Technical First drive and a problem

[124BC1]

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I'm not at all impressed with the belt tensioner set up, for me very basic and agricultural. I definitely don't like the floppy pulley on the stud until the nut is tightened, they bush the i.d. of the bearing but they don't bush to the stud . . . or am I missing something?

The stepped washer I mentioned fits into the bearing/bush recess and moves with the bearing as the adjuster plate is pivoted to tension the belt, then the heavy washer clamps everything tightly when the 10mm nut is tightened. I've never heard of any issues in service with the standard arrangement.

Are you sure you have the correct stepped washer fitted and that the adjuster plate is not distorted, or that the long 10mm stud that holds the adjusted to the cyl. block isn't bent? I assume there's no play in the t. bearing? It does seem to have a lot of what looks like cast-off grease? on it's front face.

When the belt is on the tensioner bearing, are both sides of the belt pressing equally hard against the bearing - my thinking is, if the adj. plate isn't sitting square to the cyl. block for some reason, the belt will press harder on one side, encouraging the belt to run offline.

Can you get a straight edge/ steel rule positioned across the tensioner bearing outer race and see if it lines up correctly in 2 planes to e.g. the cyl. block or the crank pulley?

(in the past, prior to dropping off a cylinder block for machining, I always removed the long 10mm tensioner mounting stud to avoid a possible problem)

 

[GBGraham]

A prize? Mmm.
I know, how about a free membership of *I.F.R.A.?
You're welcome.

Yes, probably best to remove the components of item 4 if you can't sort out the 8x1.00mm thread to your satisfaction - you wouldn't want anything becoming detached and caught up in the timing belt.

Despite your distributor being exhaust cam driven and the fitting of an electric fuel pump, the auxiliary drive shaft still has an eccentric on its end to drive the originally fitted mechanical fuel pump - it's this eccentric that can collide with the con rod big end of no. 2 cylinder - that's why I pointed out the correct positioning of the auxiliary drive pulley when fitting a timing belt to avoid this possibility.
{Iirc, this fuel pump eccentric was omitted on the 2 litre engines as they had all gone over to electrical fuel pumps by this time.}

Here's some pics of the aux. drive shaft, firstly showing the eccentric (arrowed in red) and secondly showing a modified aux. drive shaft with the eccentric removed.

View attachment 487742View attachment 487741



* In case you were wondering...
IFRA stands for International Fiat Renovators Association

(P.S. I made this up )

Cheers for the heads up on this, I will check where it is positioned. As for the M8x1.0 I feel my only option to make it good is to helicoil.
I realise there isn't a load of meat on the casting but do you feel it needs to be a pitch of 1.0 or could it go to a more popular 1.25?
IFRA may be in jest but in this moment you are well qualified to put such an idea into motion

 

[GBGraham]

The stepped washer I mentioned fits into the bearing/bush recess and moves with the bearing as the adjuster plate is pivoted to tension the belt, then the heavy washer clamps everything tightly when the 10mm nut is tightened. I've never heard of any issues in service with the standard arrangement.

Are you sure you have the correct stepped washer fitted and that the adjuster plate is not distorted, or that the long 10mm stud that holds the adjusted to the cyl. block isn't bent? I assume there's no play in the t. bearing? It does seem to have a lot of what looks like cast-off grease? on it's front face.

When the belt is on the tensioner bearing, are both sides of the belt pressing equally hard against the bearing - my thinking is, if the adj. plate isn't sitting square to the cyl. block for some reason, the belt will press harder on one side, encouraging the belt to run offline.

Can you get a straight edge/ steel rule positioned across the tensioner bearing outer race and see if it lines up correctly in 2 planes to e.g. the cyl. block or the crank pulley?

(in the past, prior to dropping off a cylinder block for machining, I always removed the long 10mm tensioner mounting stud to avoid a possible problem)

The stepped washer is correct and it initially came apart as such. Yes I also noticed the grease but put it down to the rebuild for some reason, is it possible this could have been repacked?
The adjusting plate was definitely flush with the block and if there is any doubts I will change the tensioner bearing.
In total agreement on removing the tensioner stud and spring, but questioning the 10mm mention

 

[GBGraham]

We used to go out on breakdowns Monday morning, car will not start, husband gone to work , we look at car and ask wife has any one touched it, answer no!
Open bonnet , new spark plugs , new contact points wrongly assembles and going straight to earth!
Ask wife again and she sheepishly replies husband may have done a "service" on car, thinking, after all it is so easy if the "oily rag" down at the garage can do it then a highly intelligent like her husband would have no problem!!!

Nothing worse than tracing or tracking down a fault when a manmade one is thrown in the equation, then they complain about the excessive labour charge, tuff I say they should be truthful

 

[124BC1]

Cheers for the heads up on this, I will check where it is positioned. As for the M8x1.0 I feel my only option to make it good is to helicoil.
I realise there isn't a load of meat on the casting but do you feel it needs to be a pitch of 1.0 or could it go to a more popular 1.25?
---------------

I thought you said you wouldn't be able to install a helicoil for reasons of access and your left wrist issue?
But helicoil inserts are available in the size M8x1.00mm and in various lengths (I checked!).

If this was my job to sort out, at home, without access to professional engineering facilities, this is what I would do :-

1) If possible, I would obtain an 8 x 1.00mm thread tap, preferably a 2nd rather than a taper or plug version and run it through the thread in the block, then check with a mirror + light to see how the thread now looked. If the thread cleaned up well, I'd obtain a new bolt of the correct length and install it.

2) However, if the thread didn't clean up so well, I'd obtain a longer bolt which would then protrude through the rear of the threaded boss on the cyl. block, install it (including the tensioner spring components) and then put a locknut on the protruding thread at the rear of the boss, to allow proper tightening and prevent it loosening. (I don't think there is enough space to screw the longer bolt/setscrew in from the rear and fit the locknut at the front)
(for the uninitiated :- a bolt has a plain section then a threaded section, a setscrew has threads the full length, i.e. no plain section)

3) If however, the thread in the block looked very dubious after using the tap, I might drill out the thread, insert a bolt (it now wouldn't have to be an 8x1.00mm) from the rear through the boss, and secure the spring components with a locknut (Nyloc or similar). Ideally, the *rear of the boss* should be faced-off flat and parallel to the front block face to accept the bolt head and you might also need to relieve one or 2 flats on the bolt head a little to get it into position. Note, the coils of the tensioner spring are held in place by a bolt, not a stud.
*Rear of boss* is arrowed in red in pic:-

As regards changing the thread pitch to 8 x 1.25mm (seeing as you have a suitable tap and 8x 1.25mm bolts are readily available)?
If you take, for example, over a 10mm length of thread - an 8x1.00mm bolt would have 10 threads (obviously) and an 8x 1.25mm bolt would have 8 threads, so I'd imagine a lot of mangled threads - the 8x1.25mm tap could only correspond exactly with the existing 5th and 10th threads of the 8x1.00mm threaded hole in the block.

One thought that did occur to me was to perhaps run a 5/16" UNF tap through the 8x1.00mm threaded hole and use a 5/16"UNF bolt and nut.

5/16" = 7.94mm ; tapping drill size is 6.90mm BSI recommended, but BSI alternate size is 6.80mm. 8x1.00mm tapping drill size is also 6.80mm.
5/16" UNF has 24 threads per inch (1" = 25.4mm), 8x1.00mm has 25 threads in 25mm, or 25.4 threads in 25.4mm or 1", both threads have a 60* angle.
So, existing mm thread has 25.4 tpi, new UNF thread = 24 tpi, pretty close, might just work.

I reckon this might be a better option than to run a 8x1.25 tap through the existing thread.
But, of course, I don't know your situation as regards availability of UNF taps, bolts and nuts, maybe there's a garage that caters for classic British cars near to you? If you do opt for UNF, you might leave a note for the next person to work on your car to avoid confusion. (I always check the bolt
head markings when working on old cars )

 

[124BC1]

The stepped washer is correct and it initially came apart as such. Yes I also noticed the grease but put it down to the rebuild for some reason, is it possible this could have been repacked?
The adjusting plate was definitely flush with the block and if there is any doubts I will change the tensioner bearing.
In total agreement on removing the tensioner stud and spring, but questioning the 10mm mention

It is certainly possible that the tensioner bearing was repacked with grease, even if a new bearing was being fitted, some prefer to add a little more, as often there's very little in a new bearing. These bearings usually don't give any trouble, most just replace them as a precaution, if there no rock in the bearing and it sounds smooth when *spun, I'd just wipe off the excess grease and re-use it. (*Iirc, new tensioner bearings don't spin due to seal drag).

The 10mm stud I'm referring to is the long stud that projects from the front block face and carries the tensioner bearing/adjuster plate, it's also the stud over which the stepped washer and heavy washer are fitted - it's 10mm thread diameter and takes a 10mm nut (17mm spanner/wrench size). On Fiats, bolts are sized by the thread diameter not the head/spanner size e.g a 6mm bolt has a 10mm head/spanner size, 8mm bolt = 13mm head/spanner size etc.
I always removed this long stud before submitting a cyl. block for machining, it sticks out c. 50mm and could potentially be damaged if left in situ.

 

[GBGraham]

I thought you said you wouldn't be able to install a helicoil for reasons of access and your left wrist issue?
But helicoil inserts are available in the size M8x1.00mm and in various lengths (I checked!).

If this was my job to sort out, at home, without access to professional engineering facilities, this is what I would do :-

1) If possible, I would obtain an 8 x 1.00mm thread tap, preferably a 2nd rather than a taper or plug version and run it through the thread in the block, then check with a mirror + light to see how the thread now looked. If the thread cleaned up well, I'd obtain a new bolt of the correct length and install it.

2) However, if the thread didn't clean up so well, I'd obtain a longer bolt which would then protrude through the rear of the threaded boss on the cyl. block, install it (including the tensioner spring components) and then put a locknut on the protruding thread at the rear of the boss, to allow proper tightening and prevent it loosening. (I don't think there is enough space to screw the longer bolt/setscrew in from the rear and fit the locknut at the front)
(for the uninitiated :- a bolt has a plain section then a threaded section, a setscrew has threads the full length, i.e. no plain section)

3) If however, the thread in the block looked very dubious after using the tap, I might drill out the thread, insert a bolt (it now wouldn't have to be an 8x1.00mm) from the rear through the boss, and secure the spring components with a locknut (Nyloc or similar). Ideally, the *rear of the boss* should be faced-off flat and parallel to the front block face to accept the bolt head and you might also need to relieve one or 2 flats on the bolt head a little to get it into position. Note, the coils of the tensioner spring are held in place by a bolt, not a stud.
*Rear of boss* is arrowed in red in pic:-

View attachment 487776



As regards changing the thread pitch to 8 x 1.25mm (seeing as you have a suitable tap and 8x 1.25mm bolts are readily available)?
If you take, for example, over a 10mm length of thread - an 8x1.00mm bolt would have 10 threads (obviously) and an 8x 1.25mm bolt would have 8 threads, so I'd imagine a lot of mangled threads - the 8x1.25mm tap could only correspond exactly with the existing 5th and 10th threads of the 8x1.00mm threaded hole in the block.

One thought that did occur to me was to perhaps run a 5/16" UNF tap through the 8x1.00mm threaded hole and use a 5/16"UNF bolt and nut.

5/16" = 7.94mm ; tapping drill size is 6.90mm BSI recommended, but BSI alternate size is 6.80mm. 8x1.00mm tapping drill size is also 6.80mm.
5/16" UNF has 24 threads per inch (1" = 25.4mm), 8x1.00mm has 25 threads in 25mm, or 25.4 threads in 25.4mm or 1", both threads have a 60* angle.
So, existing mm thread has 25.4 tpi, new UNF thread = 24 tpi, pretty close, might just work.

I reckon this might be a better option than to run a 8x1.25 tap through the existing thread.
But, of course, I don't know your situation as regards availability of UNF taps, bolts and nuts, maybe there's a garage that caters for classic British cars near to you? If you do opt for UNF, you might leave a note for the next person to work on your car to avoid confusion. (I always check the bolt
head markings when working on old cars )

Thanks for your thoughts #124BC1. I didn't say I couldn't I think I said it was the last thing I wanted to do in situ but at the moment it isn't necessary if I'm not leaving the tension spring assy in place, so it's a job for another time when I get helicoil kit. I have UNF taps and dies but not nut's and bolts to hand here in metric land, strangely there is even a 9mm in the set but I have to my knowledge I have never come across this before.
I also feel that at sometime in it's life this bolt must have been loose because the first few mm lead in there is quite a wobble on the stud.
My business, all my workshop equipment and stock got sold off before we left to sail the seas for 8 years only retaining what was in my tool chest and what be useful on a yacht and since coming back on to land I have had to replenish vastly but at my time off life does find this pointless sometimes so if and when I do helicoil it will be probably be M8x1.25 because I deem M8x1.0 as a pointless purchase for one thread.
There is also the possibility I may get an Allen bolt in from the rear and use a lock nut, I am always cautious around cast lugs as it can be not very forgiving for other than intended.

 

[GBGraham]

Congratulations - you've just managed to find the only 8x1.00mm thread on the entire engine (afaik).

It shouldn't be a stud, it should be a bolt.

I've checked and RiAuto don't list it but Autoricambi list it in stock. Here's the page:-
(there may be other suppliers or perhaps a good engineering suppliers, idk the bolt length but you could work it out from the components it holds in place and add say 10mm for the length, it's a standard Fiat '80' type bolt which afaik is metric 8.8 grade, so nothing special)
Also shown on the page is a kit of parts for attaching the tensioner to the engine incl. the stepped washer that seems to be missing from your engine:-

View attachment 487707


The very early engines didn't have a spring loaded tensioner, it was necessary to attach a spring balance to a hole in the tensioner bracket and exert a pull of 60 lbs to set the belt tension, later engines, such as your's has a spring to tension the belt. (the spring end actually goes into the hole that used to be used for attaching the spring balance).
The tensioner is locked in place after belt adjustment by tightening the long stud (10mm) that passes through the tensioner bearing and the bolt with the odd 2 x hex shapes that acts as an abutment for the tensioner spring and the pivot for the tensioner mounting bracket. The 8x1.00mm bolt only holds the tensioner spring in place, in fact, once the belt tension has been set, I reckon that the 8x1.00 mm bolt, its washers and the spring and it's spacer could be removed and left off the engine. (all you'd be doing is reverting to the earlier tensioner arrangement without the spring).

Here's a pic of the tensioner spring mounted on the 8x1.00mm bolt - there's not a lot of room to work on it. (and your twin carb manifold makes access even worse). You might be able to get an 8x1.00 mm tap (if you can find one, it's an odd size) in from the front to clean up the thread.

View attachment 487706

The stud that passes through the centre of the tensioner bearing/bracket should have a stepped washer fitted (as you surmised, for support) topped by a heavy washer (iirc, c. 6 or 8mm thick) and a Belleville washer (a type of dished spring washer favoured by Fiat, you'll see these in various sizes all over the car), and then a plain nut. Here's a diagram from the Haynes manual showing the tensioner components:-

View attachment 487704

Here's a pic of the original pulley marks to be aligned when installing a timing belt (I know you have non standard adjustable cam pulleys fitted) but note the auxiliary drive pulley has a timing mark/small hole - I've marked it with a red dot in the approx. position - this is what is mentioned in the text above about setting the aux. drive pulley to 34* from the 12 o'clock position (= approx 3 teeth on the circumference) - this is to prevent the fuel pump drive eccentric on the auxiliary drive shaft from making contact with the big end of no. 2 cyl.

View attachment 487705

Okay I have managed to helicoil for the cambelt tensioner retainer. Just a query, one of your pictures seems to show two large washers to either side of the springs spacer but all the parts list show only one to the outer side, a worthwhile mod or just ignore

 

[bugsymike]

Personally looking at the picture from @124BC1 at #45 I would use both large washers as they locate the coil of the spring to guide/align it to the tensioner and also keep the spring coils from rubbing the aluminium of the cylinder head.
I could only find this from a Fiat Regatta which is not very clear apart from the outer washer.
Actually when you zoom in it does show a large shiny washer behind the darker coils of the tensioner spring so both washers n place.

 

[GBGraham]

Personally looking at the picture from @124BC1 at #45 I would use both large washers as they locate the coil of the spring to guide/align it to the tensioner and also keep the spring coils from rubbing the aluminium of the cylinder head.
I could only find this from a Fiat Regatta which is not very clear apart from the outer washer.
Actually when you zoom in it does show a large shiny washer behind the darker coils of the tensioner spring so both washers n place.

Thanks for the info and I should get my own manual in a little more than a week . There wasn't an extra washer on, this is why I am asking because these are conflicting pictures

 

[bugsymike]

Thanks for the info and I should get my own manual in a little more than a week . There wasn't an extra washer on, this is why I am asking because these are conflicting pictures
View attachment 488398

Can you offer it up both ways and see which looks right to you.
I assume you have the spacer (51) that sits inside the spring coils, presumably that stops the coils getting compressed, but does it rely on the design of unthreaded part of the bolt?
As usual I am only offering an idea/thought as no recent knowledge.

 

[GBGraham]

Can you offer it up both ways and see which looks right to you.
I assume you have the spacer (51) that sits inside the spring coils, presumably that stops the coils getting compressed, but does it rely on the design of unthreaded part of the bolt?
As usual I am only offering an idea/thought as no recent knowledge.

Nothing wrong with offering #bugsmike and in the sense of engineering I should and will find and fit an inner washer on what I class as a very poor initial design bit I'm sure it won't improve it.
Another thought for you or anyone that cares to throw into the ring, I've managed to trace the camshafts to be Colombo and Bariani race medium profiled camshafts ,
1 x FB.114.300C.A
1 x FB.114.294C.S
my question is do you think this will put extra stress to the standard cambelt

 

[bugsymike]

Nothing wrong with offering #bugsmike and in the sense of engineering I should and will find and fit an inner washer on what I class as a very poor initial design bit I'm sure it won't improve it.
Another thought for you or anyone that cares to throw into the ring, I've managed to trace the camshafts to be Colombo and Bariani race medium profiled camshafts ,
1 x FB.114.300C.A
1 x FB.114.294C.S
my question is do you think this will put extra stress to the standard cambelt

I have no knowledge of those camshafts.
My only thoughts in that direction was years ago working on new and nearly new Mazdas, compared with English cars of the time they seemed more responsive/powerful for a given engine size (we used to joke their horse power readings were higher as they had smaller horses.) However what I felt was the cam lobes were more aggressive and whether it was that or the longer length the timing chains ran on OHC engines, but we had many issues with high timing chain wear and modifications down the line from single row chains, double row chains hydraulic tensioners , ones with five tooth, ones with seven tooth and so on.
So in a roundabout way what I am saying is a high profile "sporty" cam may put more strain on the drive gear, whether chain or belt driven in my "humble" view.
Another view may be that race type profiles usually encourage the engine to breath better at higher rpms so another source of higher wear?

 

[s130]

Following parts image for the Strada / Ritmo Abarth 2000cc engine may be of interest. Many of the parts are common across the twin cam engine and you can note all the parts numbers.

 

[GBGraham]

Following parts image for the Strada / Ritmo Abarth 2000cc engine may be of interest. Many of the parts are common across the twin cam engine and you can note all the parts numbers.

View attachment 488406

Thanks so much, this is enlightening to the issue of is there or . . . . ,