>>>*Morning!
I just answered your email privately, but I will add some more here.
The 261C is actually our middle cam design if we use the "small, medium, large" method most suppliers use.
I probably manage to confuse folks on that since the actual advertised duration figure is meaningless. In fact, that can't even be measured, it is a computor generated number.
What matters is the difference in degrees between theoretical and actual @ .050" lobe rise. Plus the most important event, the intake valve closure point.
Simlarity between the very nice TRD designs and ours ends at the point where they look alike and bolt in.
The 268C/Torkr is 50 degrees, the 261C is 39 degrees. That TRD is 48 degrees. Thus the 261C is a much faster early rise ramp than the 268C, so we expect it to have a mild chattery idle.
Add in a very free flowing header, and other mods?? Yep, the idle at stock setting starts to get sloppy.
Fix that by speeding the idle up a bit, make sure the added manifold vaccum isn't making the EGR bounce.
4 Crawler beat me to the leak possibility, check for that too.
Now if the old head had been surfaced, of course that effectively retards the valve timing. Power moves up the RPM scale, add in a mellow intake ramp and a crossflow design like that TRD1 is?
Yep. Smooth idle and late powerband.
You can tune most of the bouncy idle quality out of her, or you can just grin at the folks sitting next to you at the stoplight when they turn to look at you if you like the way she runs.
Of course you could just stick that TRD back on there if it isn't worn, you might like it better, driving style is different with everyone.
*It won't hurt my feelings any.....*Snif**.... <img src="/forums/images/graemlins/lol.gif" alt="" />..
Bet if you do it now should be smoother with much lower end than before with the old stock head.
Here is a neat rrick to smooth her out some, just increase the valve lash to stock settings, .008" and .012". There will be more tappet noise, that is harmless, but this effectively reduces duration. She should noticeably smooth out..
*I hope this makes sense?....*EB
