I'd check the coolant temperature right at the manifold crossover tube as it comes out of the head. If there's a significant discrepancy in temperature you might have a flow problem

 

bleed the block by loosening the heater hose that comes off the manifold or drilling a hole in the T-stat.

I built 100's of SBCs, don't know of any to way block off coolant flow to one head.

Keep in mind the coolant flow pattern when trying to solve this. out of the pump, into the front of the block, thru the block to the back, up into the head, thru the head to the front and out to the intake water crossover/t-stat housing.

 

Tom. Correct me if I'm wrong. Doesn't the coolant split at the pump, flow down each side separately and come back together at the intake? If there is an obstruction at the pump or in the block on one side, Would that not reduce flow on one side?

 

Thanks for the replies. Sounds like bleeding the block at the heater hose might be helpful. Please keep the ideas coming so I can try to figure it out this weekend if I possible. Would hate to screw something up by overheating on the one side and have to start over from scratch.
Jeff

 

I would change the temp guage to the other head to verify the temp difference. Head readings will always be hotter than the intake x-over. I do the same as Tom mentioned. I always drill an 1/8th inch hole in the flange of the t-stat. If you look at a lot of newer car t-stats they have a "jiggler" that allows watter to flow through the t-stat even in cold temps. Very little, but it allows for air to flow if cought behind the t-stat.

 

on my first intake swap, 267 in my camaro, I accidently used two passenger side intake gaskets, which ment the coolant block off at one end of the gasket was at the front of the motor on the drivers side, blocking the intake crossover passage. caused overheating and an odd gurgling noise when the engine ran. Took me forever to figure out what was wrong.....

 

Unless a coolant passage is physically blocked, if 1) the thermostat opens; 2) the engine is running; and 3) you have the six "steam holes" in the head and head gasket--there is no air trapped in the engine.

Air is not magic; it does not "hide" in the engine and require some special process to eliminate in our older cars where the radiator cap is the highest part of the cooling system. It rises to the top, and as soon as the thermostat opens--it's GONE from the engine. You'll find it in the radiator, where it's considered a "low coolant level".

DO YOU HAVE steam holes in the heads AND the head gaskets?



I've never seen a Chevy small-block intake gasket that didn't have coolant passages on both ends; there is no left/right difference. But then, I haven't seen every gasket ever made.

 

My thermostat is in the driver side intake manifold (don't have any place in the heads to put one. I could switch to the other side of the intake where the heater hose is located, would this tell the difference in temps form side to side? Also, If the gauge where it is reached 210 then cooled back down to 175-180, I would assume the thermostat opened and flowed coolant correct? Could it still be keeping air from bleeding from just the one side? The heater hose is also very hot so assume water is flowing through it. Could the block be blocked somewhere on that side and some water getting over to the other side via the intake? Just don't know enough about how this all works, so again, I am very thankfull for all of your replies and ideas.
Jeff

 

Thanks Shurkey. I did not assemble the engine, it was done by the machinist, so I assume that the correct gaskets were used (will ask him monday). There was a significant drop in water level in the radiator when I checked (about 4 inches) which probably represents the displaced air then. Any other ideas? I have an IR temp gauge I am going to try this weekend to see exactly what the temp difference is side to side.
Jeff

 

do the temp check and post back here. Check the temp at the front end of the heads if you have access. If not check it at the intake where the water passage meets the head.

 

Sounds like an problem I ran into years ago. A company truck came in with the complaint of no heat. Engine was coming up to temp, thermostat was working fine, cycling thru open/close normally. A flow check of the heater core found it to be fine, but still no heat. Just for the heck of it I decided to check the flow through the heater with the engine running. So with a 5 gallon bucket in position, a kill switch with in reach I removed the inlet heater hose to see how long it would take to flow a couple of gallons out of the hose. What a surprise I had when the hose was removed with the engine runnng and not a drop of coolant came out of the hose or the open nipple at the heater core. An even bigger surprise was to be had when I hit the kill switch and the engine shut down. Water started flowing from the hose and the heater core and at a very rapid rate. While I cleaned up the mess I was trying think of any reason why this would happen. After a quick check in the service history I discovered a water pump had been installed the summer before and a quick disaasembly of the pump revealed the cause. It had been built with the wrong impeller installed. It was moving the coolant in the wrong direction starving the heater core rather then feeding it. This is a long story but the same thing could also be the cause of passenger side of the engine running hotter then the other if you can not find any other cause.

 

I would expect the heater core to be supplied with hot coolant from a fitting on the intake manifold; after the coolant passes through the core, it would return to the water pump (or, in some cases, to the "cold" tank of the radiator.)

If that is the case, I don't see how an impeller of any sort could starve the heater of it's supply of coolant, since the force pushing the coolant through the heater core comes from the outlet of the pump, but only after the coolant has already been through the engine.

Now, if the heater hoses had been connected so one went to the water pump, and the other went to the cold tank of the radiator--sure, there'd be no pressure to push coolant through the heater core with the engine running since both hoses were connected more or less to the suction side of the water pump; but after the engine was shut down and the coolant temperature began to rise through heat-soak, there'd be plenty of coolant getting blown out the open end of the heater core; and out the open end of the heater hose. The issue in this case wouldn't be the impeller of the water pump, but rather that the heater core "supply" hose wasn't connected to the proper fitting.

I don't know if that could have been the case with the truck you worked on, but at any rate--if that truck's pump could move coolant enough to provide engine cooling--it would have moved enough coolant to supply the heater core if the heater hoses were connected to the proper fittings.

I consider the truck you worked on to be something of a mystery; I wish I could have seen it.

 

I've had to pry out of onna the freeze plug holes a piece of loose metal casting crap and I think it was in my 406, but it's been years?

Mighta been my BB?

So crap does happen.............

pdq67

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another long shot is possibly the passenger side has the bypass hole in it on your block and water pump, maybe the coolant is flowing more through the bypass than the engine? I know by plugging the bypass my car ran easily 20 degrees cooler. All i did was tapped the water pump and put an allen headed 1/4 pipe plug in it. Just an idea. Good luck!