Technical Valves/head

[JakeF]

Hi,

Today I finished the top end. Cleaned the carbon deposit(dont know if the right word) from burning chamber and valves. All smooth and clean now.
I have a top end gasket set with 4 o-rings for the valves?Autobooks says that o-rings is fitted only on the intake valves? Haynes does not mention this one( or am I wrong)?

Where actually does the o-rings must be mounted? And in every valve or just inlet, old ones only on inlet valve, they were snapped.
Just wondering the meaning of this o-ring. Should it seal the valve and guide? If I mount it around the valve the seal goes up when the rocker pushes the valve down(valve opens)?

:idea:

 

[jjacob]

Jake,

Answer is here:

http://www.fiat500club.org.uk/clubchat/viewtopic.php?f=1&t=7168&hilit=valve+seals

John

 

[JakeF]

Thanks. This was clear, only on inlet (in the groove) because exhaust valve is hotter and needs cooling.

One more question to head/cylinders. The original pistons are not flat at the top of the piston. There is a higher area on the center of the piston maybe 5-10mm high and 10mm wide? The 499cc aftermarket pistons are flat? More compression?

 

[jjacob]

Sounds like higher compression aftermarket pistons. Have you measured the bore of the cylinders? There is an aftermarket kit that fits the 110F block without modification that increases the bore to 70mm (from 67.4mm) and also raises the compression ratio.

I believe that there are high compression pistons available for all of the bore sizes:
67.4 = 500cc
70.0 = 540cc (aftermarket kit)
73.5 = 600cc
77.0 = 650cc

John

 

[JakeF]

Took off the cylinders today. In both pistons the upper piston rings were snapped. Also some dry marks on the pistons. In the piston it is marked 68 mm.
Guys, what do you suggest? I planned to buy the whole kit, ~250€ all.
I can't find this kind of pistons which I now have, all are flat ones

Is this kit ok, does it work with standard head?
http://www.fiat500ricambi.com/fiat500/Engine+parts/MO1035

Some pics of the pistons

 

[jjacob]

Jake,

That kit would be correct as the standard, original pistons and cylinders. The compression ratio will be lower than the pistons that are currently in your engine, so the standard pistons will make less power. I don't think I have ever seen pistons that looked like yours.

If you want to rebuild the engine, but not want to do a lot of machining to make a bigger engine, I would be tempted to use the 70mm kit. This kit supposedly will bolt right in, raise your compression ratio and increase your engine to 540cc. I have no experience with this kit, maybe someone else can comment on it.
http://www.passione500.it/index.php?route=product/product&path=37_104&product_id=571

There are a variety of suppliers that offer this 70mm kit.

I don't know your mechanical ability, so please do not take offense at my comments. You need to determine why the piston rings cracked, and the pistons are scuffed. To me they look like either low oil pressure or overheating or both.
Low oil pressure can be caused by a worn oil pump, worn crankshaft and bearings. Overheating can be caused by low oil pressure, or a non-functioning thermostat for the air cooling flap.
Seeing the condition of the pistons, you will need to inspect the camshaft and crankshaft for wear, as well as the valves and valve rocker assembly.
Hope this helps,
John

 

[JakeF]

Thanks again.

Took of the oilpan and checked the camshaft. Looked fine to me, no scratches or worn. Same for the rockers, looked fine to me and everything was oily. Also the pushrods, their both sides were fine. The oil and filter was also clean.

It's weird thing that the pistons are worned only at the other side. There were a quite lot carbon also on the lowest(oil rings)piston rings.
Tryed to google these pistons, no matches. Can these be too big/wrong ones?
Anyway, I think I'll go with the 499cc kit. Enough for me and like to keep it standard.

Thanks alot!

e: have not much experience of 4-stroke engines. Checkin valvels and timing belt chages+normal service for my Ducati I am common with but never stripped down a 4-stroker. Intresting and cool.

More common with 2-strokers, stripped and rebuilded Vespa engines and mopeds. My 133cc rotary Polini kitted Primavera got more power(+18hp) than my 500F. That's fun to ride I'd say.

 

[JakeF]

Ordered the 499cc kit plus gaskets etc from John recommended sit. Good prices, 219€ the cylinder kit

Jake,


If you want to rebuild the engine, but not want to do a lot of machining to make a bigger engine, I would be tempted to use the 70mm kit. This kit supposedly will bolt right in, raise your compression ratio and increase your engine to 540cc. I have no experience with this kit, maybe someone else can comment on it.
http://www.passione500.it/index.php?route=product/product&path=37_104&product_id=571

John

 

[Bambino]

The arrows on your rather odd pistons are both pointing the correct way, so that shouldn't have caused the wear.

Chris

 

[JakeF]

Ok.
Haynes says the conrod nuts must be replaced with new ones if unbolted? Guess how forgot to order these . They are not re-usable?
Maybe a stupide question, are they some special stuff or normal nailon nuts?
And am I right that no washers, in critical components when the right torque is used no washers?

e: The topic has expanded abit I am sorry.

 

[jjacob]

Jake,

Most automotive engines require that you replace the connecting rod bolts when they are removed. This is because they are designed to stretch when torqued. This is a one time only stretch!
Order new connecting rod bolts and install them with some high strength thread locking fluid on the threads (like Loctite Red). Make sure to use a torque wrench when installing.
Make sure pistons and connecting rods are installed facing the correct way.
John

 

[jjacob]

Looking at Jake's pistons again and considering the broken top ring, I am going to say the engine experienced severe knocking /pinging (not sure what you call this in Europe), or even detonation because of high compression ratio and low octane gas. This would also explain the damage being limited to the pistons and cylinders.
John

 

[JakeF]

John,

I will do this, new nuts in list. It's kind of weird that the engine worked fine(to me). Always started at first(cold/warm), idles well etc etc. Maybe abit slow on small hills, top speed 95km/h.
The lower rings had also much carbon on it and were also abit jammed. The same on burning chamber and valves(and stems).This can also be a reason.

Dont know if this have happeded during my time, believe not. Have owned the car only 1 summer.
Anyway, I will check the engine carefully now .
The bodywork is restored quite well, the engine is original...i believe.
Thanks!

 

[JakeF]

John,

Do you mean that I need new bolts+nuts or just nuts?

Can't find on fiatricambi or other sites these. Do you remember the size and thread?

some of these self locking nuts?

http://www.fiat500ricambi.com/zoeken/?zoek=nut

 

[jjacob]

Jake,

You need to replace both the bolts and nuts. They are available at this supplier:
http://webshop.fi500.com/en/search/query?desc=on&sdesc=on&keywords=103787

They are also at this supplier. They call them piston bolt and piston nut.
http://www.fiat500vdlaan.nl/en/webshop.php?CategoryID=6

The nuts you showed are not correct.

John

 

[JakeF]

Unbolted the conrods from the crank. The bearings were in good condition, no marks of wear etc. I looked also closer to camshaft, no wear .

 

[JakeF]

Im starting to rebuild the engine end of thin week. Just asking for sure about the o-rings in the intake valves. The red arrow in the picture, does it show the correct place for the o-ring? In the bottom of the groove under the cup locks?

 

[Toshi 975]

That groove is where the collets fit in order to hold the valve, spring & valve cap in position. The o-ring pushes further down the valve stem and plays a kind of floating role.

 

[JakeF]

Ok. Thanks.

 

[JakeF]

Re: Engine rebuild, Valves/head

Got the cylinders fitted, all fine. Next step is to fit the head.

Btw. How to open the bolt which is inside the oil slinger, need to change the gaskets+seals. How to lock the flywheel?