How Cold is Too Cold?

Discussion in 'Street/strip 400/430/455' started by johnriv67, Oct 29, 2019.

  1. johnriv67

    johnriv67 Well-Known Member

    The thermostat that came in my Riviera was a 195 and kept the stock car running fine.

    I added a cam, shorty headers, full exhaust, and converter, hopping up the performance and installing a 180 degree thermostat.

    I will soon be installing ported heads on the same shortblock with a B4B intake. I intend to use a 160 degree thermostat, as my dynamic compression is approaching 8:1. I will be running pump gas 93, and I am wondering if this is too cold for the engine.
     
  2. Mark Demko

    Mark Demko Well-Known Member

    180 is good
     
  3. Stevem

    Stevem Well-Known Member

    Too cold is when you want to run normal oil change intervals which means running a high enough coolant temp to allow the oil to get up above 212 degrees to boil off condensation.

    Condensation in the oil holds onto the the byproducts of the combustion process which contain acid, and acid in your oil will eat up the soft metals that make up Bearings and Pistons over time.
    If IR gun your oil pan after a 30 minute long drive and it's still not reading back above 212 degrees then you had better plan on changing your oil every 500 miles!

    Keep one other thing in mind, that is fact , that a internal combustion engine is powered by expanding hot air .
    This means the more heat that is in the chamber when the fuel/ air charge is lit off by the plug then more power the motor will make and milage will also come from that hotter burn !

    I would start off after your mods you make by running a 180 stat and if you have no part throttle ping or full throttle knock , forget about running a 160 stat.
    Keep in mind that with ported heads your going to need to jet up some on the secondary side of your current Carb , and maybe even on the primary side also.
     
    Last edited: Oct 30, 2019
    johnriv67 likes this.
  4. Bens99gtp

    Bens99gtp Well-Known Member

    I run a 160 in my race motor, but when I do street motors of any brand I use a high flow 180
     
  5. 1969RIVI

    1969RIVI Well-Known Member

    Hi use a hi flow 180 also and my car seems to run at 190-195.
     
  6. johnriv67

    johnriv67 Well-Known Member

    I’m thinking I’ll go back to my 180
     
  7. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Ive run 160s in everything for years with out issues. I change the oil once a season in my cars and the oil is as clean coming out as it is when poured in.
     
  8. johnriv67

    johnriv67 Well-Known Member

    Damn and almost in Canada too:D
    So basically just flog it once the coolant temp stabilizes to get the moisture out if its ever an issue?
     
  9. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Yeah. Water boils at 212° as we all know. It'll also evaporate at 33°. Oil temps are higher than coolant temps as well. There will be no issues burning condensation out of the oil even at lower operating temps than 160. Don't over think it.
     
    1972Mach1 likes this.
  10. 1972Mach1

    1972Mach1 Just some guy.....

    I also have 160s in everything. And one with a gutted thermostat (read: always open) for years and many miles. No worries. 160 is plenty hot unless you're driving in the winter. And I do that too. Your heater just doesn't work as well.
     
    Last edited: Oct 31, 2019
    johnriv67 likes this.
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Oil does not need to get to 212* to drive out moisture. Just put a pot of water on the stove and put your hand over it. You’ll feel your hand getting damp long before the water boils.
     
    rmstg2 and 1972Mach1 like this.
  12. Bens99gtp

    Bens99gtp Well-Known Member

    After normal driving the oil will be up to temp no matter what stat you have in there.


    I have an oil temp sensor on my car and on ab average 1/8th mile pass is see +20 ok temp gain on the the first pass. I try to stage with it near 160 and it finishes about 180......after several back to back runs I've seen a tick over 200
     
  13. 72gs4spd

    72gs4spd Well-Known Member

    I run electric fans and a 160* thermostat. I set fans to come on at 185*. This way I have good circulation when the fans come on when I’m not on the highway.
     
  14. Schurkey

    Schurkey Silver Level contributor

    What happens to your piston-to-wall clearance when the block doesn't get up to proper (expected) temperature?

    Hint: Marine engines that typically run "lakewater" cooling usually get honed for an extra .001--.002 piston-to-wall clearance, or they scuff pistons. Piston temp is relatively independent of coolant temp. Pistons expand about the same no matter what the coolant temp is--they expand based on combustion BTUs. Cylinder walls expand based on coolant temp. An engine that has "cold" coolant has small cylinders and normal-sized pistons.

    I wound up with an entire case of 160 degree high-flow Robertshaw thermostats, and I almost hate to sell them because as far as I'm concerned, they're too "cold". I do use a 160 my boat...but it has an extra .002 of P-W clearance, a functional PCV system, and thin synthetic oil.
     
    Last edited: Oct 31, 2019
  15. Stevem

    Stevem Well-Known Member

    Great info in the above and should really make you see why for long efficient engine life engineer's found that production motors need to come off the assembly line with 195 stats in them.
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    OK, 160* is probably too cold for a typical street car, but for a race car, not so bad. Having said that, most guys use a 160 as a crutch for a cooling system that isn’t getting the job done. They typically still run up around 190 or more. I think 180* is the perfect compromise and I am certainly not worried about my block not expanding enough at that temperature, 195 might be great with microprocessor controlled FI and smart ignition systems with knock sensors, but for our street driven big blocks that run too hot, that might induce detonation that one might not hear, the death knell for any engine at WOT. I’ll take my chances at 180, my engine runs right there with a 180 stat. How much cylinder wall expansion does 15* make anyway.
     
  17. Stevem

    Stevem Well-Known Member

    Some folks here seem to be fixated on answering questions in this mostly street section in terms of how they relate to race motors, disregarding the fact that most race motors get fully inspected once a season and rebuilt after every 2 to 3 race seasons.

    The OP on this string is talking about his 8 to 1 street motor and his question needs to be answered within that frame work!
     
    B-rock likes this.
  18. johnriv67

    johnriv67 Well-Known Member

    That's true Steve, even though this one is going to be 10.2 : 1 with ported iron heads and a mild cam.
     
  19. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I'm fairly certain they switched to the 195 stats for reduced emmisions. I read that in a service manual somewhere .

    Sucking an endless supply of 50-70 degree lake water is a far cry from a 160 stat.
     
    1973gs likes this.
  20. B-rock

    B-rock Well-Known Member


    So many questions get sidelined this way, The OP question gets churned into a now race question and whats good for a race motor must be good for a street motor, But for those who don't know the difference.....
     

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