Hmmmmm... Interesting.

Thanks for that.

- Eric

 

Lots of lol in this thread. People here havent seen the bypass blocked before?

 

Okay, having reviewed the diagrams in the CSM, I just want to go through this from scratch, because I find it interesting.

The water pump, essentially, pulls water from the bottom of the radiator into the bottom of the pump, pushes it out through the back of the pump into the block, through the block and the heads, out the top of the intake through the thermostat, and into the top of the radiator.

In addition, it pushes water out through the heater fitting on the right rear corner of the manifold and through the bypass fitting on the thermostat housing, and pulls water in through the two fittings on the top of the pump.

So, water has two routes it can follow that do not go through the radiator.
One of them is through the heater core, which cools the water if the heater fan is switched on. This route is blocked if you have A/C and the selector is set to the coldest setting.
The other route is from the top of the intake, through the bypass hose, right to the water pump.

If you have A/C, with the selector on COLD, and the engine is cold (thermostat closed), then the only way for water to circulate through the engine is through the bypass hose.
With the bypass hose blocked, water will sit in one place (with probably some movement from convection), until heat is transmitted to the the top of the intake, and it gets warm enough there for the thermostat to open.
During this time, the water pump will be "spinning its wheels," turning in water that will not move.

I do not know whether it is bad for the water pump to spin against a non-moving mass of water, but I do know that cavitation can slowly erode surfaces inside the pump when the cooling system pressure is inadequate. My gut feeling is that the pump turning against non-moving water will create resistance (steal horsepower / fuel economy), but will not cause cavitation, but I do not know this.

I also do not know whether lack of movement of the water in the block (except through convection) would cause hot spots that could damage components, such as the head gasket, but it at least seems possible, especially since the hottest water, at the heads, will have very little space to rise, and the coolest water, at the bottom, will have no reason to rise from the bottom of the block. That being said, that leaves a relatively small distance for hot water to travel by convection, from the heads to the top of the intake, where the thermostat is located, to open the thermostat.

I will also note that Chebby has an internal bypass for smallblocks, and an external bypass for bigblocks (as described in section 6K of their CSMs), so this is not a unique Olds feature.

It would seem to me that, accepting Ozzie's comment that "As an experiment, on a hot day, I removed the thermostat and plugged the bypass. It seemed to reduce the upper operating temperature by about 15-20°F..." one could potentially increase cooling on hot days, without damage to the engine, by installing a valve in the bypass hose, closing it when it was hot, and running with the A/C setting on something other than COLD until the engine just began to warm up, then sliding the A/C setting to COLD and running with no bypass.

- Eric

 

I fail to understand how that article has any relevance to this topic. Olds don't use that type of by-pass arrangement. At least for the Gen II models. The by-pass on an Olds is open all the time regardless of what the thermostat is doing. It's like a straw man argument that doesn't relate to this topic. We all know there are plenty of cars that don't use the Olds arrangement and work fine.
What that articles shows is newer versions that have internal by-passes which have no bearing on this thread.

MD, water still flows through the block with the thermostat closed. It travels through the water jacket passages. It's just not making a passage through the radiator until the thermostat opens.

 

Eric,

Your description seems accurate to me. Based on my initial experiment and your comments, I'm planning a bit more sophistication to the original design.

It would seem to me that, accepting Ozzie's comment that "As an experiment, on a hot day, I removed the thermostat and plugged the bypass. It seemed to reduce the upper operating temperature by about 15-20°F..." one could potentially increase cooling on hot days, without damage to the engine, by installing a valve in the bypass hose, closing it when it was hot, and running with the A/C setting on something other than COLD until the engine just began to warm up, then sliding the A/C setting to COLD and running with no bypass.

- Eric[/QUOTE]

 

That's what I said, George.

- Eric

 

Some of you guys were right.
I borrowed a big proform carb from a friend and the car runs cool and pulls hard at WOT...SO ALL MY PROBLEMS WERE FROM A LEAN CONDITION.

Now the big decision what carb to buy ?
The engine is a 455 with big cam (don't know specs) performer intake,
x and y exsaust manifolds.
I figure I need at least 750 cfm maybe 800 (opinions ?).
JEGS has an Edelbrock 1407 (750cfm) for around $300.
Holley 3310c (750cfm) also $300
Edelbrock 1412 (800cfm) $400

What are your opinions ?

750 or 800 ?
Holley or Edelbrock ?

 

i vote for the unlisted option, a properly set up rochester quadrajet.


bill

 

Bill,
If I knew of someone local who could set up my 750 q-jet reasonably,
I'd be all over it.

 

Got the Holley 3310...solved all my problems.
Took the car out for a 2 hr ride last night 86 degrees and fairly humid out.
Went down a popular busy strip in Deerfiend beach with stop and go bumper to bumper traffic for 2 miles and never ran over 195 degrees.
Stopped for gas and she went up to 205...after 5 minutes on the road back down to 185.
Cruising temp was between 180-190.
Now I just need to fine tune for more performance.

For the guys who pegged the overheating to a lean condition....THANX !! : )

 

Glad the carb worked. I like the 3310 and have one on my car.

 

I know a guy in PA that's been racing Olds since the 50's and he told me the exact same thing. If you want the engine to operate roughly 20 Degs cooler, then block off the bypass.