exhaust pulse

[fordboy]

I have to use the original 289 Ford HiPo exhaust manifolds for my drag car. Being a math teacher, I wanted to know what was going on in the manifold so I cut 8 pieces of rope, 9 inches long to represent the ex. pulse in the manifold. I used 300 ft/sec for the pulse velocity and 6000 rpm and placed the rope according to the firing order-- 13726548. I would reposition the rope for each 90 degree of crank rotation. To my amazement, I found that two ropes were EXACTLY on top of each other . Two cylinders are trying to empty into the same spot at the same time in the manifold. No other cylindrs had that problem. Is this a problem? Do you think it would good to change the firing order to prevent this? Thanks, Alan

[Mike Stark]

This is a common problem with many engines. Chevrolets often swap #4 and #7 firing orders to help with crank deflection and pulse. It's worth very little HP though. I wouldn't be overly concerned with this situation. A well tuned EX system from the manifolds back will help to remedy this.

[uwonemo]

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