What's wrong in these pictures?
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Northstar Engines and System Technical Discussion Discussion, What's wrong in these pictures? in Cadillac Engine Technical Discussion; This is a test, this is only a test.......... What do you see wrong in these pictures???...
  1. #1
    dloch is offline Cadillac Owners Fanatic
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    What's wrong in these pictures?

    This is a test, this is only a test..........

    What do you see wrong in these pictures???
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    JimD is offline Cadillac Owners Connoisseur
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    Re: What's wrong in these pictures?

    The arrows on the pistons?

  4. #3
    dloch is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    Quote Originally Posted by JimD
    The arrows on the pistons?
    That was quick... I should have taken crappier pictures. Hopefully Bbob will look at these and provide a clue as to what I should do next.... The rods are installed correct. I think the guys on the line who built this motor were a little confused that day. :disappoin

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    Aurora By Olds is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    I would like to know how you got the piston heads so clean....I tried everything to clean the huge layer of carbon off of mine, and I ended up using a Roloc.....
    Now I keep the carbon out the easy way.

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    zonie77 is offline Cadillac Owners Connoisseur
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    Re: What's wrong in these pictures?

    One of the power increases in older (60's) Mopar big blocks was reversing the pistons to change the rod offset (those had offset). It supposedly caused a little more ring wear. If there is no offset it wouldn't matter as long as the valve reliefs matched up. It might worry me a little though.

    Tell us about this block...

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    Re: What's wrong in these pictures?

    The pistons are in backwards. No way it was built that way on the line. There are three levels of checks to confirm the arrow direction. Unlikely that those made it past the errorproofing. Besides, there are no paint marks on the pistons that the plant uses. Either someone had it apart or replaced pistons or cleaned everything up....

    The mopar trick was to reverse the pistons to reverse the PISTON PIN OFFSET in the piston.....not to reverse the rod per se.... The pin offset is in the piston to eliminate/minimize piston slap. The pin offset side loads the piston slightly to control the motion of the piston at TDC when it reverses direction. If the engine is run as the pistons are installed now there will be severe piston slap....won't hurt anything...but you will get tired of the ticking....

    You cannot just take it apart and turn the piston/rod assembly around.... the pistons and rods are all identical..but there is a "right" and "left" assembly orientation. Once oriented and subassembled to the rod the piston/rod assembly becomes a "left" or "right" assembly....so those pistons will have to be reversed on the rod...i.e...take the pin out of the piston and reverse the assembly.

    You know how to identify the rod for "right" and "left" orientation....???? Hint....look closely at the rod beam at the big end....it is NOT in the center of the big end bearing flange....it needs to be installed so that the rod beam offset is toward the center of the crank pin.

  8. #7
    dloch is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    Quote Originally Posted by bbob
    The pistons are in backwards. No way it was built that way on the line. There are three levels of checks to confirm the arrow direction. Unlikely that those made it past the errorproofing. Besides, there are no paint marks on the pistons that the plant uses. Either someone had it apart or replaced pistons or cleaned everything up....

    The mopar trick was to reverse the pistons to reverse the PISTON PIN OFFSET in the piston.....not to reverse the rod per se.... The pin offset is in the piston to eliminate/minimize piston slap. The pin offset side loads the piston slightly to control the motion of the piston at TDC when it reverses direction. If the engine is run as the pistons are installed now there will be severe piston slap....won't hurt anything...but you will get tired of the ticking....

    You cannot just take it apart and turn the piston/rod assembly around.... the pistons and rods are all identical..but there is a "right" and "left" assembly orientation. Once oriented and subassembled to the rod the piston/rod assembly becomes a "left" or "right" assembly....so those pistons will have to be reversed on the rod...i.e...take the pin out of the piston and reverse the assembly.

    You know how to identify the rod for "right" and "left" orientation....???? Hint....look closely at the rod beam at the big end....it is NOT in the center of the big end bearing flange....it needs to be installed so that the rod beam offset is toward the center of the crank pin.
    The pistons are that clean because I cleaned them, that's when I noticed the arrows. If there was a paint mark on top I could have cleaned it off with the laquer thinner or acetone I used to clean them as you see them now. I looked at the bottom of the piston for the cast mark in the pin area and it confirms with the arrow on top. The big end of the rods are correct, the beam offsets are in the center, sooooo whom ever put this thing together didn't do something correct. In any event I need to pull those two pistons and flip the piston on the rod. You confirmed what I thought if the pistons are facing the wrong way, piston slap. This is the same motor that had the crank/scraper not installed correctly. Also the bolt for the intermediate timing sprockets was about 3 -4 threads loose. Don't know if that bolt could back all the out and fall... I'd hate to see the carnage if that were to happen though. I've seen enough motor parts outside of the block that were suppose to be inside....

    I don't know the previous life of this motor, it was obviously a running motor in something at one point, it is a LD8 version. Maybe that's why it's out of whatever it was in.

    Now for the next questions. You and I talked in a previous post about not reusing the rod bearings after I split a rod, does the same hold true for the rod bolts? I believe the manual says to replace them. If I replace them do I use the sequence of tighten to a torque, loosen to zero then tighten to a torque plus a twist? Three steps.

    The manual also says to replace the flywheel bolts once they are removed, is that also correct?

    Are there any other fastners I should replace?

    When I start putting everthing back together can I use moly-lube on the mains, rod bolts and fastners that don't require a sealant of some sort?


    Aurora By OldsI would like to know how you got the piston heads so clean....
    Like I said above I used laquer thinner and acetone to clean them as you see them. There was no carbon build-up on the crown of the piston only a oily like grease substance so it came right off. The thinner and acetone is great for getting the duct tape glue off as well.

    zonie77If there is no offset it wouldn't matter as long as the valve reliefs matched up. It might worry me a little though.

    Tell us about this block...
    The relief slots weren't my concern, the piston slap was and Bbob confirmed it so I will fix it.


    zonie77Tell us about this block...
    Long story here..

    I have a 97 STS with a headgasket leak. I knew it had a coolant problem of some sort when I bought it.... The price was very right so I bought the car knowing I was going to have to fix something. I chased down all the obvious things, loose hose clamps, etc. I drained and refilled the coolant system and added the barsleak gold. Everything seemed alright until I really layed into on numerous occations on a road trip back from Pittsburg. The next day which was very cold, I was going over to the boat house and when I stopped at a traffic light I had steam coming out from under the hood...... not good.. . So I pulled into a shopping center and looked for where it was coming from, it looked like the water pump, mind you the previous owner had just replaced the water pump about 6 months previous. (Although he also replaced the alternator as well which the bearing went out on me a week after I got the car, but that's another story.) So I replaced the water pump. When I started and ran the car in my heated garage everything looked right with the world. Not leaks, no drips....... So I pulled the car out and it sat in the driveway until I went to work the next monday. It was very cold that weekend.... So I get in the car monday morning and drive to work..... get to the first stop light and I have steam coing out from under the hood again. Pull over and take a look, I see coolant sprayed on the rad and exhaust manifold in front, but no spitting of coolant. By this time the car has come up to temp and I can't see anything leaking. Next day same thing... I see the steam at a light. I only noticed the steam when the car was extremely cold and the coolant temp was between say 40 and 140-160 degrees, above that everthing is fine. Next chance I had I lifted the hood and had the girlfirend get in and start the car and put it in gear with both feet on the brake and the parking brake set.......... Not that I don't trust her....but.... Not stupid either. Anyways with light throttle like you would see accelerating from a light I saw the coolant spit out from the head and block area of the front head onto the exhaust manifold and make steam..... plus that sweet smell..... Had her put the car back into park and I let it warm up, once it got to temp no leak....... fixed itself.. it's magic... Till the next day. That weekend I did the pressurize the # 8 & 6 routine and I see bubbles in the coolant tank... suspicion confirmed.

    So now I have the motor in temporay remission with a double dose of barsleak until I get this motor complete in which case I will do the switch. If I lay on it to any great extent I can smell coolant... so I've been gentle.... which is making me crazy.

    The motor came from a friend of a friend deal, beyond that I don't have a clue as to it's previous life, which is fine by me beauase I was going to tear it apart and timesert it anyways.

    So the timeserts is done as you may be able to see in the pictures. The gaskets have been purchased and are on there way. Now I'll get some rod bearings and some rod bolts and I will flip the pitons on the rods. I also need to get some valve springs since this motor is a LD8 and not a L37. I will probably take the intake cams out of my motor when I yank it and put them in this one, hence the changing of the valve springs to match my motor and red line of a STS PCM.

    The intention is to sway motors and then timesert and fix my oringinal motor and either sell it or buy another car with a bad motor and do the swap exchange thing. In my spare time.... Between work and my offshore racing activities I am very tied up. Working on this stuff is what I like to do to get my mind off other things. Mind you I also have a 94 Impala SS that I have had on jack stands with the motor out of for eighteen months now.

    So that is the story, now let's all finish our cookies and milk and take a nap......

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    Re: What's wrong in these pictures?

    You can reuse the rod bolts one or two times...I wouldn't be too concerned about replacing them....but it can't hurt if you are getting new ones..


    The flexplate bolts need the loctite on them. They are spec'd for replacement due to the preapplied loctite patch. If you use a good grade of thread locker on them they can be reused.

    Definitely do not reuse rod bearings.......

    The rod bolts are spec'd for a torque/angle pull down. Don't remember what it is off the bat, though. But use the torque/angle strategy. Don't use moly lube on any fastener threads....ESPECIALLY if it is a torque only fastener. With torque/angle the effects of the friction reduction with the moly lube are somewhat mitigated but it will then make the fastener that much easier to loosen on it's own and fall out...... I never use the stuff on bolt threads.


    It sounds like that engine had some sort of problem and was partially torn down looking for the problem and not put back together very well.....

    There were a number of "scrap" engines purchased some time ago from the GM Livonia engine plant that were sold for aluminum scrap....that we later learned were sold "as is" as complete engines.....unfortunate since all of them were sitting in the scrap pile due to known difficiencies....maybe that engine was one of them......hmmmm.....

    Is there a VIN stamped on the pad on the side of the block that would indicate that it was installed in a car at some point....????

  10. #9
    dloch is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    bbobYou can reuse the rod bolts one or two times...I wouldn't be too concerned about replacing them....but it can't hurt if you are getting new ones..
    I'll get new rod bolts if I'm going to get new rod bearings. Is GM the only place to get bearings?

    bbobThe flexplate bolts need the loctite on them. They are spec'd for replacement due to the preapplied loctite patch. If you use a good grade of thread locker on them they can be reused.


    What about the flywheel bolts themselves?
    bbobThe rod bolts are spec'd for a torque/angle pull down. Don't remember what it is off the bat, though. But use the torque/angle strategy. Don't use moly lube on any fastener threads....ESPECIALLY if it is a torque only fastener. With torque/angle the effects of the friction reduction with the moly lube are somewhat mitigated but it will then make the fastener that much easier to loosen on it's own and fall out...... I never use the stuff on bolt threads.



    Will not use moly on anything, will use oil where recommended.

    bbobIt sounds like that engine had some sort of problem and was partially torn down looking for the problem and not put back together very well.....

    There were a number of "scrap" engines purchased some time ago from the GM Livonia engine plant that were sold for aluminum scrap....that we later learned were sold "as is" as complete engines.....unfortunate since all of them were sitting in the scrap pile due to known difficiencies....maybe that engine was one of them......hmmmm.....

    Is there a VIN stamped on the pad on the side of the block that would indicate that it was installed in a car at some point....????
    That's what I am beginning to think. The rod caps don't even look like they have been split. They still have the paint across the parting line and over some of the rod bolts, like they would apply at the factory.

    Where is the pad that would have a vin number stamped on it?

    Do you think I should split all the rod's and have alook see? The other six pistons are installed correctly and as I said the rods don't look as though they have been touched.

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    Re: What's wrong in these pictures?

    The VIN pad is on the right front lower corner of the engine block I believe....look for a small "shelf" sticking out with a flat surface designed to be stamped into.....

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    Re: What's wrong in these pictures?

    I would use the GM bearings....don't know what else is out there nor anything about them...

    Find out what the two you have to take apart look like. If they are all fine (other than the orientation) then probably the rest are. Visually inspect them for bearing inserts and move and "rattle" them to check for free play and movement on the crank pin and side clearance. If one felt tight or something then I would take it apart.

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    dloch is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    Quote Originally Posted by bbob
    I would use the GM bearings....don't know what else is out there nor anything about them...

    Find out what the two you have to take apart look like. If they are all fine (other than the orientation) then probably the rest are. Visually inspect them for bearing inserts and move and "rattle" them to check for free play and movement on the crank pin and side clearance. If one felt tight or something then I would take it apart.
    Will do.. Thanks

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    dloch is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    I pulled the two pistons last night. BTW those things are a thing of beauty I might add. It seems the factory marked the bottoms of all these pistons on one side of the pin casting with the corresponding cylinder it should be installed in. They also stamped a dot on the other pin casting that is to represent the front of the piston, same as the arrow on top pointing forward but from the bottom. Well those two pistons had the marks 180 degrees out from the other six.... So my thinking is that the rod was installed in the piston based on the dot and number on the bottom of the piston not based on the arrow on top or the casting mark on the bottom.

    Bbob, what was the intention, or forward thinking intention of the machined hole throught the center of the block behind the upper intermediate timing chain mounting bracket? My intial though was that it would be an ideal area where a balance shaft could be positioned.

    The bearings that came out of those rods looked like the day the engine was assembled, very, very little scuffing, as do the pistons. Those pin retainers/snap rings are a bit of a PITA though, I would suggest to anyone removing the pistons from the rods to get new pin retainers/snap rings because your going to distort them when you take them out. I ordered new rod bearings, bolts and pin retainers. BTW Clevite now manufactures Rod and Main bearings for the Northstar, I got mine from the GM Dealer.

    In fact the stuff just showed up.........

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    Re: What's wrong in these pictures?

    I'm glad to hear that the pin retaining clips are a PITA!!!! That is a good thing!!!!! That way they are less likely to fall out some day at an inoportune time...LOL When you reassemble, make positively SURE that the clips are in the grooves and seated completely. I know this sounds obvious...but it is really difficult to make sure that the clips are in place completely. The factory clips are installed via automation and verified several ways . Just about every time I see someone install a set on a proto engine by hand I look at them and find a clip that is partially unseated or not completely in the groove. Triple check them.


    I really beginnning to think that you have one of those orphan engines from the factory. It quite possibly was set aside due to the piston misinstall and was later sold as "scrap"...only to surface in the aftermarket. There are a number of those out there, unfortunately, it seems. Often, at the end of model run an engine or two will be left sitting in the plant and it is easier to scrap it than dissassemble it and recycle the parts...plus it eliminates the possibility of any mixups or damaged parts. Scrap means to melt down....not sell to commerce.


    The large bored hole up the middle of the block is for windage/breathing in the lower end. Realize that the engine is an air pump. It pumps 4.6 liters of air thru the top side of the pistons every two revolutions. What people forget is that it pumps 4.6 liters of air around the crankcase EVERY revoution underneath the pistons. That breathing in the crankcase , or windage, is vital to making power as it is just a sap on power if the windage cannot happen. That is why those large holes are in the bulkheads above the mains...to allow air flow from bay to bay in the crankcase. If you look at the block and lower crank case the main bulkheads almost completely block the air flow from bay to bay as each pair of pistons is completley walled off from the top to the oil pan by the bulkheads. Good for strength...but bad for windage. The holes help. If you want 5 "free" HP, take the rest of the engine apart, get out the grinder and bellmouth and radius those holes. Improving the flow thru them is analygous to "porting" the heads....

    If you look at the hole, you will notice that it is smaller at the rear bulkhead due to the buldge in the valley for the starter. It would be nice if it was the same area as the rest.....catch my drift....????

    BTW.....Lexus put the LS400 engine in production in 92...it was obviously a direct competitor to the Northstar and a very similar engine...but down a little on power to the Northstar. It had no holes in the main bulkheads. Two years later....it showed up with more power...and holes in the bulkheads like the Northstar. Who copied who....????...LOL

    The hole had no reference to a balance shaft. No need for one with a V8 and the V6 Shortstar was not even on the radar screen. The balance shaft in the Shortstar is in a different spot anyway as the cam timing drive is completely different in that engine.

  16. #15
    dloch is offline Cadillac Owners Fanatic
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    Re: What's wrong in these pictures?

    I will be certain to triple check the retainer pins. The windage/breathing didn't dawn on me...... now it makes perfect sense especially with the scraper/baffle this engine has.

    Got the drift. I will do that to the engine that is coming out I'm living on borrowed time with my current headgasket leak.

    BTW I talked at length to Alan at Chrfab yesterday.. Very knowledgeable and interesting individual so say the least. He is getting some monster power out of some of Northstar creations..... As a point of interest I asked him if he timeserted all his blocks... his response was not really. He said he inspects all the head bolts as he removes them for any signs of thread material, if there is then he will otherwise no. He does use studs with most of his blown/turbo motors though, ARP makes a stud for him with the correct metric thread on the bottom american on the top, sort of like the rod bolt heads of a N* rod assembly... :rolleyes2

    I am getting the L37 intake cams and some springs from him, I am also sending him my intake sprockets to offset the intake cam installed position.... He said it should help a bunch with the converter I intend to use especially with a heavy car. With all the changes made at the same time it will be near impossiable to qualify what helped the most and where, although I will have a test mule to play with.....

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