With that said, the No. 068 cam will work with low compression, but I mostly use the modern cam designs that are specifically made for low compression; they give better vacuum and better low-end torque. The Comp Cams XE series works well. You have to consider the whole package-the complete engine build plan.
What are you doing for exhaust? Headers and free-flowing exhaust provide a huge gain for your T/A. Are you retaining the stock intake? What about ignition? You really need to make a complete plan, not just ask what cam to use.
The few examples I stated require a change in cam selection to achieve the best result. Some engine builders have custom grinds they use as well. This question is asked often, but is hard to answer without a complete plan. That is usually why there is conflicting information.
My customers (and other Pontiac engine builders' clients) do not run into this because we build the complete package and use what we know works-something to consider for your rebuild.
Can I Bolt A T56 Into A GTO?
I have a '69 GTO with a 428 that has been converted to a standard shift using a BorgWarner T5 transmission that already needs to be replaced. I have a BorgWarner T56 DAX coming. Could you tell me what I need to change? Will I need an adapter plate, and will I be able to use a linkage-type clutch setup or will I have to convert to hydraulic?Tom KingVia Internet
Rocky Rotella Responds:
As you've discovered, the BorgWarner T5 manual transmission wasn't designed to withstand the high levels of torque that Pontiac engines can generate. According to Tremec's Web site (www.tremec.com), the company now produces such manual transmissions as the T5, TKO, and T56. The maximum torque capacity of a typical T5 ranges between 175 and 230 lb-ft. So it isn't surprising to find that your 428 engine has damaged at least one T5 transmission.
With your past T5 experience and purchase of a T56, it's obvious that you enjoy the novelty of a manual transmission and want to reap the benefits of overdrive at the same time. I admire your perseverance and fall into this same category. I must admit, however, that I've never attempted to install a T56 into a vintage Pontiac. My experience with them has been limited to the factory-installed units found in late-model Firebirds and GTOs. I've been impressed with their overall construction and durability, and the effects the six forward gear ratios have on acceleration and cruising ability.
In addition to the aforementioned Pontiac models, the T56 was also installed into other late-model vehicles such as the Chevrolet Camaro, Dodge Viper, and Ford Mustang.
This has led to the development of a variety of T56s with different input/output shaft dimensions and internal gear ratios.
You mentioned that you've already purchased one and used the suffix "DAX" to describe it. I'm not familiar with that terminology, so without knowing the original application, I can only provide a few generalities about the transmission and what you could possibly encounter during your install.
Though such a kit may exist, I'm not immediately aware of any companies that offer a complete T56 kit containing all of the necessary components for your application. Though Tremec produces an aftermarket T56 (No. 1386-000-011) that's designed for use with original GM bellhousings like those found on our vintage Pontiacs, the factory-installed T56s include an integral bellhousing that matches the bolt pattern of the block with which it was designed to be used. With GM units, this limits the T56 to the Chevrolet bolt pattern. Unlike an automatic, where an aftermarket adapter plate is used when installing a transmission containing a different bolt pattern, this isn't a sensible option for a manual tranny, as it changes the relationship between the input shaft and pilot bearing/bushing.