Hot Rods Thermostat Question

I'm sorting out a brand new build (ten miles). 1930 Model A Sedan with a brand new 350 crate (290 hp) turbo 350, Walker cobra z radiator, high flow aluminum water pump, 6 blade fan, no shroud. We were driving around town the other night and the temp stayed right at the 185 degree mark for about 15 minutes, it has a 185 degree thermostat. Just as we were pulling into the driveway the mechanical Stewart Warner temp gauge shot up to 230 and within 20 feet it shot back down to 185-190. It did the same thing when we tuning the holley carb and setting the timing in the garage. There is no coolant in the over-flow tank. And the radiator is full. Do I replace the thermostat with a 160 degree unit? Or run a restrictor instead of the 180 degree thermostat. Or just replace the 180 degree thermostat? Gary

 

looks like your bottom hose is collapsed.

 

No, it is just a really sharp formed bend. I fits perfect, practically impossible for it to collapse in 3". The angle of the picture is deceptive. I think I even have a short piece of wrapped wire in it. Gary

 

Other than what hidez57 pointed out about the bottom radiator hose, I'm not sure you have a problem. It didn't over heat, the pressure in the radiator didn't open the relief on the cap. so far you only have a couple of spurious gauge spikes. I wouldn't go changing anything based on what you've posted, you need to do some more testing. And fix that bottom hose.

 

Do you have a high flow thermostat to go with water pump? I put a FlowKooler hi flow water pump on the coupe with a standard thermostat and had overheating issues. The high flow thermostats have drilled holes for flow even if the thermostat hasn't opened yet. Put one in, big difference on my 350.

 

Does it have a spring in it? Can you confirm it isn't collapsing under suction pressure from the pump at high speed?

 

The temp "spike" you'reseeing is justbefore the thermostat opens , if the temp stabalizes after that , it's nothing to worry about....

 

An air bubble can cause a gauge to jump 40 degrees in a few seconds. Since it's a new build maybe all the air isn't out of the system. Or as said, you have a bad gauge.

 

agree with rechecking temp gauge. barely can see tip of fan - too low - need a hi-rise water pump & shroud - what pressure radiator cap are you running? 160 degree thermostat would be plenty - use " wide mouth" style. air pockets can occur inside motor. to help prevent this run hose from intake manifold to water pump. need better pic of front of motor and radiator cap.

 

We were just cruising at 25-30 mph so the rpm's were low and heading into the driveway it was idling. Is a spike reading like that normal? I don't really like it...never had it happen before with SW mech. gauges...maybe a five degree swing then back to normal when the thermostat opens. I'll take a close up picture of the bottom hose tonight. Plus I know it has a wire in it. I did the hose fitment and install.

 

The fan looks too far from the radiator, and you really should have a shroud.

 

I always drill thermostats to let any air go through them. Once the thermostat opens, it shouldn't fully close again. They move slowly so the water should get warmer as it starts to close heating the wax actuator and stopping it from closing.

 

Here is a close up of the bottom hose. No possible collapse and a good fit

 

I say air in the system if it's intermittent . If if continues probably not air.

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Summit once published info that cyl wall wear is 3 X higher with a 160 vs 180-195.

 

I vote for air in the cooling system (actually a steam pocket). They will cause the rapid increase on the temp gauge and drop. Run it up and down the road a few times and bring the rpm's up and down to get some circulation going. Let it cool and check coolant again. It should drop a bit if it has much air in it.

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Hi flow thermostat with at least one 1/8" hole. Short or not, always have a spring in a lower hose or a metal one with short hoses on each end. A fan within 3/4" of the radiator will not need a shroud. Good luck
PS: I hope you flushed out the new engine while it was still out of the car because they are known to have sand left in them.

 

Thanks for the input. Tomorrow I will run it down the road at highway speed. Yes there is a wire in the lower hose. The 17" fan is maybe 3/4" from the radiator at the bottom and 1-1/4 at the top. I can't add a 1" spacer. Like I said it does not overflow. So I have a couple options to try out. Gary

 

I was having the same issues so I moved my radiator closer to the fan...added a shroud....added a Robert Shaw 160 and all is good...good luck on the fix

 

I second the Robert Shaw thermostat, expensive but trust worthy..With engine idling I sometimes squeeze the upper hose to help system "burp"..If it does not stay hot so I would blame the gauge some how..

 

New thermostats are designed for EFI engines. They have to warm up quicker, then quickly go to normal temp. Best bet is a high volume like a Shaw or drill a hole. Went thru three thermostats before someone told me about the new style thermostats. And now that I think about, I also replaced the sending unit which made no difference.

 

Bad gauge? T-stat? Easy enough to find out.
Best $30 you'll ever spend.

 

I learned my lesson ... this is the only way to fill a cooling system!


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Could I suggest a Zips or Snow White WP riser, the fan is too low and needs to be higher to be more effective. Once that has been done add a shroud and swap the thermostat over. Then you are good to go.

 

Doesn't sound like a problem to me (at least not yet). I would just watch it for a while. The IR guns are a good idea. Don't go to a cooler thermostat, engine will run better at the higher temp.

 

What's wrong with the garden hose?

 

Agreed, works for me. the small hole lets some of the water pass, will help eliminate the spike you are seeing. We have been doing this for years, but recently I bought a high flow tstat and didnt drill it. I saw the same 230 degree spikes on my 36 chevy. took it back out and drilled two 1/8" holes, she stays right at 190 now.

 

The only thing that can make a good mechanical gauge move that fast is a steam pocket. Jack the front end up as high as you can and run it for a while, see if it doesn't burp some air into the radiator. If that doesn't help, change the gauge.

 

I had a 290 hp crate motor. Had similar problem, even with a drilled t stat. The 290 hp crate motor does not have the water pump bypass drilled (small hole on block and water pump on passenger side). I put a by pass hose in line with the heater hose to the top of water pump, problem solved.

 

Your fan to radiator distance is good...raising the fan would be good...add a properly designed shroud (about 1/2 the blade in the shroud and 1/2 the blade out), drill the stat (or purchase one that is pre-drilled) and you should be ready to tackle the heaviest traffic on the hottest of days while maintaining your (and your engines) cool.

Nice detail on the engine btw.

Off topic...how/where do you add oil and what are you using for PCV?