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71 runs super cold after Big Block radiator and Standard chevy water pump/accessories
So I feel like this is the opposite of most C3 owner problems...my 71 350 runs way too cold. I had the original water pump go bad, but had a set of SBC pulleys and brackets from another build, so I swapped everything over to standard SBC orientation.
The car takes forever to register temperature (verified temperatures are low with laser thermometer at the sensor, thermostat neck and radiator. When it does I'm only a few needle widths on the scale. Only if it's super hot out and a run on the highway do I get even remotely near normal operating temperature.
I feel like I must have bypassed the thermostat when plumbing with the surge tank. Or somehow it's stuck open or allowing too much coolant to bypass
Can anyone confirm my connections?
1)Lower heater hose to heater core is off the manifold
2)Upper hose goes to the back of the water pump
3)Surge tank overflow goes to upper right side of radiator
At this point I feel like taking the radiator out, having a pressure cap/overflow fitting welded on the passenger side like the later models and put a heater hose return nipple on the radiator. Get rid of the surge tank.
Why don't you just check the thermostat and make sure it's working correctly? If you want the car to run warmer, put a warmer thermostat in it.
Don't remove a great working radiator...
Most guys would kill to have your problem.
Odds are, your temp gun readings are not accurate if you are shooting the laser on that shiney thermostat housing. The fail proof way of really knowing what the temp is, is to add a second temp gauge (mechanical) and just hide it in the cabin for a back up. Odds are, it's not as cool as you think.. I'd be willing to bet its at least 160*...unless it's really cold outside and you are running a thermostat bypass hose.
Not that it would cause low temperatures, but doesnt what you are calling a "surge tank" have two connections on the bottom which are supposed to be inline with the hose going to the heater core?
Another question why are you running a radiator cap with such an extreme pressure reading 29-31 PSI?
Here we go again...if you are SURE the gauges show low temp...
The only tying that makes it run too COLD is a thermostat that does not stay closed. The rated temp of the thermostat is where it just begins to open. Period. Stick a new 180 in it and move on.
Just to confirm, the hose connections are correct? It was in my setup that I was wondering if I was creating a thermostat bypass.
Why do I think it's reading low...prior to the radiator water pump swap it would read about half way up the gauge on a hot day. After that it barely registers.
However I also changed the pickup location as I moved the temperature sender to the back of the manifold, drivers side. I'll pull it out, make an extension harness and bring out a boiling pot of water to see if it reads similar.
I'll check the thermostat in said pot o water. I can't remember it might be a high flow type. I think a good cheap parts bin might help slow the flow. Pressure cap was one I also had lying around, but I don't mind going back to a 16 lb unit.
I wouldn't ditch the radiator but it would be nice to ditch the surge tank setup. Bleed the car with the nose in the air if needed.
On a side note, I would replace that rubber fuel line ASAP. Many a Vette has burned to the ground because of that install.
What do you suggest then? Braided from the fuel pump to the filter? Next year she's going Multi Port EFI. My guess is many have burned down because people don't replace the soft lines when they should, especially with methanol fuel.
Just to confirm, the hose connections are correct? It was in my setup that I was wondering if I was creating a thermostat bypass.
Why do I think it's reading low...prior to the radiator water pump swap it would read about half way up the gauge on a hot day. After that it barely registers.
However I also changed the pickup location as I moved the temperature sender to the back of the manifold, drivers side. I'll pull it out, make an extension harness and bring out a boiling pot of water to see if it reads similar.
I'll check the thermostat in said pot o water. I can't remember it might be a high flow type. I think a good cheap parts bin might help slow the flow. Pressure cap was one I also had lying around, but I don't mind going back to a 16 lb unit.
I wouldn't ditch the radiator but it would be nice to ditch the surge tank setup. Bleed the car with the nose in the air if needed.
The temp sending unit in the aluminum intake manifold up close to the thermostat housing will likely read a few degrees cooler then having the thermostat housing in the head. (if thats where you originally had it)
When you say it used to run "half way up the gauge before", you still don't know how hot that was, maybe it was running way hotter then what you thought it was, and now its running cooler..
Basically, you have no idea what the temp really is. Repro temp sending units suck and usually are not accurate...And factory temp gauges aren't that accurate either across the whole range.
My factory temp gauge in the middle is 210*, this is with the temp sending unit in the head (big block), my mechanical gauge also reads about 210* with the sender in the intake. However at cooler temps, my mechanical gauge will read 160* (which is what my thermostat is), and my factory gauge barely reads about a needle passed 100*..... So the scaling range is way off on the factory gauge is my point...
Simplified:
Mechanical gauge: 210*
Factory gauge: 210*
Mechanical gauge: 160*
Factory gauge: 120* ish..
Using 2 different laser temp guns, you'll get temps all over the place....basically those are useless...They are measuring metal temp, not coolant temp.
So before you go swapping parts or thinking you have a problem, you need to verify temps accurately.
What do you suggest then? Braided from the fuel pump to the filter? Next year she's going Multi Port EFI. My guess is many have burned down because people don't replace the soft lines when they should, especially with methanol fuel.
Yes. That or steel tubing. A leak after the pump will spray so much fuel you won't believe it.
If you verified gauge is correct, your hose arrangement is irrelevant...water would still not get out unless the Thermostat allowed it ... your Thermostat is stuck open,, replace it...$10
The temp sending unit in the aluminum intake manifold up close to the thermostat housing will likely read a few degrees cooler then having the thermostat housing in the head. (if thats where you originally had it)
When you say it used to run "half way up the gauge before", you still don't know how hot that was, maybe it was running way hotter then what you thought it was, and now its running cooler..
Basically, you have no idea what the temp really is. Repro temp sending units suck and usually are not accurate...And factory temp gauges aren't that accurate either across the whole range.
My factory temp gauge in the middle is 210*, this is with the temp sending unit in the head (big block), my mechanical gauge also reads about 210* with the sender in the intake. However at cooler temps, my mechanical gauge will read 160* (which is what my thermostat is), and my factory gauge barely reads about a needle passed 100*..... So the scaling range is way off on the factory gauge is my point...
Simplified:
Mechanical gauge: 210*
Factory gauge: 210*
Mechanical gauge: 160*
Factory gauge: 120* ish..
Using 2 different laser temp guns, you'll get temps all over the place....basically those are useless...They are measuring metal temp, not coolant temp.
So before you go swapping parts or thinking you have a problem, you need to verify temps accurately.
I have exactly the same issue with my rebuilt/modified L-82 355 that was done in 2014 (.030 bored, roller cam 219/225, lift .525/.525, duration 110, 10.2:1 compression, AFR 180 heads). The OEM motor had an aluminum Dewitt's radiator, Stewart aluminum Stage 2 water pump, and a Stewart specified specially modified 180 degree thermostat with 3 holes drilled in the thermostat base. In my case, I think that the thermostat always allows a certain amount of coolant to pass around the thermostat even when closed which results on cold days for the engine to never reach full operating temp....just like ajorthm states, the temp gauge will barely come off of 100 on the gauge. On the highway, the engine will eventually reach the first hash mark on the gauge....half way between 100 and the 12 OClock position of 200. During the summer, the engine will eventually get to half way between the first hash mark and 200 which is 180 degrees. I think that the guage like you say is not linear and is running more than the gauge indicates when the temp outside is cold. In my case, I am thinking of replacing the gauge with a standard Robertshaw thermostat WITHOUT the 3 holes drilled in the base but I will drill 1 or 2 holes in the base rather than than the 3 holes...may try 1 bigger hole in the base rather than the 3 smaller holes to see what happens.....Thoughts?
Stewart Aluminum water pumps do not have the built in by pass for the coolant. I tried using a standard thermostat initially and the coolant temp on the guage fluctuates drastically as the thermostat opens and closes, thus the thought on having just 1 hole instead of 3 holes.
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Your title says it all, BIG BLOCK radiator in a small block, It probably has 3 or 4 rows of tubing instead of 2 or 3. Your over cooling your motor but if it does get to operating temp it should run better than if its too hot. Test it by blocking half the radiator with a piece of cardboard, it should warm right up. then just put in a higher temp t stat
do you get heat out of the heater?
bypass of the thermostat is standard in a SB.
drilling of t-stat is a waste of time.
and it's Ethanol, not Methanol.
fix the bad t-stat, test the gauge and sending unit, or borrow a radiator cover from a diesel truck...
I suspect that the sender wire from the temp sensor got damaged when you made the location move. If that line has a break in continuity, the gauge will always read at the low end of the scale.
Folks drill a hole in the T-stat to allow trapped air to escape the system. Totally unnecessary if you leave the radiator cap OFF while the engine warms up. Once it gets warm enough for the T-stat to open, any trapped air will burp out the radiator (or overflow tank). Then you can add coolant to get system filled and install the cap.
This method also allows you to verify that the pump is working and that the T-stat is doing its job.
people drill the t-stat because they mistakenly think they need some bypass to the closed radiator cap, which they don't with a SB because that is a design feature of the cooling system if it is a stock setup...
and yes, there are better ways of burping the system than drilling a hole.
having larger cooling capacity (BB radiator does not affect the cooling capability at all.)
the thermostat determines min. operating temp. if it starts running cool the stat starts to close and regulates the temperature.
I install BB radiators in all my cars, to ensure I have adequate cooling capability.
change the Thermostat.
03-25-2017, 09:31 AM
71 runs super cold after Big Block radiator and Standard chevy water pump/accessories
