I'm neck deep in the middle of an LS4 swap into an '88 GT. I'm doing this job for a customer, I don't know if he is a member of this forum. I'll leave it up to him to reveal his identity if he choses to. We have been discussing the project via email for about two years, and I finally accepted the job. The engine was purchased from Schram Auto Parts, a complete dropout from a 2006 Impala SS with 7 miles. Schram provided the complete drivetrain; engine, trans, ECM, TCM, column, pedal, etc..

The Fiero will be getting a lot of other performance mods, but I'll start off the thread off with the engine/trans. A lot of the stuff I post is already covered in other threads, but I think some of you will still like to see it again. The list of mods so far goes something like this:

GMPP LS hot cam, 219/228 duration @ .050", .525"/.525" lift
LS6 valve springs
GMPP Racing hydraulic roller lifters
Increase compression ratio to 10.6:1
LS2 intake and throttle body
Eliminate DOD
Torsen LSD
Upgraded torque converter
Shift kit

All the research I did told me that any standard LS cam would fit in the LS4, but nobody could confirm it. Well now it's confirmed. The LS hot cam which was designed for the LS1 does fit in the LS4, so I assume any other LS cam would work. Although the stock LS4 lifters would likely work with the new cam (with DOD disabled), we chose to install a set of GMPP 8000 RPM lightweight race lifters. The new lifters also required new guides from GM. Here are a few pictures of the engine after the cam and lifters were installed. Pretty boring pics, but you can see how clean the engine is with only 7 miles on it. There was some soot on the pistons but it wiped right off.






The LS4 heads are the same '243 heads that are used on the LS2. We decided not to port the heads, figuring that if they are good for 400hp on a stock 6.0 LS2 then they should flow plenty for this little 5.3. The GM cam kit comes with LS6 valve springs which fit without problems. I had .035" milled off of the heads to reduce the combustion chambers to 60cc which will raise the compression ratio to about 10.6:1. I used GM MLS head gaskets and ARP studs. Here are some pics of the heads after milling and deburring.





The LS4 valley cover got replaced with an LS2 valley cover. This wasn't a necessary change, but it removed a pound or two and made extra clearance for the LS2 intake. The oil pressure sensor port needed to be modified to clear the LS2 intake. I also welded up the crankcase vent because it won't be used. The mods are not done yet in the pics.




The LS2 Corvette intake bolts right on (after the oil sender mod) along with it's fuel injectors and rails. The LS4 injectors and rails will not fit the LS2 intake.




More coming soon.....

Jon

Good to see another LS4 Thread starting up. The more that are done the more information gets put out there which makes the swap easier. Any plans on making the needed engine mounts for the LS4 swap? I made my own but only after alot of trial and error to get the motor lined up and level. Pm sent also.

The mounts are drawn in CAD and I have a CNC plasma cutter in-house so I can make them for anyone who is interested. They are not bolt-in mounts, it will require some welding to the cradle. The ones for this car are out for powder coating along with the cradle, I should have them back on Monday. I will continue with more pictures then.

Jon

This thread should be great, any pics of the car?

quote Originally posted by FieroAddiction: The mounts are drawn in CAD and I have a CNC plasma cutter in-house so I can make them for anyone who is interested. They are not bolt-in mounts, it will require some welding to the cradle. The ones for this car are out for powder coating along with the cradle, I should have them back on Monday. I will continue with more pictures then. Jon

COOL, one more LS4 thread I am doing mine as stock possible, but I love to see what I could do to it latter

I already had my mounts welded on the cradle, BUT could you post a price with pics of your design?

I thought the LS4 had LS6 heads? You say they are LS2?

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quote Originally posted by FieroAddiction: I'm neck deep in the middle of an LS4 swap into an '88 GT. Jon

This should be good. If only you could lend your considerable talents to perfecting a manual transmission LS4. The auto transmission is a non-starter for me, (no pun intended)

I sent the torque converter to Pat's Converters, I have used them before with good results. Within about a week they had it shipped back to me, modified to match the application.
http://patsperformanceconverter.com/index.htm

I installed a Torsen LSD from GMPP. They're available with a couple different ratios, we went with the stock ratio. The stock HD differential is removed by first removing the case extension, then forcing a wedge (chisel) between the diff cross shaft and the left axle shaft to compress the spring clip on the axle. Once the spring clip is compressed, the differential slides out. The whole deal only takes about 15 minutes with the trans out of the car.






The contents of the Thrasher shift kit shown below. I won't go into details about installing it, their instructions are pretty good. It took me about 30 minutes. I went with the level 2 setting.


Jon

quote Originally posted by FieroAddiction: I installed a Torsen LSD from GMPP.

price of this puppy???????? if you don't mind. i wan't one for my fiero

Oh boy, Oh boy. This looks like is going to be fun to watch. I will be following this thread closely.

Fiero Addiction,
Thanks for starting this thread. Keep up the good work, and the good pics and documentation.

~Bob

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"Its nice to be important.
Its more important to be nice."

The Torsen sells for about $1400. They are only available through GM AFAIK.

GM part number 88958682
Torsen Differential
• Used in GM 4T65E Racing’s FWD drag racing programs
• Tested to 900+ horsepower
• In drag-race style, straight-line acceleration runs, this
results in a close to ideal 50/50 power split to both
drive wheels
• In cornering, while accelerating out of a turn, the Torsen
biases power to the outside wheel, reducing insidewheel
spin
• Provides constant and infinitely variable drive
• Power is transferred automatically without the use of
normal friction
• Extremely strong and durable, since it is gear operated
• No plates or clutches that can wear out
• Comes with new pinion gears already loaded

quote Originally posted by FieroAddiction: Funny you should mention that. I have a jig to put the LS4 starter mounting boss on a manual trans. The LS4 looks real nice bolted to an F40 Jon

I happen to have an "extra" F40 sitting around. If by some chance some one could reprogram the stock PCM to run the LS4 with a manual, I would DEFENATLY get in line for it. Could you give more info on the starter swap on the F40? Flywheel? Axles?

I think everyone should know that independent testing by Duttweiler has proven that the LS2 intake, despite it's larger TB, is 10 HP worse than the LS6 intake. The FAST LSX is 10 hp better than the LS6. So I don't think your intake swap actually gained anything.

quote Originally posted by Isolde: I think everyone should know that independent testing by Duttweiler has proven that the LS2 intake, despite it's larger TB, is 10 HP worse than the LS6 intake. The FAST LSX is 10 hp better than the LS6. So I don't think your intake swap actually gained anything.

I don't quite understand your reasoning, we went from an LS4 intake to LS2. The LS6 or FAST intake may be better, but that doesn't mean we didn't gain anything with the LS2 intake. It's difficult to see in the pictures, but anyone who's looked at an LS4 intake can see the huge restriction right behind the throttle body. The Duttweiler tests were done on a 6.0 liter AFAIK, so I don't know how much the results apply here anyway. The FAST intake is quite expensive, and since we are not building a maximum effort race engine I didn't think it was worth the extra expense. The LS2 has the slight advantage over the LS6, being a Gen IV which means it uses the new EV6 fuel injectors and I don't need to change the injector plugs. It also takes that nice LS2/3/7 throttle body.

Jon

Nice build! I can't wait to see more! just saved to fav.

quote Originally posted by Isolde: I think everyone should know that independent testing by Duttweiler has proven that the LS2 intake, despite it's larger TB, is 10 HP worse than the LS6 intake. The FAST LSX is 10 hp better than the LS6. So I don't think your intake swap actually gained anything.

ANY manifold swap onto an LS4 will be an upgrade. Even the 5.3 truck engines have more power than the "SS" LS4 car engines. The LS4 has a nasty bend and blockage problem inside. The other manifolds don't have to bend around the DOD plug and have larger runners along with higher profile for less restriction inside the plenum.

At last; a HOT RODDED ls4! This is going to be great! FYI, SUPER CHEVY mag. Oct 08 pg. 80 (some good info on the 5.3)

Nice project but lots of work!!! However, I would have just hung a turbo on it and put in 8-9 psi. of boost. Turbochagring is easy to do and you gain about a 30-40% increase in power with no hassles. Want more just intercool and apply more boost!!!
In other words you could easily be at 400HP with moderate boost at a far lower price and with far less work. I saw an LS4 swap on a post here a while back and the guy had to do some serious cradle mods to get the engine to mount. Good luck with the project. I knw that you will succeed.

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Parts are back from powder coating, they look great. The exhaust manifolds and crossover are Jet-Hot Sterling ceramic coated, but I decided to put all the heat shields back on anyway.







The trans mounts are the standard bolt-in 4T65E brackets and poly mounts that I already sell.

quote Originally posted by FieroAddiction: Parts are back from powder coating, they look great. The exhaust manifolds and crossover are Jet-Hot Sterling ceramic coated, but I decided to put all the heat shields back on anyway. The trans mounts are the standard bolt-in 4T65E brackets and poly mounts that I already sell.

Mounts look good and are similar to what I did on my swap but your are of course alot cleaner looking. Wish these would have been avaliable before I make up the set that I did but good to see they are being offered now for future swaps.

manifold debate aside, Excellent build.

Has anyone tried to make a stroker crank for the LS4? Could you machine down the crank of an LS1 or LS2 to make it the right length? That'd be pretty sweet if it could be done. Otherwise really nice build!

It's the same stroke as everything but the 4.8 and 7.0, so for the same cost as building a 5.3 stroker, the block could be sleeved for a bigger bore. The engine could go as big as 387 cid or 6.35 litres with the stock crank.

Jon, I'm just curious about the piston-to-valve clearance with the bigger cam and the milled heads. When i done my ls4 swap i was going to do the hot cam also, so i called comp cams to see what they had available. I was told that the ls4 had vary tight piston-to-valve clearance and that i would have to do a piston swap to use a larger cam. At that time nobody had done one yet, so because of that and the bottleneck in the intake and exhaust, i decided to leave it stock for now. BTW, good work, the mounts look great.

Ron

Yep, bore it to 4.065, put in a set of LS3 pistons and you've got a 6.2 liter LS4.

MAN THAT THING IS A BEAST! That's one good lookin' engine! I don't think I'll ever do this swap, but how hard is that thing to mount to the frame? Honestly I would love that much HP without a turbo. . .

quote Originally posted by FieroAddiction: Yep, bore it to 4.065, put in a set of LS3 pistons and you've got a 6.2 liter LS4.

Can you bore the LS4 block that far or does it have to be sleeved?

I clayed the heads, there's plenty of PTV clearance. I don't remember the actual numbers, but it was not close enough to be a concern.

Jon

It can't be re-sleeved in the same sense as a 4.9 can.
Having an LS1 "sleeved" is a not a standard rebuild practice. It is for performance only and is similar to having a Honda block sleeved. The stock bores are machined completely away and a sleeve that braces against the outer wall of the block is pressed in place of them. The fact that the Gen III/IV's have the head bolt holes in the outer wall of the block allows this, of course.

Looking good. PM sent.

Is that a starter, behind the exhaust? Do you have any other pics of the starter?
A really nice swap. I like it, when someone takes the extra time for details.

[This message has been edited by RumbleB (edited 10-29-2008).]

quote Originally posted by RumbleB: Is that a starter, behind the exhaust? Do you have any other pics of the starter? A really nice swap. I like it, when someone takes the extra time for details.

Yes that is the starter. It is mounted to the tranny. The LSX engines don't have the starter boss on the left side of the engine like the V6. So GM modified the tranny bell housing for a starter instead of recasting the block and oil pan for a starter on the "wrong side" of the block. The OIL pan has oil passages cast through it and they come to a location were the V6 starter location should be. This makes for a tight fit for a starter in that location.

If you wanna spend, you can get an LS4 block done to use the darton sleeves, allowing a 4.125" bore. For stroke, use the same crank you would for an LS3, but the balance depends on the rods and pistons used. Having a 427.65 ci LS4 is practical, for a price. That's 7 liters. As for the conventional aluminum 5.3 blocks going to 3.908", that gives you about 384 ci with a 4" stroke.About 6.3 liters.

The LS4 crank is shortened at the extremities compared to the cranks used in RWD engines. I'm not sure of the exact differences, but I don't think any of the forged or billet cranks currently on the market are viable for an LS4. The only aftermarket crank option would be a custom billet crank with the accompanying design fee. Given that choice, I'll stick with a 6.35 litre, top it off with the 7 litre top end and just rev it a bit higher.

Any GOOD machine shop could turn the ends of the crank to match. Yes, it's more work and cost. But if you want an outwardly-legal trroker, without any questionable adapter plate, this is what's involved.

From GM media:
"The LS4’s aluminum cylinder block shares its basic architecture with the 6.0L LS2 V8 available in the Chevrolet Corvette. This Gen IV small block’s identifying feature is its external knock sensors, moved from inside the V, or valley, to make room for advanced technologies such as AFM. Yet refinements in this latest small block go much deeper, with features such as deep-skirt cylinders, six-bolt cross-threaded main bearing caps, a structural oil pan, and other vibration-reducing, weight-saving design elements.

The 5.3L LS4, however, was designed to mount transversely (sideways), compared to the longitudinal installation of the 6.0L LS2 and every small block V8 before it. Its crankshaft is shortened 13 mm – 3 mm at the flywheel end and 10 mm at the accessory drive end – to reduce the length of the engine compared to the 6.0L. All accessories are driven by a single serpentine belt to save space. The water pump is mounted remotely with an elongated pump manifold that connects it to the coolant passages. Revised oil pan baffles, or windage trays, are incorporated into the LS4 to ensure that the oil sump stays loaded during high-g cornering. With its front-drive layout, the LS4’s exhaust manifolds are joined by a crossover pipe, with a single, high capacity underbody catalytic converter."

[This message has been edited by FieroAddiction (edited 10-30-2008).]

quote Originally posted by Isolde: Any GOOD machine shop could turn the ends of the crank to match. Yes, it's more work and cost. But if you want an outwardly-legal trroker, without any questionable adapter plate, this is what's involved.

Just build up the stock block with the stock LS4 crank an use the stock LS4 serp belt system.
The manual tranny is going to need a custom flywheel any way. Build the flywheel to the LS4 crank.

Great work Jon! Can't wait to see this come together. I have been waiting to see a new project from you. Keep up the great work!