timing issue on '85 Iroc
 

ok, the other dayi pulled the valve covers on my 85 Iroc, hoping to find the cource of a rattle upon acceleration under load. From what ive read, here and other sites, most likely its loose rocker arms, several were semi-loose so i figured id adjust them all again and see if it solved my issue, BUT now i have another issue. I set the motor to TDC according to the timing pointer on the motor and the rotor points to where #8 terminal is on the distributor. I didnt touch the distributor at all, i just took the cap off. From past experiences, TDC should put the rotor pointing at about the back drivers side of the carb, this is now pointing at the back passenger side of the carb. So right now im stumper as what to do. The car ran with how the wire were currently setup so im not gonna start moving wires around. The other thing that i noticed was that the timing tab is in a different spot than where im used to it being on previous SBCs ive worked on. The others you could see the tab right next to the power steering pump, but on this motor, you have to look down through the middle behind the water pump. If the Tab was where im used to seeing them, it would put the rotor at #1 terminal and then everythign would be fine. What do you suggest i should do?

ok, i did more research, and found out somethign i honestly didnt know, GM actually had 2 different locations for the timing tab and TDC, from reading dozens of posts on TGO, this is what i got, "apparently sometime in the late 70s/early 80s they switched from the 2 o'clock TDC position to the 12 o'clock position" but thats not true from lookign on summit and on tpi cars i have here, but anyways . so i have the 12 oclock TDC setup timing cover on my 85 BUT that still doesnt explain why at TDC my distributor points at #8 terminal, UNLESS the balancer was changed at one point and is for a 2 o'clock TDC position. if i put on a aftermarket timing tab, and set the balancer mark at the new TDC mark, it would be pointing at #1. And the car ran great before, so i know it cant be off one whole terminal. To figure this out for sure, i'm going to get a piston stop tool and find out true TDC this week, and ill also buy a timing tab on a hunch, and if true TDC is actually at the 2 o'clock position, then it should all work out.

maybe just the timing cover on my 85 was replaced with the wrong one... i guess once i use the piston stop tool and do all that, then ill know for sure.

I was jsut about to say that about hte timing cover. I put a chrome one on once and bolted the tab to it and immediately noticed that the TDC marks werent in the same area

yeah im leaning toward the fact that it has the wrong timign cover on the motor. When i first got the car I assumed it was all original mileage, at 186k, but after i pulled the valve covers and saw the condition of the top of the heads, i am almost convinced the motor has been rebuilt, mainly because there is NO sludge deposits anywhere around the rocker arm or on top of the heads. Its very clean up there and ive pulled apart motors with 100k miles with tons of gunk built up.

another thing im gonna chekc is if there is a scratch or old paint line, further around on the balancer. basically ill put the grooved timign mark at around 2 o'clock and see if theres any type of marking then at the 12 oclock position, maybe they used the wrong balancer but remarked it.