Oversize pistons? Undersize bearings?
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 15 of 30
Northstar Engines and System Technical Discussion Discussion, Oversize pistons? Undersize bearings? in Cadillac Engine Technical Discussion; Does anyone know of any company that manufactures and/or markets these items for the '92-'99 N* engine? Thanks!...
  1. #1
    mechanix's Avatar
    mechanix is offline Cadillac Owners Member
    Join Date
    Jan 2005
    Location
    Southern Oklahoma
    Age
    61
    Posts
    84

    Oversize pistons? Undersize bearings?

    Does anyone know of any company that manufactures and/or markets these items for the '92-'99 N* engine? Thanks!

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    74
    Posts
    26,626

    Re: Oversize pistons? Undersize bearings?

    Check the dealer and the auto parts stores. My nephew manages the second most profiable NAPA store in the world and they specialize in locating hard to find parts. Go to a big central store that services the commercial accounts. Big automotive machine shops are also well connected in this area.

  4. #3
    mechanix's Avatar
    mechanix is offline Cadillac Owners Member
    Join Date
    Jan 2005
    Location
    Southern Oklahoma
    Age
    61
    Posts
    84

    Re: Oversize pistons? Undersize bearings?

    My local GM dealer tells me that oversize pistons/undersize bearings are not available from GM, and my NAPA store tells me that the only thing they can find is .025mm under main bearings. I have also checked several websites of piston manufacturers, hi performance parts distributors, etc., with no luck.

    Also, do you know if '93-'94 N* engines were 4.6L? I've been told they were 4.9L during the first two years of production. And what the HP ratings are for these engines? I understand there are two basic models: 295 HP for the DeVilles, and hotter cam/higher HP versions for the SeVilles and Eldo's. Thanks from a Caddy fan in training! *lol*

  5. #4
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    49
    Posts
    9,577

    Re: Oversize pistons? Undersize bearings?

    I think that undersized bearings and oversized pistons are pretty hard to find...there just isn't much call for them.

    All Northstar engines were 4.6 liter. During 1993-1995 both the Northstar and the 4.9 liter pushrod engine were produced but they are not the same, not even related... There was never a 4.9 Northstar despite rumors to the contrary...

    In 1993/94 the Northstar engines were rated at 270 HP (LD8) and 295 HP (L37). In 1995 the engines gained a little power with the intake manifold redesign so that they were rated at 275 and 300.

  6. #5
    mechanix's Avatar
    mechanix is offline Cadillac Owners Member
    Join Date
    Jan 2005
    Location
    Southern Oklahoma
    Age
    61
    Posts
    84

    Re: Oversize pistons? Undersize bearings?

    Thank you, gentlemen, for your input and information. In glancing through the Service Manual, I see some pretty tight tolerances for crank journals, cylinder bores, etc. Am I to assume, from the lack of availability of oversize/undersize parts, that these Northstar engines hold their tolerances much better than engines typically do? It seems to me that any wear at all will put a crankshaft or a block out-of-service according to the service limits published in this manual. In what kind of condition have you been seeing these engines in after 100K miles? Or 200K? I realize there are a lot of variables that will affect the service life, but I'm speaking in general terms here. You guys have been fooling with these Northstars long enough to see how they hold up. What have you seen? Thanks!

  7. #6
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    49
    Posts
    9,577

    Re: Oversize pistons? Undersize bearings?

    I think that you will find that general clearances inside the engine stay pretty close to the original specifications. Cylinder bores typically still have the factory hone pattern in them and no ridge at the top of the cylinder at all with 150K on the motor. Crank journal wear is negligable. Pictures are posted on forum of main bearings with over 100K on them and they are good enough to reuse. From a wear and tear standpoint there is little to remachine or refresh on most engines unless there is some sort of failure that creates collateral damage.

  8. #7
    mechanix's Avatar
    mechanix is offline Cadillac Owners Member
    Join Date
    Jan 2005
    Location
    Southern Oklahoma
    Age
    61
    Posts
    84

    Re: Oversize pistons? Undersize bearings?

    Thanks, Bbob. Your expertise is much appreciated, as always. Just a couple more questions: I'm sure the electronics would be different, but are all the basic, N* engines physically interchangeable between '93 and '99? And could I expect a '99 STS PCM to re-learn on an engine out of a '93 DeVille and function ok, aside from the obvious drop in HP, that is? Thanks again!

  9. #8
    Loose screw is offline Cadillac Owners Fanatic
    Automobile(s): 94 concourse, 99 sts
    Join Date
    Feb 2004
    Age
    58
    Posts
    150

    Re: Oversize pistons? Undersize bearings?

    One thing Bbob had previously enlightened us about, was the crank should not be turned. The crank has "rolled" fillets to strength them (pre-stress them I think) and turning down or welding the crank will not only mess that up it can cause the crank to change shape and not be true and will weaken it. That is one reason undersized bearing are not available fro GM. Also never undo a rod to take a look at the bearings, the rod bearings MUST be repalced if they have been run in the engine and the rod caps opened. The bearing are cruch fitted in the rods and will loose that if the opened and they will spin if you resuse them after loosening the rod cap and retightening. Also rings show very little wear and seldom have to be replaced. Most of the time they are just stuck from cabon which can be corrected without tearing the engin down. So if you are burning oil or have low compression try that first.

  10. #9
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    49
    Posts
    9,577

    Re: Oversize pistons? Undersize bearings?

    Quote Originally Posted by mechanix
    Thanks, Bbob. Your expertise is much appreciated, as always. Just a couple more questions: I'm sure the electronics would be different, but are all the basic, N* engines physically interchangeable between '93 and '99? And could I expect a '99 STS PCM to re-learn on an engine out of a '93 DeVille and function ok, aside from the obvious drop in HP, that is? Thanks again!

    Well.....there are some differences in the PCMs and such that make this an un-simple answer. The 93/94/59 engines and PCM's were a speed density fuel injection system that did not use a mass air flow sensor. The 96-99 engines use mass air flow and are OBD2 compliant. In any given model car the controller and calibration won't care which "engine" is in the car...i.e..the complete engine mechanical assembly.... as the control system will operate fine. So, if one were to put a 95 Northstar into a 97 model car you would want to use the mass air flow meter and such off the 97 model car and hook everything up to the 95 engine and it would run fine....and vice versa. If you took a 97 and put it into a 95 then you would just delete the mass air flow sensor and hook the mechanical engine assembly up to the electronics of the 95 and it would be fine. No "learning" to do as the computer wouldn't know the difference. The 93/94 Northstars had a large plenum style intake with the silver top cover actually the working cover of the intake manifold with the plastic tuning tubes for each cylinder inside the manifold enclosure. This arrangement was replaced with the single piece injection molded plastic intake manifold for 1995 that has been used since then. The heads and EGR system changed a bit with the manifold change. There is no real controller problem with interchangability of the 93/94 engines with others (they were speed density systems) but the actual hardware is hard to interchange as part of the injector wiring harness and sensors and such were all inside the intake manifold on the 93/94 and that stuff moved outside on the 95 and later. But it all can be cobbled to work in a fashion.



    Just to clear things up....the crank isn't a throwaway and can be reground slightly...it just needs to be judicious grinding and the optimum situation is to have the fillets re-rolled after grinding. The 4.5/4.9 cranks were also rolled fillet cranks and they are routinely ground undersized and re-rolled at the engine re-man facility. Just that most crank shops do not have the necessary equipment and tooling to re-roll crank fillets so it is a bit restrictive of a re-work.

    Cracked cap connecting rods are also a bit different to re-man since the cracked surface of the cap cannot be machined to gain material for re-sizing the bearing bores so a special bearing that is undersized (for crank journal resizing) and oversized on the OD (for rod bore re-sizing) must be developed.

  11. #10
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    74
    Posts
    26,626

    Re: Oversize pistons? Undersize bearings?

    What causes fatigue cracks is stress reversal. Rolling the fillets introduces controlled stresses into the fillets that are high enough that they do not reverse in use. Welding in the fillets relieves these stresses as does machining. Now the crank will fatigue crack. I have seen cranks with rolled fillets that have been carefully ground 0.010" under and left the fillets untouched that worked out okay. I also had a rolled fillet crank with a spun rod bearing that was repaired with welding by an absolute artist that confined the welding to the journal with none in the fillets. As a general rule, rolled fillet cranks are not repairable in the field.

  12. #11
    Loose screw is offline Cadillac Owners Fanatic
    Automobile(s): 94 concourse, 99 sts
    Join Date
    Feb 2004
    Age
    58
    Posts
    150

    Re: Oversize pistons? Undersize bearings?

    Thanks for the additional information. I have been try to find out online for some time now what exact part of the journal is the fillet, the term is to me or I have just forgot what it is. I am assuming it is the oil hole? fill-et - fills the journal with oil, am I right?

    But I did find a good 2002 article with great pictures of inside of the engine.
    http://www.autospeed.com/cms/A_1569/article.html

  13. #12
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    74
    Posts
    26,626

    Re: Oversize pistons? Undersize bearings?

    The fillet is the junction between the bearing journal and the crank cheek.

  14. #13
    Loose screw is offline Cadillac Owners Fanatic
    Automobile(s): 94 concourse, 99 sts
    Join Date
    Feb 2004
    Age
    58
    Posts
    150

    Re: Oversize pistons? Undersize bearings?

    I thought that at first because that is where I could see stress having a big part to play but the name got me so on the Northstar it is groves on the edges of the journal. and rolling process pushes hard on this areas - depressing it, right? I think I go the whole picture now.

  15. #14
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    74
    Posts
    26,626

    Re: Oversize pistons? Undersize bearings?

    The rule of thumb in aircraft is that once a fatigue crack starts at a fillet, the crank will fail in 75 hrs. running time. The most startling crankshaft story I have heard: The Continental factory test engineers had a six cylinder crank set up on an electronic shaker table(imagine a super sized radio speaker armature that applied twist or torsion to the crank). When the applied frequency of the torsional shaking reached the resonant frequency of the crank it could be seen with the synchronized strobe light that the crank was winding and unwinding a quarter of a turn. All the engineers turned and ran. This story was related to me by the runner in the lead.

  16. #15
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
    Join Date
    Jul 2004
    Location
    Fairbanks, Ak
    Age
    74
    Posts
    26,626

    Re: Oversize pistons? Undersize bearings?

    Because the resonances and harmonics of crankshaft torsional vibration can cause exceedingly high stresses in propeller blades, aircraft engines have all sorts of ocsillating vibration dampers like pendulum weights, caged ball bearings, high hysteresis rubber couplings, and the lord knows what. Automobile engines are not immune. Early DOHC Ford Indy engines had extreme dynamic variations in valve timing due to torsional resonances in the cam drive train. Chevrolet/Ilmore had the luxury of witnessing all these monkeyshines so they came up with the elegant solution of driving the cams and accessories off the flywheel end of the the engine.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting