Northstar 4.6 bottom end
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Northstar Engines and System Technical Discussion Discussion, Northstar 4.6 bottom end in Cadillac Engine Technical Discussion; Well, As the disassembly of the 98 STS continues, I have faced something I really didn't want to do. Unfortunately, ...
  1. #1
    98eldo32v's Avatar
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    Northstar 4.6 bottom end

    Well,

    As the disassembly of the 98 STS continues, I have faced something I really didn't want to do. Unfortunately, the half case seal and the oil pan needs resealing.

    The oil pan didn't concern me too much, but the half case seal did.

    The motor is on the stand and I can clearly see toward the rear of the motor the half case seal has been "sweating" oil for some time. This motor has 150k on it. I have read the procedure with the new gm sealant, but what I'm a bit concerned with is "disturbing" the lower end.

    In order to reseal the bottom correctly the half case has to be disassembled, which means disturbing the crankshaft. If this were a cast iron block, I wouldn't been even concerned about the procedure. Yet, this isn't. Aluminum is a soft and finicky metal. One twist too much, we've got problems.

    Another concern is the main and rod bearings. If I disassemble the bottom end the mains will have to be replaced. Do I leave the rod bearings alone and just service the seals and bearings? The crankshaft states it shouldn't be cut. Do I re-use the main bearing bolts or get new ones? I was planning on replacing the oil pump.

    I just want to do this one time and for get it. I also believe in if it's not broke, don't fix it. I don't want to disturb anything that I really don't have to, but while I'm in here doing studs and re-sealing I want it all done right.

    Any input will be greatly appreciated.

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    johnny kannapo's Avatar
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    Re: Northstar 4.6 bottom end

    You have it on the stand ready to go, now you have the do the half case & crank seals or its just plain negligence.

    The mains are probably good if you know the the history of maintenance.
    You may want to check the upper rod bearing half & see if it has worn through a metal layer or 2.
    I would be scraping piston grooves & re-ring if the gaps were big.

    If I was there I would leave no stone unturned
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    97EldoCoupe's Avatar
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    Re: Northstar 4.6 bottom end

    I've seen a lot of worn rod bearings lately. My 97 ETC was checked yesterday (sort of an on-going, off the side project) and the bearings are worn to the point where I would not re-assemble the engine in this condition for fear of low oil pressure and future rod-knock.

    Take care of things ahead of time and you will not be sorry.

    Ron, just be careful- when you pry the two halves apart, and when you retorque. Follow the GM procedure to the very last little detail (at least when it comes to torque specs and sequence) and you will be fine.


    Need parts for your Northstar Engine? www.northstarperformance.com

    Jake Wiebe, developer of the SureGrip™ Cylinder Head Stud Kit

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    Re: Northstar 4.6 bottom end

    You can re-use the original main bolts but check the threads for aluminum particals, wire brush if need be, check for stretch (VERY IMPORTANT!). If the bolt is stretched (this happens in the M10x1.5 threads) it will snap during the final torque pass and then you're into disassembly again to get the broken portion out. There are 12 main bolts that are VERY sensitive- oil is pressure fed around the shafts of these bolts and comes in the backside of the main bearings to provide lubrication. If one were even just loose, oil pressure will drop to an unacceptable level because it will bypass by the head of the bolt.

    You're wise to take care of the bottom end while it's out. The myths of the bottom ends being bulletproof are something I'd already argue with after what I've seen lately. I talked to Scott at GMRP in Roseville and he's said the same thing. Four cars in a row that needed the rod bearings replaced. Main bearings tend not to wear as much. It depends heavily on how the vehciles are maintained.


    Need parts for your Northstar Engine? www.northstarperformance.com

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    Re: Northstar 4.6 bottom end

    Thanks for the replies guys.

    At this point if the bearings are going to be swapped, are we using standard size bearings? If not, normally one would plastigage the bearings to get the correct size. Yet if the bearings were to go to a different size, normally we'd cut the crank to the size we need, but that's a no-no?! I'm asumming we're going back to stand size if the journals are good.

    Jake, now you've got me nervous and on the fence about re-using the main bolts. If one of those bolts snap in that block, I'll probably faint. That's why I have the tendency to get all new bolts. I feel like I'll be playing russian roulette if I don't.

    The rod bearings are also eating away at me. I'm accustomed to replacing everything when I have it apart. Yet, if I do the rod bearings also, do I have to get new rod bolts? Why are the main bearings WAY cheaper than the rod bearings? I guess like you said Jake, the problems are with the rod bearings wearing.

    Jake which manufacturer are you using for bearings in your rebuilds out of curosity?

    If I take out the rod bearings, I might as well put piston rings on.......it never ends.

    In late breaking news:

    I took off the valve covers, timing cover, right bank chain and tensioners. Left bank chain and tensioners, removed the Vin 9 intake cams. The lifters looked very good on the intake cams, but we had a problem with the rear cylinder head.

    The rear cylinder head has a crack in it?! I said to myself what in the world is this? With the valve cover removed, at cylinder number 7, on the exhaust side, in between the intake and exhaust cams you can see a crack. It almost comes from the outer most exhaust seat and spreads towards the intake seat above it. I was shocked. I was told this motor ran without a problem, except that it needed headgaskets of course......

    I had wondered if the engine lift bracket bolted to that head caused the problem, but that's impossible for for it to do that. The crack almost looks like something exploded from underneath the head and tried to force it's way outward through the casting.

    I guess I'll have to use my eldo heads and throughly inspect them before bolting them on. I'm disappointed because I wanted a spare set of heads to work on.

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    Re: Northstar 4.6 bottom end

    Clevite Perfect Circle, standard size bearings with a mint, polished crank checked for roundness and wear. Cannot have any nicks, marks, gouges, rust, or wear spots.

    I will have a stud kit for the bottom end soon. I have the M10, M11, M12 1.5 thread rolls now to make these.

    Use new rod bolts.

    Cracked heads are a rare occurrance.


    Need parts for your Northstar Engine? www.northstarperformance.com

    Jake Wiebe, developer of the SureGrip™ Cylinder Head Stud Kit

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    Re: Northstar 4.6 bottom end

    Thanks Jake.

    I'm just wondering what caused the crack, especially in the location that it's in. I guess i won't know untill I get the heads off, which will be later today.

    I guess once I get the heads and the crank out, I'll be reporting my findings.

    Thanks again everyone.....

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    Re: Northstar 4.6 bottom end

    Quote Originally Posted by 97EldoCoupe View Post
    The myths of the bottom ends being bulletproof are something I'd already argue with after what I've seen lately.
    "Bulletproof" : As in - tough, long-wearing, high rpm potential without failure.

    98eldo's engine has 150,000 miles on it. An overhaul without lower end checks, bearings, seals and gaskets would be pointless. Nothing wrong with gauging the crank and dropping in a set of standard main and rod bearings.

    I believe you should replace the oil distribution plate. New one........
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    Re: Northstar 4.6 bottom end

    Sorry Jim- I misinterpreted the definition that everyone meant- The good news is the bearings are wearing before the crank journals (usually no damage to crank journals). At 150,000 miles if a set of bearings is required that's not all that bad.

    New oil distribution plate for sure.


    Need parts for your Northstar Engine? www.northstarperformance.com

    Jake Wiebe, developer of the SureGrip™ Cylinder Head Stud Kit

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    Re: Northstar 4.6 bottom end

    Why is the oil plate critical to replace?
    Deformation after being torqued down previously?

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    Re: Northstar 4.6 bottom end

    Thanks guys for all the replies.

    I'm definitely getting a new oil distribution plate. Jake stated that the oil pickup tube grommet usually cracks/ tears. Plus it has that sealer on it around the edges, a potential for leaks. With that said, better safe than sorry.

    When I get the crank out, I'll post what I find. I was wondering if Sealed Power Main bearing set #7319MA is a good choice as a replacement. Rod bearings are all over the place, Bi-metal, Tri-metal? I'm a bit baffled, but I'll sort it out with some help with you guys.

    I need an oil pump too, I believe Melling M188 is the part #.

    I'm excited that I'm at this stage, but I want it to go smoothly. I don't want to wonder or doubt.

    Like I always stated, "when in doubt, pull it out!"

  13. #12
    ternstes is offline Cadillac Owners Fanatic
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    Re: Northstar 4.6 bottom end

    Why do you think you need a new oil pump?

    I chose clevite main and rod bearings for my 2000 STS rebuild. Rock Auto had the best price I could find. Advance Autoparts has plstigage for checking clearance on the new bearings.

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    Re: Northstar 4.6 bottom end

    Nobody is stopping you from replacing the oil pump. You could disassemble & inspect the cover plates surfaces for
    irregularities or just run it and save that cost because before you know it you are spending more than planned.

    If it was trouble free the oil pump can always be replaced at a future time if it becomes
    a problem & since it's external It's not nearly as labor intensive to replace.

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    Re: Northstar 4.6 bottom end

    Johnny,

    I may trust you on the oil pump.

    It's just that I have everything apart now and the pump does have 150k on it. If it's the original pump too boot.

    I just figured since I'm in here now, just take my time and round it all up.

    Yet, like you said I can find myself spending more than I had planned. I guess from all my previous motor builds I've always followed the safe than sorry rule.......

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    Re: Northstar 4.6 bottom end

    Why is it I can't find a 10mm 1/2" drive hex bit to remove these head bolts?! I had to unfortunately settle for a 3/8" drive after I went all over town looking for a 1/2 drive, do they even exisit?

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