By pass hose neede??
Thread Starter
Instructor
Joined: Mar 2017
Posts: 111
Likes: 7
By pass hose neede??
I have a 69 with a 350 and when I purchase the car the heater core was not connected and the water pump and intake both have plugs in them. Should I at least have a by pass hose from the intake to the water pump to relieve some pressure prior to thermostat opening? At least until I get around to fixing the heater core even though I have enough heat coming thru the floor to heat the interior as it is. Haha.
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 787
From: Lebanon Township New Jersey
There is absolutely no need for a bypass hose, and it looks stupid. If there was some back pressure issue that caused problems, why would the factory have put the vacuum controlled shut off valve in one of the hoses. That stopped flow (when it worked) just like the plugs do.
Melting Slicks
Joined: May 2002
Posts: 2,717
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Some GM vehicles came with heater core bypass valves and others came with heater core shut off valves. A little research shows that the 69 vette with a SB chevy came with a heater core shut off valve.
Most SB chevys have a bypass built into the block and pump, without an adequate bypass the pump can capitated and cause other cooling issues. If its working fine without any cooling issues than I wouldn't be concerned with it.
Neal
Most SB chevys have a bypass built into the block and pump, without an adequate bypass the pump can capitated and cause other cooling issues. If its working fine without any cooling issues than I wouldn't be concerned with it.
Neal
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
On a smallblock (most of them), the bypass is internal. On the block face where the pump bolts up, on the passenger side there is a small hole below the lower water pump bolt. On the water pump, there is a corresponding hole that feeds to the water pump impeller housing. The purpose of the bypass is to promote more even heat up of the engine when the thermostat is closed. It also helps to eliminate steam pockets and prevents pump cavitation.
On bigblocks, there is no internal bypass and you can see the hose running from the top of the water pump to the intake manifold.
The bypass has nothing to do with the heater system. Plugging the water pump outlet for the heater core causes no harm to anything.
On bigblocks, there is no internal bypass and you can see the hose running from the top of the water pump to the intake manifold.
The bypass has nothing to do with the heater system. Plugging the water pump outlet for the heater core causes no harm to anything.
