Fix wiped cams on the 2zz-ge engine

I am addressing the oil gear and a wiped inlet cam of my 2zz-ge engine – both culprits of the 111r 2zz design.

It can be indicated by OBD errors P1302 and P0303 but not necessarily:

The cam replacement can be done clam on, with only the cover lifted, the chain is always mated to the crankshaft sprocket.  Because i had taken the engine out for other reasons i got access to the timing cover and chain, and oil pump.

crankshaft quarter turn before cyl 1 TDC

links for reference:

I removed the cams according to the instructions which can be found all over the net, crosswise pattern etc.

This reveals the rockers and more importantly – the rocker pads for the high cam. On the inlet side they are clearly worn. I think they wear faster because they are pressed into the rocker seating wheras the exhaust side the pads are pushed away from the rocker seating as the rockers are rotated on that side. Just a guess though. Anyway, i will need 4 new rockers and a cam.

From my aeromodelling days i was used to be able to compress a valvespring by a fingertip. (those valves are only 7 mm diameter).

To my suprise you cannot force a valve to open by hand in our motors. This is confirmed by the specs of a MWR valve, as the seating pressure is 60lbs and it requires some more 95lbs of pressure to open one of the two valves.

That is a whopping 150kgs of force to open the inlet valves for just one cylinder at high cam. No wonder a slider pad needs a lot of oil which should stay intact at all temperatures and revs!

The cause of the frequent lobe wear is still unclear – apart from the somewhat inferior materials used. The spray hole on  cyl 1 inlet is situated at the longest distance from the oil feed of the cover, or at least check for blockage. I am not aware of fixes on the jets (basically just holes in the tube), but i will dig into it.

i have run 10w60 castrol ‘supercar’ the last seasons as the oil temp rises to 130deg+ at the end of a stint (no additional coolers other then the donut), i do not know what the previous owners used or did with the car, nor did i open the valve cover during my ownership. I guess the 10 grade wouldn’t still be too thick as i always store it in a heated garage and never drive it in winter. The US models with oilcoolers were the first to report the problem, so maybe the wear is worse when the oil stays too cold for too long.

The question is, if i’d stick to OEM parts – how long will they last – or is it just another consumable like toe-links, steering racks or gearboxes 😉

Cyl 1 inlet high cam:

This is the plan as i have no special tool to lift the valves without the cam…

– replace rockers and cam
– reassemble
– measure valve clearance and judge shim cap size
– remove cams again
change shims
– reassemble
– final measurement
– get a life..

Progress! I got out in the snow to shop for some feeler gauges and, a torque wrench 5-30 Nm, and assembly lube.

The re-assembly stage hase begun. Fitted the uprated (billet) pump and new gasket;

New inlet rockers as the old ones were wiped together with the cam:

Cam shafts in place:

The red stuff should act as initial oil film as the drained engine and pump is regaining oil pressure, normal engine oil will sag over time if a build takes more time than expected.

New sprocket and chain

Aligning all timing markers – EX dot of the exhaust cam must be half a teeth above the equator, the inlet dot must be spot on the equator, the colored links of the chain on the appropriate dot, as well as the drive shaft sprocket link and dot. Closest cylinder 1 at top dead center.

Very happy to be assembling again. This week i expect the covers back from the powder coaters. I need the timing cover to install the chain tensioner before i can check the valve clearance. I do hope it is okay right away – otherwise the cams must be taken of again to replace the shims or cups. Fingers crossed.

Note to self: do not forget to exchange the lift bolts! :no

Lift bolts: check!

Mounted the chain tensioner damper and slipper.

With the pistions still in default assembly position (number 1 cylinder top dead center) it is already possible to measure the valve clearance on 4 out of 8 lobes. Only the clearance between the ‘normal’ / low cam lobes and the roller rockers are to be measured. With feeler gauges i found all of them are in the green tolerances.

If that indicates the other 4 tolerances will be ok after the timing cover and chain tensioner is fitted (needed to rotate the crankshaft one revolution) i am happy. No new shims or cups needed then.

Unfortunately, after fitting the timing chain and revolving the engine one revolution the number 3 cylinder inlet tolerance was tight, so i removed the cam again and reshimmed that:

Re-shim 2zz-ge valve caps

In interesting read about wiped cams in relation to oil coolers – although mine hasn’t.. any: