: 2001 Deville flat or domed pistons

08-29-13, 07:31 PM
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?

08-29-13, 07:37 PM
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.

08-29-13, 09:36 PM
This should answer your question.


08-30-13, 04:30 PM
Thanks....I purchased a master rebuild kit from Rock Auto. The pistons are domed in the center. I will be returning the kit.

08-30-13, 05:14 PM
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.

08-30-13, 05:18 PM
That's good to learn.

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

08-30-13, 10:12 PM

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

08-31-13, 09:53 AM
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.

08-31-13, 10:59 AM
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?

08-31-13, 11:24 AM
Yes. That happened with the 2000 redesign when compression was lowered from 10.3:1 all the way down to 10.0:1.

08-31-13, 11:38 AM
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.


08-31-13, 01:02 PM
Maybe that's just a stock photo?

09-02-13, 10:11 AM

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..

09-02-13, 11:06 AM
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 ?

09-08-13, 02:32 AM
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..


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

09-08-13, 09:55 AM
Good info - thanks for the photo. You made out like a bandit with the dealership honoring the GM TSB instructions on excessive Northstar oil consumption - within the warranty period - for engines that did not respond to the new piston ring cleaning procedure posted by GM. The original TSB was 02-06-01-009C - probably superseded or updated - it says replace the rings only (and not to deglaze the cylinder walls).

The above TSB also makes reference to Corporate Bulletin 01-06-01-011 (oil consumption) and the text in both of those bulletins specifically addresses the proper oil fill amount and dipstick reading level for Northstars.

Did you or the dealer do the studs ?

09-11-13, 01:30 AM
I got the studs from Northstar Performance / Jake and had the Cadillac dealership install them in 2010, about 22,500 miles ago. Great studs!

09-11-13, 11:56 PM
I got the studs from Northstar Performance / Jake and had the Cadillac dealership install them in 2010, about 22,500 miles ago. Great studs!


09-28-13, 07:39 PM
Northstar's had a few pistons. I think 2 on the Gen 1 and 2 on the Gen 2
These are the originals and the GM TSB pistons

http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/HPIM3403.jpg (http://s224.photobucket.com/user/AJxtcman/media/Northstar/HPIM3403.jpg.html)

http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/HPIM3402.jpg (http://s224.photobucket.com/user/AJxtcman/media/Northstar/HPIM3402.jpg.html)

http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/Picture013.jpg (http://s224.photobucket.com/user/AJxtcman/media/Northstar/Picture013.jpg.html)

http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/HPIM3395.jpg (http://s224.photobucket.com/user/AJxtcman/media/Northstar/HPIM3395.jpg.html)

http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/HPIM3398.jpg (http://s224.photobucket.com/user/AJxtcman/media/Northstar/HPIM3398.jpg.html)