Slow Z28

iTrader: (19)

read that topic up above and maybe I missed it. What size throttle body are on the cars? Stock size 78mm like an LS1/LS6 or a 90mm like an LS2 or something even smaller?

Injector size on these cars?

Slow Z28

iTrader: (19)

Another one would be, does anyone know if the wiring harness on the coils is the same as a vette/f-body in regards to RPM output signal

TiredGXP

iTrader: (2)

I finally found my calipers, so I thought I'd go do some measurements.

MAF is 78mm. The strange thing is that the TB measured out to only 76mm. Tried it three times measuring across the horizontal dimension where the machined surface extended out to the inlet, same result each time.

Slow Z28

iTrader: (19)

thanks man! and it looks to be a 4-bolt TB like the LS2 stuff compared to the 3 bolt of the earlier LSx.

MagnaPilot

It is a 4 bolt setup, same one used on some 6 cylinder cars. Problem is, the intake manifold will not support mounting a 90mm TB on it. I don't know for sure on the harness, but I can verify that they are the same coils used on a LS2 GTO, and the same ECU is used as well, to common sense would dictate that most likely they are the same wiring.

Slow Z28

iTrader: (19)

Thanks for that info. Woulda been cool to be able to swap a vette TB on the thing for dirt cheap, but guess not, haha.

But for the ECU and the coil stuff, that info is greatly appreciated. If it's the same coil, has to be the same wiring if it ends up being the same prt #

MagnaPilot

Well, the slightly good news is that supposedly the LSx intake manifold can be mounted in either direction. So in theory, you can mount a ls2 or whatever manifold on the LS4. The only major complication is that the Displacement on Demand oil sensor is slightly in the way of the neck of the manifold. If that sensor could be moved, then in theory you can mount a different manifold easily, along with a 90mm throttle body. I'm hoping to try this myself sometime later in the year, once I get a garage to work in.

Taz34SS

iTrader: (2)

Problem is that our TB have the Drive by Wire system. There is no aftermarket TB that will work as of yet on our cars.

Also, the Fast 90/90 intake is 1" to big for our block aswell. trust me, I tried.

TiredGXP

iTrader: (2)

Yeah, there's two things in the way of an aftermarket intake and/or large throttle body.

The oil pressure sending unit (opsu) mounts on a ~1.5" boss cast into the valley cover. Just milling the boss down doesn't help because the opsu is larger in diameter than the boss - It's the real restriction to mounting an aftermarket intake. There's also an issue with the DOD solenoid electrical connector, it needs to be modded or removed to allow an aftermarket intake to sit flush. Both of these things are at the back of the other LSx engines where they don't interfere with the TB or intake throat.

I have another valley cover being delivered this week, so I'll be able to mock up the mods required to relocate the opsu. If it works there may just be a FAST or Street Warrior intake coming this spring

Taz34SS

iTrader: (2)

I hope your right about that, but when I last talked to the guys at Fast, they said that there was no plans on doing an intake system or TB with the drive by wire system for the LS4 cars.

TiredGXP

iTrader: (2)

I'd heard that too. I'm attempting to modify things so that an LS6 compatible intake will fit. GM makes a 90mm electronic throttle body that should be compatible, just no point in trying to adapt one to the stock LS4 intake.

TiredGXP

iTrader: (2)

The stock calibration shows a rated injector flow, at 0 kPa, of 3.57 g/sec, which is just about bang on for 28# injectors.

supercatxr7

iTrader: (5)

What about heads, will aftermarket heads for other LS motors bolt on and work with our manifold?

TiredGXP

iTrader: (2)

Well, we already have the cathedral port '243' casting from the LS6 Vette, so we probably already have one of the better LSx heads (not counting LS7, L92).

The LS4 uses the same bore centres as the other LS series engines, so in theory other castings will also fit, the issue is our smaller bore (96mm or 3.76") may have clearance issues with some of the larger valved heads designed for the 4" bores.

Taz34SS

iTrader: (2)

Also our block is shorter then a true LS2 or LS6, so again you would have to either drop in a new block or just get used to the fact that there isnt much LS4 aftermarket parts for these cars.

TiredGXP

iTrader: (2)

IIRC, just the crank is 13mm shorter, block is the same length. Differences do exist for starter mount (we don't have a starter mount on the LS4), and transmission mount.

Taz34SS

iTrader: (2)

The LS4 is a smaller 5.3 L (325 in³) version of the Generation IV block. Though it has the same displacement as the Vortec 5300 LH6, it differs in that it has an aluminum block rather than an iron one and it uses the same cylinder head as the Generation III LS6 engine. A version of this engine is adapted for transverse front-wheel drive application. In order to fit into the smaller engine compartments designed for V-6s, the LS4 engine block had to be shortened by one inch.

Taz34SS

iTrader: (2)

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.

ChipC

I disagree. Swapping the block would have no impact on parts availability. The cam blank is the same as other GenIV blanks, just different profile on the DOD cylinders. The AFM/DOD system could be removed. Headers are obviously unique to this platform, but are not impacted by the block. Heads are the same as used on the LS2, so rockers and springs will swap. Crank is machined differently, but the core architecture is still the same. The LS4 shares quite a number of parts with other LSx engines. The biggest problem with the LS4 is the fact that any cam changes basically require dropping the cradle and engine out of the car.

And of course, there is the turbo kit that looks to give killer performance.

Chip

Taz34SS

iTrader: (2)

I shouldve said motor as that would help with aftermarket parts.

As for changing out the cam, thats easy on these cars, but there is not a cam made for the "LS4", only LS1,2,3,6,7.

Alot of guys with the old L67 motors have been putting cams in their cars by lowering the engine down and getting to it through the driving wheel well, just need to remove the wheel, brakes, etc.

As for Turbo, yeah anyone can slap on 5600.00 worth of turbo parts, but as most of us know, your going to need to either A: Beef up your tranny as these 4t65HD trannys do not last or B: Save up for a new tranny.

So, you can take the 5600 and then add probley another 2-3k in tranny parts just to make the car have that extra power.

Headers are easy, just need enough people to jump on the project to have the castings made.

As for parts, the only thing we could use from the LSx cars is rockers, springs, pushrods, etc. Because of the DOD, there is alot of work that would need to be done to make the LSx cams work and its really not worth it when the cam we have now is good enough, just add some 1.8 rockers with springs and tune. You will be on your way.