Pajero Io/ Shogun Pinin, Camshaft replacement Options

[Guy968]

I recently bought a Pajero IO 1999 (LWB, 1.8l, engine type 4G93 3A3S) in Australia.

Unfortunately it had a noisy cam which didn't respond to valve adjustment. To cut a long story short, it turned out that one of the Number 4 exhaust cam lobes was worn off, and beyond regrinding. (I gather this happens if the oil is not changed frequently enough.)

I thought my experience might be useful to anyone in the same boat:

In Australia, this is a relatively rare vehicle.
New camshaft (Mitsubishi) = AUD775, Roller rocker AUD88 inlet, 80 exhaust, head gasket AUD150, Timing belt approx AUD 90.
Camshaft and rockers shipped from Japan - 4 weeks!
Second hand cam - none found in Australia. Second hand cyl head - none found in Australia, second hand Engine - One in NSW (>AUD 1000).

I came accross a Lancer cam from a 1.8 with 4G93 engine (don't know which model, or year), which looked the same, and ULTIMATELY works.
The cam timing angles appear to be identical. Judging by the valve clearances after changing the cam, lobe heights are the same.
Differences: 1. Cam profile is very slightly different in terms of rise and fall rates of both inlet and outlet cams. 2. The lancer cam does not have an M8 female thread machined longitudinally into the back end (for electo-magnetic position sensor) 3. the cylindrical recess in the back end of the cam is of a smaller diameter on the lancer cam, and the pajero position sensor will not fit.
The good news is that 30mins of any machine shop's time can easily rectify 2 and 3, and the engine runs smoothly and quietly despite the different profiles.


For anyone who hasn't changed a cam in this engine type, here are a couple of things I found out the hard way!:

Replacemen parts you need: Camshaft, cam front oil seal, rocker arm(s) (if the roller is worn), cylinder head gasket, cylinder head coolant flange 'O'ring, +/- rocker cover gasket. Oil and filter. Some garages suggested I changed the water pump (- I didn't). Coolant (or additive)
Silicone gasket maker.

Some tips: (DISCLAIMER: DO ANY OR ALL OF THE FOLLOWING AT YOUR OWN RISK - I ACCEPT NO RESPONSIBILITY FOR ANY DAMAGE OR MISHAPS THAT OCCUR AS A RESULT OF WHAT IS WRITTEN HERE, ERRONEOUS OR NOT)

Cam shaft is removed from the cylinder head back end, so (as far as I could see) can not be removed with the cylinder head in the car.
Cylinder head can be removed with both inlet and exhaust manifold attached (saves gaskets and almost certainly, time)

Remove:

Battery earth lead
Grille, radiator
all wiring loom connections to engine, air inlet pipe (both pieces between filter and throttle body, throttle cable
coolant connections from inlet manifold and baulkhead. spin washer bottle neck through 180 deg.
all vacuum connections from inlet manifold
Exhaust heat sheild.
3x exhaust manifold to downpipe nuts and 1x manifold bracket nut (just adjacent) (from under vehicle)
2x inlet manifold mounting nuts (under vehicle)
Rocker cover, both rocker shafts.
Check cam timing against crankshaft position, as per manual (link below), to ensure you are happy with all the refence marks/postitions. Remove cam belt sprocket (Right hand thread, block rotation of sprocket) and belt, cylinder head bolts (in correct order)
At the back of the cylinder head, there are 3 separate fittings you can feel: cam position sensor housing, coolant flange (with push-in pipe entering) and a small bracket securing the coolant pipe running to the inlet manifold). The first 2 do not need to be removed. The 3rd is undone with a 12mm spanner (1 bolt).
Remove any other obvious connections to the cylinder head/ manifolds I have forgotten about.

Cylinder head can then be lifted off (rear coolant pipe may stick in flange and required some ****ling).

The rear position sensor cover can then be removed from the head, and the cam slid out.
The Lancer cam needs machining (as above)
Clean up block and head with a flat scraper and degreaser. Check for flatness.
Fit position sensor to back end of new cam.
Fit cam with plenty of oil. Fit new front seal. Fit sensor cover with silicone gasket sensor.
Fit new 'O' ring to coolant pipe (back of engine) to engage with coolant flange at back of head.
Fit new (or reuse) exhaust downpipe gasket. Position head gasket. Oil cylinder head bolt threads.
Carefully refit cylinder head (being sure not to damage mating surfaces OR coolant 'O' ring.)

The remainder is the reverse of above. All torque settings in manual:
http://www.scribd.com/doc/11525718/4g93-Lancer-Engine

I recommend fitting a new cam belt: instructions as per the manual. Use a long lever with 1/2" drive) for crank bolt (RH thread, block engine rotation by removing starter motor and engaging a screw driver in slots in flywheel (Not the starter ring teeth!))
Time the cam as per the manual.

Once it is all together, set valve clearances cold (easiest with spark plugs out)
Reconnect battery terminal. Refill coolant!. Check oil level.

Fire up, and run until thoroughly hot. Then stop.

Drain oil.
Reset valve clearances (They get bigger, I believe, when the engine is hot, so you will have to close them down more, and the engine gets quieter as a result).
Change filter, and refill with oil.

I changed coolant again (in case oil had got into the waterways during head-off, which might give an "oil swirl" in the coolant.)

Thats it!

(Only prob I had was with coolant 'O' ring at back of head: I hadn't changed it, and I split it putting the head back on. I was able to change it by removing the flange fitting from the head, and repaired it with some super-glue. I refitted it with some silicone gasket. No probs since.)


Result:
Car runs quietly and smoothly. Its a pleasure to listen too.
I possibly doesn't pull quite as well below 1500rpm (eg pulling out of a rolling junction in 3rd, but I'm not even sure!.)
Fuel economy is the same as before.

Cost:
Lancer cam AUD130. Machine costs? (Born by dealer)
Pattern Gaskets: Head AUD85, Rocker AUD15
Front seal AUD 5
Timing belt AUD 90
The remainder was sundries, and a few tools.

Time: Well prepared, this would take me a day. However, you will need the old cam out to measure up, if you need to machine a second hand Lancer cam to fit. This means the work has to be split.


I hope this is helpful to someone.... one day!