[VintageLambo] Re: Engine manual, Camshaft timing

Nash, It appears that "Crane Cams" are more conservative than I was in my clearance recommendation. However measuring at 15 degrees is more relevant for "colder cams" and the exhaust valve to piston clearance actually increases by advancing the (exhaust) cams. I found my old Excel spreadsheets on the summary of the Power/Torque vs. cam advance simulations as well as on finding the angle for minimum valve-piston clearance (older Excel version and quite small, 100kB). These are mostly numbers and graphs with no comments, therefore can be hard to read, but I will be happy to post them if there is interest and someone, Fred? Jack?, can tell me how. Best regards, Laust --- In VintageLambo@yahoogroups.com, "nashbap " wrote: > Laust: > > Thank you for clarifying the settings. > > For those who are interested in this discussion, the minimum piston > to valve clearance recommmended is 0.10in. for the intakes and > 0.12in. for the exhausts as per the Crane Cam website to be checked > 15 degrees before and after TDC in the overlap zone; presumably for > Detroit iron. > > Regards, > > Nash > > > > --- In VintageLambo@yahoogroups.com, "lgpdk " > wrote: > > Nash, > > > > That is right, I used 6 cam degrees (=12 crank degrees). I ran the > > simulation for the standard cam setting for the engine and was > > encouraged by seeing the shape of the curve being close to what has > > been published. At that time I was also encouraged to see that the > > peak HP was close to 350 HP. I then increased (and decreased) the > > cam timing individually, I think up to 8 cam degrees and found that > > the 6 degree advance on both cams provided the best result without > > almost no side effect, except the risk of valve piston > interference. > > I then calculated difference in valve piston interference (0 to 6 > > deg cam advance) to be 1 mm. With that knowledge I measured the > > actual cam – piston clearance (I have forgotten what it was) and > > decided that it was safe to take 1 mm out (and I stand by a prior > > statement that a final .060" clearance should be safe). I used cam > > centers as the parameter to adjust, which takes the valve-lash > > uncertainty out of the measurements (you don"t have to question > what > > valve lash is assumed for the quoted 32/64 inlet opening/closing). > > In the case of the inlet the cam center would be (32+180+64)/2- 32 = > > 106 ATDC. Since the cam top is flat, the center is found as the > > angular mean between same height between a rising and falling edge. > > Using cam centers pre-supposes a symmetric motion as a function of > > cam (and crank) angle, which I strongly believe is true and > > certainly did not have contradicted in the results I got. > > Since I did many things to the car I cannot separate this effect > > form others, but I certainly am very impressed with its low-end > > torque. It effortlessly and smoothly motors uphill (around Laguna > > Seca Golf Club) in 5th gear with four people at 1000 rpm. The > > smoothness I am sure is helped by the fuel injection which does not > > require high air-flow to get good fuel spray. > > > > Best regards, > > Laust > > > > > > --- In VintageLambo@yahoogroups.com, "nashbap " > > wrote: > > > Hello: > > > > > > I recently finished reviewing the engine rebuild manual on the > 400 > > GT > > > site and was extremely impressed with it. Jack, this is excellent > > > work. Congratulations and Thank You! Laust, your work on the > > Espada > > > is equally impressive. It takes courage to do the changes that > you > > > effected. > > > > > > You mention that you have advanced each cam by 6 degrees (approx. > > 4 > > > vernier holes). I am thinking of trying out the same on my Espada