It has fully ported, closed-chambered Edelbrock heads with 2.11 and 1.66 valves. Traditionally, opening up the intake port would reduce port velocity, which affects low-end power. In this case, the early onset of boost compensates for it, and Jeff will definitely feel the extra rush on the top side. The intakes flowed 304 cfm and the exhaust managed 232 cfm (both at 0.600-inch valve lift). Static compression ratio works out to be a boost-friendly 7.96:1.
Here's where things start to get really fun. MCR did an absolutely masterful job of building a pair of stainless steel, 2-inch turbo headers that mount 70mm Turbonetics units, with Evolution 35mm mechanical wastegates keeping each of them under control. They, along with a 2.5-inch Bell intercooler and a 3-inch exhaust, fit beautifully inside the stock '67 GTO profile. A 70mm Accufab throttle body gives Jeff total control of the entire operation by way of his right foot.
The heads received the full...
The heads received the full porting treatment on the intake and exhaust sides.
Ignition is fairly straightforward: an MSD crank trigger distributor, which was modified for a cam sync sensor so a FAST computer can sequentially control the 83-lb-hr injectors. We'll go into more detail about the FAST box and how it makes this project possible when we get to the dyno session in Part II.
Assembling something like this is mostly straight forward, but there are a few things you need to know to avoid making the wrong kind of history and reputation for yourself. However, since we want to provide all the information we can on the combination and how the parts work together, we won't detail all the clearances and torque specs that are normally contained in an engine build-up article as they don't vary significantly from a typical high-performance buildup.
Next month, we'll bolt this monster to Wheeler's dyno to see how much power it makes.
Here you can see the bowl...
Here you can see the bowl work. The chambers were opened up to 90 ccs from an advertised 87 ccs. A three-angle valve job (30/45/75-degrees) was performed on the valve seats.
The valves that came with...
The valves that came with the heads were retained. They are stainless steel and measure 2.11/1.66 inches.
The valvesprings feature a...
The valvesprings feature a seat pressure of 140 pounds and an open pressure of 360 pounds. Since this engine will rarely, if ever, see the other side of 6,000 rpm, they suffice. A set of Comp Cams 1.5:1-ratio aluminum rocker arms keep valve action in order. Smith Brothers 3/8-inch diameter, restricted pushrods with 0.040-inch holes were used so that full oil flow could be maintained for the lifters, yet still be restricted to the rockers.
The intake didn't escape the...
The intake didn't escape the grinder, as its ports were matched to the heads.
Since Jeff will push things...
Since Jeff will push things just a little with pump gas under boost, a rock steady MSD crank trigger ensures accurate timing.
MSD also supplied a cam sync...
MSD also supplied a cam sync distributor so the injectors can be run sequentially, which reduces stress on the fuel delivery system since the injectors aren't opening all at once. Also, the tuner has control over each injector separately should the engine have a cylinder with a special need. Ignition timing can also be controlled per the individual cylinder.
These 83-lb/hr injectors are...
These 83-lb/hr injectors are from FAST.
There's a 70mm Turbonetics...
There's a 70mm Turbonetics unit perched on each side of the engine. The obvious advantage of twin turbos is that you can run two smaller ones, which spool up quicker, and therefore can make more boost at lower engine rpm, but still not run out of room on the top end.
The boost needs to be accurately...
The boost needs to be accurately controlled, so each side also has a Turbonetics Evolution 35mm mechanical wastegate. Boost can be controlled with these units by changing an internal spring and/or by sending some of the boost to the lower side of the diaphragm.
Notice how cleanly everything...
Notice how cleanly everything is tucked in alongside the block. MCR did a brilliant job of fabricating all of the plumbing. In the next issue, we will dyno the engine to reveal the performance figures.
On the receiving end of the...
On the receiving end of the turbos-and by way of a 2.5-inch Bell intercooler (that you will see in Part II)-is a 70mm Accufab throttle body and plenum.
Because turbo boost is a function...
Because turbo boost is a function of engine load-not directly controlled by throttle position and engine rpm as with a pulley driven blower-some provision must be made to bleed off excess boost when the throttle is closed quickly. Turbonetics calls its blow-off valve "Godzilla" because it can sound somewhat like the scream of that classic beast.