308 valve clerance

Hmmm Good Question. It requires a sensitive "feel" using feeler gages and measuring clearances. From what you measured you do know your clearance is within the 0.20 - 0.25mm range. In my view this is acceptable. If there was a slight drag when inserting the 0.2 gage then I would change the shims as needed. But from what you've shown I think your fine. Let's hear from the more experienced out there....please let us know.

 

If it were on the exh side id open it up,its an inlet so you will be ok,
if you drive the engine very hard then you must ajust it,

cheers
Dale.

 

It's a judgement call I think. But Dale's statement for the extra clearance on the exhaust side is very sound. The idea is that since the exhaust valves experience more heat than the intake side, there is more material expansion reducing the clearance during operation. Also the more clearance allows more heat transfer time from the valve while against the valve seat. Mechanics have told me that they will set the exhaust clearances as close to the max as they can get. It's a lot of work for a valve that may be technically okay clearance-wise. I also agree with Dale in that if you are going to drive the car hard, adjust the valves to maximum allowed clearance on the exhaust side. The intakes if in spec are fine. But if you drive the car on the street and occasionally whip on it a bit, but rarely if ever track the car, you should be fine as long as your in the factory specified range. It really is up to you since it's your car. In my opinion if street driven then within spec is fine, if tracked than max exhaust clearance needed.

 

If its a lose 0.30 by the way you describe it, you should be ok,
try to take into account how hard or not you drive the engine,
with tappet clearances its a good idea to keep records of the gap's,then in future checks it gives you a idea whats going on with valve and seat wear,
leave it and run it on good fuel,

cheers
Dale.

 

I talked to Dema Elgin (the cam grinder) about this when getting a set of cams repaired. He opined that one of the reason the lobes wear is that people don't change the shims and over time the shims become dish-like, albeit the clearances measure fine. We then looked at a cam lobe. Sure enough, we could see the tell tale wear marks (horse shoe pattern on the lobe) and once through the hardening, the lobes disappear v. quickly. His advice was to replace all shims with new ones when doing the 30K valve adjust.

On the "where should you aim to get them", presumably Ferrari thought the posted tolerances were acceptable. However, a bit more seat time on the exhaust valve will keep it cooler and more clearance rather than less will achieve this.

Last, as you probably know, the exhausts in paricular tend to tighten over time as the valve hammers itself into the seat.
HTH
Philip

 

That is what I do, I replace all of the cam seals during a valve adjustment. Make sure to write down all valve clearances before pulling cams out. ALOT easier when cams are out of the way, no compressing to mess with. Recheck valve clearances on reinstallation of cams though.
Process very similar to Lambo engines as most or all of them use the shim underneath the tappet cup.

 

I got my valve adjust tools from GT Carparts: 623 780 2200, I think I paid about 80.00 for them many years ago. It works well for the Ferrari.