Technical Valve clearances Punto 1.2 8v

[pastamasta]

Hello, I'm proceeding nicely with the head refurb on the punto my brother gave me, so much more fun when you don't need the car the next day!!!

Head has has a light skim and looks like new, the valve were in good nick so we're just removed, cleaned and lightly lapped back in, the petrol test revealed no leaks.

I have just checked the valve clearances ( in the comfort of my warm kitchen! ) and amazingly they are all within tolerance. Obviously some are closer to the edge of the tolerance than others, I have swapped 2 around to bring them closer to the centre of the tolerance but one exhaust valve is right on its upper tolerance and I wondered if it was worth buying a shim or am I wasting my time as I imagine it will only get tighter as the valve settles?

 

[Brendan W]

Ours were all still in tolerance at 110k miles - never had to touch them.

 

[bluejohn125]

It depends how far the tolerance is out compared to the other exhaust valves. If you're doing it properly and at your leisure then why not get the right shim... for that engine they should be easily and cheaply available from Fiat, or your local engine centre.

I had my Tipo's head refreshed a couple of years ago (different engine but still SOHC with shims)... when the head went back on the mechanic didn't do the clearances (he said he did..) and the car just wouldn't run right. This summer I finally decided that the clearances could be the only remaining reason for the bad running / misfire, so I went right through them checking and they were wrong with some being really tight. Went through them again with the mechanic swapping around and adding new ones, and got everything correct. The engine runs great now...

But I don't see how you can really check them off the car... you put the cylinder head on first with the main bolts correctly tightened, then put the cam carrier on that with its bolts tightened, then you connect the cambelt to the cam sprocket. After that you can turn the engine and check the clearances.

How can you join the head and cam carrier tightly together in your kitchen and spin everything round?

 

[pastamasta]

I have ordered a couple of shims and then they will all be close to the centre tolerance.

Blue John maybe you are thinking about a 16v head? With the 8v the cam is just held on by 3 cam retainers held on by 6 bolts the main head bolts merely hold the head on the block. I used a gator rubber strap wrench around the cam pulley to rotate the cam........easy!

 

[bluejohn125]

OK so the camshaft on the 8V FIRE fits straight on the head, and the head bolts down as one piece. The 16V is quite different, it has a cam carrier on top of the head but in addition it has hydraulic tappets so no shims or adjustments needed.

Hopefully you'll have a sweet little engine when it's all back together. And a damn sight less complicated and "clever" than the latest evolution of the FIRE 1.2 8V that is surviving in the current 500s and Pandas.

 

[pastamasta]

Hello again fellas, we'll all the valve clearances are now pretty much spot on the middle........manky old engine, blue printed head ha ha!

Yes bluejohn hopefully it will be sweet as it was quiet and sweet with a ropey head on it! Just waiting for a dry weekend to pop it back on the block, not in a rush so not stressed.

I've never done a modern ( in my world ) water cooled engine mainly old air cooled British motorcycles so I have a few questions.


1. I presume the gasket goes on dry, no sealants etc.
2. I have an accurate snap on digital torque wrench and I understand the torquing sequence and the angle torque at the end. In my experience I would always leave around 1/2 hr between the operations to allow the head to settle.
3. My main question however regards the head bolts as I understand they are the 'stretching' type. With older engine designs I have always slackend the bolt in question and then retorqued it. Is this ok with this type of bolt as I presume it only stretches in the last torquing operation ie. The angle at the end.
4. I was always taught never to oil the bolts as this can result in over torquing.

 

[Brendan W]

Gasket goes on dry.
Never waited between torque, angle , angle and never seen a requirement for it on water cooled cars.
They are stretch and it's recommended that they be replaced. I have reused them one time only and not had trouble. Never backed off a car bolt before carrying on.
Oiling is not required and in theory they go back dry. Good luck with that . I have put them back less than perfectly dry with no issues. You are angle tightening which takes the oil issue out of the equation.

It's not clear from your post but there are two angle stages after the setting torque is applied.
Modern gaskets, even airhead bikes, are faced with sealer so traditional sealing practices can do more harm than good if the added sealer reacts with the gasket. That said I had a bad surface on a cylinder base gasket on an aircooled bike recently and I used spray aluminium paint on the gasket as insurance.
Obviously this is for fibre and not mls gaskets.

 

[bluejohn125]

Yes just follow the standard procedure for torqueing and rotating the stretch bolts, they are reusable once at least. Check that the head gasket is the right way up etc, so that no flows are obstructed.

With a slight head skim, the valves reseated and the clearances adjusted all should be well hopefully.

 

[pastamasta]

Ok fellas, seems straight forward.

Regarding backing off the bolt before a re torque, I never used to do it until I did the head on my 750 triumph and the very knowledgable blokes on the forum introduced it to me. But thinking about it only one torque figure is given so the second torquing is to take account of the gasket settling, the increasing torque values and the angle takes care of this automatically?

Also the methods were different depending on wether you use a copper or composite gasket.

 

[Brendan W]

.............. and the angle takes care of this automatically?
Also the methods were different depending on wether you use a copper or composite gasket.

Pretty much. The torque is set to produce a stretch of a certain amount. That assumes a known roughness or friction in the threads and under the bolt heads. Hence the fretting about oil on the threads allowing too much stretch for the same torque. By putting on two 90 degree steps the bolt will get stretched half a pitch one way or the other. If they have gone plastic you will feel it as the load will stay constant or even fall off as you go to complete the angles.