Luckymonkey

Ok - a stock cam in one piece arrived (hurrah), so we set about fitting it to the racecar. At the moment, we haven’t taken the step of removing the head to replace the springs - because we’ll need to change the head gasket, get new head bolts etc etc - so this is just how to change the cam (with pictures).

Read more after the jump.

So, to do this, you will need the following :

• 10mm socket - for rocker cover and cam cap bolts
• 13mm socket - for belt tensioner and crank pulley bolt
• 13mm spanner - or something else with a 13mm socket to use at the same time as the 13mm socket
• 17mm socket - for the cam pulley bolt
• Adjustable spanner - for holding the cam in place
• Some instant gasket stuff
• Spark plug wrench or socket
• Flat ended screwdriver
• Feeler gauges
• Magnetic pickup tool - very useful for removing the shims and buckets, if you are going to go on and do the springs

Ok - so here we go then - take the spark plug leads off (because they get in the way) and take the rocker cover off. You’ll need to remove the plastic filler plug to get at one of the bolts. Ours was a PITA to take out.. once it’s off, you’ll see something like this.

You might have to clean some old instant gasket-type stuff off the surfaces at that point. You don’t want it falling into the head and going off around the engine.

To make life easier, remove the spark plugs - I just loosen them right off but leave them in the wells. This allows the air out past the plugs and makes turning the engine over about 100 times easier.

The next job is to measure the clearance between the old cam and the shims - this is so we have an indication of the change between the old cam and the new cam. Get your feeler gauges, and see what the biggest combination of gauges you can get between the cam and the shim (which is the bit the cam would press on).

Write these all down. From the front of the engine (where the cam pulley is) to the back of the engine (where you might have a distributor) they are :
EX1, IN1, EX2, IN2, IN3, EX3, IN4, EX4 (EX = Exhaust valve, IN = Inlet valve)
You’ll need to crank the engine over until you’ve got all of those down… all done?… good, now it gets fun.

Now, set the engine to TDC. There are marks on the standard crank pulley and cam pulley which line up with the block and head. Alas, ours isn’t standard, so I can only show you what we have. Firstly, put a 13mm spanner or a ratchet with a 13mm socket on it onto the crank pulley bolt. We’re going to turn the engine over until we get it to TDC.

On our engine, somebody had cleverly put a mark on the cam pulley to indicate when it was at TDC. This lines up with an indentation in the head.

At the bottom of the engine, our original crank pulley is hidden behind our timing disk. Thankfully, somebody had also painted the TDC mark on that. If you don’t have a timing disk, then you’ll have mark on the block and a mark on the crank pulley to match up.

With the engine at TDC, you can now loosen off the belt to remove the camshaft. If the engine wasn’t at TDC, you don’t know where it should be when you put it back together again. With an interference engine like the Fiat, that’s bad, because if you tried to turn the engine over, you might have pistons coming into contact with the valves - best avoided.

So, 13mm socket on the belt tensioner, and loosen it off.

Once that is loose, you should just be able to slide the belt off the cam pulley. You can now start loosening off the camshaft caps, and the two end pieces. Use the flat screwdriver to prise the oil feed out of the head (the small pipe which runs alongside the cam).

The front end of the cam has a oil seal on it, careful not to damage it when removing it from the end piece. Once all of that is out, you should have something like this..

So, on with the new cam..

Our new cam - ready to go, and in once piece this time

Use the adjustable spanner on the camshaft to hold it in place while you use the 17mm socket on the end bolt to remove the pulley, then swap the pulley on to the new camshaft. The cam is keyed, so the pulley can only go on it one position.

Now, put the cam back into the head at TDC and put the caps back on. It makes sense to put a bit of oil over the bearing faces and lobes at this point, just so there is something there when you turn the engine over. Make sure you put the cam back on at TDC so you don’t force open any valves which don’t want to be opened.

Don’t forget the oil feed pipe back into the head.

Then tighten the caps back up with a suitable torque wrench. IIRC, the setting is something like 10Nm, but check.

We first did ours to 5, and then to 10 in two passes, working from the inside out.

Once that is done, all you have to do is slide the belt back over the cam pulley, and tighten the tensioner back up again. This is where I found it useful to have a spanner on the crank pulley at the same time as tightening up the tensioner, just so I didn’t turn the engine over while we were doing that.

Then go back through and measure the clearances. The spec cam comes with the tolerances, so you’ll be able to tell if it’s sensible or not. We found ours were very, very tight, so we’ll need to re-shim the engine before we can run it.