Well the old gold Camaro has been quiet for a while. Early this year a friend of mine closed his "speed shop", which was really an engine building business. He has been in the business since the early 70s and has customers from all over the place. When he was cleaning out his stuff he came across a mint 73 factory LS6 "289" block in standard bore. He also had a collection of various winters heads, 163 intakes, you name it. In his stuff he was clearing out was also a brand new Autogear M23 transmission. I have a good friend who needed a better transmission for his nasty Mark Jones built oval port 467 so we went to go buy the transmission. While there I couldn't help but snoop around all the old High Perf GM goodies. My buddy, Jim, kept asking if I knew anyone interested in buying the mint block and any of the heads etc... HMMMMMMM lemme think.... No I don't know anyone. Well as he was showing my other friend, Ross, the transmission, I wondered back to looking at the assortment of winters heads (because I'm not very smart and something about this one set of heads drew me in like a tractor beam). This guy Jim can tell I want this stuff even though I haven't said anything. He says, "Hey kid, I'm willing to sell that stuff.... if you know anyone?" Ok FINE! I am interested, I want this 73 LS6 block, and this pair of 074 heads. He said ok fine but you also need to buy this crank, rods, 163 intake, GM deep sump "L88" pan, lifters, cam etc... Needless to say, 3 or 4 days later he gave me price I could not refuse. The 074 heads were absolutely MINT! I could tell they were ported by someone who knew what they were doing, luckily they left their stamp on them, however I haven't been able to find any information about this head porter. The stamp reads "AUTO SPEC. 3.118" My guess is Automotive Specialties?? I have no clue but I THINK they've been in CA for a very long time, Jim owned them since the mid 90's. He told me he traded some parts with a customer of his back then who raced historic CAN AM McLarens. The heads are both from 1972.
So now I have all this stuff and had to decide what direction I would go with it. I decided on leaving it a stock 4" stroke. I had the block fully machined; bored .030" over, line honed with studded mains, and square decked to 9.785". The combustion chambers measured in at 120cc. Looks like there was more unshrouding than factory and the exhaust side was give the "Vizard Plateau". The heads were already milled and the valve job was already done by Mikio Yoshioka. He also set up the valve springs and shimmed them to perfection. (I ended up disassembling the heads to get them vapor honed for a factory fresh finish carefully separating and labeling each set of springs and shims with their corresponding chambers). With the stock 6.135" rod I decided on the Mahle 28cc powerpak piston, which is .004"-.005" in the hole. This piston with a, .032" head gasket would have a really tight quench and good compression at 10.3:1. It should be noted I have an INTERNALLY balanced Eagle forged crankshaft and their forged H Beam rods. Everything was balanced at RevCo Balancing in Long Beach, CA. My pal Ross, who bought the transmission from Jim and who is mildly responsible for getting me in the situation
, is really impressed with his oval port 467 that Mark Jones built. We discussed the cam spces in that motor and the head flow numbers. My heads flow pretty close to the same and lost flow after .600 lift so I thought why reinvent the wheel here? So I decided to use the same Isky hydraulic roller which he ensured me it would rev. In my opinion the cam seems small on paper but I think it was the right choice. Lift is .578 intake and .608 exhaust. Intake duration comes in at 238 @.050 while the exhaust is 248 degrees. It was ground on a 110 degree lobe separation.
After mocking up the motor, I determined I needed more clearance on the main bearings and went with Clevite "X" bearings which give you an extra thou. Mains were all set at .0025" and the rod bearings have .002" clearance. The pistons were all between .006"-.0065" cylinder wall clearance. After everything was verified, the engine went together without a hitch. I stuck an L88 style short windage tray on the main studs and used a Melling M77 oil pump with an ARP shaft. After sticking the cam in "straight up" I discovered that was actually 3 degrees advanced so I retarded it 2 degrees bringing in at 109. After measuring the pushrods, I ordered a set of Chromoly Manley pieces along with their adjustable guide plates to ensure correct valvetrain geometry. COMP Cams pro magnum rocker arms were used. Next up was the 163 intake. I milled the plenum divider down about half way to hopefully help it out on the top end of the power curve. Fitting the intake to the heads was probably the biggest hurdle of the build; I had to get the intake machined twice to finally achieve the perfect fit!
Now that the engine was together it was determined a dyno test was mandatory, no guessing games. I made an appointment with Westech Performance in Jurupa Valley, CA. This was my first engine dyno experience and it was a blast! The engine performed great and surprised the dyno operators at Westech. This mild "LS6" made a peak torque of 556 lb/ft at 3900rpm and a peak 576 horsepower at 6100rpm and carried 550 all the way to 6500rpm. We tried a 1" open carb spacer and it made no difference, actually lost a little torque with no horsepower gain. To say I was happy was an understatement. The engine didn't blow up and it made great power. I think this new bullet will be right at home in "The Prospector" Camaro giving it a fresh look and a new attitude.