This is a post I’ve been wanting to write up for a while but it’s taken time to find someone willing to make the investment in their engine and then we had to wait for their belt service anniversary to come around. However, the stars aligned and earlier this year we got the job done.
This piece of work is something I recommend to anyone who has a “keeper” 360 but many owners don’t even know about the benefits. In the race to the bottom, UK workshops don’t like to promote this service – some because they lack the skills to perform it, but mostly because it’s a job that is difficult to offer a fixed price that is attractive to the customer and still make money on (due to the time involved).
360 engines left the factory in Maranello timed up on scribe marks made on the camshaft during manufacture. Although the marks are adequate for the engine to run well, the best performance is made when the engine is timed up properly by adjusting the position of each cam individually so that the valves open and close as per the engine design. The difference between an factory set engine and properly timed one is small yet immeasurable. The engine will run a lot smoother and be a joy to drive – it is very difficult to set out in words.
Before the adjustments can be made, the cam covers need to be off and the spark plugs removed. New timing belts need to be installed and the tension set (new tensioner bearings are also a good idea). Now is a good time to replace the cam seals and to remove the exhaust cams to inspect the variators. Access is through the firewall and the seats need to be removed.
A DTI needs to be installed into cylinder #1 (I can wholeheartedly recommend the Hill Engineering TDC kit). As the picture below demonstrates, there’s not much room to work with (even more so with a spider roof cassette getting in the way).
When cylinder #1 is at TDC before the start of the combustion stroke, the timing marks of the rear of the cams should all be aligned with the grooves on the cam caps. The scribe on the cam is just about visible in the following photo (click to enlarge).
A degree wheel needs to be installed on the crank and set to TDC.
To measure the timing of the intake cam a DTI needs to be positioned so that the tip is resting on the bucket of one of the intake valves of cylinder #1. Note that the middle valve cannot be used as it has a different profile to that of the outers. This DTI needs to be zeroed in this position (apologies for the poor picture but the camera re-focused on the top of the gauge).
If we take a moment to think about the situation the engine is in, it should be straightforward to understand how the intake timing is measured.
- Cylinder #1 is at TDC before the start of the combustion stroke. The intake valves are closed.
- The engine is then rotated so that #1 piston completes the combustion stroke and is part way through the exhaust stroke (ignore what the exhaust valves are doing).
- At this point the DTI that is resting on the intake bucket should still read zero as the intake valves have not yet begun to open.
- The engine is rotated until #1 piston completes the exhaust stroke and reaches TDC.
- At this point the intake valve will have started to open and the DTI resting on the intake bucket will have moved. It is this measurement that defines the timing. The valve should have moved downwards 1.66mm.
In this case, the valve had moved just 0.92mm which means the cam was opening the valves too late (note that the DTI in the picture below has moved counter-clockwise).
In order to rectify this the cam needs to be moved in relation to the crank. First the pulley wheels are locked in place. Note the green mark across the cam and pulley.
The pulley bolts are then loosened and the cam rotated in the correct direction (counter-clockwise in this case). The pulley bolts can then be torqued up and the timing checked again.
It is then a case of move and measure until the timing is correct. There is a 0.12mm tolerance on either side of the 1.66mm measurement which allows a small window to aim for.
To give an idea of how much the cam had to be moved note the final position of the green mark and how far the pulley bolts have moved off their witness marks. There was nothing wrong with the running of this engine yet this cam was quite a few degrees out.
Turing attention to the factory mark, it can be seen (click the picture to enlarge) that it almost off the groove on the cam cap…
The exhaust cam is measured in a similar way. A DTI is placed so that the tip is resting on a exhaust bucket of cylinder #1.
The engine is then rotated until cylinder #1 is 9 degrees before TDC at the end of the exhaust stroke.
The DTI on the exhaust bucket is then zeroed.
Again, if we take a moment to consider the position the engine is in, the timing measurement should be easy to understand.
- Cylinder #1 is nearing the end of the exhaust stroke. The exhaust valve is closing but remains part open.
- As the engine is rotated further the piston finishes the exhaust stroke and begins the intake stroke.
- During this operation the exhaust valve fully closes.
- The DTI measures the travel of the valve as it closes. This distance should be 0.60mm.
In this case, the valve moved 0.18mm which means the cam was opening the valves too early.
As per the intake cam, the position can be moved relative to the crank by locking the pulleys and rotating the cam (clockwise in this case). Once the cam has been rotated it is a matter of measuring and repeating until the timing is correct. Again, there is a window to aim for – 0.08mm either side of the 0.6mm.
The following picture shows how far the cam had to be moved:
And here you can see that the factory scribe is off the groove on the cam cap…
Once the RHS of the engine has been timed it is then all repeated for the LHS side, using cylinder #8 as the reference.
Although it is straightforward to write out, performing the work is demanding not least as the consequences for getting something wrong can be disastrous. However, the results are a beautifully running engine…
Other posts in this category: Engine and Drivetrain
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