Project Sirius Black LT1 Camaro


I have moved this project from my TPICHIPS.COM website to the HARRISHIGHPERFORMANCE.COM website since its not really a TPI build.   I built this car in 2005 right after the Harry Potter movie came out that inspired the name for the project.

This Camaro was originally a wimpy 170hp 305 TBI automatic car with 2.73 gears on top of that.  To say performance was pitiful is an understatement.  First thing that went was the gears.  3.42 gears with the zexel torsen limited slip borrowed from a 4th gen went in the car back while it still had the 305.  I moved up to a vortec 350 engine with mild cam and it ran strong but some injector issues on new motor caused it to have a short life.  So I built the project as it appears below.

first I bought a LT1 from a Caprice with trans for $400. LS1 stuff at the time was just out of my price range. I bought some stock aluminum LT1 heads off ebay for $200 and sent them out to  and went with the entry level 180cc cnc porting which they no longer offer.  190cc is their entry level now and if i had it to do over again with a 383, I would go with at least the 200cc porting or go with a set of AFR 210 heads.  but the 180cc flow numbers were about 5 cfm higher than AFR 180cc LT1 heads.

180cc Aluminum SBC Cylinder Heads
Part # Plug Type Combustion Chamber
908 GM LT1 55cc or 65cc


180cc Street Head Flow Chart
.200 .300 .400 .500
Int 138 198 240 260
Exh 110 158 190 207

Test conducted at 28″ of water (pressure) on Superflow 600
Bore Size: 4.060″, 3/4″ radius plate exhaust, 1 3/4″ curved pipe

which is vastly better flow than stock LT1 heads and it makes good power dont get me wrong but I built this engine in the era of LS1 and when LS3 motors came out those great flowing heads changed the world.  This car still does just fine against a mild LS3 car but these days, I would have gone with better flowing heads.

The intake, I just gasket matched to the heads but I did have the throttle body holes cut to match a 58mm throttle body which it does have on it along with the larger mass air flow ends for as much air flow to the motor as I could get.

For camshaft, Advanced induction recommended a cam that is just a little more than the Comp cams CC306 cam.  If it were a race only car it sounded awesome and ran great but had terrible drivability.  too much camshaft for the 2000 rpm stall and 3.42 gears caused it to do too much cam chuggle and just cruising around under 65mph.  so I put in a white performance clone of the GM LT4 HOT Cam in it.  which is a 218/228 duration @ .050 and .525/.525 lift with 1.6 rockers which I am running comp cams chromoly 1.6 full roller rockers on a 112 degree lobe separation angle.  cam doesnt sound as cool but its drivability is very good.  Cruise around with my wife down the beach with the top down and very enjoyable.  I think a comp cams 07-503-8 cam would be a good compromise between the 2 cams and still have decent streetability.

For the rotating assembly, I went with a internally balanced (no weight on flywheel) 5.7″ rod 383 kit with 2 valve relief hyper pistons which with my 53cc heads gave me a 11.4:1 compression ratio with a .051″ thick head MLS Cometic head gasket.  I wish I had gone a little lower on that compression ratio.  Something in the 10.7-11.0 range.  the 11.4 is a 93 octane only motor.  put 91 in it and it will ping.

For the exhaust, the front half is a little restrictive because 3rdgen Camaros are low to the ground and the floor design was not designed for good exhaust especially if you have sub frame connectors welded in which I do since my convertible had more than a little flex even with the lame 305.  I am running the D port shorty headers for 3rd gen with LT1 then dual 2.5″ cats along the stock routing over under the passenger seat with 2 2.5″ catalytic converters on to rear of trans where it meets up with a flowmaster y300400 collector to merge those pipes with my 4″ mufflex mandrel bent cat back setup which goes to a single spintech muffler with single 4″ tailpipe tucked up and drops out the rear bumper for very little visibility.  I painted it high temp black to hide it even further.  Exhaust is LOUD.  sounded AWESOME with the first cam.  A bit tamer now but I still lined the whole car with .080″ dynamat to keep it tolerable inside the car.

Rear Project Sirius Black

So how does it run? On the stingy mustang chassis dyno that I use it pulled 342hp and 346 torque.  For comparison the manual trans 2013 Camaro on this website with a cold air intake pulled 370hp and 366tq so their pretty tight factoring in automatic versus manual transmission power losses.  Below 4000 rpms though the 383 LT1 does just kill the LS3.  just the nature of LS motors.  forgive the graph.   it wasnt until even later that we figured out what we were doing wrong with the graphing process on the dyno machine and that is why it looks funky and I lost the original dynojet numbers when the project was first completed.  these dyno numbers were done years later after changing the throttle body.  I was running a 54mm bored stock throttle body for a while.  The 58mm only picked up like 3hp.

GM fuel injection for the average guy