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Pulley smb 350

 
CapriceOval
I love my Chevy Chevette!
Posts: 2
Joined: 06/14
Posted: 06/01/14 04:52 PM

I bought a street stock dirt track car and it looks like the water pump is going bad. its a chevy small block 350, the pulley that goes from the water pump to the main pulley doesn't have a tensioner. how should i remove it and is that bad for the motor?

Thanks  

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wayne712222
V-6 Camaros rule!
Posts: 90
Joined: 11/13
Posted: 06/02/14 12:42 PM

if you make a careful note of the belt numbers. so you can get exact replacement belts if you need them.. always a good idea to keep one spare with you.. that is a custom fit belt.. no parts store will have that listing..  but will have the belt if you have the numbers from whats there..

to remove and replace that belt. you have to loosen the 4 bolts that hold the fan blade and or water pump pulley in place.. when you loosen the bolts the pulley will drop slightly and allow you to remove or replace the belt..

is there a chance the belt is too short.. ??? could be.. exerting excessive force on the water pump.. absolutely ..

belts a measured by the  outside surface length..

belts are measured by the width of the belt..

belt numbering varies from brand to brand..

a conventional chevy alternator and water pump belt is a gated 7480..  or 13480 or 48013..   can you see the pattern.. its a 48.0" belt..   either 7/16" wide or 13/32 which is actually 1/32 narrower that 7/16..  14/32 would be 7/16"

if you can post the size of your belt.. i might be able to figure out depending on what brand is available to you.. the next length longer.. sometimes its only a fraction of an inch.. sometimes half an inch.. sometimes a whole inch..

when you ask for a replacement water pump... please match the casting numbers on your pump..    if you have an aftermarket pump.. it could be modified for racing internally...

you will want to run a thermostat restrictor disc.. or break the guts out of a thermostat.. you don't want if you race.. full flow of the water pump at high speed flowing thru your radiator..  its too much flow..  its going too fast to allow the air thru the radiator to cool it much at all.. the pressure created by the water pump can blow the top tank off your radiator.. and something that nobody talks about in circle track racing..  why one needs to keep  using new radiators after every race...
they just don't cool.. they get so clogged that there is no air flowing between the tubes.. and it won't wash out..  if you looked carefully.. one would see that the oval tubes had expanded and crushed the thin material between them  and prevented air flow. this is because of the high rpm water flow and the 30 pound radiator caps exerting massive pressure beyond the 16 pound design rating for most radiator tubes..

if you run a restrictor disc.. or even better a decent thermostat with a bypass circuit from the  front of the intake manifold to the inlet on the water pump. you will have a cooling system that works better and does not overheat.. even at high rpms..

the thermostat blocks the water pump flow into the radiator.. building pressure inside the block and heads..  increase of this mechanical pressure increases the boiling point of the coolant or water. 3 degrees increase for each pound of pressure increase..   the bypass hose allows the coolant to circulate thru the block.. forward thru the heads past the closed thermostat and back thru the bypass again.. this equalizes the coolant temp in the block and heads.. until it get to the thermostat opening point..  then the cooler coolant in the radiator swaps position with the hot coolant in the engine.. as soon as it gets to the thermostat.. it closes.. stopping the flow in the radiator so it can be cooled by ram air or the fan pulling air thru the radiator..  this will make the head and head gaskets last longer as there are less thermal cycles..  limiting to one warm up and one cool down per race.. instead of twice a lap..  depending on the track..  this is just my opinion.. it is a known fact.. but most people won't admit it or don't understand it as that's not what everybody else does..  or is it???  i can go farther if you have specific questions .. if i have not overheated you..  

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CapriceOval
I love my Chevy Chevette!
Posts: 2
Joined: 06/14
Posted: 06/06/14 07:30 PM

its just a stock 350 and Ive only raced it twice, but should i put a belt tensioner on the  pulley. If not why do they run them without the tensioner?
           i will also look into the bypass hose and or restrictor disks. thanks again  

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wayne712222
V-6 Camaros rule!
Posts: 90
Joined: 11/13
Posted: 06/07/14 05:49 PM

sure... install a tensioner..  but the crank to water pump belt only is a LOT easier if you get the exact length belt and thats a trial and error thing of probably 3 or 4 belts to get the perfect fit..  and the perfect tension..

install temporarly a pressure gauge..  use braided line not a nylon tube into the crossover passage in the intake.. so you can monitor the mechanical  cooling system pressure while you are running the engine..  just for kicks..

there is a picture in one of the many magazines here of a water pump test mule engine.. it had  temp and pressure gauges installed all over the place on the engine. this allowed the designer to check the equal pressures and temps of the cooling system...  

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