[font size="1" color="#FF0000"]LAST EDITED ON 27-Feb-01 AT 12:53 PM (EST)[/font][p]You are correct in saying the 7.3 is an overbored 6.9. The 6.9 is about 421 cubic inches whereas the 7.3 is 446 cubic inches. The stroke is the same on both engines. My previous post indicating 446 cubic inches is 6.9L is incorrect. 446 cubic inches is 7.3L.

 

Joe are you the guy at the Melrose Park works ? Have you been with navistar since it was IH ?

 

[font size="1" color="#FF0000"]LAST EDITED ON 27-Feb-01 AT 07:09 PM (EST)[/font][p]Otto: I am not from Melrose Park but Indianapolis which is where all of the engines in question are manufactured. The Melrose Park facility manufactures the inline 6 cylinder engines. I started working for International Harvester in 1970.

 

For those of you who are interested: I just found out this past week that for the 2002 model year Navistar and Ford will be switching to Texaco OAT "Long Life" coolant which will NOT require the anti-cavitation additive as in the past. This ethylene glycol based coolant already contains nitrites. Ford and Navistar have done extensive testing using this coolant and have found no evidence of cavitation.

 

[font size="1" color="#FF0000"]LAST EDITED ON 04-Mar-01 AT 10:45 PM (EST)[/font][p]Excuse me,but I thought International owns Navistar.International Harvester,International's farm division,is now owned by Case IH who is now owned by New Holland who also owns Ford's tractor division (notice the word Ford in tiny letters on all NH tractors).Navistar is a division of International,I'm pretty sure,www.Navistar.com,you see the International logo.I don't know,Joe works there I guess he know more than me,that's just how I took it.


Anyway that's beside the point.I did not know the old IDIs were gas conversions.I have a question,why did any company use indirect injection in the first place?It's virtually obselete now,since the Chevy diesels demise and the rise of the Duramax,everyone is direct injection,Cummins,Navistar,Isuzu,all of them.Does Navistar even produce an IDI engine now?

 

Ben Towe: Actually, Navistar is the parent company of International Truck and Engine Division (at least that is what we are calling ourselves this week). The reason for Indirect Injection (IDI) is they are somewhat cleaner (exhaust emissions) than Direct Injection (DI), at least they were before Navistar invented the HEUI (Hydraulically controlled Electronically actuated Unit Injectors), but they are somewhat less effecient (fuel mileage) than DI. DI, on the other hand, has traditionally been dirtier but more efficient. The HEUI injector solves this problem by stepping up the pressure of the fuel being injected, with a 7 to 1 step up piston inside the injectors -- that is, 3000 PSI of rail pressure becomes 21,000 PSI of pressure at the point where the fuel enters the combustion chamber. All of the GM diesels were IDI except for the new Duramax. Navistar no longer produces an IDI engine.

 

Well, you seem to have a good handle on this cavitation thing and the ability to put it into words as well, although I'm not sure what it has to do with civil engineering. Don't be too quick to blast the engineer for "not doing his homework" as you say. When the engineers at Cheverolet were just begining to formulate what form the small block was going to take, (the most successful engine of all time) the head of Cheverlot called a meeting, walked in and said, "I've got one thing to say, iron is bought and sold by the pound." You may be correct in saying if the cylinder liners were thick enough, cavitation would not be a problem but how thick is thick enough? How much weight would it add to an engine that Ford is already complaining about being too heavy? The reason engines are better today than 25 or 30 years ago is because the technology is still developing and many of the things we know today were discovered by accident. You might do well to get out of civil engineering and go into mechanical engineering and make this world a better place instead complaining about who "didn't do his homework."

 

the engine can be sleeved back to std.it is not junk

 

dt 466 kept us in business, trust me it wasn't 6.9. somebody can't add. 7.3 is 444 like in t444

 

Hello all.

I have been in trucking since 1974 and have spent 10 years or so either supervising or managing repair shops for three trucking companies. Cavitation has been an occasional issue on both the Detroit Diesel small and big blocks as well as occasionally on the Cummins N-14 engine. If the coolant maintenance is done properly there has generally been no problem. We have had occassional cavitation of the liners but it took 500,000 - 700,000 miles. My current employer has a fleet of @1,400 tractors, 130 or so of them my shop's responsibility to maintain. Out of my fleet I can recall three or four engines that had to be rebuilt off the top of my head in the last three years.

All this is to say cavitation is a problem that occurs in diesel engines. It usually shows up more in hard worked engines, as was posted earlier.

Just a little info - hope it helps.

Dave

1995 F250 PSD 5 spd 4x2 extended cab long bed 3:55 diff - best truck I ever owned and I am nearly half a century old.

 

Post #15 corrected the mistake about the 6.9/444 issue. The engines built in Melrose park are excellant engines and I'm sure they have contributed nicely to the company's bottom line. In most ways they are higher quality engines than the engines built in Indianapolis which makes them more expensive to produce (they probably have a higher profit margin as well). So lets do some math. From 1983 to 1994 we build 1.8 million 6.9/7.3's. From 1994 to date we've built just under 1.7 million NGD (Power Strokes) for a total of 3.5 million units at $800 each. Do the math, Mr. IH. How many engines has Melrose Park built since 1983 and at what profit margin?

 

Another way around the cavitation problem besides thicker cylinder walls or the best a ceramic block, would be to fill the cooling system with a fluid that does not require pressure to increase its boiling point. That is the point blank problem here. Imagine your the coolant in your 7.3 and you running up hill pulling a trailer. The engine is humming along and the temp is about 230 degrees Farhenheit, no problem there, not overheating, but unpressurized that is well over the boiling point of water, you see where the problem comes in. Now the coolant reaches an area of the block where the pressure is not at the 15 psi that is maintained by the radiator, and bam, it boils and remaind as gas bubbles traveling in the fluid until it reaches an area where pressure is increased and the boiling vapors re condense, and bam,. except this time damage occurs at this site. Guess where pressure is highest, where heat is greatest.
Unfortunately we must use water in our enhine blocks, it is our most abundant resource.

 

Your scenario is correct as it pertains to water/ethylene glycol coolants. I don't necessarily agree that the answer is to increase the thickness of the cylinder walls. I think a better answer to the problem would be to use a propylene glycol coolant and use a reverse flow cooling system (this proposal would have to be studied to see if it is feasable for a Diesel engine). Propylene glycol boils at a much higher temp (I don't know what the freezing properties are) and because of that fact it is my opinion that the cavitation could be abated with its use. I believe the block is capable of running much higher tempratures that they presently do and the heads should be running at lower tempratures than they are now. It would work like this: Cooled coolant from the radiator would go to the heads first then the block then back to the radiator and if the boiling point of the coolant were, say, 350 degrees, which is, as I understand it, the boiling point of pure propylene glycol, all localized hot spot boiling could be eliminated. This would allow us to run our gasoline engines at a higher compression ratio on the same octane fuel with out detonation thereby increasing thermal efficency. It is possible that the cavitation problem could be addressed without using the reverse flow system. Propylene glycol is expensive which may be why they don't use it. But the fact is, the boys from engineering didn't ask for my opinion.