QUOTE(rick 918-S @ Nov 28 2007, 11:14 PM)
I'm using a Mercedes Key. I had to grind the half moon flat but it fits the slot width fine.
I'm having a friend (mechanic) stop over tomorrow. I'm freaking myself out over this silly cam thing. I don't know why, I used to drag race and built lots of BBC's But tonight I just walk away from it. This thing is costing me big. I'm afraid to start it now. I checked everything 4 times so I'm sure everything is good to go but... just needed to vent a little here.
Rick - a lot of guys, even mechanics, don't really know how to check piston to valve clearance. I do, and if your problem is right at TDC, it most likely wouldn't be #1 hitting but the companion cylinder (the one at overlap). Additionally, it won't be right at TDC, it will be just before when it is chasing the intake or just after as the exh valve chases the piston.
Companion cylinder = at TDC at same time. So, for firing order, split in half and lay above each other, the ones that line up.
So, say firing order on a SBC 18436572
1823
6572
companions are 1 and 6, 8 and 5, etc. So when 1 is TDC, #6 is TDC during the overlap events. #6 is where the valve to piston clearance is an issue. Just write out your firing order and do same thing - the one under #1 is where you want to measure if you are around TDC FIRING of #1. When you are "180 out", you are trying to fire #6 when both valves are open.
If you really want to be sure, either get what is known as a checker spring (a simple spring that is easy to depress by hand and htere just to hold the valve up) and a dial indicator. Put the checker spring on #1 intake - or if the valve stem seal will hold the valve up, just forget the spring - and get to about 120 degrees (so you are coming up on "180 degrees out"). You should have the rocker on to follow the cam and a dial indicator on the retainer or right above the valve stem on the rocker arm will do.
Now, with your degree wheel on, check the piston to valve on the intake by pushing the valve down 'til it hits the piston and look at the indicator. Should be a bunch, if it even touches the piston at all. Go 10 degrees, should be less, go another 10 and check.
You should find that the tightest clearance is not TDC but before it. Go back to that 10 degree increment and go 1 deg at a time and measure until you find the tightest value. YOu need at least .080" to be safe on the intake - the alumimum heads buy you a little extra too so you could be tighter, maybe down to 065" but I wouldn't recommend that. Now, at TDC (180) or just after, the exh valve should start to open. Measure clearance at TDC on the exh, go 10 degrees, measure again blah blah until it starts increasing again. Go to where the tightest and move thru that 10 deg increment 1deg at a time and find the tightest amount. You want a minimum of 0.100" on the exhaust. I would prefer to see you have 080 int and 120 exh. If you are less than that you will probably bend a valve. If you are half those values, you will bend a valve for sure.
Best of luck - be safe, not sorry, it is much better to be gun shy than drunk and waving the thing around
That takes a long time to type but an hour at the most in practice if you have a spring remover that you can use with the head on the motor. If you need to verify what I mean, just PM me and I will shoot you my number. I check this during the day when work doesn't get in the way of my pleasure
edit - it's late and I just proofread AFTER posting. Big mistake. I got the valve events backwards and that is probably obvious. The piston chases the EXH at overlap (pushing out hte gases) and the INT chases the piston (to suck in the charge). So check exh on the way up and int on the way down. The method is the same of course.