: LD8 non-interference motor?



GXPN*
01-27-13, 02:11 PM
Hello My name is Danny this is my first time posting anything. I have been looking at this site for 2 days and all of you seem really knowledgeable. I have a 2004 Bonneville GXP. I have looked at bonneville sites but no one knows northstars there. So here is the issue. I started the car after leaving the store and when i went to drive away it made a loud noise and started to rattle like some one put marbles in the front valve cover. I shut it off and had the car towed home. I pulled the valve cover off and found all the cam followers on the intake cam could be pulled out with no effort (the followers on the exhaust cam are all tight) . in fact i touched one and it fell out. I also found a long thin piece of nylon like material laying down in a channel next to the timing chain. it seems to me that all the lash adjusters on the intake side are stuck i pulled them out and they don't move at all. the top side of the timing chain has a aluminum guide that is just flopping against the chain when i crank it over and makes a horrible noise. So that is where i am at. I Say all this because i have no clue if any of this is wrong or right i am not familiar with these motors. I know old chevy engines not north stars but i want to fix this issue. I know I am not very knowledgeable with this , actually pretty dumb, but that's why i am asking for help. By the way all this is on the head at the front of the car not back at the firewall.Thanks to anyone wanting to comment here I appreciate it.

Submariner409
01-27-13, 02:22 PM
With that much mechanical damage my guess is that you're in for an engine overhaul - just too much broken and moving around, in addition to the real possibility of metal shavings throughout the oil system. If the cam followers did actually leave the face of the cam and lash adjusters then you also have cam problems. A simple (???) left head pull won't fix this one................

basscatt
01-27-13, 02:54 PM
that really sounds strange unless the car has hundreds of thousands of miles on it -

GXPN*
01-27-13, 05:27 PM
Yes the car has 198000 miles on it. The sad thing is it was running great and the head looks awesome no gunk or build up at all. So what your saying is that I have to get a new motor or rebuild this one. the followers never left there place until i moved them the cam looks good but there are metal shavings in the oil.

Submariner409
01-27-13, 05:35 PM
Yes the car has 198000 miles on it. The sad thing is it was running great and the head looks awesome no gunk or build up at all. So what your saying is that I have to get a new motor or rebuild this one. the followers never left there place until i moved them the cam looks good but there are metal shavings in the oil.

Overhaul time with some very dedicated cleaning of every oil passage in the engine. Many parts stores and online sources sell kits of various length/various size bristle brushes for just this job.

basscatt
01-27-13, 05:45 PM
Yes the car has 198000 miles on it. The sad thing is it was running great and the head looks awesome no gunk or build up at all. So what your saying is that I have to get a new motor or rebuild this one. the followers never left there place until i moved them the cam looks good but there are metal shavings in the oil.
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you can get more information in the Northstar Performance forum -

http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/

GXPN*
01-28-13, 08:48 AM
ok cool thanks for the help

GXPN*
01-28-13, 12:29 PM
I read some where and just want to check if itís true. There was a site that said the Northstar LD8 in my 2004 GXP was designed so if the timing chain ever went bad or the motor jumped time there was enough clearance that the valves and piston would not be damaged. Anyone know if this is true?

Manic Mechanic
01-28-13, 01:54 PM
EDIT: It is interference.

Vernon

GXPN*
01-28-13, 05:13 PM
What do you mean by "free wheeling"?

Manic Mechanic
01-28-13, 05:42 PM
It means under normal build specs the valves and pistons won't be able to contact each other, so you can turn the flywheel freely with the heads on and timing chains off without concern of valve train damage. It is the opposite of interference.

Vernon

GXPN*
01-28-13, 06:55 PM
Well the reason i ask the question is i think i may have jumped time when i went to take off the other day. I posted something about it on the deville forum (not knowing at the time there was a Northstar forum) but there was a bang sound then the engine sounded like some one put marbles in the valve cover. found all my cam followres on the LI cam could be pulled out by hand. Wondering if i bent valves and the might be stuck down.

Manic Mechanic
01-29-13, 12:25 AM
I saw your other post. I looked into this some more tonight and I must retract my post. I studied on my technical information and factory repair guide sites during lunch and could not find anything relating to the Northstar LD8 being an interference engine. And when timing my cams no instruction for anything I did mentioned it. I know the repair procedures are really random and there's not a step by step to assemble one from scratch but usually if an engine is interference their is plenty of warning. Not so on this one. After researching it again I've found much evidence of the Northstar in fact being an interference engine. I was careful with mine but I hope no valves are bent. I might drive it off a bridge if so. I also cannot think of any likely reason why all of your LI followers are loose other than bent valves, the fact that your tensioner was slacked and damaged only supports the jumped time and bent valves theory. Based on you previously stated high mileage I would take a good look at the rest of the car. If the rest is really good and you really like the car get a lower mileage 2004+ LD8 and put it in. Don't try to fix yours, it's already got 200K on it and not worth what it would take to fix it again. There's little to nothing to be gained from rebuilding the engine when you can't change it from the $1200 one in the salvage yard with under 100K on it. I'm just finishing a overhaul on mine and it's a lot of work. If a salvage 2000 spec engine wasn't just as prone to blow a head seal with my driving habits I would have swapped one in.

Sorry I was incorrect. I made an assumption based on lack of information and never having heard of a N* bending valves in the past.

Use this site to look for a salvage engine if that's what you decide to do: www.car-part.com

Vernon

GXPN*
01-29-13, 08:04 AM
Thanks alot for looking into it I figured that i had pretty big problems. I am going to start pulling the motor and looking for a new one. Once again thanks alot for the help

Submariner409
01-29-13, 10:06 AM
Threads merged to keep same info in the same place.................

For grins and kicks, Google "cadillac northstar engine interference" or something close. You'll get a lot of "yes, it is" and "no, it's not".

For a pretty definitive answer, call Tim Carroll at Carroll Custom Cadillac in Washington state or the guys at CHRFAB.

http://www.carrollcustomcadillac.com/Pages/NorthstarInfospecs.aspx

maeng9981
01-30-13, 05:35 AM
The valve travels far enough to hit the piston top if the timing is off.