Too small or no bypass hole can cause some weird temp spikes and even over temp problems during warm-up. While building the Hemi for my Cuda, I sized the bypass down to the same size that I had ran on the wedge it replaced.

For several weeks after install, I fought the weird warm up issues with the new Hemi. Fortunately, I happened to mention the temp spikes during warm up to Ray Barton. He immediately asked if I had messed with the by-pass.

He said that he had seen those issues many times with a plugged or too small bypass.

I opened the bypass up a little and the problems disappeared.