xschop's 928 LS1 build...repost from frenemylist

Original posts here....

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Alright, time to talk tech. I PROPERLY designed a bolt-on TT adapter for the 928 to mate the vette C5 2-piece BH and 5-speed torque tube.

I want to take it a step further and make sure the same adapter can be used on the 928 auto. I do not have a 928 auto coupler to measure. So If you have one handy and a good mic, please post dimensions.

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Got dims from DOZ.....

Red= 76 mm
Blue= 51 mm
Green= 67.4 mm
When I start my build, I will post part #s as they all will be the same as I did on the 948 swap. The sweet part is the 928-LS headers are off-the-shelf and require NO mods which is a big expense for the 944-LS swap. The same BH adapter for the 944 is used and modded to fit the 928 rotating coupler. I'll shorten the tube and exclude the 1.00" thick pilot bearing adapter. Just one less part to machine/install.....

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Sanderson makes 3 sizes headers that will fit. I'll use part# LS-134 as they are 1 3/4" primaries. They have LS-158 and LS-150 which are smaller primaries.....

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For the Conversion clutch disc, I use SACHS part# BBD-4163. Should be good for 400HP.

A stock 2000-2004 Camaro/Vette Flywheel and pressure plate will work, but I will use Centerforce CF-360010 pressure plate and a LUK billet steel flywheel (inexpensive).

The billet adapter I designed uses a Standard T56 throwout bearing Dorman part# CS-360058 and easily allows -3an stainless clutch line.
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Make sure the D951004 casting is on the alloy housing....


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I made an inexpensive adapter to mount a 7/8" or 13/16" Wilwood Clutch MC to the 944 firewall and will do the same for the 928 if it's Clutch MC cannot push enough volume....

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You can do the mod with a dremel tool....

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Thanks to GM, the off-the-shelf roller pilot bearing that needs no 928 bearing adapter is....
AC Delco # CT1082
GM # 12557583.

For the 5-speed swap you can only use the 2-piece bellhousing to clear the pressure plate...
GM part# 12554980

For the Auto swap you can use the GM auto bellhousing. It has a smaller curvature for the flexplate.
GM part #12551118

I'm going to run this same ebay billet oil-relo kit as it has extra NPT ports for aftermarket OIL pressure sensors and oil-coolers. I ran the Wix oil filter on the 948 as it has more filtering surface than the Fram...

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Water temp gauge made easy to match oil pressure gauge....

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We need a 928 VSS kit!!!... The 928 CV's are essential 930 CV's

The 944 cam gear is 40T, coincidentally what the LS PCM requires for VSS signal.

I just cut the middle out the 944 cam gear to fit over the rear axle cv (8mm holes on 86mm PCD) Then made a braket for the GM VSS sensor. Works perfect. I'll develop one for the 928 as it's CV's are 10mm holes on 94mm PCD.

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My OB-LS donor didn't come with and engine or a radiator....so...

What is this?....

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and this?.....

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I did find a all-alloy radiator that fits perfect. Northern Radiator # 209628. I'll just have to make a bracket that holds down the top side by the radiator cap. I have welded bungs into these, but I think I'm going to keep the billet thermometer cap and rid the overflow tank on the passenger side....

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Ready for the LS powerplant....

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I dropped the engine mount height holes another 1/2" so I can build a custom (thicker) Strut Bar. I also mill-slotted the X-member bolt holes to allow for engine set back when the Vette trans installs.
Did these on the Bridgeport and started with only the best, cold-rolled CrMo 4340, 0.25 x 3.0 and then machined a bolt-compression tube (4.25" matches Camaro engine mount) to keep it all square as I weld it up...

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With The QT BH there is less clearance as the BH curvature is different than the factory BH. No one knows what the GM 6 speed Auto trans will set at yet unless Dinsdale has a twin working on it.

The factory top radiator stay on the driver's side need to be chopped and 3.0" extention welded in...

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Even lower profile pan I'll be using from Alper motorsports. Came with a pickup tube too.

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5.75" total depth and 6 qts. Extra 0.5 Qts when I install the oil relo kit. I talked with Jason and it's a new design that they are in full production and will have new stock in 2 weeks. He's going to email me the part # and I'll post. He also said the new batch of pans will have an extra baffle for road race. Mine has a double trap door baffle as is.

The oil pan is Procomp # SM2676

Fit the motor mounts up after paint dried. VHT Hi Temp Yellow. I'm actually surprised that they sit parallel without having to heat/hammer the X-member in this area. I had to drill 1/2" dia. holes exactly 1.125" from center of the factory mount holes towards the fenders.....

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Also surprised how very little rust is on this car. Where the spare wheel set and the battery box had some light rust. After wire-brushing everything, I made a soln. of rust converter using flat-black Rustoleum brush paint and 15% Phosporic Acid.....

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The factory MC volume lacks when it comes to the Wilwood 6-pots. So I'm installing the trusty LS430 monoblocks (4x43mm pistons) until I can mod up a Corvette master cylinder later.... The OB spindle has the same radii geometry as the 87-up 944 NA that I put this same setup on. So I just had to tweek the design some for the OB spindle ear offset.......

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Luckily Stainless braided 944 lines fit the 928 and the LS430 calipers.... I had a spare red-coated set...

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16"  993 wheels fit the Boxster-S rotors with this caliper......
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I removed about 100 lbs of more unnecessary rear seats and all the padding which was alot heavier than the 944 padding. The 928 has an extra 1/4" thick rubber mat on top the heavy foam padding.

Factory seats are gone and next I'll be building some race seat rail adapters for another 60lb total weight redux

Not sure what other people ran into putting aftermarket seats in the old 928, but here's what I'm doing...

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All 4 together weigh in a touch over 3 lbs.....

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Made some door pins some to match my billet shifter. I have the tech drawing for the 944 billet door pins I made before.

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I'm picking up a new oil-pan gasket for the Alper pan I posted dimensions on. Eric sent that pan only as a cover for the Fedex pallet trip the engine made.

Just so we're clear, you saw it here first, in case Hack re-posts these pics somewhere claiming his new LS swap kit lol.... The extension tube indexes on the re-profiled billet adapter plate and allows the 928 front shaft and coupler to fully rotate within the sleve ridding the need for a pilot bearing adapter....

Pics are XSchop approved....

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Well, one thing's for sure. It'll be much easier to swap a cam in the 928 than the 948 with the amount of room in front of the new engine. The shorter adapter set the engine back another inch :rockon:

Installed new billet flywheel, clutch then I pulled it back out the bay after final fittment and gave it some bling with all new gaskets, new starter, F-body engine isolators and new F-body harmonic balancer as I'll be doing billet F-body assesories.....

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I'll need a bigger Ice-chest as the LS engine has crazy room left....

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Did not touch the oil pan, just ground down the rear X-member lip and moved on. I will not even build the billet-poly trans mounts to have a 3/4" set-back as I originally planned...

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Even with the 1" setback of the TT adapter, there is still room for 1.5" setback of the engine if desired with the curvature of the factory 2-piece C5 bellhousing....

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And the kicker, The dual 928 exhaust will bolt right up with exhaust adapters when I weld in the front O2 bungs....

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Last plumbing enigma.... mate GM PS pump to 928 rack.

Bottom (BLUE) is the high pressure port and return (RED to PS pump) is top port.......

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The 928 Rack is a 14m x 1.5 banjo bolt. I'm just going to plumb in -6an braided line. The factory return line can be re-used with hose clamps.....

For the PS line, you'll need....
2ft of -6an Teflon-lined braided SS hose and
1ea Russell part# 648060 (attaches to GM PS pump)
1ea Russell part# 610160
1ea Russell part# 613090
1ea m14 x 1.5 banjo and bolt to -6an (attaches to 928 steering rack)

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Didn't have an LS flywheel lock. The higher gear ratio of the 928 box allowed for dropping trans in 1st gear, setting hand-brake, and using an XS cheater bar to install the new F-body harmonic balancer.:biggulp:

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I thrice heat-tempered an M16 x 2.0 x 120mm bolt with anti-seize to start it half-way, then removed it and installed the rest of the way with a stronger ARP crank bolt with anti-seize.....no problem.

Thanks for the info ASP, the 948 hybriders/track whores use the Turn-1 PS pump. I'll track mine to work daily. 120mph off-ramp exit with 7-11 coffe in hand lol....:biggulp:

$35 bolt is getting rediculous, I'll machine my own next time round and have it quench-hardened....
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The 928 fuel line fittings are back-assward. As I don't have the fuel-line tool, I sent them off to Eric at TPC to have fuel lines press-fitted to mate these to the easy-connect fittings on the filter....

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Did a lot of fuel line plumbing and new billet fuel rails with Russell fittings.
Fuel Filter fittings are done. Looks like a high-pressure hard line from the 928 feed is the way to go with O-ring snap fittings at the filter. The return line is simple fuel line with a hose clamp. The adapter from the filter to the rail is a -6an Russell fitting (640940)....
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Talk about lucky, the Ford Contour fan (95-00 V6) shroud fits perfectly with a top-hanger boss and the bottom of the shroud has two areas that are perfect alignment for the radiator bottom lip to drill 2 holes and zip-tie them up.....
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The exact same filter I used on the 948 swap sits perfectly in the area of the shroud that deflects the radiator heat.... Spectre 9732 (10.25" x 6.0")

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The original PS pump pulley bolt and washer was bothering me as it was fugly...
So I Lathed out a 0.375 x 1.125 x 0.20" thick billet washer for the PS pump pulley....
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Headed to the shop later to build one of these...
Will be mounting 2ea of the 6-spot fuze blocks to tie-in the GM ECM

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The diagram I posted fits the fuze blocks nicely and will have room for 4ea relays for the ECM. I used 3/8" aircraft grade phenolic waferboard I had at the shop...

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Decided to put on a 14 psi Rad. cap and may install a surge tank later, but don't know where I'll put it just yet. Built a bracket from 1.5" x 0.1875" thick alloy and poly bushings....

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There are 2 ways to mount the Wilwood 13/16" clutch master. The easy way clocks the fluid intake at 7'oclock which may cause bleeding issues. The other way will clock the port just like factory (10' oclock) but will require an adapter.
The pushrod can easily be modded by cutting off exactly 2.90" from the 928 pushrod and welding it to the Wilwood pushrod leaving the factory adjustment at the 928 pedal clevis....

I looked inside the 928 master and it has a "spooge hole" that are infamous for clogging and causing disengagement issues too.

On a side note if you want to keep the factory 928 Clutch MC, you'll want to use an M12 x 1.0 to -4AN adapter to the -4AN clutch line.


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I realize looking at some of your threads, the sway bar mount on the chassis is weak. The bar I cut was CAST and 26mm Dia. So I'll mod it up to clear the oil-pan and use a beefier hollow 4340 DOM tube and machine step-out adapters and TIG-weld them in the sweet spot...

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