365 GT/4 2 +2 valve clearance adjustment

"check clearance" does not mean it will be off in such a reduced time-frame. Aside from the flat tappets, there is also a long timing chain that stretches and needs to be adjusted. Incorrect valve clearance and timing will make the car noisy and sluggish (massive loss of dynamic compression): definitively not what Ferrari wanted for their most expensive car.

The manufacturer back then was probably more conservative on the maintenance schedule compared to the cheaper cars. I would be curious to know if the recommendation for the Daytona and BB were less stringent?

 

Your mileage (pun intended) may vary... Got my car at ~50.000km and the valve clearance was badly out of spec. By contrast when I dismantled my engine at close to 100.000km the clearance had not significantly evolved. The chain had stretched though. My brother's 365 was also totally out of spec at 60.000km, whereas the engine had been fully rebuilt at 50.000km (the owner who got the car during this period was careless). All in all depending on how you baby the car the valve train will behave vastly differently, but it's clear that with proper maintenance you could expect to drop the valve-covers much later than 15.000km.

On a side note only the timing chain does require a visual inspection whereas out of spec valve shims are easy to "ear". So unless you've got some rattling Spanish castanets in your engine, I would not immediately drop the exhaust camshaft covers. Removing just the timing chain covers and the inlet camshaft cover should be good enough for a 15.000km inspection. From then on if the timing and clearance are dubious on this side you may decide (or not) to remove the exhaust side (which is holds the carbs/injection ancillaries and is a pain to remove).

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On the 412, they recommend to check valve clearance every 30.000km, that's a significant difference compared to the 365. Here are a few reason I could think about :

The 365's redline and max HP are at higher rpm than the 400. Also the 365 cams are much more aggressive than on the 400 (carb) which in turn is more aggressive than 400i/412 (these last two do use the same camshafts with a different timing offset). Aside from camshaft duration and overlap, there are no lift figures provided in the O.M, but I would assume that the lift on the 365 is much more important judging by the size of the valve recess.

Here is a 400i we used to have with standard Borgo pistons :
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These pistons are used on the 400 carb, 400i gen1, 400igen2 and 412 (except that the 412 uses the second oversize).

Here is my own car with 365 pistons (the reason I have such pistons on a 400i is a long story). You can see that there is provision for additional lift.
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More lifts and more rpm means more wear on the valve-train... At the end of the day these 365 are just as powerful as a 400 carb with less displacement so you've got to accept a bit more maintenance.

As far as the chain is concerned, there was a discussion long ago on the subject: improper timing means a loss of 30psi! If you want these engine to run at their best, you have to adjust the timing sprockets frequently (every 15.000km is not a bad idea).

 

I dont have specs in front of me but Ferrari is pretty consistent in what they do ratio-wise. The 365 has a shorter stroke so to achieve a ratio of what I assume is 8.8:1 then the dome is higher than what would be found in a longer stroke 400 engine. The relief size is a by-product of the higher dome, not cam-lift related. And on the subject of valve reliefs, the exhaust valve relief isn't needed under normal operation, its only there in case an engine is over-revved and experiences substantial valve float. When doing a piston to valve clearance check the exhaust valve is hundreds of thous away from the piston.

 

Both GTC4 & GT4 do share the same WSM and owner manuals (texts are identical, only the illustrations do differ), so the 15.000km recommendation is actually based on the reduced history of the (fragile) GTC4. The recommendations for the early (1979) 400 are even more conservative : 12.500 / 25.000 / 37.500km ! So the early engines had to be monitored a lot. By contrast the 30.000km on the 412 is backed by significant evolution coupled with 2 decades of experience on this engine.

As @Newman suggested these engines do all deliver 8.8:1 except for the 412 ( 412 > 9.6:1 , 400i gen 2 > 8.8:1 , 400i gen 1 > 8.8:1 , 400 > 8.8:1 , 365 GT42+2 > 8.8:1 , 365 GTC4 > 8.8:1 ). Also @Newman is (certainly) right on the lift... I only have a couple of photos from long ago, but it seems that aside from the longer skirts, the 365 pistons do have a slightly higher dome. So the bigger relief could indeed compensate this and not necessarily the lift.

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Here are all the evolutions that were made to the valve-train:

The 365GT4 2+2 already had a few upgrades compared to the GTC4
1) More beefy chain tensioner (365GTC4 had an automatic one),
2) Anti-starvation flaps in the sump (implemented on the later 365GTC4)

So one would expect the 365GT4 to require a bit less surveillance than the GTC4, but it seems the factory had to further enhance the engine timing. These are the evolution that occurred after the 365 :
1) Bigger timing sprockets (implemented on the later 400, some early 400 carb do have the small ones for sure)
2) More aggressive camshafts lobes on the 365 compared to the 400 (the O.M states there is more duration)
3) 365 could run on SAE 40 oil... (did not help on cold startup)
4) higher rpm on the 365

Not sure these explain why one engine has to be checked every 12.500km whereas the later one only need an adjustment every 30.000km. In any case retrofitting the late 400 timing sprockets in a 365 would certainly make sense, as well as using the 10w50 oil recommended for the 412.

 

So what we really need is real world data on these engines. How much adjustment is needed after 12,500 or 15,000 KM?

 

One difference between 365 GT4 2+2 engine and 400 engine is located in the Timing Controls, the 2 free wheeling sprockets are 21 teeth for the 365 GT4 2+2 and 19 teeth for the 400 (smaller diameter). I ordered by mistake the 400 type free wheeling sprocket for a 365 GT4 2+2 engine believing it was the same for all 365/400/412, as a consequence the timing chain tension could not be adjusted (excessive amount of slack)...

The timing chain is supposed to be the same on all engines 365/400/412, so I assume the dimensions of the timing system are different between the 365GT4 2+2 and the rest of the series.