Timing Belt Replacement Procedure
First, this is a procedure that if done wrong, could seriously damage the engine. If at all possible, I suggest having this done by a competent professional. Second, this is the kind of procedure that, for the sake of the long-term value of the car, is best done by an authorized Ferrari dealer, complete with documentation.
If the possibility of decreased resale value and the fear of wrecking a $10,000 engine aren't enough to scare you off, here's the procedure. Please note that I'm posting this reluctantly as I fear possible retribution for mistakes and omissions or lack of clarity. Therefore, for practicality's sake, I feel the need to say this:
** I assume no responsibility for the accuracy of this document. Because of model variations, the procedure stated below may or may not apply to your particular engine and/or chassis. For reference, the model from which this procedure is derived is a 1981 308 GTSi, built to U.S.A. specs (with A/C). DO NOT ATTEMPT THIS PROCEDURE IF YOU'RE NOT SURE YOU HAVE THE SKILL AND TOOLS. As far as I'm concerned, this entire document is a work of fiction. If you repost this or add it to a web page or archive, please post it with all disclaimers in tact **
* Do not turn the engine (either with the starter or by hand) when the cam belts are off. Serious valve damage can result. Also, don't turn the engine with loose cam drive pulleys. When the procedure calls for you to rotate the engine, do so only if the alignment marks are at or only a few degrees off the ideal position.
* Keep the new belts away from the action until it's time to put them on. They need to be as clean and unmolested as possible.
* It's probably a good time to change the accessory belts, too.
* It's probably a good time to do the valve adjustment.
Combo wrenches, offset wrenches and sockets of the following sizes: 10mm, 13mm, 17mm, 19mm, 22mm
36mm socket wrench and 1/2 or 3/4 drive ratchet to turn engine at the damper
Screwdrivers (flat and Phillips)
Cam belts (2).
Cam lock tabs (0-4 as needed)
Valve cover gaskets
Cam end gaskets
Distributor base gaskets
Valve shims (qty and size as needed)
- Disconnect the battery ground strap
- Remove the clutch / flywheel inspection cover (just below the oil filter)
- Remove the distributor(s) and their bases from the cam ends
- Remove the wires and plug ends, keeping the order recorded for reinstallation.
- Remove the air cam end cover (front valve cover intake)
- Disconnect the throttle linkage from the throttle lever and remove the cable from the front valve cover.
- Remove the engine reaction rod (rear cam cover to firewall).
- I usually remove the spark plugs, as makes turning the engine easier, but this is optional.
- Remove the valve covers
- Jack up the rear and support on jack stands.
- Remove the right rear wheel and fender liner.
- Turn the engine (slowly, by hand) at the damper (with the 36 mm socket) *clockwise* until the PM 1-4 mark on the flywheel is in alignment with the alignment marker.
- At this point (assuming the engine ran before) the cam alignment marks (4 each) should be aligned with the index marks on the cam journals (4 each) closest to the belts. If this is not the case, turn the engine one complete rev (slowly, by hand) until the PM1-4 aligns again. If the cam index marks are not aligned (or close), then you're using the wrong markings on the flywheel or not looking at the right index marks.
- Remove the rear cam belt cover (easy).
- Remove any and all heat shields that will allow access to the front cam belt cover, alternator and compressor.
- Loosen the alternator on it's mount and move it toward the engine, to loosen it's belt.
- Loosen the A/C belt tensioner pulley assembly and remove it.
- Remove the accessory belts
- (on later cars there are 3 belts, I'm not sure of the order of removal)
- Remove the lower compressor mounting bracket from the front cam belt cover and compressor.
- Disconnect the oil dipstick tube from the top of the front cam belt cover.
- Dismount the compressor from the upper compressor bracket (pay attention to spacers and bushings)
- You don't need to remove the compressor to complete the job. It does make it easier, but without a reclaim system, it can be very costly to refill with Freon. For those without A/C, well, skip this. :-)
- Move the compressor away from the cam belt cover as best as possible. The inlets to the compressor can be swiveled to allow movement. Normally, there's enough room to accommodate the remainder of the procedures.
- Remove the top compressor bracket from the cam belt cover
- Remove the front cam belt cover (tough to do & cramped)
- Each cam belt has a tensioner bearing that is attached to a tensioner bearing assembly. On those assemblies are self locking (nylock) nuts that lock the tensioner in place. These nuts need to be loosened, the tensioners retracted and the nuts retightened with the tensioners compressed. Be careful not to assert axial loads on the tensioners, as they tend to be quite fragile that way. I usually use a lever of some sort (pry bar) to compress the tensioner, but don't lever it by the roller bearing!
- Remove the cam belts. Once the belts are off, DO NOT ROTATE THE CAMSHAFTS except for a tiny bit (3-5 degrees max) when reinstalling the belts to gain perfect alignment.
- Sometimes a thin piece of cardboard (matchbook cover) under the closest cam journal will keep the cams in place when working with the pulleys. You can install them before you remove the old belts to keep the cams from "slipping" in place (the forward bank intake likes to "jump" off lobe). Remember to remove them before attempting to turn the engine.
- Now check the condition of the tensioner bearings. Spin them by hand. If there is any abnormal noise, excessive amount of hissing, or any abnormal rotation at all, replace them. I usually replace them as a matter of course, simply because that's the best thing to do and they're very hard to get to.
- Also, check the condition of the tensioner spring when loosening the locking nut and "feel" the force of the spring. Compress and release the tensioner and make sure it does so smoothly.
- If you replace the tensioner bearings, you need to remove the tensioner mechanism from the engine. Remove the bearings carefully, possibly with a puller made for the job. In many cases, the bearings self destruct in the removal process.
- When installing new tensioner bearings onto the carrier, clean the shaft the bearing fits on with ScotchBrite or a similar product. Very lightly lubricate the shaft and bearing inner race faces. Press the bearing in place with a suitable press USING THE CENTER BEARING RACE. Otherwise, the bearing may self destruct.
- Reinstall, if necessary, the tensioner carriers with tensioner bearings. The tensioner should be retracted to the mostly compressed state.
- Install the new belts. When installing, do not bend the belt over itself at sharp angles (crimp) and do not bend the belt around (twist) more than 90 degrees. Avoid getting oil, grease, coolant & cleaners (or anything else for that matter) on the new belts. If necessary, clean the engine face, cam belt covers, etc, beforehand.
- Install the belts such that the teeth that were in contact with the drive pulleys are in the same positions as the removed belt just removed. The belt can be removed and remounted at this point to facilitate alignment of the camshafts, but do not apply the tensioner at this time.
- Keep in mind that when you apply the tensioner, and the belt tension "evens out" the cam index marks will move a few degrees. To compensate for this, what I do is to align the marks as best as possible. Then I release the belt tensioners to apply tensioner pressure and then lock them down again. Now turn the engine *clockwise* (slowly, by hand) two full revs and bring the PM 1-4 into alignment. Don't overshoot the PM 1-4, since you won't want to turn the engine backwards. If you do overshoot, go around two more revs.
- Now, if all is well, all the alignment marks will be nice and even (PM 1-4 and all four cams). I use an extendable mirror to read the forward cam indexes. If the alignments on any cam shaft is not dead-on, there are two possible ways to realign them. Usually a combination of these methods is required if the former alignment wasn't perfect.
- Method one is to loosen the belts and move the errant cam one pulley tooth in the appropriate direction.
- Method two is to remove the pulley locking bolt at the end of the camshaft (use a large adjustable wrench on the hex face between the pulley and oil seal to hold the camshaft steady). Also, there is a lock tab washer on the pulley that will need to be replaced after use. I usually keep a stock for my belt jobs, since they're not that expensive. There is a drive pin in the pulley that will need to be removed and reseated. Sometimes you can tap the pin out from the back of the pulley with a punch (gently).
- There are a series of holes in the pulley that are "interference" fit to a series of holes on the camshaft. Rotate the camshaft to the aligned position and turn the pulley so that two holes align. If there is no definite fit, move the pulley one tooth to the left or right under the belt and try again. When you find a good fit, secure the pulley with the pin and tighten the locking bolt temporarily.
- Repeat the procedure of retensioning the belt and turning the engine clockwise two revs by hand. If the alignment is still not right, consider the changes you made an the net effect. Go back and repeat the alignment procedure until you can rotate the engine around and have all the marks line up. The first time you do it, it may take a few attempts. Also keep in mind that every time you loosen the tensioner and retension, you must turn the engine two revs to "equalize" the slack.
- Once you are satisfied with the alignment (I've always been able to get the marks "dead-on", by the way), reinstall any lock tabs needed on the affected pulleys and bend the tabs over as before. Tighten the cam locking bolts (again using a large adjustable to hold the cams steady).
- Don't forget that the tensioners must be applied and the tensioners "locked" down. Don't leave the tensioners floating on the spring or the tensioners will apply uneven (harmonically induced) pressure and prematurely break the belt.
- Once everything is tightened, check alignment again and turn the engine two more revs (one last time) to be sure!
- Reinstall all the other pieces in the reverse order of removal. Reinstalling the compressor and it's mounts is a pain!
If you're confident that everything is in order (the accessory belts are tight, the cam timing is correct), you should be ready to go.
This procedure can be modified to include valve adjustment simply be performing the normal valve adjustment before or after the new cam belts are installed.
You may want to replace the cam shaft oil seals if degradation or leaks are detected, or it's been a long time or many miles since the last time they were replaced. Doing so requires the removal of all the cam drive pulleys. Don't mix up the pulleys! Label them before removal.
Early 308 camshaft pulleys are a hybrid of fiberglass (or some hard plastic) and steel. Others are solid aluminum or solid steel. For the hybrid parts, the lips on the edges of the pulley are easy to break off. When handling these pulleys or installing and removing belts, be careful not to break them... they're quite costly to replace. Also, the cam belt is a different part number depending on the pulley type. On OEM Ferrari cam belts, the part number is often screen printed on the outside of the belt. If possible, make sure the belts you order are the correct application. Just knowing the year and model is not always enough.
Tightening torques (lb/ft):
Valve covers 6.5
A/C Compressor to support 15
Timing belt stretcher 40
Pulleys to camshaft 79
There, I did it. Revise, improve, and embellish if you wish.
[ Home ] [ Up ]