Mossy66

I have the MSD Atomic EFI on my engine which allows me to change timing and AFRs by pressing a few buttons.
The engine is a 489 with Brodix race rite rec port heads at about 10.3:1
Factory '66 L72 aluminum rec port intake manifold.
Factory '66 exhaust manifolds feeding 2-3/8" flow path side pipes.
Tremec 5 speed.
Hydraulic roller cam. 224/234, .578 lift 109 sep.
850 rpm idle.
15" vacuum at idle.
AFRs set to 14.5

Right now I am running with 26 degrees initial with about 12 degrees of vacuum advance. With the computer controlling the vacuum advance, the idle timing is about 35 degrees. Total advance is 37 all in at 1800 rpm.

My question is, why is this working for me when the consensus is 18-20 initial? Balancer is new and lines up properly with the timing marks.

Thanks
Gerry

427Hotrod

It's not unusual. Think about all the folks who run around on the street with timing locked at 36-38*? I haven't played with the MSD system...I'm assuming it has a cranking retard feature maybe that is helping it crank?

I like all the initial it will stand..sure makes it responsive!

JIM

Mossy66

Jim,
No cranking retard, although you can set the timing curve starting at 500 rpm. That lets you use a lower advance at cranking rpm, and still bring the timing up aggressively to be all in at 1500 rpm at the earliest. I don't do that though, and I have no problems with hot starts at 26*. Maybe I can use more?

What determines all the initial it will stand? Bucking against the starter on hot starts?

Thanks,
Gerry

MelWff

My guess you are getting away with 26 due to the characteristics of the camshaft. Not knowing what the intent of your car is, isn't the all in by 1,800 low for anything other than drag racing, more typical would be all in by 2,800 to 3,000.

Mossy66

Actually, I think I was getting away with 26 because of the leaking intake gaskets that I discovered on our last trip to Arizona and New Mexico. It was puzzling to everyone else on the trip. If I kept the rpm below 2k, it used no oil, but over 2k, it used a quart on every tankful of gas, but didn't smoke! So the engine is out now, and it looks like the fix will be to deck the block. That will make the intake fit better, as well as even out my deck heights which are all over the place on the odd side. The pistons on the even side are consistently at .012" in the hole.


Gerry

babbah

IMO 18-20 initial advance with that cam is too much. Sounds more 12-14 should be good with your setup.