Bittersweet cavitation test results

[OldIron82]

It's rude, it's crude, and I'm still in disbelief it worked, but it worked. I traced the new head gasket and drilled holes accordingly. I then drilled a center hole big enough to install the tip of the blow gun. I raised the piston to just below the suspect area and sprayed a good amount of Simple Green ( cleaner that is soapy ) on the top of the piston to cover the suspect area. Used a thick shop towel as a half arsed gasket, and tightened the bolts. I then gave it a shot of air. Well...the piston went down and another one went up and cracked the plate scaring the bejesus out of me. Ok, so I pulled the plate, added water and more soap to cover the suspect area and tried again. The constant pressure was blowing some liquid past the piston and it was running off the bottom of the crank. I held it for a good two minutes and then slowly lifted off to bleed the pressure, and removed the plate. Using a flashlight to shine into the water jacket............soapy suds running down the cylinder wall against the cam side. Not much, but a hole is a hole.

So that's it. No cheap and fast way out of this. Unless I find a running 6.9, I gotta go from the ground up. So be it. I reassembled the engine loosely and I'll be returning it to the salvage yard tomorrow and purchasing the 87 6.9 in the ambulance I spoke of months ago. This was a "if I find a good non ******* block I'll slap it together" gamble. Didn't cost me anything other than time. This was the engine I got the Roto-Master ( banks turbo ) off of early last summer. I knew it had a blown head gasket and water in the oil but I did hear it run so I figured it would be worth a chance. If it was good I would have installed the typ4 cam, studded it, installed my freshly redone heads with a valve job ( just the seats, guides in decent shape. ) and would have very happily pulled the tired 7.3 and installed her with the turbo.

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[Plowmaster]

Sounds about what I'm planning on doing when replacing my 7.3. I've got my first and original 6.9 in the barn with a busted head bolt that will be getting all of my good parts.

That's a good leak down test. did you watch the air psi?

 

[OldIron82]

No I didn't. The regulator was set to 90-95. I don't believe this test is very feasible because if wanting to test a entire cylinder water would have to be filled almost to the top. I don't know if enough air pressure could build. I knew the suspect spot I was looking for and filled accordingly so the air and suds would breech any hole. I just barely filled past the hole.

 

[laserjock]

Interesting. I haven't seen a 6.9 cavitate in my readings.

 

[OldIron82]

I should also add there were crosshatch marks on the bottoms of the cylinders and the pistons said Mahle. Were those pistons from factory or was this engine freshened up? The odometer was 80,000 which I ASS-U-MEd was 180,000 but maybe 280,000? 380,000? Who knows the run time on the block, and it was also always turbocharged. With that kind of mileage I suppose even the beefy 6.9 walls could fall to the worm if no sca was ever run.

 

[FORDF250HDXLT]

Interesting. I haven't seen a 6.9 cavitate in my readings.

this is now the second one iv read of.it goes to show ya the importance of properly adding and monitoring SCA's in all high compression engines.

 

[icanfixall]

All idi engines had Mahle pistons from the factory. Note to anyone attempting to pressure check a block for cavitation. NEVER pressurize above 13 to 15 lbs. Reason for this low pressure is those freeze plugs will blow out of the block like a gun firing a bullet. They can hurt you bad too. Only thing blowing out of our engines that has the potential of actually killing you is a broken stuck glow plug. Some owners have removed them when they brak off and are stuck in the plug hole in the heads. They are being forced out by around 500 lbs of cranking pressure. Some have actually started their engines to help force out really stuck plugs too. Lots of shop rags and some plywood or a 2x4 will slow them down. But they are really leaving the heads with some force.

 

[Plowmaster]

Jiminy I was thinking maybe 20 pounds of air

 

[OldIron82]

Holy Hannah good to know. I didn't pressurize the block, just the cylinder. That is scary. You got to think, pounds PER SQUARE INCH. That's a lot of pent up power that can be released.

 

[Plowmaster]

Well....I was only guessing at 20 pounds. I wonder how much air it needed to move the crankshaft

 

[sgallaty]

...

I'll be returning it to the salvage yard tomorrow and purchasing the 87 6.9 in the ambulance I spoke of months ago. k

I'm looking for certain ambulance parts from that era - the ambulance you are looking at, where is it? Maybe we could go in it together and I can defray some costs? I don't need engine, trans or harness.

I want a barndoor body - poptop is optional. if it's a cutaway or dually, that's not as useful for me.

 

[OldIron82]

Out of curiosity I took a look at the body today on the ambulance when I returned the cavitated 6.9. I wish you would have messaged me sooner I could have got specifics for you. I can say this, it definitely has a barn door in the rear because I opened it to take a look. Passenger side single door. I cant recall a door on the driver side. Unfortunately I believe it is a dualy. I am just purchasing the engine. Soon as they pull it I will be notified and I'll go fetch it. I can find out specifics at that time.

 

[sgallaty]

passenger side single door sounds like a slide. I need barndoor side. Sliding door hits the rear tire (and misbehaves when dirty)

Grab a picture? =) I really want a shot of the seats, doghouse and passenger side body as well as the bumpers if they are special duty.

I appreciate it!

PA is a long ways away, but you drive where you gotta.

 

[rustygold]

Could you just sleeve that one cylinder?

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[OldIron82]

I most certainly could, but that's not what I had in mind for this build. Any major work like that I will go from the bottom up. That was the other factor in the coveted 87 6.9. The bolt in cooling jets.