Thread: three deuce help

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“…You'll find that the cruising speed in a hotrod or custom with 3 deuces is a lot less than your daily driver with FI….”

Not necessarily true Bob …….it depends on the car and how it’s set up. My Tri-Power Plymouth is normally driven at 75-80 (Interstate) and 65-70 on most 2 lane roads around here. It also got 19-21 MPG at 75 MPH while on vacation last year (yeah, surprised the he!! Out of me too . )

I am the first to admit that I got very lucky with the cam/gear ratio/tire size selection and happened to hit a sweet spot at 2600 RPM (cruise RPM at 75 MPH) with my engine. My particular combination is a 354 (365 Ci with overbore) 10:1 compression hemi, and 4 speed (OD) transmission with 4.10 rear gear set (with the OD trans the rear end ratio is effectively 3:00).

My comment about the outboard carbs kicking in at 80-85 MPH is based on the way I drive my car. I set the Tri-Powers up to so that the under MY normal cruising conditions I am only running on the primary carb. As I mentioned I set this on a straight flat stretch of road and set it a bit higher than 75 so that when pulling small hills it doesn’t start opening the outboards every time. The springs on the end carbs are also stiff enough that the cruise control will not overcome them which is also a nice feature in that it allows me to choose when the outboards open.

Shine's comment about throttle position is correct. It’s the reason I set mine on straight level ground.