308 GT4 timing belt replacement process

Here is a writeup on changing 308 GT4 cam belts and tensioners. I have this as a Word doc too if anyone wants it. See pics below (first is cam pulley marks before removal, second is crank mark, third is new belts and tensioners installed, fourth is overview when put back together).

Andrew Watry
andrew dot watry at lexisnexis dot com

This is how to change 308 2V timing belts and tensioners if you are confident the cam timing is already correct, or in the ballpark enough not to need checking. This method does not involve removing the cam covers to verify the timing marks, or to alter the timing relationship between the cams and cam pulleys. If you don’t know your cam timing, or otherwise want to adjust it, you’ll need to go the more involved route to remove the cam covers to check the timing marks, separate the pulleys from the cams, etc.

I did this job myself in my home workshop on my 1975 American 308 GT4 with AC and both air pumps intact. It took about 12 hours to peel everything down, 4 hours cleaning and screwing around, and 8 hours to put it back, including removing and replacing the water pump and thermostat housing. My rear belt cover was hell to remove because of being fitted by studs, rather than bolts, which kept it from clearing the frame. Having bolts would have saved a couple hours at least. Getting the AC out isn’t fun either.

I bought my belts from Dennis McCann for $20 each, and tensioner bearings for about $50 each. Water pump rebuild kit (small bearings) came from GT Cars for $85. I paid $110 to have the water pump bearings and seals removed and replaced. Total cash outlay about $300. Total hours about 24.

I bought Verell Boaen’s nice cam locking tools, but for no good reason (basically I forgot) did not use them. They would help ensure your cams don’t move at all when you have the belts off. I also made some timing marks on the old belts, to transfer to the new belts, but decided to rely on timing marks on the pulleys and engine instead.

Caveat: This process worked for me, but maybe it won’t work for you. My engine having been rebuilt 2500 miles ago and running great, I felt pretty confident of the cam timing. I have almost 30 years working on different cars, mostly Alfas, so this stuff is not a mystery, though working on a Ferrari can make you lightheaded at times. It takes a moderately experienced mechanic who understands timing, etc., and has a reasonable shop and tool selection, to do this job. If you get in over your head, or lose the cam/crank relationship and don’t know how to get it back, flat-bed the car to a qualified mechanic; don’t turn the engine.

1. Remove flywheel timing cover. Get engine to TDC on 1 and 4 (you can get close by removing the rear bank dist cap and getting the rotor to #1). Put car in neutral. Remove air cleaner assembly and snorkel. Remove spark plugs.
2. Jack up RR, remove wheel, and remove inner fender liner. Support and block car.
3. Drain cooling system.
4. Remove two-piece stainless heat shield between right gas tank and exhaust.
5. Remove rear “splash” plate in front of muffler.
6. Remove large water pipe running from thermostat housing to in front of alternator.
7. Remove air pump belt, alternator belt, AC belt.
8. Remove alternator adjustment arm and drop alternator back away from front belt cover.
9. Remove rear air pump and check valve and hoses, if fitted, to rear belt cover.
10. Remove AC compressor and push out of the way as best as possible, or remove entirely if it’s discharged. Remove all the studs from the mounts to get it out more readily. Watch order of spacers, washers, and rubber mounts.
11. Remove three bolts/nuts holding on rear belt cover. If cover has original studs, double-nut and remove studs or use stud extractor, or pull cover off as far as it will go and remove studs from behind with vice grips.
12. On GT4, loosen all four engine mounts from underneath slightly and jack up rear of engine/trans combo to get clearance from frame member to remove rear belt cover. May also need to loosen torque arm on rear cam cover, and shift linkage (I hear this can be a bad idea though, due to selector forks dropping off shaft). Watch for anything binding and loosen as needed. Let engine back down after you get the cover off, but don’t tighten the engine mounts.
13. Remove bolt holding dipstick tube to front cover. Remove bolts or nuts on front cover and remove it.
14. Verify flywheel is at TDC 1 and 4. Now make clear viewable marks on crank pulley, cam belt drive pulleys, and four cam pulleys and corresponding spot on engine in each location. White marker works well. I made a corresponding TDC 1 and 4 mark on the crank pulley. And I made “straight across” marks with a ruler on each pair of cam pulleys just below the cover stud. Recheck your marks several times. Turn engine over by hand clockwise a few times to make sure all marks come back and align.
15. If you’re going to use the camshaft locking tool, now is the time to install it.
16. Loosen rear big timing tensioner nut, push tensioner to fully compressed position by hand, and retighten nut. Rear belt should now be removable by hand. Twist belt gently at bottom to get it past crank pulley.
17. Remove tensioner nut fully, and pull off tensioner bearing. If it’s stuck, remove whole tensioner assembly and press tensioner bearing off on bench. Replace tensioner assembly but leave bearing off for now.
18. Clean pulleys, and work new belt on gently without binding. Start on drive pulley, holding belt on with binder clip or gently with small vice grips. Keep it taut and pull it to exhaust cam. Feed it onto cogs on that pulley. Hold with 1” binder clip. Now work around to intake cam, similarly feeding onto cog, so belt is tight, and distance relationship of drive pulley and two cam pulleys is same as with old belt. Hold on intake cam with binder clip.
19. In a small juggling act, loop belt around where tensioner bearing will go and push new bearing onto tensioner shaft. Once belt is in place, install tensioner nut loosely and let tensioner push against belt. Tie wrap can help to compress tensioner spring; once it’s all in place, cut the tie wrap off.
20. Verify that your marks still line up. In this process, you might have very slight changes due to belt stretch, etc., having moved the pulleys slightly to feed on the new belt (turn them back to their marks after the belt teeth drop in) but otherwise you can only be off in multiples of belt teeth, which are big, visible jumps.
21. If you installed camshaft locking tool, remove it now.
22. If your marks line up, tighten tensioner nut down til washer is still a bit loose. To set tensioner tension (by internal spring) and check timing, turn engine over clockwise slowly two full revolutions by hand. Stop and investigate if you feel any resistance. If everything feels good, ensure your timing marks line up after two turns. Drive pulley marks will get out of synch every other cycle, but you’re mainly concerned about the relationship of the crankshaft and cam marks. Turn over two more times just to make sure.
23. If marks still line up at your marks, tighten tensioner nut.
24. Check tightness of belt. On long belt run (between drive pulley and exhaust cam), you should be able to turn the belt 45-55 degrees by hand before you feel strong resistance. If you get to 90 degrees, the belt is too loose. If you can’t budge it at all, spring is too strong, or you haven’t loosened the tensioner nut when turning the engine over. If the tensioner spring is good, you’ll have the right tension. If the spring is weak or strong, it may be off a bit. This is a subjective, “feel” area. I ended up helping my tensioner springs a little by hand and then locked them down. Check and recheck the belt tension, and the timing marks you’ve made, after any adjustments of tension.
25. When you’re happy with the timing and the tension of the rear belt, torque the tensioner nut to 40-45 lb/ft (I couldn’t find the torque value in the factory manual), and then turn it over two more times to check timing and tension. If OK, you’re done with the rear belt.
26. Move to the front belt and do the same thing, except that on this bank, the long run of the belt, and the way you feed and clip it, is from the drive pulley to the intake cam, then the exhaust cam, then the tensioner. But the idea is the same. Note that though the crank turns clockwise, the belts turn counterclockwise.
27. Once done, replace the covers, hoses, belts, plugs, dist cap, engine mounts, antifreeze, etc., and button everything back up. On a GT4, you may have to re-jack up the engine slightly to get the rear belt cover back in place, even if you replace the mounting studs with bolts. I don’t know if the GTBs and GTSs have this clearance issue, or other issues that GT4s don’t have.
28. If you’re extra cautious, turn the engine over by hand a couple more times, and/or spin it on the starter with the ignition disabled. Once you’re confident no mechanical mayhem will ensue, enable the ignition and fire it up. Should be fine, but listen and watch for leaks, things you forgot to tighten, etc.
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Thanks for the followup Verell.

Yes, I feel really silly having set the whole thing up, and having forgotten to install your tools. I even had them out on my toolbox. If the cams had seemed inclined to move at all when I started to remove the belt, I was going to install them. But they didn't.

A friend here in Berkeley has a mostly Alfa shop, but also works on 308s, and has done quite a number of 2V belt changes and says he's never seen the 2V cams move. As you've mentioned, QVs may be a different story.

The only reason I "helped" the spring a bit was because after setting the tension, and letting the belt slack distribute itself fully around all the pulleys on several turns of the engine, I could twist the belt more than the 45/55 degree angle you mentioned earlier. I could get probably 60/70 without too much effort. So it seemed to me the belt wasn't quite tight enough. I didn't help it much; just light hand pressure.

Andrew