BACK in the 70s I used to get an American magazine called Car Craft, and I think it was the first place I ever saw a car referred to as a ‘street machine’. My interpretation of the term back then was of a muscle car or shoebox that is driven on the street and drag-raced. Since then though, the term ‘street machine’ has evolved to describe a wide variety of cars. Maybe I’m getting too old, but to me a true street machine will always be a street-andstrip car. Doesn’t mean I don’t appreciate other kinds of cars, but to me street/strip is where it all began.
Speaking of which, a very interesting topic came up the other day: manual versus automatic for street/strip applications. It’s almost like a Ford versus Holden argument; both sides have staunch advocates. But if you take the emotion out of the argument and use software like Quarter Jr, you’ll find that in most cases a manual is slightly quicker than an automatic, depending on the weight of the car, tyre width, gear ratios, converter, diff ratio, shift points, etc.
The first thing that often gets overlooked is that, generally, stock factory-fitted transmissions are not performance gearboxes. There are exceptions, but very few factory manuals or automatics (or drivelines) are suitable for drag racing. The quickest way to find the weak link is to rev a motor up and drop the clutch in a manual; I’ve lost count of the cluster gears I’ve had to change in the poor old Holden four-speed. I used to destroy one clutch after another behind my 308s and 396 bigblock back in the 70s, but things have come a long way with aftermarket manual transmissions and clutches since then.
Very few of you would have ever driven a stock two-speed Powerglide with a stock converter. I remember piloting a stock six-cylinder Holden with a two-speed ’Glide and it was probably the slowest car I’ve ever driven in my life. Yet that same pathetically slow two-speed is referred to as a ‘poor man’s Lenco’ when used with a highstall converter and modified with bulletproof parts.
They can be a very competitive gearbox on the drag strip, but they’re not so good on the street.
Similarly, the TH400 is regarded as one of the strongest automatics, but in stock form it isn’t all that flash. It still needs modifying and a high-stall converter for high-performance use.
But automatics are boring with a capital ‘B’ when compared to drag racing a manual. I gave Jai Schluter a call and asked him about setting up a really good street/strip manual. He has one of the toughest manual Falcons in the country, and for many years it ran with a 1000hp 504-cube big-block. The ‘Killer Tomata’ XC weighed 3445lb and ran 8.55@158mph in that guise, but it’s now running a 311ci high-winding small-block that’s making 850hp (2.75hp per cube). Jai has shut off at the 1000ft mark and run 9.34 on a 9.55 index in H/MP, which is a 10.5-per-cube class.
The Falcon also gets penalised 150lb because it’s a five-speed. The old big-block ran 1.25sec 60ft times, while the small-block is breaking the wheelie bars with 1.32sec 60ft times. It launches like a bullet every pass with the front wheels in the air. A set-up like his would be well worth thinking about for street/strip applications.
I asked Jai what he’d recommend for a car like my old ute, which weighed 3200lb. He said for under 500hp he’d recommend a Tremec five-speed, and a Jerico for over 500hp. And even though his Falcon has a mechanical linkage, Jai strongly recommends a hydraulic throw-out bearing.
The clutch he recommended was either the 2500lb McLeod Mag Force or the similar Ram clutch, or for high-horsepower applications, a McLeod Soft Lok. These clutches are a dream to drive on the street with their soft clamping pressure; it’s like pushing a Hyundai clutch in.
They’re set up to slip and are centrifugally assisted so they add 300lb of clutch pressure for every 1000rpm above their base setting. For instance, if the clutch is 2500lb at 3000rpm, it will have a clamping force of 3400lb at 6000rpm.
Soft-locking clutches like this are crucial to reliability and hook-up, as they bring on the power gradually. If you dropped a standard clutch and everything locked up the tyres would spin instantly, and even if they did hook up, the driveline parts would be breaking like the old days.
To emphasise how well a soft-locking clutch works, Jai told me about a BF Turbo ute he’d helped a guy with. The gearbox, diff and driveshaft were totally stock, but the engine is making 820hp and runs 10.8s at 128mph with a soft-locking custom clutch set-up.
Jai mentioned he has now gone to a Liberty gearbox in his Falcon; it’s really easy to access parts for Tremec gearboxes now that they are owned by Liberty. Price-wise you’re looking at around $1500 for a soft-locking clutch kit, $700 for a steel bellhousing and around $5000 for a Tremec five-speed.
Of course, having a killer custom clutch and fivespeed transmission isn’t much good if the driver can’t shift properly. But that’s another story. s