Cooling upgrade with single thermostat?

[hatzie55]

I have a complete early 1996 normally aspirated engine that I'll be installing in my 1976 project truck. It has a single thermostat crossover and serpentine accessory drive.

I've read many of the posts and the article on dual thermostat with 130GPM water pump upgrade. One of the interesting pieces of information I gleaned is that dual thermostats only increase flow to the radiator 7-9%. 74% of the flow improvement is routed through the block via the open bypass.

I have 2 questions.
Is the Bypass port diameter the same size in the dual and single thermostat crossovers?
Can the 130GPM pump be used with a NON-Bypassing single thermostat without a dangerous pressure increase in the block?

-Dave

[JFerg65]

There were some discussions on a couple of previous threads on this subject. As I recall, some felt / were concerned with the pressures causing freeze plugs to pop. (some had actually seen / hard of it happening) Some ran this setup as you describe with no ill effect. I think it would be worth trying to dig up any previous threads on the topic, as well as any new feedback you might get.

There is a reason they changed the design from single to double thermostats. The other option here is also running 180 degree stats versus 195's. And of course there are some things to consider here also. JK Diesel has some good info on his web sight about those options.

[AKMark]

A friend of mine put one on his 93 Humvee with a 6.2L. It's been on there for three years, no ill effects.

I was going to put one on my 91 6.2L that I rebuilt, but I needed it running right away and couldn't wait for one to get shipped to Alaska (where I was living at the time.)

[Robyn]

The 180 Stat is a great place to start. I posted a sticky thread on this subject a short while ago with the part number for the GM or Delco version to use.

The main reasoning behind the HO water pump was to stir more coolant through the block and heads.
Tests revealed "dead Zones" that were somewhat stagnant and were contributing to the cracking issues in the heads.

The higher velocity and volume with the 130 GPM pump eliminates this issue.

As far as the HO pump Blowing out the soft plugs. ????????????

I have no experience with this but the cautions are out there and probably worth heeding.

The biggest thing you can do is to make sure you have a radiator that is totally clean and with your 76 truck, be real sure its large enough.

The diesel radiators are far larger than the ones used on a 350 and in some cases even a 454.

The core support on the 76 should be able to hold the proper radiator but you may have to do some creative work if not.

A good shroud is mandatory as is the huge fan.

With a project like this in a state of flux I would say get the lower temp fan clutch from JK along with the big fan used on the DMAX

If you find that your core support is lacking, check with your local radiator folks and see what they can build you that will have enough Square inch frontal area to do the job.

The factory cores on the diesels are a 2 row (large tube) aluminum with a core measuring 19" high X 34" wide (core only)

If you have to use a slightly smaller core you are going to need one that has larger tubes or possibly 3 rows.

The aluminum tube radiators are the way to fly on these critters too.

Possibly one of the older 4 row Brass copper "desert coolers" would do the trick.

The bottom line though is that these engines make tons of heat and you have to be able to get rid of it.

Best and good luck

Robyn

[More Power]

A single non-bypass blocking t-stat probably wouldn't cause the pressure surges when using the high output water pump.

Remember - a single t-stat can pass about 90-gpm. The high-output water pump can move 130. If you're using a bypass blocking t-stat, a single t-stat becomes a problem.

Aside from the 90/130 issue, the complete package is required to fully benefit from the high-output water pump.

Jim

[GMC Hauler]

I am in the same boat that you are:


I have 2 questions.
Is the Bypass port diameter the same size in the dual and single thermostat crossovers?-Dave

No. The single thermostat crossover port can be ground out to be no different than the dual thermoatat in that respect.


Can the 130GPM pump be used with a NON-Bypassing single thermostat without a dangerous pressure increase in the block?
-Dave
In my opinion, yes. But only if you switch thermostat types and ground out the bypass port.

Most here will direct you towards the dual thermostat design with high flow water pump. It is a proven GM design

[hatzie55]

I have an RF-31 mill and boring head so opening up the bypass port diameter will not be much of a challenge. I think I'll start there.

I need to do a little more research on the radiator but I'm leaning toward a 3 row triple flow copper/brass radiator. I still need to make/find a shroud to match the DMAX fan. I don't intend to turbocharge the engine or tow with it.

[More Power]

I have an RF-31 mill and boring head so opening up the bypass port diameter will not be much of a challenge. I think I'll start there.

I need to do a little more research on the radiator but I'm leaning toward a 3 row triple flow copper/brass radiator. I still need to make/find a shroud to match the DMAX fan. I don't intend to turbocharge the engine or tow with it.


If you're not planning to tow, the 87-gpm water pump would probably be enough.... ;)

Jim