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Thread: 2001 Deville flat or domed pistons

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    960deville is offline Cadillac Owners Member
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    2001 Deville flat or domed pistons

    Help...I am rebuilding the engine in a 2001 Deville. All the engine rebuild kits I have seen online state that the pistons are domed from 2000 to 2003. The pistons in my engine are flat top. I checked the block number and it matches the vin of the car do it hasn't been changed . Question...can I use the recommended dome pistons in this engine without valve issues?


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    Submariner409's Avatar
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    Re: 2001 Deville flat or domed pistons

    The pistons were flat topped with valve fly cuts - Go up to Vendors and check in with Northstar Performance in Canada (the stud makers) and/or Google "carroll custom cadillac" and talk to Tim (the other stud makers).

    Your compression ratio is 10.0:1

    Why are you rebuilding the engine ? A thrown rod bearing or broken piston rings is one thing - total overhaul, but head gaskets do not require even touching anything below the block deck.

    The cylinder hone grit and pattern are special - be careful........ and those cylinder liners won't take much overbore.
    Last edited by Submariner409; 08-30-13 at 04:19 PM.

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    Re: 2001 Deville flat or domed pistons

    This should answer your question.


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    960deville is offline Cadillac Owners Member
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    Re: 2001 Deville flat or domed pistons

    Thanks....I purchased a master rebuild kit from Rock Auto. The pistons are domed in the center. I will be returning the kit.

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    Re: 2001 Deville flat or domed pistons

    in 03.5 GM upgraded their Pistons to a raised piston, this was to reduce Carbon Knock Issues, and to increase clearance between the piston and the head, it is now the Factory GM Replacement for the 2000-2003.5 as well. You do not have to return the pistons they will work in your engine.


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

    Evrett, Sales Executive of the SureGripô Cylinder Head Stud Kit

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    Re: 2001 Deville flat or domed pistons

    That's good to learn.

    RockAuto seems to list the domed (small, center) piston for all the 2000 + Northstars now. Live and learn.

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    Aztec ETC ECS's Avatar
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    Re: 2001 Deville flat or domed pistons



    Yeah. The piston shape was a real problem. REALLY important & necessary to redesign.

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    Re: 2001 Deville flat or domed pistons

    Snooping on the telephone and online - seems the redesign piston also addressed some of the notorious Northstar "cold carbon rap" experienced by owners of cars that rarely see aggressive "exercise" throughout the total rpm range. You'll notice that the piston in Aztec's picture has the anti-scuff coated skirt, too.

    Cold carbon rap is discussed in the articles way up ^^^ in the top black bar - the Cadillac Technical Archive.

    But - 3 compression rings in addition to the oil control ring set ? ......... or is that narrow groove a dirt/gas bleedoff channel ?

    EDIT: This thread has been moved from Deville to Engines in order to reach a broader population of Northstar owners.
    Last edited by Submariner409; 08-31-13 at 09:06 AM.

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    stoveguyy is offline Cadillac Owners Connoisseur
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    Interesting how center of piston is raised which reduces gap from piston to sparkplug area? Didn't the fuel requirement drop from premium to reg about this time also?

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    Re: 2001 Deville flat or domed pistons

    Yes. That happened with the 2000 redesign when compression was lowered from 10.3:1 all the way down to 10.0:1.

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    Re: 2001 Deville flat or domed pistons

    Looking online, this Sealed Power piston for 2000 - 2004 N* is the third different domed piston that I have found. Something must have been changed to the piston deck height to keep very close to the 10.0:1 compression ratio.

    Notoce that, in the below link, the piston is offered only in standard size - in keeping with the GM service manual which says "No oversized pistons are available" (from GM) and goes on to say that boring is not recommended.

    http://www.fme-cat.com/overlays/part...=#.UiIA2387vms

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    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    Maybe that's just a stock photo?

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    960deville is offline Cadillac Owners Member
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    Re: 2001 Deville flat or domed pistons

    dnj_084620.jpg

    OK guys....you think the domed piston design will work in my motor. Rock Auto get's this kit from DNJ. Part number EK3162. I called DNJ and this is the recommended kit for a 2001 Deville.........I was just concerned about going from a flat top to a raised piston design..
    Last edited by 960deville; 09-02-13 at 09:30 AM.

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    Submariner409's Avatar
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    Re: 2001 Deville flat or domed pistons

    After doing some more snooping and phone calling (neighbor Cadillac dealership shop tech), that set should work - the crown looks to have been relieved just enough to allow valve clearance, create the dome, and not change compression ratio.

    We now need to re-think the 2000+ Northstar piston recommendations. In 2000 the shape of the combustion chamber (head) was changed, and if GM went to a domed style piston in 2003.5+, then it must have something to do (as posted) with combustion flame travel (carbon buildup prevention). In the 2000+ head, the spark would occur just about at the center of either that flat top dome, the round top Sealed Power dome, or the flat-top ridge shown in the earlier AztecETC post.

    Maybe we'll have a guinea pig or two for reports on driveability and fuel mileage with the new units.

    Evrett, Tim - have you guys built any of these yet ? Does CHRfab source an 11.0:1 piston, and what does it look like ?

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    BetterNorthstar is offline Cadillac Owners Member
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    Re: 2001 Deville flat or domed pistons

    Submariner409, both my two (2) 2001 Devilles had the new piston and rings installed by the dealeship under warrany, too much oil consumption and carbon buildup.

    I just this past week had the heads off one of the Devilles again, this time for another head gasket repair and this is how the dealer installed pistons looked, domed. Looks like the one Rock Auto sells now..

    20130903_101401 compressed.jpg

    Hope this helps show what the new dealer pistons look like, domed.

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