| Author |
Message |
Phil Hughes (Ferrarifixer)
Junior Member
Username: Ferrarifixer
Post Number: 134
Registered: 7-2003
| | Posted on Monday, September 01, 2003 - 10:06 pm: | |
Tight clearances will go out of (under) tolerance sooner than loose ones, due to the nature of valve seat wear being faster than valve gear wear (on direct ohc ferrari engines).
Setting all valves to their upper tolerance will mean longer intervals between adjustments....especially on new engines that settle in faster than a bedded in engine. |
Andrew A. Illes (Andyilles)
Junior Member
Username: Andyilles
Post Number: 189
Registered: 10-2002
| | Posted on Monday, September 01, 2003 - 9:23 pm: | |
The reason for running a tight clearance is that you gain "free" duration... ergo, Philip's LeMans numbers. For that reason, I like to set intakes to the tight limit. On the other hand, exhausts should be on the loose side for the additional cooling time on the seat, as Bill, Rob and Phillip all note.
There is no real "harm" in looser settings. Contra, be mindful that clearances narrow as valves/seats wear, so tight settings can get to the point where the cam-lobe heels actually keep the valves open, with the results Rob suggests.
The "book clearances" are fine. I'd suggest the tight limit for intakes, opposite for exhausts.
Best regards,
Andy |
Philip Airey (Pma1010)
Member
Username: Pma1010
Post Number: 401
Registered: 7-2002
| | Posted on Monday, September 01, 2003 - 8:57 pm: | |
Jeff
When setting up my 308 with P6 cams, the reason Bill cites was exactly the logic for staying with stock operating clearances. FYI, the data we had (for the LM car) had tighter clearances. |
rob guess (Beast)
Member
Username: Beast
Post Number: 280
Registered: 5-2003
| | Posted on Monday, September 01, 2003 - 8:56 pm: | |
Jeff;
If your clearances are too loose you will have a ticking sound come from the engine. With too little clearance you run the risk of having the valve burn and the valve seats become pitted. your cranking compression will also decrease.
Rob
|
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 522
Registered: 5-2001
| | Posted on Monday, September 01, 2003 - 8:48 pm: | |
Jeff,
If clearances are too tight on an exhaust valve, it will loose some cooling potential so the valve will run hotter. |
Jeff Green (Carguy)
Member
Username: Carguy
Post Number: 492
Registered: 10-2002
| | Posted on Monday, September 01, 2003 - 8:42 pm: | |
All the anguish I'm experiencing over valve clearances has got me wondering. Just what would happen if the clearance is too big or too small? I can see if clearances are too small that the valve opening and closing events take place sooner and later respectively. And the opposit is true for too much clearance. But what does it "do" to the engine? Does it reduce power, increase emissions? |