Why so much inital timing???

mopowers said
Just looked at the cam card. IVC is 39* @ .050". Since advertised duration is 275* and @ .050" duration is 231*, does that mean seat IVC is 61* (275-231/2 + 39)? I recalculated SCR again based on notes in my file. Looks like it's right at 9.7:1. Heads are 65.2cc, Pistons are speed pro L2316 with a -7.5 cc volume and are .015" out of the hole. Gaskets are 521SD felpros with 4.18" bore and .054" compressed thickness for a quench distance of .039".

The carb on it now is a 85670 Holley 670 street avenger. It's on the small side since the throttle bore and venturi sizes are the same as an 1850, but I've also got a 650 proform double pumper with throttle bore and venturi sizes of 1-3/8 and 1-11/16. I've also got an old 4-corner idle 4779 to try as well.

Thanks.
I don't think you have the static compression you think you do based on the piston choice. Best bet would have been using the 1" downfill method and measuring the volume to calculate static ratio. That piston has a lower top ring, and tapered "flat" top so there's more wasted volume than typical math might account for. The intake valve closing can be anything really. I wouldn't assume the ramp is designed such that your math works for it. I've always used the KB site calculator. If I use tht and add a couple ccs for the dead space I'm coming up with 9.3 static, 8:1 dynamic. Given you have the big bore, the huge gasket (not sure what that was needed there), and the dead volume around the piston, the timing lead is probably warranted. I would have done things differently myself but that's neither here nor there. If you want to know why, in my opinion that's why: excessive volume in the chamber. I will never, ever use a vacuum gage to set timing either so we're already taking different approaches to performance. But someone posted this sentiment early on: if it likes it, run it.