Problem with cam timing chain 1967 2000 Dino coupe

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bhiggins2
Posts: 53
Joined: Wed Jun 24, 2020 5:54 pm
Dino: Fiat Dino 2.0 Coupe

Problem with cam timing chain 1967 2000 Dino coupe

Post by bhiggins2 » Mon Sep 14, 2020 3:28 am

Today I tackled the job of removing the drivers side exhaust cam to get the valve shim heights. My exhaust valve clearances are out of specification and just a little too tight. The crank was lined up with marker, all cams dead on the timing marks. I loosened the timing chain tensioner which gave me plenty of play to remove the exhaust cam. There was no need to disturb the intake cam and it remained in position with proper tension on the chain on the intake side. I got the info I needed. I was not happy to see a combination of mostly series one valve shims on valve stems under tappets but one was series two with valve shim on top of tappet. I plan to return all to series one style. When I went to put the exhaust cam back in, I inadvertently lifted/bumped the chain just enough that it popped off the intake cam. I should have jammed a wood wedge in between the cam and the head - will do that next time. Now I cannot get enough chain to put the cams back in place no matter what I do. The chain tensioner is fully retracted into the bore, the chain appears to be on the lower gear correctly, but the chain is too short. I now appreciate Vittorio Jano's other version of the engine in the twin cam Alfa Romeo's that have a chain with a removable link. I tried taking the sprockets off the cams, putting them in the chain then onto the cam, but again, the chain is too short. I hope I don't have to remove the timing cover to fix this, especially since I just installed a brand new water pump. Should I remove both cams an rock the crankshaft back and forth a bit to see if the chain is kinked under the tensioner? I'm at a bit of a loss here. Any help would be appreciated. Thanks, Ben. bhiggins2@aol.com if you want to send me suggestions directly.

dino176
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by dino176 » Mon Sep 14, 2020 12:04 pm

Have you also loosened the retainer bolt on the front of the engine. If not, you can loosen the bolt for the tensioner, but it wont back out.
Regards Jesper

dinoverde
Posts: 271
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by dinoverde » Mon Sep 14, 2020 5:37 pm

you are in for a lot more work than you expect.
You will have to loosen the front pocket bolts(you will need to bend the metal tabs that keep them in place first)..to make sure your cam shafts do nor move while doing so..place a little piece or card board under each cam shaft retainers and torque to 10ftlb..
Push back the chain tensioner and lock it(so there is no tension on the chain)
take your camshafts out if you did not set your engine at top dead center on number 3 piston before you worked on the valve shims..if you did you are in a better place,..if not you will have to take the camshafts out so you can rotate the engine and be sure you have no interference between the pistons and the valves...once you are there get back to me..
Regards
Hervé

bhiggins2
Posts: 53
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by bhiggins2 » Mon Sep 14, 2020 7:43 pm

Crank pulley is ATDC 3-4 as per timing marks. I popped out both cams and wiggled the crankshaft a little and the chain came loose much easier than I had anticipated. I guess it had a kink under the tensioner that I could not see. Cams are back in, chain is on. Now I am having a heck of a time getting holes on sprockets to line up as I did remove the bolt and pins and didn't mark which holes the pins were in before disassembly. A little more trial and error and I hope to have it back together. I am making a little slide hammer to pull out pins. They go in easier than they come out.

I've been working on Alfa Romeo twin cam 4 cylinder engines of the 50s-80s for 30 years, so the engine is basically the same. Tensioner is a little different. Pins aligning cam sprockets are different. I wish the Dino had 9 mm valve stems as I have several sets of 9 mm valve shims. The 750 series Alfa Romeos also used 8 mm shims/valves. Not surprising, the tabs were no longer with the cam shaft locking retainers. I have new ones. I might give the cardstock under the cam caps a try later this afternoon.

On the Alfa cam shaft, I think there are more holes on the sprocket and cam and no matter how you mate the two together, at least one hole lines up and there is one tiny bolt instead of pins. It is escaping me now how I can have cam alignment marks lined up and have no holes that line up on the sprockets. If I take the sprocket off, rotate it a tooth or two and put it back on I get one hole lined up. There must be some secret I am missing? Ben.

Dario
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by Dario » Mon Sep 14, 2020 8:59 pm

You can get a long bar and leverage back the tensioner (once it's loosened), then tighten it up in the compact position. Now, you can get a pair of strong lock pliers around the camshaft and rotate it into position and hold it there. Once all is good, release the tensioner. If you havent done the counter-bolt modification to the tensioner, it's a good mod.

good luck,
Dario

bhiggins2
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by bhiggins2 » Mon Sep 14, 2020 10:00 pm

Dario, what is the "counter-bolt modification" that you mention? Ben.

bhiggins2
Posts: 53
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by bhiggins2 » Mon Sep 14, 2020 10:13 pm

I should have mentioned this is a series 1, 2000 coupe. The chain tensioner screws in and out. I don't believe there is a spring in this style. Ben,

dinoverde
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by dinoverde » Mon Sep 14, 2020 11:28 pm

To get the little pins out you will have to use the correct size bolt and thread it inside the pins(probably an 8 or 7mm (can not remember..) If you can't get the pins back where you want them to be you will have to take the sockets out and rotate them of the chain that but them bak on the chain and camshafts..until they face where they have to be.. Remember that the marks on the cam shafts are just approximations and really will depend of a lot of variables like lob ware and valve seat wear..It is important during this whole process that you make sure your camshafts stay put(therefore the thin cardboard or paper under the camshaft keepers(acts like a brake)..Once in place then you push the chain tensioner back and lock it in place.. The chain tension can be measured with balance spring as explained in the book..a lot more tight than on an alfa...
When you have everything back then you can rotate the engine and see that the cam marks end up where they should be after a full 2 turns..do it slowly by hand plugs out and if you feel any resistance do not force anything..If it orates then you can check your valve clearances and make sure they are right..
Now remember not to bend the new taps back yet on the pocket bolts yet..
The hard part now really start..you have to degree in the cams..you will need to put a degree wheel in the front with a pointer.. when the engine is in the car ..not easy..specially with the radiator in..
this is the only way you can be sure your valves open and close the way they should..you can go by the marks on the cam shaft..but your camshafts will be most likely a few degrees of..if you feel up to the task.. i will walk you through..
but before you do this be sure your valve have the proper gaps one intake and exhaust..

bhiggins2
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Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by bhiggins2 » Tue Sep 15, 2020 3:48 am

I got the measurements on the valve shims and need to do some calculating and then order some correct thickness shims. The cams are all back together. I was able to do the passenger side without disturbing the alignment and without removing any pins. The driver side is back together too, but the timing is just a little bit off as I had to turn the cam to align with a hole on the sprocket and there wasn't a clean hole where the cam timing marks were. I left it with one pin for now and I'll deal with that when I fit the correct valve shims. They are close enough that there isn't any interference when rotating the engine by hand, but I wouldn't run the engine the way it is now.

I took the threaded top portion of a spark plug [broke off the ceramic] I think it is 3 mm, and welded it to a 3/16" piece of round steel stock, added a slide weight and welded a 6 mm nut on the end. So I have a little slide hammer that works great. Everything is out of the engine compartment except the bare motor, less intake and top plumbing, and wiring harness bits that could not be removed, so fitting a timing wheel is not out of the question. I have not checked to see if my Alfa set-up will work on the Dino. If not, a spare crank bolt and a little MIG welding and I can make that work. I just finished painting the engine compartment and all the area up in front of and below the radiator. I'm sure glad the engine compartment is bare for this, it would be a real bear to get at the tensioner for the passengers side with all the plumbing in the way.

Is there any literature on the process for degreeing in the cams with the index holes on the camshafts? The manual just skips over that part of the engine rebuild and I just don't see how it is possible when I have trouble getting a single hole to line up, and not on the timing mark.

On the last 2000 cc Alfa engine I built, a friend was adamant that we degree in the cams with the degree wheel and specs. It was a bit interesting since I was installing Euro carburetor cams in a SPICA fuel injected head that came with different cams. Everything was new, so there were no wear issues. After several hours of messing around with it the difference between the "degreed in" cam location and the timing marks on the cams and cam bearing cap marks was about the thickness of the timing mark itself. I'm not sure that made any difference in performance. How much off can one expect to find actual "degreed timing" vs just aligning to timing marks on the Dino? As you say, it may vary depending on wear.

Thanks, Ben.

dinoverde
Posts: 271
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Dino: Fiat Dino 2.0 Spider

Re: Problem with cam timing chain 1967 2000 Dino coupe

Post by dinoverde » Tue Sep 15, 2020 7:42 pm

i recently degreed in the cams on a low mileage dino 2 liter. The marks are at best just a reference point. Degreeing the cams is essential in my opinion..
Dino parts sales a very good degree wheel that fits over the crankshaft pulley. You will have to degree in both camshafts intake and exhaust.. If you have the workshop manual the infos are on page 21. If you provide me with a email i can send you scanned pages of it.. It does not go through how it is done, but if you have done an alfa engine..the idea is the same..you have to find opening and closing.. The difference is to do so you have to set the camshaft gap at .50mm both on intake and exhaust to do so. I recommend doing measurements on 3 and 6 (away from the mark) easier to set up measuring tools.
I use a very heavy metal brick to set up the magnetique arm used to hold the measuring gauge..Once done you have to rest the cam gap correctly on 3 and 6..
Hervé

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