Had to remove distributors today. Put them back in and checked the timing. It had been set at 0 by the last mechanic that built the motors. Is this ok?

What engine?? What year?? Carb or EFI ??
If it is a mid to late 90's Merc 454 efi, then the initial timing in BASE TIMING MODE with a scan tool should be set to 8 degrees.
With Merc ignition, you must have a scan tool to set it properly. The engine must also be warn and running at 1800 rpm while being set. Hope that helps. I imagine the carb version is the same.

These are GM 502 crates, carberated with prochargers.

With superchargers, forget about initial timing. You just want to set total as per prochargers specs. That will depend on boost, CR, and octane. Check with procharger before you run it or you might melt a piston.
My guess is that you're running a standard V8 Merc Thunderbolt ignition module. This would give about 26 degrees of total advance with about 0 initial. 26-28 degrees total is pretty common on SC engines.
If your idle sucks or the plugs foul out, you can switch to the V6 module. This will give about 10 initial and 26 total.
Gary

Contrary to what's been said, I believe that initial timing is important. Don't worry about what Pro Charger says because they don't know your particular motor. However, I can guarantee you that if you do ask them they will tell you the following:

A Pro Charger motor that has advance in the distributor your initial should be set at 8-12*. The amount of advance you have will decide that factor due to the amount of total you'll get because of the advance.

You CAN run a PC motor with full advance (32-36*) without detonation or problems, WITH THE PROPER SET UP!
There are many factors that come into play with what can be considered the "proper set up".

To answer your question directly; No. I would not try to run initial timing at 0.

Feel free to email or PM if you'd like I'll get you set up the best way possible.

DAVE

If you find that you want to run a merc v6 module to get plenty of initial timing, I just went to locked timing and have my v6 module availiable. Let me know if you need it.

I think the GM crate motors typically run 8.75 or 9.6:1 CR and iron heads. 32-36 degrees is probably not a good idea unless you've got 100+ octane fuel.
my $0.02
Gary

I ran 35* total with 8.6 static 7# of boost with iron heads on Sunoco Ultra 94 octane. Initial + MSD advance of 25.
According to the computer dyno I was making AROUND 850 hp out of a crate 502.

In the beginning of this year I ran 9# and 31* total (same set up)(10+21) I was gonna increase it to 33*(12+21) but never got the chance...I sold the boat. If I could have gotten it tuned in to get my full rpm range the computer said around 900hp.

When I removed the heads the chambers and piston heads were in perfect condition. NO signs of detonation.

Like I said, there's alot of factors that go into the "proper set up" which I obviously had.

Gary, you are right on the money when it comes to roots blowers. PC's are a different animal however.

DAVE

Dave F
Damn, 850hp! Was that a blow thru carb system or EFI?
BTW, I wouldn't call yours a "proper set up", more like an "exceptional set up".
Gary

It was a single 800 holley carb done by Nickerson.

Stage 4 Pro Charger.