: Northstar Rebuild --- Chime In, I have questions...



97BlueDeville
01-24-05, 03:34 PM
Hey there.. Sorry to be a 1st poster and posting about a problem. I post alot in LS1 forums as I have a 720RWHP 99' SS Camaro. I'm pretty well versed in working on motors as and a friend of mine and I have rebuilt LS1/LT1 motors in recent years. Never touched a Northstar though..

Northstar Problem..... You guessed it.. HEADGASKET........

I have a 1997 Deville with 146k miles.. Car has been very well taken care of since 65k miles when my father bought it. I've had it for 6 months, bought it from my father 8k ago. He's driven it with ease and had it well maintained, as I did some of the work myself. The motor does go though a little oil, about 1 qt every 1000 miles using 10w30. I put in non Syn 15w40, and that helps with the oil consumption.. Trans feels just fine and shows no sign of failing soon.. All in All the car is in great shape and looks wonderful.. People find it hard to believe I have 146k on the odo..

So now to my questions..

Yes it is a headgasket.. Car only overheats when the engine is under heavy load like on the hywy, or climbing a hill. If the country side is flat, I could drive it around being easy on it. It can handle 50 to 60mph on a level hywy, but climbing a hill, or heavy on the gas provides too much cylinder pressure, which creeps into the water jacket and pressurizes the cooling system and the coolant sprits out the vent hose from the coolant tank.. Bars leak, and some black cube stuff I got from a local speed shop wont solve my problem. Didn't expect it to, since I knew it is only a bandaid.

So.. Having access to a lift and a shop as I do, I can drop the motor, as it would be easier to work on that way.. How much is entailed in removing the heads.. I'm sure I can still get away with using the same cams, crank, rods, perhaps pistons.. I have a honing kit for the cylinder walls. I was thinking taking her apart, and taking the block and heads to get magnafluxed and milled if nessary.. Throw everything back together with new rings on the origional pistons w/ the cylinders honed, new headgaskets, a complete gasket set, water pump, belts etc.. Or I can just take the heads off and have them checked, new head gaskets and call it a day... Do I need special tools?? If so what??? How long do these valve springs last? Cam bearings? If I get into the block I will change the Crank and Rod bearings, but I can't emagine the Cam bearings needing replacing since that really don't see a lot of pounding..

Let me know what's involved in this Northstar re-build.... As I'm slightly in the dark... Oh and of course a local caddy dealership wants 3 to 5K to do the job, with no guarentee if it will solve the problem... Bad..... I said.. Ummm I don't think so.....

Let me know....

Clint

zonie77
01-24-05, 05:44 PM
Here you go!

http://cadillacforums.com/forums/showthread.php?t=5052

zonie77
01-24-05, 05:47 PM
ALso, you probably don't have to do anything but replace the appropriate gaskets and headbolts. The cylinders will probably still have hatchmarks on them! I don't remember anyone needing the heads redone either. Check them with a straightedge to be sure.

BeelzeBob
01-24-05, 07:48 PM
Just replace the head gaskets and the head bolts. Use the OEM factory head gasket kit as that is the best gasket for the engine. Nothing else should need replacing. Lots of other posts on this subject if you read down the pages....and/or search using "head gasket" and read up.

Timeserting the head bolt holes is a popular insurance policy against stripping a head bolt hole or a subsequent repair of the head gasket... Lots of timesert info also if you search using the forum search feature and "timesert"....

The timing drive in the engine is good for at least 300K so no need to replace chains or guides or tensioners or anything.

Forget touching the heads. Clean up the head gasket surface and put them back on. Heads at 150K usually look perfectly fine. The valve seats, valves and guides will usually run forever.

The lower end is equally bulletproof. I wouldn't even touch the pan or anything unless there is an oil leak that need attention or something like that. IF you are tempted to look inside and do take a rod cap off to inspect the rod bearings be aware that the bearing is a one shot deal and MUST be replaced if you dissassemble it. The rod inserts will loose their crush and will not have the necessary integrity if you reinstall a used bearing shell. You will spin a bearing shortly. I would leave them totally alone as they , too, will easily go for 300K or so.

There really isn't much to do other than dissassemble and replace the head gasket and timesert the head bolt holes if you see fit. ONLY use timeserts, not helicoils for reinforcing the head bolt holes.

Get a service manual for the engine before tearing down as there are some unique steps in assembly and setting the cam timing and such.

The harmonic damper is a heavy press fit so you will need a proper puller to remove it. Install the damper with some antiseize on the crank snout and with a proper puller NOT the OEM damper bolt. Using the bolt to pull the damper on will damage the crank and the bolt threads. Use the puller to seat the damper and tighten the damper bolt correctly... It will take almost 300 ftlb to tension the bolt to the correct torque and angle so if it is taking way less something is wrong.