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Old 11-04-07, 09:16AM   #1
RamAirRocket
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Default Reverse Cooling for 55-58 cars?

Anyone know much about the reverse cooling setup on the 55-58 Pontiac V8's?

Chevy brags the 92-97 LT1 was first reverse cooled V8. This is incorrect. It is a pretty good design (I have one), and coolant temps are VERY stable.

I would like to know if it is even possible to modify the reverse cooling setup that Pontiac used on the modern 67-up Pontiacs (sorry, I am not familliar with the 66 and older engines, they were similar, probably mostly interchangeble, but I can't confirm....)?

Makes me wish I kept that 370 I found for this Pontiac nut case in the St. Louis area....

Thanks!!

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Old 11-05-07, 01:50AM   #2
Pontiac Jack
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[Reverse-cooling was used '55-60]

I haven't found anyone who "knows a lot" about it, in spite of my postings on Pontiac forums of the question "Why did Pontiac not stay with reverse-cooling?". To me, the most believable reason was to free up the fronts of the cylinder heads for accessory mounting- and possibly to reduce costs.

Even though I've built and run a fair number of '55-60 engines, there's been nothing remarkable in my experience with their cooling systems. I ran as high as 13.5:1 compression ratio on the street without problems, but who knows- might have been fine with a normal-flow system.

Back then, Pontiac claimed that reverse-flow facilitated the grinding of exhaust valve seats directly in the heads- but I believe that other engines (without reverse-flow) also ran without exhaust seat inserts.

Sorry I can't be of more help.
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Old 11-05-07, 09:53AM   #3
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I know of warranty issues with the "gusher" cooling system, the copper tubes that directed the water at the exhaust valve seat area corroded. But no one seems to know the customer complaint.

The big advantage is the cooled radiator water hits the heads first, keeping them cooler, allowing for higher compression with lower octane fuel. Like my LT1, I run 87 octane fuel with 10:1 compression. The PCM helps a lot with being able to specifically tune out one specific rpm/MAP (vacuum) cell that has a ping sensitive area.

Any idea where the thermostat was on the Pontiac V8? The LT1 put it AFTER the radiator, so it managed coolant temps so that temp is what goes into the engine (they used a 180 thermostat) so 180F water went into the heads. The block was warmer, so the oil was thinner, and always up to proper temps (engine oil coolers were all std), so you got best mpg too as oil never got too cool with the shock to the block with the cooler water hitting the block first (imagine the water in cold weather, like -10F!), the block is getting pretty stressed and oil is gonna be tough to stay thin like it should be.
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Old 11-06-07, 01:13AM   #4
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Quote:
Originally Posted by RamAirRocket View Post
1) I know of warranty issues with the "gusher" cooling system, the copper tubes that directed the water at the exhaust valve seat area corroded.
2) Any idea where the thermostat was on the Pontiac V8?
1) I think you've been misled. The water distribution tubes that I've seen have all been stainless steel- probably close to a dozen pairs of them I've had my hands on over the years. If the '58 engine for my truck wasn't all buttoned-up, I could show you how they look brand-new. Hmm... having said that, I realize there's probably a pair in some other '58 heads I've got- I'll have to pull them out for photos sometime. Admittedly, my engines have been mostly '57-'60, so it's possible that '55-'56 weren't stainless. However, I was "into" cars by then, hanging around repair shops, etc, and have no recollection of any such problem.
2) Thermostat was in the familiar intake-manifold-water-outlet location, like any other engine.
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Old 11-06-07, 10:57AM   #5
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My source of info was a HPP article that mentioned them. Copper seemed like a dumb idea if you ask me!!! Glad that was wrong!

If you ever get pictures I would love to see them. And the odd thing, GM got sued pretty bad over the reverse cooling, as they stole the idea. But GM owned it already! They pioneered it. Seems GM forgot it all..... The reverse cooling went away because of the lawsuit. Can't believe they forgot......
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Old 12-05-07, 12:37AM   #6
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Car Craft has some info on the reverse cooling of the LT1 in the Jan 08 issue.
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Old 12-06-07, 01:08PM   #7
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598TransAm picked a good article and it touches on the reason that it was not popular earlier. The problem is nucluoid boiling. The hottest spots can change the state of the coolant, which will change back but gasses are released that cause problems. With the standard cooling direction the flow goes bottom to top and this is the natural tendancy for the gasses to move. When they transfer enough heat to the surrounding coolant, they will condense back into liquid. With reverse cooling, the flow goes top to bottom. This causes problems as the hot gasses do not want to go down through the system and tend to create a large hot vapor pocket at the back of the heads. If left that way, you will insulate the hot vapor and the back two cylinders will have a very nasty melt down. That is why the LT1 has vent lines off the back of the heads.
If done right it is a very effective cooling system but it is also a good bit more comlpex than what most of us are used to.
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Old 04-23-08, 05:51PM   #8
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Jim Hands book touches on the subject only briefly. He states that it was an "unique and effective reverse flow design" pg 8.

On page 11 he states with regards to the technical changes in the 1960 engine "...the reverse-flow cooling system was replaced with a more conventional bottom-feed system. Indications are that the warrenty problems concerning the distribution tube prompted the change"

Various Society of Automotive Engineer (SAE) papers published by GM engineering staff around the same time support this.

all the ones I ever saw made before 57 were actually BRASS. after that they were stainless. As were the NORS parts. It really was not a unique design as anybody familiar with flat head cooling systems will see definate similarities. The Brass/ stainless tubes were designed to direct cooling water directly to the exhuaste valve seats and stem locations to facilitate cooling of those areas. On flat head engines when they experience overheating it is likely that they will crack the block in this area. That aspect of the cooling system was carried over from flat head design. as horsepower increased it became less effective over-all and that combined with warrenty issues and initial cost made it problematic.

I believe there were emmision issues as well. The cooling of the exuaste gasses caused a change in the composition of the cooler exuasted gasses.

It is also common knowlege that exhuaste gasses travel more efficiently if they maintain a higher temperature. this cooling system might thwart those efforts compounding the initial cost and maintenance/service/warrenty issues during an escalating horsepower war.

Also I believe there were problems with exuaste systems rusting out sooner on the older cars due perhaps in part to the cooler running exhuaste system.

Last edited by michael : 04-23-08 at 06:15PM.
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Old 04-23-08, 06:06PM   #9
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Which is why I was surprised GM got sued over the LT1 design. My guess is the steam tubes.

I would love to see some good picts of the Pontiac reverse cooling system....

So what specifically were the warranty complaints if the tubes were stainless and survived?

Quote:
Originally Posted by michael View Post
Jim Hands book touches on the subject only briefly. He states that it was an "unique and effective reverse flow design" pg 8.

On page 11 he states with regards to the technical changes in the 1960 engine "...the reverse-flow cooling system was replaced with a more conventional bottom-feed system. Indications are that the warrenty problems concerning the distribution tube prompted the change"

Various Society of Automotive Engineer (SAE) papers published by GM engineering staff around the same time support this.
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Old 04-24-08, 06:57PM   #10
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the warrenty issues were not specifically with distribution tubes although they went to stainless in part to address the isssue. alot of overheating issues were wrongfully blamed on the tubes. They were probably replaced more often than needed and under warrenty the company was charged accordingly. probably a lot of unrelated cooling system problems were wrongfully blamed on a "new and improved" cooling system. The cooling tubers were not really part of the reverse flow cooling system. They were a carry over technology from the flat heads.

Alot of people when they think of a warrenty issue think a part is bad/broke, fix/replace it! makes perfect sense. But the mechanic must remove several other parts to get to the offending part and the re install all of those other parts correctly again to finish the job. The car remains still under warrenty so should any of those other parts that were fine and worked well cause additional problems as a result of incorrect reinstallation they then also cost time and money to fix under warrenty. if their failure cause additional damage or problems then that aslo must be fixed under warrenty. It goes on and on. Plus you start to have to deal with a leagion of unhappy customers so there are additional costs there too.

If you just simplify the system and eliminate problems at the design stage rather than through a warrenty period you save enourmous amounts of money. Simpler system, fewer parts, less chance of failure, less cost. It all starts on the drawing board.
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