Ignition timing with SCJ heads

Had a 533 on the dyno today with Ford SCJ aluminum heads. First time we've had these heads on the dyno. Engine is going in a truck, not sure on the intended use, maybe street plus mud or something. Had a Weiand dual plane intake and a hyd roller cam so obviously not an all out drag motor. Ran on pump gas. Made 650 hp at 6000 rpm and 640 torque so a nice healthy pump gas combo.
Interesting thing was the engine builder recommended 34 degrees of timing which seemed too much to me. We ran it at 34 since that is what the engine builder wanted but then we dropped it to 30 degrees total and pick up almost 20 hp. Engine builder was surprised.
If it was my engine I would've played around with the timing a bit more. I've heard that the SCJ head might make even more power at 28 or 29 but we didn't have the ability to do any additional testing. We do have a 521 with SR71 heads up next on the dyno and we will have more time with that engine. The 521 is a more serious drag race engine so we'll try a full timing sweep on it. I think we'll start at 27 or 28 with the SR71 heads and then add a little bit to see what happens.

Start low and give it what it wants, the chambers are pretty good on both those heads and the typically do not require a lot of timing.

I have never seen the aluminum SCJ's, (even with low compression), want more than 31 degrees total; usually less.

Good to know, I'll pass it on the engine builder who brought this engine to us. He said that he had been setting his SCJ builds at 34. We hadn't run them before but I'd seen some info posted on line about those heads working better with less timing.

I’ll be watching this thread for updates. My SR-71 headed 521 is getting completed in the next month or so. Are you running a Dominator on gas or Alcohol?

We are running 112 race gas. Shooting for 12.8 AFR but might be a little lean at the moment. The widebands on the dyno read 13.1 on the last pull but they can't always be trusted. The EGT was in the 1250 to 1300 range so should be okay. Plugs look okay, might be a little lean. Not much color on the plugs yet since we've only made a couple of full pulls.

What camshaft is in the engine ? Duration / lift ?

I don't know what cam was in the SCJ engine. Another shop built the engine and dropped it off for testing. Didn't give us the specs.

Get your degree wheel out and plot the cam if the lobe numbers aren’t stamped on it.