Restrictor instead of thermostat?

Discussion in 'Race 400/430/455' started by BUICKRAT, Apr 2, 2019.

  1. BUICKRAT

    BUICKRAT Torque Rules!

    My car is no monster, but it's a healthy 550-600 hp motor. Ron Davis radiator from T/A, T/A water pump, 180 stat. Proper shroud, 5 blade clutch fan that is properly spaced 1/2 way into the shroud. It gets hot on warm days in traffic. Too hot. And keeps climbing.
    My thinking is that the coolant is either not staying in the rad long enough, or too long. I'm not wanting to buck up for the electric cooling fan setup from T/A yet, as my current set up should cool this motor.
    Anyone running a restrictor instead of a stat and what size?
    Any other input appreciated.

    Thanks guys!
     
  2. Bens99gtp

    Bens99gtp Well-Known Member

    can I ask what your timing is. we had an olds 400 stroked to 44x cubes in a customers 442 that fought over heating for years....not instant hot and would actually cool down at idle but warm up going down the road. we put a dual electric fan on. I think 2 12" from his single 16". and locked the timing out.

    I can tell you on my iron head 464 that when I locked my timing out and had 32 at idle instead of 12ish.. ..my egts dropped more than 400 degrees.

    customer had the car out the other week temps were low 50s said he was 155-160, before same temps he would be over 190.
     
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  3. BUICKRAT

    BUICKRAT Torque Rules!

    My base timing is 26, no vac advance.
     
  4. Bens99gtp

    Bens99gtp Well-Known Member

    when you say base timing.......are you talking it is cranking with 26 then swings up from there??? or is 26 including full centrifical advance at say 3000ish rpm. are you using the vacuum advance at all or not?

    couple other minor things, have you checked or replaced the cap. a leaking ca will cause not enough pressure to be built in the system and not keep the coolant in contact to all the arts of the motor. it is possible to get little steam pockets inside the cooling system.

    we had another customer years ago with a 41 Plymouth and a 350 lt1 in it.....on trips he would slowly climb temps and just never come down.......even though we gelled it with a high flow water pump and stat. we put Evan's cool in his and it now never sees 200 even on hot ohio days in the upper 90s+ with his a/c running.

    do you have a high flow stat or standard unit.

    you could always add fans to the other side of the rad. to push air when needed. is it only getting hot in traffic. we used 2 12s from maradyne on the olds motor and they move alot of air
     
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  5. buicksstage1

    buicksstage1 Well-Known Member

    I would not recommend locking the timing in on a pump gas street car, also when locking in the timing on any engine make sure to re phase the rotor.
     
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  6. buicksstage1

    buicksstage1 Well-Known Member

    When using a electric pump I knock the center out of a T-stat and use it as a restrictor, but with you set up it should run cool. If you try the stat knocked out Put it in facing the same way it normally go's in. Timing should be 15*-20* initial timing depending on how it starts in the heat and 34* total. Is it just hot around town and fine on the hwy?
     
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  7. buicksstage1

    buicksstage1 Well-Known Member

    If it is hot just in town but fine on the hwy your most likely not spinning the water pump fast enough and might have a underdrive pulley on the crank, meaning the drive pulley (crank) is too small and the water pump pulley is too big. If you take pictures of your pulleys I should be able to tell you if that is what you have.
     
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  8. Bens99gtp

    Bens99gtp Well-Known Member


    what's wrong with locking the timing out on a pump gas street motor.........we have used it very successfully for year on chevy 502, old, buicks, pontiacs, sbc and even amc. every customer we have done the change says they cant believe it makes such a difference in idle, temps, and driveability.

    we used an msd 6520 box that has 20* of cranking retard, so even with 32* it only sees 12* cranking. they start right up idle super smooth. no more centrifugal and advance causing the motor idle at 1200 one stop light and then having to cover the gas at the next one.

    yes I use an adjustable rotor to properly phase it.
     
  9. BUICKRAT

    BUICKRAT Torque Rules!

    I do have an underdrive crank pulley, and a stock water pump pulley. It only gets hot at low speeds/traffic/city driving(stop and go). You may be on to something, the more I think about it.
     
  10. DasRottweiler

    DasRottweiler -BuickAddict-

    I'm pretty sure that I have 2 stock 455 crank pulleys in da basement, I'll check numbers , and if needed , they are yours Steve.
     
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  11. BQUICK

    BQUICK Well-Known Member

    I was getting horrible spark knock when I hit the starter hot with locked timing on pump gas. Like a sledge hammer hitting the piston. Can't be good for rod bearings.
     
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  12. Bens99gtp

    Bens99gtp Well-Known Member


    were you just cranking with full timing or were you using a starting timing retard, with the 6520 box and cranking retard I've never had that happen on any of the builds
     
  13. BQUICK

    BQUICK Well-Known Member

    I had the 20 deg start retard but it didn't seem to always work fast enough to avoid that spark knock. Maybe have to turn key to run position for a second before cranking?
    I went with a fast curve that started at 1200 and all in a 2500. Then even with 12.5 comp....starts like low compression motor even on pump gas.
     
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  14. buicksstage1

    buicksstage1 Well-Known Member

    Its a common issue, 67-68 are the worst, they used a small 2 groove under drive pulley and a large water pump pulley and that is the exact opposite to what you want. 69-70 weren't much better unless you got the cooling or AC package. In 71 they got a bit better and 72 and up were the best. Do you have a long water pump or short? There is several pulleys to choose from and you have to watch because the 3 pulley crank pulleys can have different size power steering pulley, for example I have several sets hanging on the wall. This set is part has a # 1235777 crank pulley, and its a triple pulley. Front 2 grooves are 7 1/4 OD, power steering is the small OD pulley that is 5 5/8 and gives you the most room for the power steering belt to clear the water pump, the match WP pulley is part# 1235778 and its a double pulley for the long WP and has a 5 5/8 OD where some of the other crank pulleys with 3 grooves have a larger OD at 6 3/16 power steering pulley. You want a big crank pulley and small water pump pulley. Watch for the After market Alumin pulley's also be they all seem to have the same issue's with the underdrive crank pulley and larg W/P pulley. I can't tell you how many people I have helped with under drive pulleys, it is not the way to go. If you can get me pictures of both pulleys I might be able to tell you what you have. And maybe put a tape across them also.
     
    Last edited: Apr 4, 2019
  15. buicksstage1

    buicksstage1 Well-Known Member

    Most of these guys running street cars do not have fancy IGN boxes with start retards etc. I also think most of these guys have 250 @ .050 cams and Distributors that don't have adjustable rotors to phase them. I have seen so many busted ring gears and starters/snouts to count because of locked in Distributors. Street cars are more prone to heat and heat lock etc on hot days also. Race cars yes use it if you can't set it up to idle decent. if your idle is 1200rmp it must be a race car engine.
     
    Last edited: Apr 4, 2019
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  16. Bens99gtp

    Bens99gtp Well-Known Member


    the engine I did that has this particular idle issue was a 502 chevy, 9.75 comp with afr 305 heads and pertronix dist with the flame thrower 3 set up to have some form of rev limit just incase. the dist came having 20* swing
    target idle was 800-900. and one time it would idle there, next stop light it was 1200, next one could be 500. and when u finally got it do it in the shop. the timing when it idled 800-900 was like 12 ish, when it would high idle timing was more 18ish, when low it would read like 8. just couldn't get the curve to always settle back

    yes it did require a 400 dollar box to get right.......but has worked flawlessly for 5 years now.

    but back to the full subject of this thread I agree the underdrive pulley is highly suspect
     
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  17. BUICKRAT

    BUICKRAT Torque Rules!

    I have no pre-ignition on start up.

    That's just the pistons wanting their way out. Down, sideways, just OUT.

    buickstage1, I'm going to source a larger crank pulley and a smaller water pump pulley. Spent the big money on a billet underdrive crank pulley from t/a. to reduce drag, but it may have been a fail for a street(strip) car. Good thing it's only a custom with no frills, or the alternator may not keep up either. Do you know if anyone makes a smaller w/p pulley?


    Much appreciated, Jay. Will take you up on that! Gotta get this bit$h on the street!!! Punish some ricers.
     
  18. buicksstage1

    buicksstage1 Well-Known Member

    Do you have a long or short water pump?
     
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  19. 1972Mach1

    1972Mach1 Just some guy.....

    Not on a Buick, but on my big engine I run a "gutted" thermostat as suggested as a restrictor, and that works well. It's 552" and 13.5:1 compression. With a stock starter, I have an ignition cut out on a simple on/off switch hooked to my HEI. I turn the ignition off, start cranking the engine, then just flip the toggle to "on". Fires right up, and the starter has no idea it's trying to crank something that big without the spark trying to kick everything back down.
     
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  20. BUICKRAT

    BUICKRAT Torque Rules!

    I have a short pump. It's the T/A one.
     

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