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Maximum Compression Ratio On Olds 455 - What's Your Problem?

TV Tricks
Bill Irwin; Thayer, IA: I'm building my own version of your Lester Scruggs 404ci LS engine that ran in the Feb. '10 issue. I want to put it in a street rod, but instead of a carburetor, I'm planning on running the production EFI. It appears that you have had good luck with the 200-4R overdrive automatic in your Chevelle, and I was thinking that would be a better trans to run instead of the 4L60E. How would you adapt the TV cable for the 200-4R trans to an LS-style throttle body?

Jeff Smith: Bill, that's a great question. My search led to me to Bow Tie Overdrives (BTO), which makes an adapter that allows you to connect the throttle valve (TV) cable directly to a typical LS mechanical throttle. One distinct advantage to the BTO adapter is that it is adjustable. The adapter allows you to adjust the tension on the TV cable, which will alter the shift timing and firmness. The TV cable replaced the function of the older vacuum modulator valve that uses a vacuum hose connection between the transmission and the engine to indicate load. With the TV cable, as soon as the throttle is opened, the cable moves the throttle valve inside the transmission, raising the line pressure. This affects the shift points and shift firmness. The key is to adjust the movement of the TV cable until you achieve the desired shift point changes. The BTO website offers excellent instructions on how to mount the adapter and adjust it, and the company also offers an outstanding description of how the stock TV system works (called TV Made EZ) accompanied by excellent graphics. The three-part description illustrates the stock system's shortcomings and what BTO describes as the "short spring syndrome" that causes problems with TV tuning. To this end, the company recommends using a specific BTO spring, which must be installed in the valvebody. It's a simple swap but requires dropping the transmission pan. The LS1 cable and throttle body adapter is PN TVEZLS1BR ($159.95). This cable requires a specific separate cable mount bracket (there are four different ones depending on your application) that is an additional $10. I would highly recommend you read the entire three-part series to fully understand how the throttle valve system works, which will make adjusting the system much easier and far less confusing.

While investigating the BTO website, I ran across a great adjustable trans mount that works really well with LS1 engine swaps. The mount has a slide adjustment feature that allows it to move fore or aft a total of 2.5 inches, which is more than enough to accommodate the various engine mount variables present in LS1 engine swaps. This adjustable mount may prevent the need to either drill new holes in the framerails for moving or having to make or purchase a custom transmission crossmember. This is a very slick little adapter for any car crafter considering an LS engine swap. The adapter part number is SLDEMOUNT and sells for $110.

More Info
Bow Tie Overdrives
Hesperia, CA

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