Buy-pass on waterpump function

[Robert C.]

Please let me know what would happen if you plug the by-pass hose found on HPerf. small blocks and all big block Corvettes. What is the function of these buy-pass's? (one engineer said that elimination of the by-pass will help with cooling.)


Texas Chapter NCRS

[Iron Duke NCRS #22045]

Re: Buy-pass on waterpump function

When the thermostat is closed the coolant is circulated through the bypass circuits back into the engine to speed engine warm up and to keep the pump from cavitating. All SB pumps/blocks have an internal bypass which is the small hole on one of the pump legs. Chevrolet engineering decided that a bigger bypass was required on Special High Performance engines, perhaps because they see higher revs, but this is somewhat offset by the fact that pumps are driven slower relative to crank speed on SHP engines, so I don't know the full reason(s). There's also a THIRD bypass, which is the heater core circuit. I've never tried to eliminate the external bypass, so I don't know the effects. There will always be some coolant coming through the bypasses simply because they're there, and if the external bypass is eliminated more coolant will be forced through the radiator, however, I would not suggest "re-engineering" the system to solve an overheating problem, but, rather, to go through the cooling system step by step, correct any problems that have degraded cooling system performance, and return the system to it's original design performance. A lot of guys seems to still have original or old replacement Harrison aluminum radiators that "look okay", but I bet many of these radiators are internally clogged from all the silicates and other inorganic salts that have precipitated out over the years, and the only way to check is to remove it and have it flow and pressure tested at a good radiator shop. Then if it's bad, bite the bullet, buy a new DeWitts and start using silicate, phosphate, and other inorganic salt free Dexcool.

Regulating the outlet temperature as is done with our vintage engines is not the best way to go nowadays. The problem is that in cold weather the engine is subject to thermal shock. When the thermostat begins to open cold ambient temperature cooland is drawn by the water pump. The larger the bypass circuits, the less coolant will be drawn which will minimize this shock. Many Modern engines now regulate the INLET temperature, and many inline engines flow the coolant through the engine one way - in at one end and out the other end. These methods usually reduce internal hot spots and prevent thermal shock.

Duke

[Joe L.]

Re: Buy-pass on waterpump function

Bob-----

In addition to what Duke mentioned, the by-pass provides some measure of "protection" in the event that the thermostat "sticks" in the closed position. Under these circumstances, an engine will overheat rapidly and, sometimes, catastrophically.

[motorman]

Re: Buy-pass on waterpump function

duke, i believe a lot of coolant bypasses the rad through these bypasses so i allways block the bypass in race motors. we always use a restrictor in race engines so without the bypass all the coolant is forced to go through the rad. a lot of coolant goes through the bypass on BB so if any one is trying a restrictor in place of a thermo i would also block the bypass. even with a thermo some people still block the bypass and drill several small holes in the thermo housing to act as a bypass.

[motorman]

Re: Buy-pass on waterpump function

i will make it clearer, the holes should be drilled in the flange of the thermostat.

[Dale Pearman]

Screw The Bypass

I'm one of those, "some people" who has always plugged up the bypass circuit and drilled a series of holes in the thermostat flange. Here in Tennessee it gets hot as hell and every angle to help a marginally cooled contraption like a C1 is welcomed. The cooling of 1961-62 327 engines was an assignment for Mr. Duntov who experimented at the Phoenix Proving Ground in 1961. He came up with radiator side seals mounted with Robbins clips which started in 1962 production. I have copies of his corrispondance with Chevrolet Engineering.

Varooom!