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L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

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Old 12-05-2005, 03:09 PM   #1
rons85
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Default Engine swap to Northstar?

Has anyone done this swap, or know of it being done? I've been casting around for a project - this could be it. At first glance it's intriguing - I need to figure out if the cam covers on the Northstar will fit (Narrow enough across the top of the motor) inside the A/C housing and the Brake booster (and the W/S wiper motor) on an '85. I suspect it won't be a problem - it's GOT to be smaller/narrower than a ZR-1 motor is, and That fits!

The Northstar is available in either 4.6L or 4.4L (supercharged) form. Couple of compression ratings through the years, 275 - 320 Hp (470 hp for the supercharged version in the new DTS), depending on year and model. Rear drive applications for the Cadillac CTS SUV and the XLR (of course). The CTS is even more intriguing with the AWD transfer case on the end of the Transmission....

The bellhousing pattern on a Northstar is the same as the 60░ V-6 GM family - so there are 700R4/4L60E transmissions that will bolt right up to it. There are also adapter kits out there for the Trans and torque converter. It's about 100# lighter than an all steel small block chevy, and somewhat shorter - with a pretty healthy RPM range - much more so than an L-98.

Sounds like a fun upgrade. I can't be the first to imagine it - who's done it already?

If it was short enough to leave room ahead of it (behind the steering rack) for a front differential.....
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Old 12-05-2005, 03:14 PM   #2
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I'd talk with Street & Performance - www.hotrodlane.cc
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Old 12-05-2005, 03:21 PM   #3
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While it may be true that the Northstar is narrower than the LT5 that was used in the ZR1, I wouldn't automatically make that assumption. Bear in mind that, when the LT5 was in development, one of the ironclad design constraints was that the engine MUST be narrow enough to be installed into the C4 chassis using the same assembly-line process as was used on the standard C4. Recall that engines were bottom-loaded into the C4 at the factory, thus the LT5 had to be narrow enough to clear the frame rails as it was being installed.

You're wise to have the foresight to verify this first.

Be well,

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Old 12-05-2005, 03:38 PM   #4
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Also be advised, for what it's worth, the ZR1 cars had a different evaporator case. That case HAS been used in some big block conversions. Otherwise, I can't imagine the fascination, time or money being devoted to installing a smaller engine. If you really want to accomplish something install an LS engine. 5.7? 6.0? 7.0, all aluminum?

RACE ON.
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Old 12-05-2005, 05:39 PM   #5
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I agree with some of the others: why??

If you just want a challenge, then you've found a good one. If you want more power, there are easier/cheaper routes. If you want an engine with more modern architecture, just get the whole Cadillac.

Let us know how it works out for you.

Larry
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Old 12-05-2005, 07:18 PM   #6
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Never seen one in a C4,I think it would make an excellent project!(providing it fits,etc)
Sure you can always go with a bigger engine,newest LS something,but dont see why it has to be the norm just because theyre the newer stuff on the market or make more power.Where does it stop?

Btw,Ive seen Fiero w/northstar conversions on the net.Those things are rockets with those engine swaps.Looks high tech as well.
Something different.

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Old 12-05-2005, 07:40 PM   #7
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That is at least partly the point of this idea - something different.

Big Horsepower isn't what I'm after - it would be cheaper and much easier to just build up a "normal" SBC if that was the goal. This car is a Daily Driver - averaging about 100 miles each and every day. There are now 210,000 miles on it. The bottom of the motor is untouched, the Heads and Cam have over 100K on them. It's GOT to be tired. I would Like to think it was now making about 300 hp - probably that's optimistic, considering the time the heads have on them. Even like it is there is enough to play with that I'm not feeling left behind. It's a Driver!

That said, there's a LOT of horsepower potential in the Northstar - Lots. Check out This site if you are curious - neat stuff. http://www.chrfab.com/ Doesn't look to me like I would be giving anything away with a Northstar.

One of the ideas here is better fuel mileage. I'm averaging out at about 21 mpg right now. Thats with a commute (and this is my commuter car) that's about half Interstate and half back roads - throw in just a wee bit of city stop and go. That average is consistent for as long as you want to go between resetting it. I'd like better - Without resorting to the purchase of an econobox.

Less displacement and lighter Ought to make possible better mileage. How much - don't know. enough to be worth it - doubtful, not from a strictly money point of view.

Still - it might be a neat deal. Couple of things - there is no coolant expansion tank on this '85 car. Did Any L-98 use one? Another thing is the battery location - tucked down Below the hood latch on the early cars - out of the way more. (and harder to get to..).

As for the question "Why"... Why Not! If I was Really ambitious I'd be contemplating the AWD trans and xfer case in the CTS - there Might just be room in front of a shorter motor to slide a front differential and halfshafts in there - how cool would an AWD 'vette be
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Old 12-05-2005, 07:42 PM   #8
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Quote:
Originally Posted by Bill's86Coupe
Btw,Ive seen Fiero w/northstar conversions on the net.Those things are rockets with those engine swaps.Looks high tech as well.
Something different.

It sounds like Northstar conversions are passÚ, already. Go retro. How about a 392 Hemi fitted with a modern EFI set up. You could back it up with a clutch-hydro.

RACE ON!!!
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Old 12-05-2005, 07:49 PM   #9
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One step further - How about an alloy flathead with a FAST EFI setup on it? Or even better (and Really hard to find) an overhead valve Rajo (sp?) conversion on a model B block - with EFI and maybe a blower. Something like That you just Have to slide into open frame rails though - it'd be a shame to hide it under a hood. There's a guy selling a 3.5L Aurora Indy race motor on Ebay right now.... (the Aurora 4.0 is part of the Northstar family...)
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Old 12-05-2005, 08:02 PM   #10
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I think the project sounds cool, though I'd also ask "why". I do have a few FYI's, though. The 275-300hp Northstars are FWD motors. The intake entrance is on the wrong side for RWD. The 320hp with variable valve timing is a RWD Northstar. The platforms are somewhat different, I think the blocks are different too.

There are also differences in the Northstar from 1993-99 and 2000+ for the FWD motor. The motor was pretty thoroughly tweaked.

Also FYI, the Shelby Series 1 used a '95-99 style Aurora V8 (4.0L version of the Premium V8/Northstar) in a RWD application. They also made 320hp with some cam and exhaust changes. I think with headers and a good exhaust, the 4.6L 300hp motor would make a pretty healthy amount of power. The exhaust on them in FWD fitting is pretty crappy.

Lastly, the Aurora IRL V8 is barely related to the real production motor. They probably wouldn't have a very good low-end, and I doubt you could run it up to 10,500 rpm through a 700-R4 or 4L60-E. The stock block should be able to handle some pretty decent power, though. It has a 4-bolt ladder-style bottom end, much like the LT5. The 2003-current motors also picked up a forged crank.

Oh, and you are thinking SRX, not CTS. The Northstar apparently won't fit in the CTS, which is why they used the LS6 in the CTS-V.

I'd love to hear more about your project, as I find both motors pretty awesome:

Click the image to open in full size.
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Last edited by Aurora40; 12-05-2005 at 08:06 PM.
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Old 12-05-2005, 09:16 PM   #11
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I don't think fitment would be a problem. I have seen them in a Fiero as well as a 350. Motor mounts will be a problem. The northstar has 1 mount in the front and no provisions for side mounts, not even something you could drill and tap. The northstar is week on torque in the low end, my caddy is a dog off the line. I would suggest driving one first to see if you like it and then decide if you want to go thru all the work.
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Old 12-05-2005, 11:40 PM   #12
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I have been looking at this for some time now. The oil pan will hit the cross frame angle brackets so the brackets will have to be notch out, also you would have to go to dry sump oil system with a shallower sump because the N* oil pan sits about 2 inches deeper than the stock SBC oil pan.

There is about an inch of play between the N* engine block mounts and the C4's frame motor mounts so it should fit with some custom made mounts. Also your will have to cut or grind one spot on the fire wall where the N* heads will hit, right on the edge of the foot pedal box.

The passenger side cylinder head will come very close to the front upper a-arm but I think it will clear it, by about an inch.

I have not checked to see if the hood will clear the valve covers yet.
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Old 12-05-2005, 11:48 PM   #13
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As far as the motor mounts go, the do have them on the block. I know, I have both a 2004 and a 2002 N* 4.6 sitting in my garage.
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Old 12-06-2005, 07:39 AM   #14
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My bad - Yes, it's SRX for the caddy SUV, Not CTS - of Course...
Although... didn't I read that there would be an AWD option in the next Gen CTS?

As is typical for GM, the FWD and RWD blocks are different - mostly in the mounts, but also in the water pump and accessories mounting. The Mounts are the biggest obstacle - a RWD block would have to be the starting point - it means that all of those junkyard FWD cars can't be used for a Donor. Not all bad - the current XLR is 360 hp...

Anyhow - rather than notch the frame for oil pan clearance I would look first at cutting and welding the pan itself, specially if the depth was going to be a problem too. Also (for that and for the firewall clearance question) - don't forget that the motor will be about 3/4" ahead after using an adapter plate to the existing 700R4 - if that's the way I go (simpler since it means no messing around with the C-beam). Side motor mounts are no problem - see the web site I linked above.

I made a couple of phone calls yesterday - the "local" bone yard that is about the best source for complete motors, usually, can deliver me the 4.6 out of an '05 XLR for $3000, with the transmission for $1000 more. I didn't mention my shop connections, so that's NOT the "good guy" price. I also didn't ask what it would take to have the whole car (or whatever is Left of it...) dropped in my driveway so that I could pick off the stuff I wanted.....

Looks like you could buy a brand new XLR crate motor - complete - for about $4500. With no time frame in mind I can be choosy and wait for cheaper/shop around - it isn't something I need to rush into Right Now! It's Cold outside - and the garage isn't heated
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Old 12-06-2005, 09:54 AM   #15
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Quote:
Originally Posted by CFI-EFI
It sounds like Northstar conversions are passÚ, already. Go retro. How about a 392 Hemi fitted with a modern EFI set up. You could back it up with a clutch-hydro.

RACE ON!!!
Clutch-hydro? Na... Rope Drive... or better yet - FLUID DRIVE!!!!
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Old 12-06-2005, 10:31 AM   #16
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I like creative minds. Isn't the N* a 32 valve job? and regarding mileage,
isn't the computer set up so the motor operates on 6 cylinders at
cruising speeds. Regarding the sluggishness someone stated about off the line-I wonder what the caddy weighs compared to the C4?
The N* motor has always intrigued me too.I guess the thing that would
concern me is after installation if you were not satisfied with performance-what and how much for any after market performance enhancements?

BTW-I once installed a 410 Edsel in a 57 Ford-WOW is all I can say-
that mother halled butt. Good luck-and let us know if u do.
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Old 12-06-2005, 11:21 AM   #17
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Well, its not a textbook conversion, but it would sure be interesting to see. Sounds like he's not worried about low end torque, just a driver that's a little different. I say go for it.
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Old 12-06-2005, 11:45 AM   #18
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The bottom end is very stong, in 2004 they added a forged crank with rolled fillets. Even the older N* are strong, cast nodular with rolled fillets. The folks at http://www.chrfab.com/ were telling me that with the older engines they do top end mods, cams and port jobs, throw a small blower on them, run them at 500hp at 8000 rpm with a completely stock crank.

Last edited by mrgrimes; 12-06-2005 at 11:47 AM.
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Old 12-06-2005, 12:07 PM   #19
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Quote:
Originally Posted by rick lambert
BTW-I once installed a 410 Edsel in a 57 Ford-WOW is all I can say-
that mother halled butt. Good luck-and let us know if u do.
Yeah! But you went with a bigger engine. The biggest Ford offered in '57 was a 312, which still had trouble keeping up with Chevy's 283. Too bad you didn't have a 430 Lincoln handy. The Northstar is smaller.

Quote:
Originally Posted by bogus
Rope Drive
Rope drive? I'm aware of a chain drive Mack truck, but I've never heard of a vehicle with a rope drive.

RACE ON!!!
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Old 12-06-2005, 01:02 PM   #20
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The new rwd northstar engine found in the new LR/SRX/STS share engine mounts with the LSX family of engines. Rememeber that the new vette shares a platform with the XLR. I think using a salvaged engine out on an XLR or the crate engine from GMPP would make it a swap similar to the LS1 swap discussed on the forum a while ago.

I believe the hardest part of the swap would be getting the aftermarket ecm required to control the VVT to talk to the factory pcm to retain all the functions of the pcm. This should be just as challegning as wiring up a FAST or Accel system, and thats been tackled here before too. They only problem I can think of would be generating an optispark signal from the northstar to keep the pcm happy.

I'm waiting for GM to offer the new STS-V supercharged northstar as a crate engine.
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Old 12-06-2005, 01:02 PM
 
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