View Full Version : 1998 Seville STS Performance Engine Build - STAGE I

07-20-09, 07:34 AM
Got the parts to take care of the deer damage. Also another VIN 9 block from a '98.

No more games- Caddy's aren't fast in many people's eyes. Mark99STS proved what a N* was capable of with the turbo setup and retaining FWD.

Update on the R&D division at Northstar Performance. We'll be devoting some of our recently aquired 4400 sq. ft. shop to do a perfomance build on my daily driver.

These are the plans for the four different performance build-ups.

Stage I - retains factory heads and bottom end
Stage II - bottom end modified, 2000+ head design, headers & custom intake
Stage III - all out supercharged, still FWD
Stage IV - RWD conversion w/headers, blown, and custom EFI setup

Stage I is a test. Without changing a whole lot, I want to see what can be done to the power output of these cars, starting with a factory VIN 9 / 3.71:1 car.

For starters the 93-99's had far stronger connecting rods than the 2000+. I've seen too many 2000+ with bent/thrown rods from a fluid-locked cylinder. So a '98 is a good year to start with.

I'm working on being able to swap the older forged rods into a 2000+ engine- custom piston pin bushings need to be made and I'll be doing that a bit later.

Plans for the Stage I upgrade:
-ported cylinder heads and exhaust manifolds
-custom ground cams (possibly from CHRFAB)
-slightly modified exhaust down-pipe
-free flowing exhaust system
-modified air intake system (not quite what you're thinking)
-dog-bones to hold the engine in place under WOT runs

Nothing super special is being done here but we'll see what the output becomes. We're hoping for a 20-25HP increase at the flywheel, although a wheel dyno will be used.

With all the HG jobs and stud kits we're shipping, this will take some time, but the build-up will be fully documented, photos will be taken (lots) and no B.S. "We cannot say" or "We cannot release that info yet". We're not expecting 400HP from this; we're being realistic. This is only stage 1 of the Caddy Performance project. Stage IV will be cool, and I think my Eldo is going to get elected for that one.

My STS was tearing up the streets in stock form. Let's see what more we can do with these luxurious beasts.

07-20-09, 09:23 AM
I would take it upon myself to send a sample to Mobil 1.
Just a CYA

07-20-09, 09:56 PM
Corsa for the exhaust FTW

07-21-09, 05:38 PM
Corsa, maybe. I've got Magnaflow mufflers on my Eldo and it sounds real good. Corsa puts out a mean sounding rumble though. This may be a good option.

07-23-09, 02:40 PM
I would take it upon myself to send a sample to Mobil 1.
Just a CYA
I dont know how this got posted here
Sorry should have been in the stringy oil post.
Mods can you move it please

07-23-09, 09:55 PM
Good luck with this.:cool2:

08-25-09, 03:02 PM
Great news. CHRFAB is going to be working with Northstar Performance to modify the stock Northstar in a FWD car for a little more kick. I've got a set of cams and springs on order now. My 1998 STS is back on the road with one problem- I lost 4th gear. So the transmission is getting some work done and the engine is going to receive these performance upgrades.

CHRF (Cadillac Hot Rod Fabricators) may possibly be switching to our studs for their performance engines. They're getting a set from us to try out.

If all goes well there may be a bit of a partnership going that will benefit the Northstar community.

The Northstar can be modified to have more power, and it will be.

AJ are you in on this? I'll need your help with the PCM if you have the time.

08-25-09, 03:10 PM
:thumbsup: It's about damned time. Thanks, Jake....... With CHRFAB in the FWD business there will be quite a bit of trickle-down from their sand rail and Fiero engine work. We'll all come out ahead.

08-25-09, 04:32 PM
Congrats Jake. :thumbsup: Sounds like you are off and running with the big dogs.

Did you ever apply for a patent on those studs? If you can that is. Seems to me it would be pretty easy to copy them once you have one.

08-25-09, 04:50 PM
Thanks. There's a patent pending right now on the studs, a bit more paperwork and a few more days and hopefully it'll be approved. So I'm in the clear for now.

I hope AJ will come in on this too, he's a lot further with the PCM mods than I believe anyone else is. It's about time our Caddy's got a decent aftermarket. I will be contacting more companies soon about other little things that we can do or add to our cars. Aftermarket headlamps for the Sevilles is #1 on my list as far as the exterior goes.

08-25-09, 04:59 PM
Seems to be a lot of interest (and probably money) in the front motor mounts.

08-25-09, 05:03 PM
We're not hoping for a 200HP increase- we're hoping for a realistic increase. A chassis dyno test will be done once the modifications are complete. As for dyno testing the engine itself (flywheel HP) that will be a bit tricky because the PCM has all kinds of annoying torque management controls. It will only give full power to the engine if there is no loss of traction and all the right conditions are met. So BHP would have to be measured on an engine dyno with a lot of sensor simulations - the correct inputs would have to be given to the PCM to make it think it's being driven on the road. That will come later.

We're hoping for about 340-350 HP with the cams, a bit of tuning, some head work, and some exhaust work. All of this could be tied in with a head gasket job that probably should be done anyway, and if these power packages could be offered in addition to the head gasket/engine reseal / stud job and still keep the total price at or around the cost of what GM would charge anyway, it may be a good option for many Caddy owners. The supercharger, once that's complete, should add another 50 HP or slightly more.

EyeKandyBoats & N*Caddy will probably both play a role in this as well with their expertise in the electronics and printing/decal sectors.

AJ if you read this - can you completely eliminate torque management in the PCM? I know it saves the transmission from people like me :D , but I like full power, at all times. My torque management is the weight of my right foot. Sometimes it's heavy and sometimes not.

08-25-09, 05:10 PM
CHRFAB is going to send me their suggested spark timing specs I just need to get them into the PCM and go from there.

08-25-09, 05:57 PM
You've sparked my interest here. Will definitely want to hear more about this :cool2: