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Discussion Starter · #1 ·
I have a '97 Formula with the LT1 and a 6spd manual. Looking to replace it with an LS1 from an '04 GTO.

How can I find out if it will fit and what other parts I will need?
 

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Since the LS1 was used in the 98-02 F-Bodies, it will "fit". However it is unlikely that the GTO accessory mount(s) or possibly the exhaust manifolds will work. Then there is the issue of the K-member (engine cradle). I'm pretty sure you will need the K-member and motor mount stands from a 98-02 V8 Firebird or Camaro,

If you could find a wrecked 98-02 F-Body with the front end intact, and a dead LS1, you could get most of what you need. You will also need the PCM/engine wiring harness and possibly the PCM (check to see if the GTO used the same part # as an 02 F-Body).

Then there's the issue of the trans. The LT1 T56 6-speed is different than the LS1 T56. Different bell housing, different input shaft length, and where the LT1 has the unusual "pull back" clutch with a fork and slave cylinder, the LS1 uses a conventional "pusher" clutch with the slave cylinder bolted to the front plate of the trans, no fork, pushing directly on the throw out bearing.

There is also a difference in the fuel systems..... nothing that can't be overcome. Where the LT1 system is recirculated, operating at a vacuum compensated 3bar (43.5 psi), most of the LS1 systems are dead-end feed, no vacuum compensation, operating at 4bar (58 psi).

Maybe you already knew most of that, but just thought it might help if you were not aware.
 

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Discussion Starter · #3 ·
Thanks for all the info Injuneer (Fred)!

The GTO engine I was looking at is a complete drop including the trans, ECM, etc. so I'm guessing a lot of the issues you pointed out may be taken care of with that?

The K member and fuel systems I didn't count on.

I also have a line on a complete drop from an '02 Trans Am. It's got more mileage on it, but sounds like it will be a better fit overall.
 

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The aluminum block LS1 is all much lighter than the iron block LT1. Getting the front springs with the 02 T/A would also solve that problem. Otherwise the front end is going to sit high.

Check the shifter location on the GTO T56. The tailshaft/shifter housing could be different. I honestly don't know if there is a difference. I've seen a Viper T56 and the shifter is in a completely different location. Ditto on the trans cross member. Not sure if the LT1 is the same as the LS1.

An F-Body LS1 wiring harness would also work better, because it has to interface with numerous body connectors. Even the LS1 F-Body harness will have significant differences from the LT1 harness.

The 97 Corvette LS1 had a recirculated fuel system. Might look at that setup to ease the fuel supply issue with minimum changes.

Just curious - why are you doing this? Your LT1 could be cranking out 500 HP at the flywheel with ported stock heads, matched cam, and supporting mods. Sure, the LS1 could be 550-600 HP if that's your goal. But you have the expense of the swap, plus the expense up upgrading the LS1.
 

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Discussion Starter · #5 ·
Short answer is that I'm very sure I've blown a head gasket and possibly more. The first quotes I got on just having the head gaskets replaced made me wonder what more I could get if I upped my budget a bit (especially if there's more than just the gaskets to worry about.)

I talked it over with someone I work and he suggested that by swapping to an LS1 I could pick up some horsepower as well for about the same amount of labor.

Now I'm back to wondering what I could get out of the LT1 by pumping $3,500 - $4,000 into it.

I've got a guy locally that does performance cars only so I'm going to talk to them as well.
 

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1993 6-spd T/A - 1996 C4
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$3,000 - $4,000 will get you a drop in replacement LT1 with a warranty through GM. ...something like 3 years 36,000 miles. They are completely "refurbished" and basically a brand new engine. Can't remember if it was Summit or Jegs but they are out there. LS1's are good for tuning. I don't think there are any other advantages there except for the OptiSpark not being involved. LS1's do have more HP, LT1 has more TQ. End of the 1/4, they're even. Personally, I prefer TQ. If you're going to get into tuning, LS1, hands down. If not, the LT1 Will give you so much more bang for the buck.

Don't write the LT1 off. ...at least not until you've done your homework and are making an educated decision for yourself.

Good luck with your decision.

Edit: found the engine. 30 month, 50,000mi warranty.

http://www.jegs.com/i/Blueprint+Engines/138/BPG35029CK/10002/-1

Or, using some parts from your engine that are still good. (Same warranty)

http://www.jegs.com/i/Blueprint-Engines/138/BPG35029C/10002/-1
 

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The part about the LS1 torque is not completely accurate - a popular internet misconception.

The GM authorized manual (GM Part #12497977) I have on Corvette fuel injection systems has a chart showing the HP and torque of the LT1 (Corvette version) overlaid with the same for the LS1 and the older L98. The LT1 and LS1 torque is virtually identical up to 2,000 RPM, then the LS1 torque continues to rise, while the LT1 actually drops into a small valley from 2,000-3,000 RPM, before peaking at 3,500 RPM and then tailing off significantly above 3,800 RPM. At this point, the LS1 is at least 40 lb-ft above the LT1, At 5,600 RPM, the LS1 is falling, but is still at 300 lb-ft, while the LT1 is falling and closing in on 240 lb-ft. At no point on the chart does the LT1 torque exceed the LS1 torque.

The older L98 350 used in the 3rd Gens actually has higher torque the the LT1 from 3,000-3,500 RPM, but then rolls over and plays dead above 3,600 RPM.

The LT1 is a good engine.... I've invested a lot in mine. But mod-for-mod, the LS1 will always come out 50 HP higher.
 

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1993 6-spd T/A - 1996 C4
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Whatever. ...corrected.
 

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There's no reason you can't replace the head gasket yourself. Pull the heads, ship them off to the quality porter, with the intake manifold. Pick your HP level and pick your degree of cam aggressiveness. Cold air intake, long tube headers, quality 3" catback, larger injectors, upgraded fuel pump and a good tune (mail order to start out, dyno for full engine potential).

Did you have any evidence of water in the oil? How many miles on the engine?

Good source of ported stock LT1 heads:

http://elliottsportworks.com/

http://www.advancedinduction.com/LTX/AiLTxMain.php
 

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Discussion Starter · #10 ·
I suspect I do have water in the oil. I pulled the dip stick and it looked like it was covered in chocolate milk rather than black oil.

I'm going to drain it this weekend to be sure.

The engine has about 120K on it.

I'm pretty mechanically inclined but pulling an engine apart tot this level is well beyond anything I've tried before.

I looked on YouTube and found a series of videos a guy put up they're a little iffy.

Is there a good place to go for instructions / videos / etc.?
 

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