I am in the process of putting together a.030 over 502 with a Comp cam XE268h cam and adjustable roller rockers.. Every thing else is stock .The engine is a 1997.. I have run the engine on blocks of wood to make sure of no leaks, but it don't seem to idle smooth. No codes shown I have MEFI scan and I noticed that when idling the spark is erratic. Plus 6-8 degrees to minus 4 degrees. Is this normal? Bob at MEFI BURN says it is but it don't seem right to me? Anyone else see this before? I haven't flowed the injectors but I'm looking for a good shop to do this also. Thanks Paul

Have you checked for vacuum leaks?

Yes I have
none found
I tried a new map sensor hooked to a mightyvac to simulate a steady source of vacuum and no change

Yes it's normal
My MEFI 1 on the 502 did same thing. Pulled it during repower to MEFI 3 and it does similar

Send you injectors to Smitty (member articfriends)

What your seeing is the "spark stabilization" adding and subtracting timing to keep the idle on target. Yes, I flow and clean injectors as part of my full time business so you can PM me if you have questions, Smitty

PM sent Thanks Guys for the answers, I would have never thought the timing would jump around like that. i thought it had a vacuum leak as the IAC is at 0 when idling. but it appears that the locktight in the minimum air setting has been broken loose. The manual don't go into the minimum air setting so I'm not sure if it is correct Any Ides on this?
Thanks Paul

Thanks Smitty, I'll get the package together today. I did a little search of your posts and learned something pretty quick, I tagged the oil lines when I took this engine apart and just went and looked at the routing on my engine. It seem the oil lines where backwards on the oil filter when i got this boat.. Glad I found this before I got the engine in the boat. Thanks

Little search of his posts ?
lots and lots and lots if good stuff

Smitty, Package should be there Wed. Thanks Paul

Smitty, he'll do ya right