Northstar Engines and System Technical Discussion Discussion, Finally tore the motor apart in Cadillac Engine Discussion; Well I aquired the car needing head gaskets about a year ago. Haven't had a chance till now to get ...
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?
Automobile(s): 2002.5 F55 STS, 2014 Explorer XLT FWD
MD Eastern Shore, Kent Island
Re: Finally tore the motor apart
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.
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....