350 sbc thermostat question/debate..

[QBuff02]

not technically squarebody related as the engine is in my buddies rat rod, however, it is originally a 350 sbc so... Question is, guy he bought the car from pulled the guts out of the thermostat since "you don't need heat in a rat rod that's only driven in the summer." But my concern is, the engine just seems to run "hot" and I was always told you ALWAYS want to run a thermostat, no matter what. unless emergency situation. as in if you don't the engine will cycle the coolant through the radiator too fast and not allow enough heat transfer out as it pushes through the radiator. I.E. without the thermostat there isn't enough restriction to "slow" down the flow and it just blows through the radiator before it "cools" off. Now, I have not yet put my heatgun on the radiator to determine difference from top to bottom But I also know that the sensor/sending unit for the electric fan "turn on" is in the bottom of the radiator which I believe is a no-no! so we are going to move that to one of the heads this weekend, and we are going to move the temp sender for the gauge up onto the intake by thermostat or to the other head. How this all started is, (and its a fresh build) once it was ran and up to operating temp, you'd shut the car off and after a few minutes it would be hard to start and you could smell gas at the carb. Now, at this point it had an Edelbrock carb on it, which you could not adjust, wouldn't run right, never idled, etc. and I've never really been a fan of them. So, here in comes the Demon 650 from reserve status, we stuff it on there, make a few adjustments, and she's a screamer! Idles, runs, drives, is smooth, crisp throttle response, has good cruise manners, etc. Shut the car off after getting it dialed in, and what do you know, all of a sudden the gas starts climbing in the primary fuel bowl, you can see it bubbling in the clear filter ahead of the carb, until it fills the bowl up and starts fogging into the throat of the carb. Grrrr... heat soak! Now, I suspected this prior to the demon carb swap, and now I can actually see it with the clear sight glasses on the fuel bowls and the newly added clear fuel filter. So, in comes the 1" phenolic spacer between carb and intake to try and help combat the problem. Of which, it makes quite a difference, but just not 100%.. Still some boiling/percolating of the fuel in the carb. So after all this messing around, I decide to feel the carb, and it's warm to the touch, the new spacer is warm to the touch, and the intake, well, you can NOT touch it as it's like scalding hot! And it's an air gap intake. So this has me going back to the original issue I had of wanting to move the temp sender, the electric fan switch, and wire in a MANUAL switch to the electric fan circuit as well to over ride it when it's warm/hot. And in the middle of all of this, that's when my friend tells me the guy he bought the car from had made mention that he "pulled the guts" on the t-stat. Which threw a red flag.. So I told him that if we're going to drain the coolant and take the time to switch sensors and senders around, we're also going to throw at least a 160-180 degree t-stat in it as well. Back to the engine, for a little i.d. It's a local engine builder that did the engine that's probably one of the most reputable sbc/bbc performance guys in the area. 350 4 bolt main, .030 over, flat tops, good scat complete rotating assembly, roller cam, roller rockers, aluminum heads, air gap intake, open headers, etc. Builder claims it should be right at 400hp and crisp. and I've driven this little pack of gum with all that, and it's pretty impressive! Although the lack of weight I know helps! So, back to the original debate here in all of this novel, begs the question to you guys, Arguments for/against running a thermostat/not running a thermostat? Anyone with real world experience have similar problem if you did not have a thermostat installed. Have you ever heard of people having issues with that situation?I will add that I also think the cooling system might be a touch undersized but there is a definite space limitation here, so I'm crossing all my t's and dotting all my I's and making sure that the basics are good.

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[74 Shortbed]

It gets hot because the water is constantly flowing and don't stay in the radiator long enough to cool down.

 

[smoothandlow84]

X2...I always run with a thermostat. It may run hot also because the radiator is undersized, partially blocked or the fan is improperly sized or pitched for the proper airflow, especially if no shroud is being used

 

[Honky Kong jr]

I run a 165* in SBs and BBs....but then again I tend to lean on my stuff a little hard. Rod looks good needs decapitated about 8" tho lol

 

[QBuff02]

Thanks for the responses guys, they only reaffirmed what I was thinking! So last night we did a quickie thermostat swap (because he was still a tad skeptical Lol) drained enough coolant to change it out and put in a 160 degree t-stat and filled it back up and needless to say when we fired it up and took it for a test drive it hovered right in the 160-170 degree range! Now I get that it wasn't 90 degrees outside, but it was still mid-upper 70's.. So then with the electric fan switch not being relocated yet and I believe its got to be a 195+ degree switch the fan obviously never kicked on until we "forced" it to heat up and then once it did it seemed like it just couldn't quite keep up.. So he's going to try and find a temp switch that works in the 170 degree range for when we go to change that, the fans kick on sooner than they are. I told him that I feel like if we can keep the temp down we can control the rest of the fuel issues! A 20-30 degree temp difference in coolant and engine temp is huge..

 

[QBuff02]

I run a 165* in SBs and BBs....but then again I tend to lean on my stuff a little hard. Rod looks good needs decapitated about 8" tho lol

I agree! He bought it mid summer right after the guy had got done installing the engine and when we drove it home I think there was less than 150 miles on the drivetrain and frame mods. For a '28 it drives extremely straight, like take your hands off the wheel at 60, not pee your pants, no wandering in the lane straight! So his plan was to work the bugs out of everything else and this winter he is going to take 6" off the roof line and have glass made for the rest of the car. He bought a whole bunch of old gas/oil cans with the logos on them and some "rough" old signs that he is going to cut up and line the interior with, I think it's going to look pretty good come spring time!

 

[shiftpro]

It sounds like your on it QBuff. He's lucky to have you on board.

 

[4WDKC]

A proper cooling system will keep the engine cool above 30 MPH, going to a lower temp switch could cause the fan to run all the time. IMO he needs either a better fan or radiator/cleaned, my vette has a 160 t stat and I programmed the fan to turn on at 200 at off at 190 so the fan wouldn't run at the 189 temp I was seeing running down the interstate. Fans aren't made to run continuous and doing so will shorten the life of the fan, possibly overload the relay if its not rated to the amps at continuous use and the wiring can even be an issue if not using a larger gauge than recommended.

 

[Handy Andy]

I know this isn't exactly what your looking for, but you mentioned finding a sensor to control the fans at a different temperature. If he doesn't mind spending a little cash, tell him to check out autocoolguy.com. They sell electric fan controllers that have soft starts built in. This means that they start at 0% output and slowly speed up as the temperature of the engine increases. I purchased one and installed it on my 400 Small block that I recently built to make a little power and torque for pulling my boat. I have yet to have it out on the road yet as I'm still doing some other work to the truck, but, I have fired it up and ran it with the new controller on. It now Idles at 195 where previously it idled at 205. I should also add that sitting at an idle, the fan does not run anywhere even close to 100%.

The awesome thing about these controllers is that as stated previously, they have a soft start built in so there is no big huge power spike and no relays to burn up and replace. Also, it modulates the fan speed to maintain the desired temperature setpoint. If the fan only needs to run at 30% to keep the temp down, it only runs at 30%... the temperature range on this thing is 140-190 so it will work in a wide variety of applications.

I ordered the NB-100 from them. This has the No-buzz box built in so the controller is silent. It is rated for 100 amps of continuous draw, and is internally fused at 120 amps. It took me all of about an hour and a half to install and ended up costing me about $230... Best $230 I have spent so far..

 

[Honky Kong jr]

I know this isn't exactly what your looking for, but you mentioned finding a sensor to control the fans at a different temperature. If he doesn't mind spending a little cash, tell him to check out autocoolguy.com. They sell electric fan controllers that have soft starts built in. This means that they start at 0% output and slowly speed up as the temperature of the engine increases. I purchased one and installed it on my 400 Small block that I recently built to make a little power and torque for pulling my boat. I have yet to have it out on the road yet as I'm still doing some other work to the truck, but, I have fired it up and ran it with the new controller on. It now Idles at 195 where previously it idled at 205. I should also add that sitting at an idle, the fan does not run anywhere even close to 100%.

The awesome thing about these controllers is that as stated previously, they have a soft start built in so there is no big huge power spike and no relays to burn up and replace. Also, it modulates the fan speed to maintain the desired temperature setpoint. If the fan only needs to run at 30% to keep the temp down, it only runs at 30%... the temperature range on this thing is 140-190 so it will work in a wide variety of applications.

I ordered the NB-100 from them. This has the No-buzz box built in so the controller is silent. It is rated for 100 amps of continuous draw, and is internally fused at 120 amps. It took me all of about an hour and a half to install and ended up costing me about $230... Best $230 I have spent so far..

Good call I believe they make mini VFDs for them that come with resistors. Which are needed do to heat created when useing a VFD.

 

[QBuff02]

Well a little update after the weekend, as you know from previous post we already had the 160 t-stat installed, so we relocated the temp sender to the cylinder head, and we put a 195 on/180 off fan temp switch in it, and located it in the intake manifold next to t-stat instead of down at the bottom of the radiator like it was. And so far it seems to all work together pretty well! At cruise it runs in the 170-180 range, and then say in town or at slow speed, foot on the throttle "cruising" or stop and go without the airflow it will heat up to right at the point the fan switch turns the fans on and by the gauge it's right at 200-205, and it cools down nicely to right at 180 degrees and the fan kicks off like it should and then once we're moving it seems to maintain in that 170-180 range pretty consistently! So with all the good so far, we shut the car off and the fuel stays in the sight glass now once it starts to "heat soak" after several minutes, which it would not do before! Even after I took it outside of town and leaned on her pretty hard for a few miles (@HonkyKongJR) and came home and shut it off "hot" with the fan running, it never got out of the sight glass in the float bowl, it did climb some however, but it stayed in the glass where you could see it... and the car, now starts up every time hot! I also did wire in a manual override to the fan circuit as he wanted a little extra insurance in case he ever had a relay or sensor issue so that he could flip the switch and have manual fans to run to cool it off and get it home in event of failure.. So... We're going to call this problem, solved!