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4.6 conversion

auroa 4.0

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I believe the major structural differance is the smaller bore of the 4.0 at 87 mm vs 93 mm in the 4.6. Aside from a particular engine casting or mount - required by the Aurora's engine compartment, the engines might physically interchange.

However, the real problem might not be with the "dumb" parts like the engine itself, but the "smart" parts like the various sensors etc that are set up for 4.6 (assuming you re-use the 4.0 engine harness, computer etc.)

The 4.6 engine and the 4.0 electronics might not agree with each other enough, resulting in a pooly operating unit.

Then again, it might not matter at all. Fuel/air (in larger amounts) will simply adjust to whatever set ratio etc - and you'll gain 50 hp or so !

I cannot recall if the site had a similar question, but this seems like a reasonable one for Guru (Guru).

One has to wonder why Olds decided (or someone else for them) to downsize the engine anyway. Seems like the car was swoopy and all - but crippled from the get go.

Add power to leave problems behind. Most braking is just - poor planning.
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Thanks for the reply man. I just bought my car (a 95 aroura) about a month ago, and i'm not to sure on how the northstars work or what kind of UPGRADES would be worth while. If u have any info or suggestions on Gaining Wheel HP please let me know. I found a chip available only for the 95's at domesticperformance.com but are their any engine mods like maybe 4.6 heads or different cams or valves that would increase HP & Torque????? Thanks :)

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If you have searched for performance, etc - you will find a number of members have had documented success (as in higher drag strip speeds and lower ET's) installing a larger (noiser) exhaust system (Corsa pipes and Flowmaster mufflers seem popular).

A number of members have also installed K & N inlet filters only to run slower... But then again some love 'em and like more noise at the suction side of the pump - as well as the discharge. This mod may need the corrosponding exhaust un-corking to benefit. Some folks have even destroyed the inlet straightener vanes /sensor in ignorance, removed filters and whatever else (all to no avail or even a loss).

The fundemental trade-offs are typically more noise, roughness and perhaps reliability for a few hp from any aftermarket bolt-on. Is speed why you bought the Caddy? There are more cost-effective ways to race. I'll admit that a Caddy (sleeper) does surprise other folks...and that alone is worth a few car lengths.

A chip (applicable for the 94 and 95 with replaceable proms) will probably claim a lot of stuff and might "feel stronger" (as in harder shifts). They also will run the fuel/air wherever possible for performance - but tend to disregard engine heat-load issues (where GM had to warrenty the engine long term). The top speed limiter might be removed by the chip, if you need to be into triple digets a lot. You really need to think if you want some sharp lawyer finding out you installed a "hot rod chip" (in his words) after you have an accident and the other side is looking for anything...

Don't count on any cams, port jobs, undersized puellys, NOS, turbos or superchargers to discover some free or high dollar hp left on the table. The engine is just too dang computerized to mess with - compared to a small block GM OHV or a 4-banger. Other than installing a larger/noiser exhaust, the NorthStar seems to be fairly well tricked out by GM already.

Keep in mind that your 4.0 litre Aurora is about 245 cubic inches, but putting out 250 hp to begin with - with only fuel injection ! The 4.6 is a measly 281 CI yet cranking out 300 to 320 hp across a broad power band. There was a time when over 1 horspower per cubic inch - was truely amazing. Recall the 375 hp 327 CI Chevy small blocks in the Novas !

Now, if you could plug an STS's 300 hp 4.6 into the Aurora, you would notice the differance... right now !

Better yet, if GM ever offered "all the goodies" to tweak 320 hp out of the new V V T 4.6 as in the SRX & XLR (RWD).

And the latest...might be a 400 hp supercharged version 4.6 out for the new STS-V

Don't hold your breath. GM still wants to sell Corvettes... <_<

Add power to leave problems behind. Most braking is just - poor planning.
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