Replacing Timing Belts

I dont bother looking at the cam marks. I have marks on the pulleys on a straight line through the centres at TDC. Just change the belt and make sure the marks are lined up and the crank still at TDC on the pointer. I also mark the drive pulleys against the snubber as an extra check.
I dont think it matters if you change the belt with the cam marks lined up or the mark 180 degrees out.

 

Besides that, if you get it wrong & in order for anything to be off you'd be off by a whole belt tooth which will be pretty noticeable if you have a good set of marks on the pulleys.

 

Correct - when you mark the two pulleys directly opposite each other (whether you set the crank at TDC or not) - a one tooth error is hugely obvious. It is impossible to re-assemble them out of time. Well, OK, I suppose it's not impossible but IMO you'd have to be seriously inebriated to not notice the difference.

FWIW - It probably sounds silly to say this but for anyone who hasn't done this sort of thing, always mark the relevant pulleys/gears. Basically, draw a paint line across the gear edges where the gears are adjacent (closest) to each other, with the paint mark in line with the center line of the gears. Do not make a mark on the cam gear(s) and one on the engine block (like a crankshaft timing mark). That CAN result in a timing error because mis-alignment can now be spread out over twice the the "area." That, plus the parallax involved makes it possible to screw up... I mention it because I have seen people do exactly that...or, to be more precise, I have seen the results of it.

 

Birdman has a site and it has step-by-step instructions on many procedures. Jon put this site together and it is a great resource for DIYers. Timing belts are not extremely difficult and take your time.

Ferrari 308 Mondial parts and service

 

Here are a couple of pics - first shows the marks on the cam pulleys made before the belts were pulled. Second pic (a little blurry - too close for proper focus) shows the marks after belt was pulled and the pulley was nudged a bit as belt was removed - it shifted to that position. Reached up, turned pulley back, put on new belt. As long as pulleys are marked, cam movement is a non-issue, just move it (them) back to correct position.
Image Unavailable, Please Login
Image Unavailable, Please Login

 

I make 4 marks then you can check them with a straight-edge right across rather than relying on them "looking right".
Also the mark on drive pulley and snubber can be seen.

This is from the first time I did it. I dont bother locking the cams subsequently.
Image Unavailable, Please Login

 

I agree completely re using the ruler to make the marks but whether you choose to make two or four marks, or you just do it by eye, it is impossible to misalign the cams on reinstall simply because a one tooth error is so large.

RE that, it is worth understanding that the perfect, marked alignment with the old belt may not be duplicated with the new belt. IOW, when you remove the old belt you may find that the new belt teeth will NOT drop perfectly into the pulleys in their "old belt" position. A very slight shift in a cam position could be necessary due to the tolerance/wear or manufactured difference in the two belts. This is very common with cam belts/chains and is nothing to be concerned about. Typically, the shift needed is barely noticeable visually and it has no actual effect on cam timing.

The point, as far as I am concerned, re these last couple of posts, is simply to show that there is no rocket science involved here and that anyone with the time/willingness to do so can change the belts with no drama. The hardest part is removing components in order to get TO the belts.

But as I said earlier, if you are more comfortable with locking the cams/marking the pulleys and new/old belts, as opposed to doing it "free hand," then lock/mark everything.

 

100%

As a veteran of 1 belt change... I marked everything and locked everything but wouldn't do so again.

I used a small spirit level (with the bubble in the middle...) to put 2 marks on each pulley I found this simpler to do than try and put a straight edge across both pulleys and then mark both pulleys with 2 marks (I'm a human being not an octopus!)

I was struggling to get the old belts off because I couldn't ease off the tensioner - so I took a Stanley knife to the old belt, ten times easier & quicker than trying to ease off the old belt (and risk moving the cams...)

As mentioned previously there certainly isn't any need to mark the belts and the teeth as if you are one tooth out - it sticks out like a sore thumb.

Andy/Mike/Iain/Bell Bloke - you are going to put some mechanics out of work if you keep these posts up.

 

Taking that one step further, use this search parameter for FerrariChat specific results... site:ferrarichat.com followed the keyword/s

For example - site:ferrarichat.com 308 cambelts

https://www.google.com/search?q=308+cambelts+site%3Aferrarichat&oq=308+cambelts+site%3Aferrarichat&aqs=chrome..69i57.14336j0j8&sourceid=chrome&es_sm=93&ie=UTF-8#q=site:ferrarichat.com+308+cambelts
.
Image Unavailable, Please Login

 

Lots said about belt changes...... I thinks Bell's u tube video is fantastic. I have a tip that may be obvious to some but I guess I have time to jump in today. When changing belts take the time to clean all the compacted dust and debris from the sprocket groves. It will make a difference on setting the tension correctly. I used a tooth brush. Also consider verifying that the cam timing is correct before you remove the old belts (many are out). Removing the oil filler cap and flywheel inspection plate will allow you to check that the timing is correct and give you peace of mind when you hit the starter after the belt change (Bell's recommendation). If you want to verify the other three cams are set correctly the cam covers will need to be removed but certainly checking all four cams was worth the time for me. It appears that many cars are running ok but could run much better if the cams were timed correctly.

 

Stupid belt question which I'm sure has been answered several times over but I'll ask anyway. I just looked at my 328 manual and the book shows cam belt inspection every 15K and replacement at 52K. I wouldn't dream of going that long but when did Ferrari come out with changing the replacement schedule?

On the 355 most push it to the 5 year/15K mark which is probably reasonable for the 328 as well but with belts today being much better than those from the mid-80's, I found it curious to see the replacement originally scheduled for 52K.

 

Don't know of any sites to get your ass kicked. But during my belt service removing my a/c compressor kicked my ass. Infinitely worse, my Porsche buddy helped me and got the damn thing out!

I want to let it go. But beers he ingests magically reminds him of his victory.

 

Obviously, they came out with it AFTER 3x8s had ceased production since my '89 328 manual says the same thing. Makes you wonder about the horrific amount of problems they must have had with belts failing over the previous 15-odd years of making 3x8s.

Curiously, I have never read of any such problems...

 

One point I feel I have to make.

Using the above methods to swap the old timing belt for a new one is fine in and of itself. But that is all you are doing. The service manual, and all the Ferrari mechanics I have talked to, recommend to time the cams after replacing the belts. This requires taking off the valve covers, checking all the valve shimming... then changing the belts and then using a degree wheel on the crank to ensure the cams are timed to the crank by checking that proper valve lift is happening at the correct crank rotation for both banks.

The engine will run reasonably well without degreeing the cams to the crank but you are leaving power on the table if you only replace the belts with out degreeing the cams. Or maybe you get lucky.

 

That was related to US emission laws that required the manufacturer to pay for anything "emission related" that had to be replaced before 50K miles of use (so F dodging as much future $ liability as possible ). If you check the euro 328 OM, it shows replacing the timing belts every 25K miles or every 2 years (which is the shortest "official" time period ever reported AFAIK). You should be able to find a copy of the quasi-recent Service Bulletin that went to every 30K miles or 3 years (IIRC) on every model as the "official" recommendation - it's been posted many times.

 

Did Ferrari Mechs actually do all that for a belt change? I absolutely would NOT argue against that procedure but it's hard for me to believe shop mechs went to that much trouble for a routine belt change. Seems to me that one would assume that the cam timing was routinely wrong from the factory if that was the normal shop procedure...maybe factory timing left something to be desired, I have no idea. But one would like to think that a FERRARI would leave the factory with the engine in perfect tune. Whether anything else worked very well is a different issue!

 

People much more knowledgable than I have said that:

"Back in the day, the less than 12 cylinder cars went out the door with the Idiot Lines, matching or nearly so. NO additional tuning with a degree wheel was done."


Is that true?

Don't know, but facts are: they are Italian, and Enzo was not a big fan of the street car side of things, so ...................

 

That seems plausible.

It might be worth degreeing the cams once, but degreeing on every belt change seems unnecessary.

 

As I understand the process, that would require the cam specs: lift, duration, timing. Anyone know where those specs are? And I agree, doing it once is overkill, doing it every belt change seems like some serious overkill, ESPECIALLY since it is not a vernier cam wheel.

Now if you are racing and NEEd that 1/10th extra pony then degree away.

YMMV

Lester

 

Depending on the year of the 308GT4 / 308GTB/S / 308GTBi/Si, they can be found in:

The Work Shop Manual for that model/year and destination market, or

In the Mondial 8 / QV Work Shop Manual (also for the 1980-1982 308i s IIRC).


Many can be downloaded for free off The Net.

 

the cam pulleys and the cam shaft have multiple holes to make it adjustable and get within the 1 degree tolerance for valve timing.

 

Just to throw a spanner in.....
You know obviously you can change the character of the car by changing cam timing ie. Less torque more power or visa versa. Have you thought about your style of driving and how you might set the cam timing to suit?

 

Generally, you change cams for the performance profile you want, you don't change the cam timing. Sure, there is some difference available but it's very narrow and mostly would be limited to the ability to fine tune for the specific engine. IOW, the "correct" cam timing on 3 different custom-tuned engines of the exact same model might be slightly different to produce the maximum power. In reality, this means that an engine that is precisely tuned on a Dyno may NOT have the cams in the "properly timed" position.

Absent data on such changes for specific engines, there is no effective way to test cam timing changes without using a Dyno that can load the engine, not an inertial dyno. Since cam timing changes also affect dynamic compression, it is difficult to tell what's going to happen with a cam timing change on the overall range of engine performance. A timing change might get you a few HP at the top end but lose too much at the low/mid range end. The opposite can also occur. Certainly it's done but without such data for 3x8 motors/cams as there is for chevys, it's totally shooting in the dark and without a dyno to test each change it's shooting in the dark with no bullets in the gun!

 

I agree that there is a sweet spot and that will be higher up the rev range but if you are the kind if driver that doesn't drive like that then less valve overlap on the timing will give more torque.
My Aston V8 Vantage 1979 has the same cam profile for auto and manual BUT Aston Martin change the valve timing to give more torque for the auto.
Hey I'm just stirring a bit here, because I know you all rev the tits off your Ferraris but if you drive anything. like my friend who never gets over 3000rpm then maybe a more torque set up is for you.
But to be honest I'd do what the book says

 

"because I know you all rev the tits off your Ferraris but if you drive anything. like my friend who never gets over 3000rpm "

I bounce mine off the rev limiter every now and then (8200 RPM) to make sure the cam belts stay properly seated! But I usually shift at around 7300 for normal spirited driving.