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Can I get 300HP out of my 275HP motor?


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I now have a 2004 Deville. It has the standard 275HP motor in it. I was wondering what the difference is between that one and the 300HP. Could it possibly be as easy as reprogramming the computer or changing a chip?

Caddy_Grill.jpg2008 DTS
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The difference between the 275 and 300 hp powertrain is extensive.

The main difference are the CAMs, the 300 hp engine has a bit of a lope to it and its power band is from the midrange up (I think, someone correct me). The 275 hp engine is quicker off the line with a lower power band but as it continues up the band, the 300 hp engine opens up.

So you would need to change the CAMS

Then you would need to change the PCM as the timing is different and the PCM would balk at the new cams.

Then when you put the NEW PCM in, it would be expecting a different final drive ratio as the two engines also have different final drive ratios, otherwise the PCM would gave you a gear ratio error.

I dont know of anyone who has done this, its probably easier to buy a 300 hp deville.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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The difference between the 275 and 300 hp powertrain is extensive.

The main difference are the CAMs, the 300 hp engine has a bit of a lope to it and its power band is from the midrange up (I think, someone correct me). The 275 hp engine is quicker off the line with a lower power band but as it continues up the band, the 300 hp engine opens up.

So you would need to change the CAMS

Then you would need to change the PCM as the timing is different and the PCM would balk at the new cams.

Then when you put the NEW PCM in, it would be expecting a different final drive ratio as the two engines also have different final drive ratios, otherwise the PCM would gave you a gear ratio error.

I dont know of anyone who has done this, its probably easier to buy a 300 hp deville.

I would agree that it's generally accepted that the 275 hp is slightly quicker off the line because its full hp develops at about 5600 to 5750 rmp and has 300 lb·ft of torque with a power band that develops at 4000 rpm. The power band of the 300 hp Northstar, with its 295 lb·ft of torque, kicks in at 4400 rpm, and full hp is developed later at 6000 rpm. So the slightly extra torque and power band that develops earlier generally gives the 275 an edge off the line. However, I do believe the 300 hp NS is overall faster in the 1/4-mile? Correct?

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I would think so

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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  • 1 month later...
The only difference is the intake cam......... and the PCM and trans of coarse.

All of you gentlemen are correct. The LD37 or 275hp NS has a milder cam. it also has an 3:11 gear ratio. the LD38 300hp NS has an more aggressive cam and fuel/air ratio curve to match. The 3:71 gear ratio ( I think? ) snaps through the quarter faster because of that upper rpm band of 4500 plus, all the way to 6000rpm. I have experimented with flipping out computers. A base with a PCM out of the same year DTS. As I suspected and previously noted on here. The fuel gets pretty rich under WOT. and with the difference in tranny gearing the PCM is in LIMP mode from the get go. I have been all over the web, net, and cosmos looking for someone who does flashing of the PCM. That is the answer to your problem my friend. They are out there you just have to find them. I have conferenced called ADS Superchips, Hypertech, and Boss performance. They have all said the same thing. There is no market for this ECU program. So it has to be done by a special programmer. This issue is hot in the world of the wreath. I am looking for other undercover Hi-Po Cadillac freaks to help me out.

"Tiny"

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