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After setting it into place, I changed my mind on which intake to run on the 383. The Indmar fits better than the single plane and elbow. It also looks cool on the SBC and the long tunnel ram like runners should make great torque with the 219/219 @ 0.050 on a 112 LSA Erson roller cam. ~525 hp and 540 tq on E85 is a ballpark idea what it should make powerwise. I have to add a throttle body spacer to get the TPS connector past the ac compressor and it will be a 102mm to 90mm adapter so I can run the much nicer MSD 103mm throttle body. Not knocking Fitech but the MSD Atomic 103mm is a much nicer unit than the Fitech 92mm. It was a Holley clearence item but otherwise would have been 3-4x the price and the build quality reflects it. The L31 distributor is losing its cap and rotor for an EFI Connection aluminum cap to be used as just a cam sensor and oil pump drive. Also going back to perimeter bolt valve covers so that I can run my 7/16" stud 1.7 wide body rockers. I have the air intake, fuel and cooling system plumbing figured out as well. The Ford 6.2L 41.1 lb/hr @ 58 psi injectors I was already running fit right in place after grinding a couple small plastic raised tabs off that best guess helped prevent them from dropping too far into the Ford intake but was preventing the lower o'rings from sealing in the Indmar lower manifold thus also preventing the fuel rail from bolting in place, quickly corrected. Excuse the 3 years of dirt, road grime and a small china wall leak up front from the old manifold disturbing the RTV when I installed it. One thing about this manifold is it is definitely tall, especially up front where the throttle body resides. Holley fuel rails bolted right on and only the fuel line crossover needed to be flipped and a slight tweak made to the bend in it because the Indmar manifold is slightly wider between fuel rail mounting points. The regulator on it is for a Grand National and I have an adjustable one on order to be able to run 58 psi since I need the injectors capacity running on E85 and 43.5 PSI eats into that a good bit. I may delete the front crossover and add a thread on pulse dampner on each rail.
I've always liked the look of this Indmar intake but I have to guess it's well beyond being stock 3rd gen Firebird hood friendly.
I have a feeling the throttle body would make a great makeshift hood scoop through a cutout hood on a Firebird with this intake. The Express van has ~11.75" off the china wall to the roof of the engine tunnel. The single plane/elbow takes almost all of it. The Indmar takes most of it.
That being said there is a lower profile upper plenum and the plenum is reversible.
To simplify my life with throttle body clearence, idle tuning and throttle linkage connections for both the throttle and cruise control I have actually decided to use the 87mm GenIV truck throttle body in conjunction with a 2001-2002 8.1L van pedal and TAC module. The OE cruise control wiring harness already has the body side inputs needed for the cruise control and brake pedal for the TAC module and the TAC module bolts to the OE cruise control bracket in the stock position allowing the wiring I extracted from an 8.1L van harness to drop right into my existing harness. All the wiring is the right length, pinned correctly and ready to go, just swap the dual connectors from the 8.1L throttle body to the newer style connector and done. Have to open the harness up to add the LS coil wiring anyway. Setup a 2005 DBW LQ9 6.0L based tune patched for flex fuel for the P59 to run the 383 today. Still waiting on a few odds and ends to finish buttoning everything back up so I can fire it up again for the first time with the new cam and intake setup. I am revising the air intake setup as well so it no longer reaches 200F IATs around town in summer like it did with the stock air cleaner assembly breathing hot underhood air. Going to duct cool air from the stock valance to a sealed airbox. K&N had their 4" ducting compatible off-road airbox on sale for $200.
The 383 has run again with the Indmar manifold, 24x CNP ignition and DBW setup using an 87mm GenIV throttle body. The Park/Neutral 4,000 rpm rev-limiter is still in place and started backing off the throttle on just before 4K. Runs incredibly smoothly. started with a 2005 6.0L DBW 2500HD calibration and copied the spark tables, VE tables and a lot of other data from my old P59 tune. My test run was MAF only. I still have some harness work to finish and some things to finish mounting and re-installing before I can get it back on the road, get it dialed in well and have an actual impression of how it all works together.
Cleaned up and running. Still needs a lot of VE tuning but still very smooth. I might pull the valve covers one at a time and do a running valve lash adjustment. Rockers are louder on camera than in life but I think they could be a bit quieter with a running adjustment. Some of the noise it unavoidable because of the guideplates and 1.7 full roller rockers.
Just diagnosed and corrected a failing crankshaft position sensor that was acting like it had a rev limiter at 4K rpm with the 24x setup. Replaced the sensor with a Genuine GM then performed the crank variation relearn. This manifold is very torquey even in an undergeared ~7,000 lbs Express van. The torque curve seems to be extremely flat and broad. This was with 30° total WOT timing and shifting at 5,500 rpm. About to flash a tune into it with 33° total and 6,000 rpm shifts. That 219/219 @ 0.050 on a 112 LSA cam with the heads that are on this engine should carry good power to 6K and maybe a bit over. Once I have it dialed in on pump gas I will be adding pump E85 to the tank. The fuel composition sensor is showing right at 8.5% ethanol on the pump 93. I have softened the 4L85Es shifts as much as I dare without causing it to slip and have 50% torque reduction through the P59s torque management but it still shift extremely firm. I love the tunability of the LS management especially with the DBW throttle. Light throttle it is stock like, very tame and smooth. Put your foot into it and it comes alive. I am actually going to make some tuning changes to limit the maximum throttle angle at lower rpm to eliminate the wheel spin from a stop. You can reduce the maximum throttle opening at lower rpm to prevent wheel spin and get a better launch, just have not dialed it in on this one yet but have other setups.
