had to be modified with a gallery too, sounds interesting.

What viscosity of oil are you using?

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Whoever originally done the vct setup on this head has done it a completely different way to what I've seen them done. They drilled down through the cam gallery and into the vct feed and grub screwed the top hole.

I found the thread somewhere but can't find it now.

But it hasn't worked, the vct half kicks in and then the car just idles normally again. (When testing at idle) made no difference to dyno graph either.

Plus it's an auto with a 3k stall and will probably go bigger down the track.

Didn't check the valve springs honestly (we should have) but they should cope with that lift.. They aren't stock springs and plenty of people have used them on bigger cams then this. They are the 'performance valve springs' springs and ti retainers.

Not sure what you mean by weight on nose of cam, but am only running adjustable gears.

I've packed the cams up and sent them back to camtech to check out.

Put the stock cams back in just to make sure and it's back to being very quiet.

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  • 2 weeks later...

Whoever originally done the vct setup on this head has done it a completely different way to what I've seen them done. They drilled down through the cam gallery and into the vct feed and grub screwed the top hole.

I found the thread somewhere but can't find it now.

But it hasn't worked, the vct half kicks in and then the car just idles normally again. (When testing at idle) made no difference to dyno graph either.

Plus it's an auto with a 3k stall and will probably go bigger stall down the track.

^

The solenoid seemed fine, maybe it was the gear, not really sure. Anyway, no more.

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