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Triumph TR8 Edelbrock Four Barrel Carburettor Conversion by Brad Wilson |
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| Step One: Intake Manifold | ||
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On the left is the underside of the stock TR8 intake manifold. On the top side, there are no significant problems to report with regard to the Edelbrock manifold, with the exception that the mounting for the fan high speed temperature sensor (a/c cars), is not drilled and threaded. However, unlike Offenhauser, Edelbrock did at least make provision for this sensor! If your car has a/c the Edelbrock manifold can be modified as shown on the right. |  |
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The underside of the intake manifold as supplied by Edelbrock is shown on the left. There are two major issues: First, no provision has been made for the heater pipes, and second, a thermostat housing with an integral bypass hose passage is required. On the stock manifold, the heater feed hose attaches to the rear of the manifold, whilst the feed hose from the coolant pump is attached to a pipe pressed into the manifold. We have decided to blank off the connection at the rear of the Edelbrock manifold (as was Rover practice on later engines), and attach the feed hose from the heater core to the manifold pipe. |
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The stock TR8 thermostat housing does not incorporate a bypass hose. Others advocate using the cast iron housing as shown on the left. That approach has a couple of problems: First, the angle will be incorrect at 12 o'clock as viewed from the front. The stock housing produces a roughly nine o'clock angle for both a/c and non a/c cars, and is important for distributor clearance. The second problem is that the diameter of the bypass hose on the cast iron housing is larger than at the TR8 expansion tank end. At this time we are unable to source the correct housing, so it has been decided to blank off the bypass port on the Edelbrock manifold, and utilise the front pipe mounting block to create a new bypass passage. |  |
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We have now managed to locate a limited number of correct thermostat housings. This housing provides approximately a 10 o'clock hose angle. The bypass hose diameter is still an issue - either a stepped adaptor pipe or modifications to the expansion tank will be required. Preference will be given to TR7 owners wishing to upgrade to V8 specification since the stock TR8 thermostat housing is not currently available. | |
| Step Two: Carburettor | ||
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Edelbrock #1403, 500 CFM carburettor as viewed from the left (driver's) side It is possible to reuse the original fuel filter mounting bracket using a simple inline filter. Although the hose inlet on the carb is larger, the stock 5/16" hose will fit. .... and as viewed from the right (passenger) side. |
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| Step Three: Throttle Cable & Air Cleaner | ||
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This bracket design is poor. The return spring interferes with the secondary throttle linkage, and the bracket is hard to keep secure without overtorquing the carb mounting nut. If the cable is mounted at the carburettor end with the bracket supplied, which is necessary to allow correct throttle lever travel, this results in too much cable at the accelerator end! |
Update:The return spring can be secured with the valve cover bolt to prevent interference with the fast idle linkage. |
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The overall length of the throttle cable is ridiculously long for a left hand drive application. The sloping bonnet line of the TR8 makes finding an air cleaner difficult. It is essential to select one with a low profile as shown in the photo to the left. Unfortunately, these only appear to be available in the fourteen inch variety which then presents a problem in refitting the fresh air scoop. Another problem is that the low profile air cleaner interferes with the automatic choke mechanism. |
Update:It has been suggested that triangular air cleaners will work. It is also possible that oval air cleaners, or Holley's sidedraft air cleaner might work. |