The Stovebolt Site Forums The Shop Area Engine Shop Coolant port

Hi all,
I have a ‘54 Chevy 3100 with the original 235 that I’m putting back together several years (30+) after an out of frame rebuild. It has a coolant port mid block on the driver’s side just ahead of the throttle bell crank. It is tapped for a 5/16 course threaded bolt. Does anyone know what this port is for and why it would be tapped for standard bolt threads rather than NPT?
Thanks,
Doug

That's sounds like it's for the coolant petcock drain.

The coolant drain should be all the way to the rear of the block as shown in Otto's pictures. Can you post a picture of what you're seeing, along with the casting date codes on the block behind the starter so we can confirm the date of the engine? Should be a Letter, followed by 2 numerals, then another numeral. Also the casting code low on the passenger side forward of the distributor.

Are you sure it goes into the water gallery and not the crankcase? Maybe it's for the oil filter line.

Oil filter line is mid-point of the block, but should be pipe thread, not bolt thread. But some engines have engine mount bosses on the side that are straight threads (usually three on a side.)

Doug - I think your are talking about the throttle linkage bosses (there are 2 depending on the year of your block) as shown in a couple of screenshots of pictures in this Throttle linkage thread.

IIRC, both are machine screw threaded for mounting the throttle linkage pivot post, with the position dependent on what vehicle the engines were installed in. I also seem to recall that one or both were threaded all the way into the block coolant passage and the throttle pivot and screw to fill the unused mount hole needs to have sealant on the threads to prevent leakage.

Post a pic of yours and we can chat further if needed.

The drain pet cock is near the rear of the block and is 1/4 NPT. This is ahead of the throttle bell crank boss at the same height. I thought it was just another mounting boss but found out differently when I filled the cooling system. It would be hard to get a good picture of it, it’s directly behind the junction between the manifold and the exhaust pipe.

Doug

Gdads, it looks to be the boss that the throttle linkage pivot post screws into in your picture. Mine uses the rear one. I’m thinking I’ll just plug it with a 5/16 bolt and sealant. High heat RTV silicone you think?
Doug

Oh yes that dreaded always clogged and extremely hard to unplug (if you can). I hate it! I have a 216 and a 235 that it’s been impossible to unclog!

RTV silicone sealant will work fine. I'd suggest Permatex 22071 Water Pump Thermostat Housing RTV Silicone Gasket Maker as it's designed to work in the high temp coolant/engine environment.

Just a suggestion, but a machine screw as shown in the picture above may sit flush better (and seal better) than a bolt that might not have threads all the way flush to the underside of the head.