Cam / Bucket valve clearances

According to the factory shop manual the range is as follows:

Intake: 0.15-0.20mm
Exhaust: 0.25-0.30mm

Measured with a cold engine. Ideally at 21 degrees Celsius

Hope this helps

 

At the sake of being repetitive it bears mentioning that the torque specs on the cam bearing cap nuts as listed in the repair manual are way off. I dont have my manual here but it is too high....they strip easily and it will happen. Others here know the correct specs and can chime in. Jim Selevan clued me in and saved me a ton of trouble on this.

 

inlet 0.18/0.20mm
exhaust 0.28/0.30
nothing else

 

What is the explanation for the differences between the specifications for the valve clearances i.e. 'shim to cam' in this thread of respectively Nuvolari (08-04-2014) and Rosso Corso Motorsport (08-07-2014)?

The differences are small but for these critical clearances still relevant.

Are these different specs for a different year, serie (L/M/E) and/or local temperatures?

 

The measurements I quoted are straight from the shop manual so I cannot comment as to where Peter got his measurements from. Regardless, the differences between our values is so very little that it would not make an appreciable difference in the real world.

 

moreover you can only get shims in 0.05mm thicknesses so as long as you are within the spec then it doesn't matter.
Aim for midway and that gives you some tolerance

 

I have never seen a Ferrari with this narrow a spec. Impossible to achieve unless custom sized shims are available.

 

Factory specs will work fine. I prefer proper inch measurements.

.006" - .008" intake

.010" - .012" exhaust

The 6mm nuts should be tightened to 78 inch/pounds.

 

so you mean i do the impossible, that is good LOL, i always set the clearance to this spec, there is a good reason for not set to 0.15mm

 

0.006 and 0.010 is to tight for a dino Engine, a good enginebuilder know that

 

Is that because at .006 and .010 as the valves and shims wear the tolerances tighten up say heading toward .005 and .009?

 

You have no idea whether it is or not.

If you prefer a bit looser that's okay but beyond that forget it.

 

No it isn't. Works fine.

 

are you sure about that

 

As sure as you are not.

 

that was a very well educated answer from a US man

 

Technically, besides the banter, I for one would really like to know specifically the issue at hand in an educated manner, via which we would all stand to benefit.

Are the techs willing to share this?

Thank you all.

Regards, Alberto

 

The numbers I gave are right from the factory manual.

As a general rule valves should be set with enough clearance to insure they always close fully but not so much that performance is lost and they become noisy.

 

The proper valve clearance is determined by a number of issues and 2NA spelled out a couple. In addition every solid lifter cam grind has a very slight and gradual ramp prior to the actual lifting ramp whose job is to close the gap gradually to prevent excessive noise. Staying within the factory specified clearance numbers allows that feature to function correctly.


Ferrari is pretty smart about engine design and in the days prior to government intervention it was an extremely rare situation when staying within their guidelines caused any problems.


I work on a world record holding land speed record car. If I wandered around Bonneville telling engine tuners they needed to hold valve clearances to that narrow a spec they would be very amused.

 

Whenever i do the shims on my car i check the gap and to get it into factory spec i buy the next higher or lower shim to acheive this and end up with what this gives me. As far as i am aware i can only buy shims in 0.05mm increments. Once the engine warms up to operating temperature then this gap will close up considerably, what you dont want is everything to expand and bind up...that will be disastrous.

To work in much smaller band then you need shims to be much smaller and as far as i am aware they dont exist.

So imho work to factory spec and you cannot go to far wrong. I have been doing this to my car for the last 14 years and all ok so far.

I think Peter is thinking more racing applications which is probably correct for the work he does.

 

I have Dino parts high lift camshafts. they recommended 0.20mm both inlet and exhaust. I would be grateful if anyone had any experience or comments on this
Nick

 

The gap is measured when the cam lobe is pointing up so I think it would still need to be as per factory recommendations.

Don't think both would be the same as the exhaust gapping would need to be a tad bigger.

 

For the reasons above if the cams were ground intending that specification to be used that is what you need to use.