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  Topic Review (Newest First)
09-14-2009 03:34 AM
Alfisto Steve
Thermal clutch spring device in mechanical tensioner

Here is my take on how the outer spring which is connected to the thermal clutch spring works to aid the inner spring on the Alfa 12v V6 mechanical tensioner # 60588421. Tech Service Bull 01.96.01 Alfa 164 TSB 01.96.01 says that " pointer will only line up ... when engine is stone cold". The bulletin does not says where pointer is when warm but thermal expansion is working here and thermal clutch spring is doing it's job.

SO just like oil fed tensioner mechanical tensioner is both a tensioner and DE tensioner.

Confused? Hope not just understand this tensioner really has THREE springs - inner coil spring, outer coil spring and thermal clutch spring.

Starting with the pointer right on the line of the reference mark with the engine cold. The pulley usually bounces a little when engine running. This is OK. Now as the engine warms up, the pointer begins to move lower, below the reference mark. When completely warm, radiator fan running, about 200 degrees on the gauge, the pointer is almost 1/2" vertical distance below the line on the mark. Now COLD the thermal clutch spring prevents the pointer from moving much below the reference pointer because thermal spring is now contracted pulling on outer spring and aiding inner spring to keep belt properly tensioned. THIS IS WHY IS IS IMPORTANT NOT TO OVER TENSION OUTER SPRING COLD so it won't break. Thermal clutch spring has to expand to prevent stretching out spring to the max.

If you notice under that round cover with reference mark on it for the pointer to be aligned with cold is this thermal expanson flat coil clutch spring that looks like the cooking coil on a electric stove. This flat coil spring is hooked to the infamous outer coil spring that aids inner coil spring to keep belt in proper tension (unless it is broken).

As engine expands due to heat this thermal spring expands to let pulley move so belt tension stays the same. This is why pointer goes below reference point when engine is hot. So the way I see it the thermal clutch spring allows belt tension to stay constant both hot and cold.

Hope that makes sense. Think of it as a dual purpose system of both expanding and contracting to prevent over tensioning and under tensioning of the timing belt.

So my take on this is that as long as tensioner installed properly cold with all three springs intact and pulley pivot point not binding timing belt should not become loose when engine contracts back to cold state AND cam timing pulleys should not jump time (slip under belt).

Further reference TSB's to install and tension belt/tensioner: Alfa 164 TSB 01.93.03 Alfa 164 TSB 01.93.04 REMEMBER TO USE SPECIAL TOOL (needlenose pliers to aid installing belt and setting tensioner pointer when using lifting lug on tensioner body).
09-13-2009 02:13 PM
Alfisto Steve Here is info on another TSB about using TDC marks on front crankshaft pulley:
09-13-2009 11:05 AM
ChazzyD Excellent work glad it's sorted. Here is another reference TSB on the subject.
09-12-2009 03:25 PM
Rick1803 I reassembled according to the advice received on this forum, which means the prior timing belt installation was wrong. Apparently it was installed using the hole in the flywheel, that put the timing off by 2 teeth on the crank pulley! I still cant believe the engine ran as well as it did, it runs better now.

I found another page where the error is repeated, 00-38.

08-17-2009 10:22 AM
Del Yes. I support the Digest (well, I do own two 164's, plus the Milano). Need to send more money. I personally don't pay attention to most of the info in the BB, most of it being more of a social aspect, kinda car clubby. Been there done that. Really, the Digest has had better 164 problems/repair history than the BB, IMO, as it dealt with the 164 problems/repairs, mods pretty much from the beginning, although some newer information may be in the BB.

If nothing else, if the Digest were to die, it would be essential to make sure those records would be folded into the 164 section of the BB. Of course, at the rate 164's are being parted out, it may end up being a very moot point anyway.
08-17-2009 07:45 AM
MrT By the way, for anyone listening, the venue has the best archival info of which I know on the 164 and is worth supporting. It hosts what used to be the principal discussion group for 164 cars, but the binary attachments possible on alfabb have caused it to fade in popularity. Both venues are worth supporting. I fear that if the digest venue fades away, some important info currently available there will become inaccessible. But as I said, both venues are important. For instance, Rick from Wa. state (IIRC) could not have published his timing template on the digest without special arrangements, but it spread widely after it became tested through alfabb distribution and has been really helpful.

08-17-2009 07:24 AM
CorseChris Given the amount of damage than can follow mis-timing, I understand why you are concerned!! It pays to be sure.
08-17-2009 06:45 AM
Alfisto Steve
Man prints manuals and man makes mistakes

Originally Posted by Rick1803 View Post
Thanks for the detailed answers. Chris, your line by line answers are appreciated. I need to be completely assured before I commit to changing/correcting the timing.

Steve, regarding tech bulletin 01.94.04, I think I have year 1991 manual (cardisc CD), I think I found another page with the error, page 00-48, top left.

Considering the amount of info in manuals and the translation from one language to another along with all the different configurations of the 164 for the world markets it is amazing there aren't more errors.

But with places like , CarDisc International Ltd. - Alfa Romeo Manuals, Giulietta Manuals, Giulia Manuals, GTV Manuals, Spider Manuals, American Austin & American Bantam , and Alfa Romeo 164 we are muddling through pretty good trying to get out the correct info.
08-17-2009 06:33 AM
Rick1803 Thanks for the detailed answers. Chris, your line by line answers are appreciated. I need to be completely assured before I commit to changing/correcting the timing.

Steve, regarding tech bulletin 01.94.04, I think I have year 1991 manual (cardisc CD), I think I found another page with the error, page 00-48, top left.

08-17-2009 04:14 AM
Alfisto Steve Drilled hole reference in original shop manuals IS WRONG and even though scribed line is correct it is often missing once flywheel has been refaced.

Here is one tech bulletin 01.94.04 about error in manual: Alfa 164 TSB 01.94.04

Here is info from another tech bulletin 00.91.03 about crank pulley timing mark:
08-16-2009 11:14 PM
CorseChris 1. Did manual originally say “line up hole on flywheel“?

Don't recall....but it's clearly wrong if it did! Don't fret about not having the scribe mark on the flywheel, use the front pulley mark (& double-check in #1 plug hole if you like)

2. Should ALL timing marks line up when #1 at TDC?:
- front pulley; cams; flywheel;

YES (caveat being that the mark on flywheel is correct! I'm pretty sure the drill hole is for balancing so could be almost anywhere, or even absent).

What matters is not where the marks are, but where the components are, IYSWIM (yes, I know, the marks should be right....). If you are unsure, again, use first principles. DTI #1 for TDC - this CANNOT be wrong, your cam marks look to be sound as you get agreement on cam caps and template. If front pulley and flywheel marks line up at this point (they probably will), great, if not, who cares! Just make sure you can get the engine back to TDC reliably, with the cams in the right place.

3. Could engine run with cams advanced?
- I think timing belt off by 2 teeth on crank sprocket

YES - this was the state the engine I have with the whacky cam timing mark was in when I bought it. Pinked a bit but ran 'OK' Went a whole lot better once I sorted it though.

4. Has anyone heard of this error before?

See above!

FWIW, trigger teeth are 10 degrees apart (it's a 36-2 pattern) so you are about 25 degrees out.
08-15-2009 05:47 PM
ChazzyD It's time for you to start answering some questions, you keep asking the same ones.
08-15-2009 07:14 AM
Alfisto Steve Alfa V6 12v engine will run with cams advanced and retarded within reason like maybe 2 teeth max. Maybe not so with 164S cams though.

I guess I need to test the theory of exactly how many teeth advanced or retarded you can set cams before valves hit pistons.

If advanced within reason whatever that is engine loses low end power as long as valves don't hit pistons then really loses power. Usually on rear head is where problem occurs and bends #2 intake the worse and then lesser amounts on 1 and 3. I suspect at about 3 teeth advanced valves start to kiss pistons.

Anybody actually performed "lab experiment" to see?
08-15-2009 06:50 AM
MrT When I acquired our '93L from a non-Alfista P.O. in Florida (P.P.O. was Alfista), I took it by our friend Steve's place. He went through it and found a few things to be corrected. One was poor timing belt tensioner install. One of the consequences of this was that both cams were off by one tooth. As I recall, they were advanced. But it could have been two teeth. The car ran rather well in spite of this. Everything was happy when the car was re-timed.

Of course, this was an L engine. The P.O. of my wife's '92S had a timing belt jump which took both his cams 2 teeth forward, and the interference of pistons with valves resulted in a spun rod bearing, 8 valves needing replacement, and a trashed crank.

Just for reference.

08-15-2009 04:30 AM
Rick1803 “Timing mark(s) confusion” , 08/15/09, update


The engine seems to run fine.
I have not yet removed the old belt.
I can NOT find a scribed line on the flywheel (face).

When the marks on the cams line up with cam caps:
- HOLE in flywheel outer edge matches bell-housing line
- #1 piston is NOT yet at TDC
- pointer is 5.5 sensor teeth BEFORE line on front pulley
- (NOTE: 5.5 sensor teeth = 34 degrees; 34 degrees = 2
teeth on the timing belt crankshaft sprocket)

When the scribed line on front pulley DOES match pointer:
- #1 piston is at highest point, TDC
- cam lines are BEYOND cap lines, they do NOT line up

Template showed 69 and 72.5 when cam marks lined up, but
- front pulley line 5.5 away from pointer, NOT at TDC!

Based on: front pulley, cam marks, #1 piston TDC:
- I think the current belt was installed incorrectly
- incorrectly installed using flywheel HOLE to line up


1. Did manual originally say “line up hole on flywheel“?
2. Should ALL timing marks line up when #1 at TDC?:
- front pulley; cams; flywheel;
3. Could engine run with cams advanced?
- I think timing belt off by 2 teeth on crank sprocket
4. Has anyone heard of this error before?

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