Urgent Cam Issue

[Guest jumney1]

Hi everybody and greetings from sunny (I wish) England!!!

Ok, I have an imported 1993 R33 GTS-t and have had dosme problems as of last week. Driving along at about 100 - 110mph (160ish KPH) and all running smoothly, just as it happens I need to check my tyre pressure and fuel up so I pull into the petrol station.

TAP TAP TAP TAP TAP

There is a definate and very loud tap/click/knock type noise seemingly coming from the top of the engine. Immediately I switched off and called for a rescue.

Today I took the cam covers off, expecting to find a cam lob damaged or something. But nothing!!!!

The only thing I noticed was when I was turning the engine over (spark plugs out etc) and watching the cams.

The lobe which controls the front inlet valve on cylinder 6 (nearest to firewall) seems to have lots of oil on it as it spins?!?!?!?!

I'm assuming this means the lifter is not returning to its correct position and as such is not scraping the oil off???

I have just sourced a set of R33 GTR cams and would like to fit them.

Anybody done this??

Any advice??

Anybody know what parts would be required??

Any problems??

Thankyou all in advance

Jay

(PS. Definately the best Skyline board worldwide, only had mine 2 weeks so I look forward to lots of friendly advice )

[Warpspeed]

If the inlet valve is closing, and the engine otherwise runs normally, It sounds like the hydraulic lifter may have collapsed. It cannot now maintain internal oil pressure for some reason and pump up to maintain zero cam/follower clearance.

If the engine is only running on five cylinders, you might have either a bent valve, which can no longer close, or broken a valve spring (unlikely).

GTST cams have 240 degrees duration, and GTR cams have 240 inlet, 236 exhaust duration, but slightly more lift and very slightly more aggressive profiles. What the GTR cams do have though, are long clearance ramps at valve opening and closing to take up mechanical clearance of the GTRs solid lifters.

These clearance ramps hold the valves open a minute amount during valve overlap (if you keep hydraulic lifters) giving a lumpy idle. The result is, you will get a distinctive cammy idle that will sound either wonderful, or terrible depending on how you feel about it.

The slightly faster opening and closing, and lift, will give you about 2Kw extra power flat out. If you got the cams free and fit them yourself, go ahead. If you bought the cams, and have to pay to have them fitted, you will have spent a lot of money for no performance gain.

To do it properly you need to remove the cylinder head and fit the solid lifters which need to be adjusted with shims. This can only be done with the head removed. A very expensive operation to have done, and there will still be no performance gain.

[Guest jumney1]

That was the best input I've had so far on this problem!!

But could someone explain why the head has to come off to change the lifters?!?!?!?!

I was planning on just removing the hydraulic lifters and dropping in solid lifters!!!

[Warpspeed]

You are quite right of course, it is just that every time I have done it, the head has been off for a quick valve grind and check of the seats and so on.

Sorry about that.