Thanks for the year of the color up-date FFR.
Good question Bill, heres why.
By the way, in explaining how/what/why I'm doing this rebuild I'm trying to walk the line between being "to technical" and "to simple". My 15 year old is one of those people following this adventure!
The old camshaft was a solid roller lifter cam with BIG duration but the "lift" is pretty much the same as my new cam (flat tappet) will be. The OLD pistons were .030 below the surface of the block, the new ones are right at being even (zero deck height). The pop-up portion of the old piston was not really a factor in valve clearance because of the "fly cut" valve clearance area similiar to the new pistons.
So whats REALLY changed is the new pistons have moved UP in the bore by .030. That reason alone would be enough to worry about valve clearance, but theres more!
Cam's are not always exactly what the manufacturer say they are. Thats ONE good reason to "degree" your new cam, just to make sure it IS all that the cam man said it was. You could "assume" the new cam is OK and you would be right 95% of the time, no worries! But "what if" it isn't? Are you willing to risk your HIGH DOLLAR side oiler? I'm not! I WILL degree my cam and I WILL check the valve clearance.
Now let's say you want to "advance" or "retard" the cam (via some kind of adjustable gear). This dramatically alters the relationship of "piston and valve" timing events. A cam installed "straight up" will clear, but advanced (or retard) and it might cause the valve to kiss the piston!
A two step process then. "Degree" the cam to make SURE of advance\retard\straightup AND check valve clearance in those positions. That way, if you want to change cam gearing later, you KNOW it will be OK (or not)!
My Comp Cam is all ready "factory set" for 4 degrees "advance" even when I install it "straight up". Thats just the way THIS cam is designed, I'll verify that with a degree wheel later in the build.
Advancing the cam increases lower rpm response while sacraficing some high rpm performance. I'm doing a "street" motor where that low end grunt takes your breath away!
