View Full Version : Finally tore the motor apart

04-13-09, 12:05 AM
Well I aquired the car needing head gaskets about a year ago. Haven't had a chance till now to get it apart and running. I pulled the motor last week and when i went to pull the heads I noticed that the exhaust cams were retarded a bit and the intake cams were advanced a bit. What i am trying to determine is if this was done on purpose or it was an accident when someone changed the timing chains or something? I may need to have the heads decked a few thousandths to make sure they are flat and not warped so valve clearance and timing is a concern since i dont know a lot about the n* yet. Is it common to change the cam timing in these motors in that manner, and what are the ramifications tuning wise to doing this?

04-13-09, 01:59 AM
Changing cam timing is not common. I haven't seen any mention of it as a tuning aid. People that wound up 1 tooth off had driveability problems.


Here's some info that may help. There are plenty of others.

04-13-09, 08:57 AM
There is absolutely no advantage in advancing or retarding the cam(s) in a Northstar. The old adage that advancing a (single) cam 4 degrees moves the power band down about 800 rpm and the opposite from retarding it the same amount does not hold true in a DOHC engine. The Northstar is an interference engine, meaning that, if you mis-time the cam(s), you run the very real risk of one or more sets of valves hitting the pistons.

Time the cams according to the GM/Helm Factory Service Manual or subscribe to www.alldatadiy.com.

04-13-09, 10:29 AM
that is what i thought. I just found it odd that the cams weren't timed 90* to the top of the head. They were both off a bit.

04-13-09, 11:50 PM
I know the intake cams can cause valve-to-piston interferance but I don't think the exhaust valves can, as they are recessed further into the head and on a different angle. I'll have to check next chance I get. The pistons have valve reliefs too, but they won`t help in the event that a chain should snap....