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ok so apparently the best usdm kl you could get was in the millenia, to my understanding it was because they had the bigger square port runners. According to my parts system i show that after 95 they came oval port instead of square port.... are they oval port millenia engines in existence? and are they less powerful? im just curious, mainly because of the swap im taking part in with a buddy of mine, the ecu he has has the vris points set for the milly intake mani so i dont wanna mismatch ports since he has a standard mx6 de with the oval ports... any help is greatly appreciated thanks!

pretty basic the millenia is the best KL motor you can buy stateside stock for stock as a plug n' play setup. All millenia heads should be square ported from the factory, some even have the SLAs which is a nice benifit. There have been claims of oval runners on a millenia head but I have yet to see someone post and actual picture of it with the intake/car to validate it hasnt been modified (headwork at a shop that may have substitued a DE head for example)

Worst case if you do have an oval runner head with the square port intake you can but a set of intake spacers and bore them from outlaw engineering like the PT guys have done or just run it, there will only be nominal power difference, if you search theres some old dyno graphs with & w/o portmatching. The real performance difference comes from the intake design more than anything anyways.

Sleeper6 wrote:pretty basic the millenia is the best KL motor you can buy stateside stock for stock as a plug n' play setup. All millenia heads should be square ported from the factory, some even have the SLAs which is a nice benifit. There have been claims of oval runners on a millenia head but I have yet to see someone post and actual picture of it with the intake/car to validate it hasnt been modified (headwork at a shop that may have substitued a DE head for example)

Worst case if you do have an oval runner head with the square port intake you can but a set of intake spacers and bore them from outlaw engineering like the PT guys have done or just run it, there will only be nominal power difference, if you search theres some old dyno graphs with & w/o portmatching. The real performance difference comes from the intake design more than anything anyways.

as far as ive found out on my own, they only came with square port heads in 95, and thats what my infinity parts system shows, after 95 they continued to use the square port mani and mazda just mismatched heads, everything was the same but after 95 the heads went to oval runners.... idk im just confused lol

heres the diagram for intake service and repair on ALLDATA 2013

also heres the motor past 96 for a millenia this is the same part number as in my parts system via O'reilly Auto Parts,
http://engineguy.com/02-96-mazda-2-5-l- ... c-vin.html

This mismatched heads debate stems from ONE ill informed post on ProbeTalk.

Mazda likes to be different, this is true. Were they to haphazardly stuff mismatched intakes onto their engines, they would have
A). Fired a dozen or so engineers. Or B) Gone out of business for good.

/Thread, please. This is as dead a horse as they come.

In advance, I would like to prevent the "My manual says _______" argument.

Which is more likely, a team of professional engineers mismatching engine components INTENTIONALLY, or the editor of a service manual making a simple mistake, and using the same image from one KL head to another? Maybe said author didnt know that the Millenia had square ports... given that EVERY OTHER K SERIES IN AMERICA did not ship out with them.

Please, let this dead horse rest.

95 millenias in USA square port (kl31 heads) 96+ millenias in USA oval port heads (kl01) Also the oil pans changed somewhere (98+) I believe, & lost coolant lines going to oil pump & other small change. Trust me I've pulled enough of these engines apart & out of millenias @ the wrecking yards.

You are 100% correct on the oilpan, which oddly enough only affected the Millenia, and not the G4 models.

As for the oval port Millenia engine... Everybody says it, but I have never seen photographic evidence of it. Every Millenia I have ever seen had KL31 heads sitting in it; Granted, I don't document the year of every car I look at. I doubt 20+ have been 95 models, however...

I want ONE video of somebody pulling a curveneck manifold off in a junkyard, so I can see square port gaskets atop oval port heads, with typical high mile grime around the openings... That would be enough to convince me of the possibility.

MrMazda92 wrote:You are 100% correct on the oilpan, which oddly enough only affected the Millenia, and not the G4 models.

As for the oval port Millenia engine... Everybody says it, but I have never seen photographic evidence of it. Every Millenia I have ever seen had KL31 heads sitting in it; Granted, I don't document the year of every car I look at. I doubt 20+ have been 95 models, however...

I want ONE video of somebody pulling a curveneck manifold off in a junkyard, so I can see square port gaskets atop oval port heads, with typical high mile grime around the openings... That would be enough to convince me of the possibility.

Agreed. Video or at the very least, photo evidence or its bulls---.