308 Cam Belt Change

I made these aluminum pieces pinched by a bolt, worked perfectly.
I 1st put put motor @ tdc, verified I was on the correct stoke with cam mark thru oil filler cap, then used a paint pen on cam sprockets and crank pulley to make it easy to verify nothing moved, no problems.
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The 308GT4 is essentially the same as your carb'd 308. There's a factory shop manual .PDF file (among other useful documents) in Steve Jenkins Private document collection:
http://ferrari.jenkins.org/books/

There's a cam belt service procedure on the ExpensiveCar web site:
http://www.camerafilters.com/ec/ofsm.htm

BTW, your carb'd 308s cam gears are most likely plastic, thus a lot more fragile than the metal one on mcguy's much newer car.

I've made up cam gear locking tools similar to his for QVs, but matched the gear curvatures & faced them with rubber to reduce the clamping force.

However, for a 2V car like yours, there's a better/safer way to clamp the cams. There's a nice wide space on the end of the cams between the cam seals & the cam gear mounting flanges you can use to clamp the cams. So you don't need to clamp the fragile plastic cam gears or risk bending cam journels(see below). Sorry, I'm at work or I'd post a pix, but hopefully this description will make sense:

2V CAM CLAMPS:
Make flat clamps out of 1x2 or 1x3 oak or maple. Measure the spacing between the cams (it's about 140mm/5.5" but my memory may be a little off), and drill 27mm (1-1/16") holes in the center of the boards at that spacing on the 2" side. Drill 1/4" holes thru the narrow side of the board on each side of the holes. Cut the boards in half straight thru the 27mm holes. Put bolts thru the 1/4" holes & you have a pair of clamps that will hold your cams w/o risking the pulleys or cam caps.

You'll have to cut about 2" or so out of middle of the bottom piece of one clamp to clear a stud on the forward bank.

Two different situations are being discussed:
CAM REMOVAL"
When removing a cam you MUST gradually loosten all cam caps equally to avoid stress build up & breaking the cam. Removing & reinstalling a single cap can be done safely. However, you don't want to remove one of the end caps, use one in the middle as you need the end piece to be exactly in place to use it's reference marks.

CAM LOCKING:
A 'matchbook cover' is way too thick. You can bend a cam cap just enough so it rubs the cam with long-term disastrous results. Use at most a business or playing card, or a $bill folded double. Just tighten it enough to stop the valve springs from rotating the cam out of position. This method should only be used by someone with a lot of experience as the cost of overtightening a cap is big $$$$, especially if you don't realize you've done it.

Better to, make & use the clamps I described above for belt changes.

(Search the body of posts in both the current fchat & the old fchat archives for 'matchbook' and 'cam belt' for some long discussions on this.)

 

If you get them on TDC one bank then apparently the 2 valve engines don't tend to move, (mine didn't).

Also if you are happy about the way the car is running and you don't actually want to check the valve timing or change the camshaft seals, then there is no need to take the covers off, or loosen any cam bearing caps.

If you get it to TDC and mark up the cams in this position (see first photo) you can guarantee to get it back as it was.

For further safety you can also mark up the belts and the various wheels, then transfer these marks onto the new belts (counting the teeth) and then put the new belts on in the same positions as the old ones, (see 2nd photo).

Its relatively easy to get everything back on and all the marks lined up and off you go!


hope this helps
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True, the 2V engine cams are much more cooperative. Will move if jiggled a bit too much tho. Still, the wooden cam locks are easy to make and take all risk out of the process. Can still decide whether to just mark the belts & cam gears as Ham describes, or pull the cam covers independantly of whether you clamp or not.

It's the 4V engine cams, especially the front bank's intake cam that are almost impossible to keep from moving w/o locking them down.

 

Here are a couple shots of the cam locks Verell and I made for my '77. Because the cam pulleys are about an inch away from the engine, there is plenty of space to clamp the shafts themselves, rather than risk damaging the pulleys.

We made a pair of these locks in about 45 minutes from some scraps of 3/4" thick maple flooring. This is very tough wood that can be clamped securely, but the nice part is that it won't clamp tight enough to damage the camshafts because it's softer than steel or aluminum.

Birdman
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Billy,
One tip that makes it easier to be sure the belt goes on as the old one came off: mark not just the pulleys themselves, but also mark the old belt with matching marks. When you pull the belt off, transfer those marks on the old belt to the new belt, and install the new belt. Now you know that nothing moved and the belt is in the exact orientation as the old one. In fact, if something did move, you can still line it all up again. I use a silver colored sharpie marker. Works great and won't rub off like a grease pencil. Very easy to see the mark on a black belt.

The front bank is not that hard. You will need a set of stud pullers to remove a couple of the studs below the AC compressor in order to get it out of the way. (You can also do it with a couple nuts jammed tightly together I think). That's about the only thing that really gets in the way. If you can't pull the studs, you are screwed. You need to pull all the brackets, top and bottom, on the AC compressor, then just drape it over the gas tank out of the way. Once you get it out of the way, the front bank is actually easier to reach than the rear!

Be very gentle putting on the new tensioners. DO NOT try to pull one off and try again if its stuck or crooked. They come apart when you do this. Ask me know I know. Put the new tensioner on and use the mounting bolt to "press" in on. Put a little lithium grease on the post to make it go on easier...just don't get the grease on the tensioner belt surface or the belt.

When tensioning the belts (after both belts and tensioners are replaced), let the tensioner spring do the work. Just rotate the engine a few rotations and you will see the tensioner moving back and forth a little as the belt has more and less tension on it from the valves. Find the spot where the tensioner is in the furthest, so it will be providing the most tension, then lock down the tensioner. Do not assist it and make it tighter by hand like you would with an alternator belt. That will overstress the belts.

And of course, don't replace the belts without replacing the tensioners! A tensioner failure is every bit able to destroy the engine as a belt failure.

Birdman

 

I'm glad you mentioned this Jonathan! Excellent advice from everyone as usual!!! This is the kind of thing that makes this site so valuable!!

 

If you're AC is R12, working, and charged, you can get the belts off w/o having to evacuate and refill the system the AC system.

First you'll have to get stuff lose and get the lower AC bracket off. Once that is done, double nut the studs few studs that hold on the AC and belt cover and get them out. Once those are off, you'll be able to swing/twist the AC out of the way and over the top of the gas tank. I think you'll aslo have to losen those three vent lines off the top of the tank and take that vapor recovery device off (you'll know what I mean when you see it - it's right on top of the passenger side wheel).

Now you can get to that upper AC bracket , it will come off and the cam belt cover as well.

 

I would not trust someone else's paint marks. Take the cam covers off and verify the tick marks are lined up on all the cams. Get some thinner and clean off those paint marks.

If the seals are leaking, you should replace them anyway and you need to take the covers off to do that. It's really not that tough. You can take off the pulley's to replace the seals. No need to take the entire cam out.

I'd take the engine cover off anyway as it makes things 10x easier to work on.

On the fubar paint, Line up the 5-8 mark on the flywheel and see if those front paint marks don't line up. I'll bet they do.

 

If you have to pull the cam gears (ferrari terminology for cam pulleys), and you know that the cams are correctly timed so you'll want to restore the cam gear to the same location on the cam:

First, degrease everywhere you're going to be puttin paint marks as most degreasers will remove paint!

Put paint marks on the back of the pulleys & cam flanges they attach to
(There's no room to do this on a 4V car(sigh)).

Also mark the cam gear hole the pin is in, and then mark the edges of the flange thru a couple of the holes.

Put fresh paint marks across the cam seals & onto the pulleys.

BTW, I use a Testor's yellow paint stick available from hobby shops.

I 2nd Sean F's post.
So far 90% of the engines I've serviced have had at least 1 cam miss-timed by the width of the cam cap mark or more! It's your call as to whether you trust the current cam timing or pull the cover & verify it tho.

If you pull the covers & setup the marks, then before you put the covers back on, take pictures of all 4 cam marks to document that they did in fact line up. If I'd bought a car with pix of the last cam timing adjustments, then I'd be comfortable in just replacing the belts w/o pulling the cam covers for services not requiring valve clearance check/adj.

 

I don't believe anyone has mentioned this but it is a good idea to carefully examine the cam belt drive pulleys. If the bearings go it can be as bad as breaking a belt, will allow the belt/belts to skip teeth. This was caught when I did my car. Apparently a good clue is oil at the R/H rear wheel, inside. Just a thought.

Steve Schroeder

 

Can somebody explain how to rotate the engine/set Top Dead Center?

I know you turn the crank snout, right? Any special precautions? (set car in neutral obviously!)

Do I remove the oil fill cap to observe a certain mark? A picture of this mark would be helpful.

Or, do I need to view flywheel?


Thanks in advance,
Greg
1977 GTB

 

Cam locks can work but your timing will most likely be off by a few degrees effecting your performance. You need to lock camshafts and reindex cam cogs at a minimum. Never lock by the cam cogs or you will be off because you can acount for cam cog movement during belt tensioning. See my basic threads: http://www.ferrarichat.com/forum/showthread.php?t=148604
http://www.ferrarichat.com/forum/showthread.php?t=148917

This is for a 348 motor but 308 motors have all the same parts. You even have TDC 1-4 and 5-8 already marked on the Fly wheels just degree them and confirm them at least once. 348 giuys don't even have that.

 

Yes, but:

 

The "Setting up cams" thread talks exactly about precisely finding TDC or you could trust the ferrari marks on the flywheel. Your choice but I think it is always smart to measure twice and cut once.

 

Birdman can correct me if I'm wrong, but IIRC he purchased a Mondial some time ago, and when he got inside to replace the belts, found the front set of cams installed 180* off from the correct marks. It ran okay, but the point is that it is rather easy to screw these cars up by both not paying clear attention, and by trusting things other people have done in the past.

For this reason, anytime you aquire a new machine with sketchy history, you should ALWAYS start over from scratch and do it all by the book. I wouldnt have any real problem with anyone swapping marks over to a new belt from the old, if they were absolutely sure the motor was correctly timed to begin with. But when you have an unknown quantity, I really feel your wasting valuable time not to go the rest of the way and put everything right to start with.

Pull the covers, check valve clearances, retorque the heads, service the distributors, locate true TDC and then time the cams as closely as is humanly possible with a degree wheel. Then youll know its right, so when the carbs are yanking your chain or your fuel injection isnt acting quite right, you wont have to wonder if there is something off somewhere else. It can get rather frustrating when you have a running issue, and someone asks if this stuff is correct and the answer is an "I dunno". The AC compressor is almost the single biggest job of the whole thing. Get that out of the way and your just about over the hump.

Question: I have two 77 308 GTB's, and I didnt have to pull any studs on either car to fish the compressor out. So I am curious if the later cars have more constricted space, or did I just get lucky? Also, regarding not disconnecting the compressor, the second car had new AC lines on it, and one snapped off at the line fitting virtually destroying the hose. It didnt have any refrigerant and the line probably wasnt installed correctly to begin with, but I would tend to think evacuating the system and removing the compressor out of the way completely, and not torquing around on those hoses would be better than risking damaging them.

 

I think you got lucky. I always had to remove the compressor. I always cracked the lines and recharged later. It is very tight in there and w/o the compressor it is heaven compared to with it in.

I also think that there is a fundamental problem with 8cyl Ferraris when doing "just" a belt change because you cannot set-up the cams on marks precisely without unlocking cams whist you tension the belts. Just using cam locks and changing belts and retensioning is a recipe for disaster in either off timing or improper belt tension or both. Unlocking the cogs is the only way to passively allow the tensioner to do its job. We see this problem less on 348/355's because the engine needs to come out and that scares away many DIY'er's. So it is your car guys...learn to do it the best way you can. Read my post on setting up cams and degreeing cams it is just not that hard.

 

My question is can the looped end of a timing belt be crushed or radius be bent too small to safely use a new belt? I just received my timing belts in the mail and they were in a small 6.5" X 9" X 3" box with my two timing belts looped together and then the belts folded with the very heavy tension bearings in the middle if the fold. The tension bearings were wrapped in bubble wrap but they weigh at least a pound if not more. I don't think the sender realized how much damage those two heavy tension bearings could to to the folds at the ends of the timing belts. For almost a week they were thrown around in the mail. I have always read the they should never have their radius bent too small. The belts would have easily been squashed to the diameter of half inch or less! To be safe should I throw these belts out and get new? No guessing please. Does anyone know how small the radius can be on these belts? Am I right that they could have been damaged? Thanks

 

I cannot say for sure, but if there is any visible damage at the sharp bends I would discard or contact the sender for a refund/replacement. The damage would be in the form of small cracks. I don't think the internal cords would be damaged, but from what I hear the failure of the cam belts is to jump a tooth or two during operation. That causes the valves to be in the wrong position and possibly get bent or worse. Just my $0.02 and when in doubt, play it safe!

 

actually, yes the belts internal construction can be damaged by bending them in too small a radius. the engineering book i have from gates on belts shows the belt to have a minimum dia. of 1.432", any smaller and the internal threads will break. So if the belt was bent into a loop smaller than the lower pulley I would not use them.

 

Thanks for all the advice here. I am about ready to try this myself, and I feel much better about it.

 

Removing the compressor does not require stud removal. Leaving it in so as not to bleed the AC system means you have to flip it up out of the way over the gas tank. In order to do that, you must remove those studs as they block the flip over movement.