Dual thermostat bypass restrictor fitting?

[greatwhite]

So, I've been reading references to a water pump bypass restrictor fitting for dual thermostat housings.

I know there's guys out there who make their own with pipe plugs and drill presses, as well as one seller who sells a product.

But, every so often some anecdotal reference will pop up to a GM restrictor for said bypass.

Does anyone know of a GM part number or concrete reference to this restrictor?

All I've ever seen is the bypass fitting in the pump and intake, which have been smooth and open.

I'm not saying I buy in to the restrictor enabling lower towing temperatures, but I would like to know if GM actually makes one.

If that were the case, I would be inclined to believe the water pump bypass restrictor actually has a purpose other than to fuel internet hype....

[More Power]

Why would anyone want to modify coolant bypass flow beyond what GM designed? I recommend just using the complete GM parts package for the uprated cooling system that arrived in the 1997 model year.

If someone says it's better, ask that they show us the data. Without the data, I'd tend to trust the GM cooling system engineers.

Jim

[greatwhite]

Why would anyone want to modify coolant bypass flow beyond what GM designed? I recommend just using the complete GM parts package for the uprated cooling system that arrived in the 1997 model year.

If someone says it's better, ask that they show us the data. Without the data, I'd tend to trust the GM cooling system engineers.

Jim

This is exactly why I'm asking for anyone with evidence of a GM part numbered restictor for use in a 6.5......

[Kennedy]

The "restrictor" historically would be the ID of the nipple and not a loose part or at least that is what I would expect. IIRC GM made this one wide open with big ID for better flow.

[More Power]

This is exactly why I'm asking for anyone with evidence of a GM part numbered restictor for use in a 6.5......

I have a 1997 hi-flow water pump and dual t-stat setup in the shop. Both are as received from GM. Neither part has a restrictor in the bypass circuit.

Now... the earlier single-thermostat housing used a bypass-blocking thermostat designed to restrict flow through the bypass when the t-stat was open. Is this what you're talking about?

Jim

[axemann]

Bill Heath has used a thermostate bypass restrictor with great success, and even used it in his salt lake engine. He explains it well on the phone but some of the details are in the link:

http://maxxtorque.com/dieselcommunity/spring-2009/65l-diesel-cooling-upgrade

[greatwhite]

Yep, I'm familiar with Bill's restrictor and his reasoning. I'm also familiar with reasoning behind there being no additional restrictor to head flow other than what has been designed.

Lower temperatures on the gauge doesn't always mean the temperatures are actually lower in the engine or in localized spots. It just means the temperature sensor sees a lower water temperature in it's specific location.

I'm more of a make my own mind up kind of guy and usually defer to powertrain design engineers if it ends up in a "push comes to shove" scenario.

This is why I'm asking if anyone knows if GM ever produced a restrictor of their own. I would assume if they did, it would be incorporated into the nipple like it is in the heater core nipples of the older 6.2 trucks.

So far I've run in to a couple guys who have been adamant that there is a GM OEM one, but part numbers or evidence other than "I say so" has yet to surface.

All I'm asking is if anyone has any verifiable info on it.....

[More Power]

Some years ago, Bill and I talked on the phone about his cooling ideas. I volunteered to drive the 500 miles to his shop, photograph a thermocouple equipped cyl head using 3 thermocouples that sense coolant temperature in the cooling passages (front, middle and rear) on a running 6.5L TD engine in a pickup truck.

Then, we'd run a hill not far from his shop that would provide a near perfect road test. The 5-mile climb out of the Columbia River gorge is tough with a travel trailer. We could measure coolant temperature with/without the cooling mods on two runs. He said he already had the thermocouples and a modified head. Unfortunately, he didn't take me up on my offer to do a big writeup about the claimed benefits of his cooling mods.

I'm convinced by data. The offer is still on the table.

Jim