My '72, work in progress

[199th mp]

rainman, if you ever try that again, can i have your stuff?

[whiterabbit]

I darn sure don't want to go 70+mph in that thing.

[rickf]

rainman, if you ever try that again, can i have your stuff?

There won't be any "stuff" left. Just a smear on the road.

[whiterabbit]

Took her out for a hard run the other day. 20 miles full out non stop. Temp was fine in town short runs but the engine got hot on the long full out run. I had flushed the system a few times and just recently put in a new pump. I pulled the thermostat to check it out. It was an ACDelco 63 180deg. The head cavity looked real good, no build up of crud. Tossed the stat in 180deg water. It didn't open cranked up the heat to boiling. It just barely opened. OK.... Went on the hunt for the Stant one . No dice, they couldn't even get it from any warehouse. A bit of research yielded this.



I like the Failsafe thermostats but they are more $$. It fit perfectly and I cut a new gasket for the housing after giving it a fresh coat of paint inside and out.
Oh, here is that pesky carb to dizzy vent that wouldn't vent. Old one on the left.

[whiterabbit]

The "motorpool"

[rickf]

I have very seldom ever seen a bad Delco thermostat out of the box. I am curious to see how the new one works and I am also curious about the fail safe part, is that a claim or just the name? Looks the same as any other stat to me. It takes heat to open it and if it fails it will not open because the media that transfers heat to motion hes left the building. The vent looks just like you said, the tube has been jammed up in there somehow. Weird. To be perfectly honest, between the rover and the 151 I would prefer the Rover. More access to parts and generally overbuilt, unlike the fragile 151.

[lpcoating]

Nice looking trucks. I forgot what green grass looks like!

[whiterabbit]

The Rover? They truly don't grasp electrical systems in England. LUCAS, The Prince of Darkness!
And for a country that gets tons of rain you would think they wouldn't put up with water dripping on them in the rain and have a truck a little more water tight. A whole lot of ass backwards engineering and you think the M151 is slow? 55mph and she is wound out! I do love the HD axles (dana 60's) and overbuilt everything on the 109 military but the smaller 88's snap axles just by pulling out from Starbucks!
The MUTT has a whole lot going for it. Waterproof and very simple electrical, strong and flexible suspension, light, and maneuverable in thick woods.
The wife was wanting an Air Mobile LR. The are cool but damn they want $$$! That and the poor M151 I have just needed some TLC bad.

[whiterabbit]

The Delco Tstat looks like it's been in there awhile. Failsafe Tstats : Fail-Safe is designed to help protect your engine when overheating occurs. When overheating occurs, Fail-Safe automatically locks in the open position to permit maximum coolant flow.

When standard thermostats fail, they lock in the closed position and prevent coolant flow to the engine, which can possibly cause serious damage to your engine. Fail-Safe has a patented safeguard against overheating damage.

Fail-Safe thermostats are designed with a unique extra stroke that allows operation in two stages:

Stage 1: Within normal operating temperatures, the Fail-Safe operates the same as any other thermostat.

Stage 2: When overheating is caused by a deteriorating cooling system part, the Fail-Safe has a secondary stroke that activates a precision engineered piston that automatically locks the valve into a wide open position allowing coolant to circulate freely.

[rickf]

I guess with the thermostat in there then there is enough resistance to slow the flow somewhat. I can tell you many stories of guy at the track that swore that you had to run without a thermostat to run cool. First off the hotter the engine the more power it makes up to a point. Second, if the water is flowing through the radiator at full flow of a high rpm engine then it never has a chance to cool off. It is almost as hot coming back into the engine as it was leaving. Then there is the Temperature transfer coefficient. That means that the higher the difference in the temperature between the radiator and the air flowing through it the faster the water will shed heat. If the air temp is 75 degrees and the air flow is 2000 cfm, water temp of 180 you will shed 2000 btu's a minute, At the same air temp and cfm but water temp of 250 you will shed 4000 btus. These figures are fictitious but you get the idea. There is a formula for figuring out the exact heat loss for this application, I just don't have it at hand. BUT, For all of this to work the water has to stay in the radiator long enough for the air to pull the heat out of it.

My question is this, If the thermostat locks open do you have to get a new one?

[whiterabbit]

Yep. It locks open or fails in the open position. I'm not a fan of gimmicks with parts but I figure I'd give it a shot, besides they didn't have a Stant.
The more I look into it the more unimpressed I get with it. Alot of neg comments about it failing quickly. I ran the truck yesterday and it never got to 180 deg which might mean it already failed. I was planing to pull it and check it out and flush the cooling system one more time but were getting hard rain all today.
I retimed the engine and put just a hair more advance in. Runs much better.
The stupid gas cap still won't vent even after soaking in the parts washer, putting a vacuum and then pressure on it. It just won't vent. Naturally Rapco won't take it back, over 30 days since purchase.

[rickf]

If mine is sitting and idling it will stay at about 180, if I am on the road it will range a little above 180 and has been known to hit 200 on many occasions. Remember that these gauges are not accurate by any means. You would have to have a laser temp checker at the thermostat housing watching for it to open. Keep in mind that the cheap lasers are not very accurate either. I have found that out many times.

[whiterabbit]

Update,
The Stant T stat finally came in at the parts store and I pulled and swapped out the failsafe one. It hadn't prematurely tripped.
Truck will sit there all day and not get above 160 deg. Went on a 60mile road trip/shake down over the weekend. Running at 50mph and the temp never did go over 160,that was a little under 3/4 throttle, so I pushed it up to 55mph and the temp started to climb and overheat within 2 or 3 miles. That was at almost full throttle, 3/4 to 7/8 throttle. Temp went over 200+ and steamed out the radiator cap overflow tube. Pulled over and let her cool down, and topped the radiator up and then went 20 miles at 50mph and no overheating.
Timing off? Put the timing adapter on and checked it. Dead on the mark at idle.
Running lean at full throttle? Pulled the carb and went through 2 cans of cleaner. Did have some little junk in the passages in the bowl. Clean as a whistle now and it did help with the off idle stumble pulling away from a stop sign.
Lastly, still leaking a little gear oil out of the flywheel cover drain hole. Trans input seal I guess in going out. Grrrr.

Oh, got another gas cap, this one from TNJ Murry. Had 3 little crimps along the edge unlike the one from Rapco. The crimps had to be lightly filed down so they wouldn't scrape the filler neck. This one won't vent the pressure buildup either!

[rickf]

Sounds to me like you have a blown head gasket. You should not be anywhere near full throttle at 55. I cruise at 55 at no more than 1/2 throttle. If you have to push it that hard there is something wrong in that engine and I suspect the head gasket considering how fast it overheats once you push it. Also the fact that you have no power.

[whiterabbit]

Looks like I have to dig out the compression gauge and get some readings on the cylinders.