The Stovebolt Site Forums The Shop Area Engine Shop help - still can't get my 235 to run right

1955 235 engine.
I start to get close to operational and something else happens. Finally got the engine timing down and more recently a new carb insulator block, stared up the engine and noticed that by the time engine temp reached ~160, coolant was flowing out of the overflow tank (this had not happened before). So I ran a compression check, figuring a blown head gasket. The numbers ran 91/92 psi with one at 90 and one at 94. This is an older engine but I did have the head off recently and it was fully checked out, including magnaflux. Are these numbers OK? I put every thing back together again and started the engine, with the over flow hose draining to the ground where I could see it (not into the overflow tank). Within maybe 30 seconds, coolant stared pumping out of the hose - clearly not an over-temp problem. I did not notice any smell of exhaust in the coolant flowing out. Does this sound like a head gasket? Anything else I should check? Where do I go from here?
Bob

Overfilled radiator?🛠

That is possible. What do I use as a reference - just let the coolant pump out pump out and wait to see if the temp stabilizes and no more water is pumped out? Point of info - the thermostat is out for the moment. I had previously been concerned that this might be an over-heat problem. Clearly it is not.

Fill the radiator until the coolant just covers the core. That leaves 2-3 inches of expansion room until the level can reach the overflow tube. It's also a good idea to do the initial cooling system fill through the lower thermostat housing until the coolant in the radiator reaches that level, then install the thermostat and the upper hose and continue filling until you see coolant in the top tank. That totally eliminates the possibility of trapped air in the head.
Jerry

Thanks, Jerry, That helps. I will have to try to figure something out in the morning. I will be stuck with using an after market radiator for a while. It fills from the side of the reservoir.
Bob

If you're using a cross flow radiator (tanks on the sides) leave 2-3 inches of air space below the fill neck to let the coolant expand as it warms up. How far above the thermostat housing is the top hose connection in the radiator?
Jerry

Thanks, Jerry I don't have leaks but I was topping up my radiator periodically.

Jerry,

For better clarity, I have a 55 235 in a 46 1/2T. The radiator ia an "exact" copy of the original 46 radiator - close, but no cigar. The fill port comes off the side of the toip tank, towards the engine.

To answer your question, the top of the thermostat is about 9 inches below the opening into the top tank.

I will follow up on your suggestions in the earlier post tomorrow.

Bob

If it's a "zero pressure" system like original, it definitely needs expansion room.
Jerry

Jerry,

I hope that you are still following this thread. To follow up, the radiator has about a 4 pound cap. As I have mentioned, the thermostat had been removed. A couple of days ago, I ran the engine, collecting the fluid overflow, by passing the overflow tank. It started as a dribble, picked up to a steady flow and then tapered off to a dribble at about 150-160 degrees on the temp gauge. At this point, I pulled off the thermostat cover to re-install the thermostat. The coolant level was just above the top of the cylinder head. I have added about a pint of coolant that I had handy and planned to repeat the test, hoping that I can see the temp rise up above 180 (thermostat spec) and then see it drop back down. Does all this sound about right to you?

Hoping for some good observations from you,
Bob.

That sounds like a good approach. Be sure to drill a small hole near the edge of the thermostat to allow any trapped air to escape and eliminate any spots in the head that might not be wetted with coolant. About 1/8" is plenty.

Bob,

Heed HrL, not me.

However, for what it is worth: most thermostats are rated at full-open temperature. Circulation coolant should start earlier: a 180 thermostat might start opening at/before 150/160 degree. If your cooling system/radiator/engine-coolant passages are clean, your temperature should hold at 180 (except at idle or at low-speeds&RPMs).

Huh! Makes sense, would have never thought of that. The hole is drilled in the edge of the metal disc portion of the thermostat? Too bad I just finished putting it back together again, but at least it is simple enough to re-do.

Looks like I may be past the issues with my cooling system. Drilled the hole and reassembled. The coolant level was actually down to the top of the thermostat housing neck but decided to try checking out the system anyway. Ran the engine for 15 minutes at 1200-1500 RPM. No coolant was driven out the overflow. The temp gauge needle very slowly rose, JUST passed the 180 dot (it's a 1946 gauge) and then slowly dropped to where the top 1/2 of the dot was covered by the needle and appeared to remain there. Yes, I will add more coolant than I currently have in the system.

Now to attack the carb issues. My kingdom for an affordably priced Carter YF that would my 235.

Thanks for the guidance.
Bob

Nice, Bob

Thanks for posting the "report".

https://www.ebay.com/itm/Carter-YF-...evrolet-GMC-235-6-Cylinder-/173031715396

or, this one - get it rebuilt?
https://www.ebay.com/i/113119074782?chn=ps

Be advised, on that first one the seller says mounting holes are 2 5/8”, which I believe is the spacing for the 216, the 235 mounting holes are closer to 3”. And that second one is an automatic choke model. You probably want a manual choke unless you plan on converting. I have a Carter YF 788s for my 1954 235, and I know the 2100s is also a fit for the later 235

You are right about the bolt spacing. In regards of the second carb, I don't really see an indication of the choke type. I am indeed converting, but I want to go from auto to manual - the 55 engine is in a 46 truck and has the dash set up for manual choke. I would eventually like to keep that set up. That second carb just doesn't give enough detail for me to feel comfortable. 2100s is what I am looking for.

The big round black plastic piece on that carb is the auto choke

Followed the above recommendations and cooling works great - ran at idle until the gauge needle rose to cover the top half of the 180 deg dot, continued for another 15 minutes and gauge held steady; no over flow of coolant.