Attention: Engine Experts

Hello John,
The 400GT manual I have seen has the same clearances as the 365gtc4 but the 400i manual has the larger clearances.

Regards,
Terry Phillips

 

Age-old adage is that loose valves will never cost you money...

... tight ones will!

You should be comfortable setting them to the loose end of the spec for your chassis (365 GTC/4). You'll never notice any difference in performance.

 

But loose ones wil cost you horsepower.

 

But, which is more easily afforded; who are you racing and what is the prize?

 

Polution control was taking over.

 

I'm with Randy. A little "clicking" is cheap insurance (you'll probably not notice the difference unless you're standing there with the hood open).

I also doubt you'll notice any performance difference.

Split the difference and set them carefully to the tight side of the looser spec.

 

Actually, if you are in tune with your car you will notice the improved engine response of the tighter settings, at least with the inside plug engines. However, overall engine heat increase-- which can be a problem for some.

john

 

I fail to see what is insured when expensive parts are clicking against each other. I always use the smallest values given by a manufacturer. They already include a safety margin and I never drive my cars particularly hard for a long time. Best wishes, Kare

 

Clearly, you have a thorough understanding of the subject at hand. Good on you!

 

I know what is being referred to but it still is like wearing a condom when walking on the street. The values given by manufacturer always include a safety margin, and that margin safely sure as hell covers how these engines are driven today! Best wishes, Kare

 

You know this how?

Vintage Ferrari documentation frequently contains questionable data particularly when translated into languages other than Italian.

 

I guess if it "feels" better it must be. LOL

 

I think you need to know a bit my information. For instance the lift and duration of the cams used in the two different models. Historically Ferrari used different cams for pollution controlled cars and cars without pollution controls. Since 400s were never officially imported they could have very different valve timing specifications?

 

the valve clearances for the single cam V 12s hasn't changed much over the years. The 250/330 engines are intake.006"[.15mm] exhaust .008"[.20 mm]. I have just received the Jim Riff book "ferrari 250/GT Service and Maintenance. I recommend it as a primer for the mechanicly inclined but experienced lacking ferrari mechanic. The "how to" instructions are as basic and clear as you can get and the supporting drawings show it all. I would like to hear comments from anyone who has used this amnual. Is it as good as it appears??? Tongascrew

 

One thing worth mentioning is that the clearance setting of a given valve isn't always an absolute. So, for instance, if you set an intake valve exactly at 0.006, rotate the roller some and gauge the gap again, in some cases your clearance will increase or decrease. This variation is due to the out of roundness of your roller. It's not enough to warrant replacing the roller, but it's enough make the feeler gauge "feel" the difference.

I guess the moral of the story would be that if you'd like to set your valves on the tighter side to keep this little nuance in mind.

john

 

Set your C/4 valves to the looser spec. We had a 400 that was set at the tight clearance (cannot remember exactly, I think .006 int, .008 exh) and the car never ran well. We loosened them to .008-.009 intake and .010-.012 exhaust and the car runs and starts much better and you still cannot hear the valves!