Some of you may remember a post I started am month or so ago about my new street/strip small block build having strange cooling issues. The engine is a Indy headed 434 with a indy intake. We ran it on the dyno without a thermostat and had no issues. When I put it in the car I installed the 160° stat that came out of my 408 in it. The temp was all over the place and never steady like the 408 so I figured the stat was bad. I pulled the stat and drove it, never got over 140°, re enforcing my thoughts about the stat.

I finally ordered some stuff from Summit and included a new high flow stat in the order. Monday I drilled six 1/8" holes around it and installed it and had the same issues, cold to hot to cool back to hot, all over the place. This engine has a Indy intake that was not drilled for a bypass hose. Several guys had told me I didn't need the bypass hose with the stat having holes drilled in it. It may work for them but not for me.

Today I drilled and tapped the intake for the 3/4" nipple and installed the bypass hose. I filled the radiator with the front end jacked up just like I had previously to try and get any air bubbles out. After running it in the shop until the temp started coming up I took it for a spin. No more issues it runs 160° just like the 408 did, no more bouncing around from hot to cool.

Don't know if the anti cavitation plate on the Flow Kooler pump needs the bypass or what. Just thought I'd share in case anyone else runs into a similar situation with their small block.

That's good info.

Apparently those 6 x 1/8" holes werent big enough to have enough coolant circulating by the t-stat to have a smooth operation.

that confirms why Ma had such a large bypass on SB's. I've always wondered about that. On a side note unless it is a drag only I would think 160 is TOO cool. I would want 180 at a minimum