Tuning Valve Clearance

[Idleboy08]

Dear Fiat Forum

I have got a 1973 Fiat 500R with a standard 594cc engine. The car hasn't been running great recently, so I decided to do a bit of routine maintenance, including checking my valve clearances. I did have a look in the Haynes Manual but the information didn't look that clear. Anyway, I've set the gaps at 0.004 for the inlet and 0.006 for the exhaust. The car does seem to be running 100% better and felt great on a short test drive.

However, have I got the spaces correct?

Any advice or guidance would be very much appreciated.

Idleboy08

 

[Toshi 975]

If you have a 500R then you should have a 594cc engine and those valve clearances sound a bit tight to me but do not have a manual to hand as baby sitting

 

[Idleboy08]

You're correct - it is a 594cc engine! Any advice on the correct clearances would be appreciated.

 

[fiat500]

If you have a 500R then you should have a 594cc engine and those valve clearances sound a bit tight to me but do not have a manual to hand as baby sitting

I always have my manuals to hand, even when babysitting. But Master Toshi is right as always. :worship:

The 594 clearances are same as the 652;

Inlet: .0078" (.20mm)
Exhaust: .0098" (.25mm)

Hope that helps,

Peter

 

[the hobbler]

According to the Haynes "Book of words", the valve clearances on the 594cc engine is (set COLD)---Inlet;-0,20mm---exhaust:-0.25mm. Setting them as tight as you have could lead to them not allowing the valves to shut correctly when hot.

 

[BambinoClassic]

Can I jump in and quickly ask if there are differences in the exhaust and Inlet clearance for a 500 D engine? I set mine to 0.15mm both inlet and exhaust, I hope that's correct.
Sounds a bit tappety when cold but gets smoother.

 

[the hobbler]

According to the 'factory' "book of words", 6th (0.15mm) is correct for the 500D engine (type 110D)--set COLD--both 'in' & 'exh'. When I was doing my apprenticeship (on M/Benz) we always did tappets (also set cold on M/B, because "how hot is hot?") 1st thing in the morning. I will concede that this was a few years ago when quality cars were normally in for more than 1 day for a full service.

 

[F123C]

I reckon there's a safety margin built in to the manufacturer's figures for valve clearances so in theory it should be possible to set them a little smaller.

How cold is 'cold'? I'm sure it varies with ambient temperature so maybe there there should be 'winter' and 'summer' settings plus maybe another for in between times. :devil:

How hot is 'hot'? I've measured valve clearances when the engine is fully hot just to see what clearance remains. Generally about 1 1/2 - 2 thousands of an inch (0.0375 - 0.05 mm) remains, presumably to allow for an engine getting abnormally hot on rare occasions.

I've known Mechanics who set the clearances 1/1000 inch (1 thou.)(0.025mm) smaller, some even set them 2/1000 inch smaller, but I suspect they like living dangerously!

Reducing the valve clearances is a little like fitting a 'hotter' cam - the valves open earlier, close later and are lifted slightly higher. (by tiny amounts)

However , reducing valve clearances also reduces the amount of time that the valves are closed. This is especially important in the case of exhaust valves which can only lose heat when in contact with their valve seats. So to avoid burning valves and seats, I would agree with all the posts above which recommended using the manufacturer's figures.

To those who have carefully set their valve clearances and think their engine still sounds a bit rattly, there may be wear on the part of the rocker arms which contact the tip of the valve stems. This takes the form of an indentation which gives you a false reading when you set the clearances using Feeler Gauges.

If you're a perfectionist (I'm not) you can set the valve clearances using a Dial Test Gauge, or measure the adjuster screw thread pitch and calculate the number of turns required to achieve e.g. 6 thou. (0.15mm) clearance, screw the adjuster down to remove all clearance, then back-off the adjuster by the required number of turns and lock it up.
There used to be be a tool available in the U.K. which set the valve clearance by measuring the no. of turns of the adjusting screw from zero clearance, iirc it was sold by a company called SPQR?. (long time ago!).

Easier to remove the rocker shaft and dress down the rocker pads to eradicate the indentation, then just use Feeler gauges as normal.

Al.

 

[F123C]

According to the 'factory' "book of words", 6th (0.15mm) is correct for the 500D engine (type 110D)--set COLD--both 'in' & 'exh'. When I was doing my apprenticeship (on M/Benz) we always did tappets (also set cold on M/B, because "how hot is hot?") 1st thing in the morning. I will concede that this was a few years ago when quality cars were normally in for more than 1 day for a full service.

Ah! the Good Old Days!

When Mechanics were given enough time to do a thorough job and cars had grease points, none of this 'lubed-for-(a short!)-life' carry-on!

AL.

 

[Idleboy08]

Thanks for the advice guys. I've re-set the tappets to the recommended clearances and little Flossy is running a 100% better. She is so much quieter and has also stopped 'dying' when running hot. The difference is like night and day....

Thanks again.

 

[fiat500]

none of this 'lubed-for-(a short!)-life' carry-on!

AL.

I disagree with that Al. The Fiat 500's mechanical "Achille's Heel" has to to be the kingpins which obviously can and should be greased regularly. I know the greasing arrangement can possibly be improved, but they still only seem to last five minutes when you drive regularly. In comparison, the steering balljoints are technically sealed for life but as you can replace the rubbers, on my car they are the 48 year-old originals. I have a friend with a pre-sealed-for-life 1920's Morris which he maintains meticulously and which seems to need a hour's maintenance for each hour of driving. Even the Fiat 500 probably gets fifteen minute's inspection/maintenace for every full day of motoring.
My (even the gearbox sealed-for-life) 2009 Citroen has done 125,000 miles and apart from several sets of brake discs and pads, wheel bearings and top suspension strut bearings, it has needed no maintenance and other repairs apart from oil and filter changes and it definitely doesn't need a weekly "once-over".
Despite all that praise...give me the high-maintenance Fiat 500 any day.