Project #2-3 From Hooda-Caravan engine rehab

[hooda]

Howdy Folks! I'll assume that most of you aren't aware that my daily transportation is a v10 powered 2001 f250 4x4 crew cab. Great truck, obscene torque, and an overall joy to drive...until you pull up to the gas pump. Average 11-12 mpg. I've seen 14.5, and I've seen 6.7 pulling a 10,000 lb trailer, whigh it pulled @77mph no problem. Well, It's aggravating my already precarious financial situation to continue with this as my main mode of transport. So, a couple of mnths ago, I was driving past this old caravan that never seemed to move. One day as I was driving by, the owner of said van was in the driveway, so I stopped to ask about it. He said that it had a cracked block, and he just wanted it OUT of his driveway. A deal was struck, and I ended up as the new owner, and as it turns out, the van still started and drove, but not well enough to preclude me towing it the 75 miles up to my place, and the hunt for a replacement engine. Through a series of connections, and a very good friend using up one of his last "I owe you one" chips,I ended up with a used caravan engine, SAME model year, 122,000 alleged miles, sitting on a stand at my place. Well, it goes without saying that whenever one has this particular engine (3.0 Mitsubishi v6) ready to install, It is highly advised to replace the head gaskets, head bolts, and timing belt.

Once I got the engine stripped down and the heads removed, I was disappointed to see that the front left piston rings had left a "rust ring" around the bore, indicating that moisture had gotten into the cylinder and it had sat. Here's a "before" pic



After careful consideration of numerous factors, including the fact that it looks worse than it feels, I decided that I would check a few things, and if all looked right, I would attempt to hone out the "bad" spot in the bore, and allow the existing rings to re-seat, once back together. First, I checked the ring end gap. Factory spec is .012-.018" with a service wear limit of .031" These checked out @ .016" Leaving me MILES of life if this works out. The guy I bought the motor from offered me the option of a different motor, but that means $70.00 in gas, and a day shot driving to get it done, plus re-doing all the work I've done thusfar, so I decided this would be the best and quickest option. I started out with the rigid hone below, using a LOW SPEED drill, and spraying wd40 to keep the stones cutting,



After a few minutes, I had managed to get 99% of the damage out of the bore, but the worry of taper, bellmouthing, and over-cutting had me stop. I checked my work, and decided to finish up with a dingleberry hone. like this



Notice how the end is missing the dingleberries, and that shaft is sticking WAT out there? This is going to possibly hit the crankshaft so, One cutoff tool and 30 seconds gave me this



I used it to get the final angled crosshatch pattern, and the bore ended up looking like this





I cleaned the bore out, and measured the bore, and the ring end gap. All said and told, I ended up removing less than .001" from the bore, with no taper or bellmouthing to speak of, and the "ring" is all but gone.

I inspected the rod bearings, and pulled another rod cap for good measure, and thay look excellent.



The rings appear to be chrome faced, so now, my only concern is whether they will seat correctly on the fresh surface that I just created. The top ring on the "problem" piston was actually stuck in the groove a bit. So, I had to coax it out of the groove and clean things up and allow the ring to move freely enough to give itself it's proper tension. My hope is that it seats itself up in a relatively short time and goes into normal operation. I'd guess a quick oil change after an hour of running, followed by another 1,000 miles later, and It'll be as if nothing was ever amiss. More to come on this project....lots more

[sportbike]

Rings will be fine. Put it back together. Might want to replace teh valve seals while you have the head off.

[Ray]

Hooda,



You have it this far down, I go ahead and replace the rings.

TRW sells them per piston (at least they used to) shouldn’t cost too much at all.

I wouldn’t count on them seating completely, having done this before, the $12 for a set of rings is worth it.

If you can’t find a single set at your parts store, check the local machine shop, caravan engine patch jobs are pretty common around here and there are usualy some broken sets around.

[hooda]

Well, it's been almost a month since I posted on this thread, so it's update time. I ended up taking the heads in to a local engine shop. The exhaust valve seats were slightly pitted, but I figured that between that and having ALL the carbon removed from inside the ports, plus someone with the proper tool to install the valve seals, I'd bit the bullet, and get'r dun! What I got back was an immaculate set of heads, with fresh surfaces on the valves, and a 3 angle valve job. Total price: $110.00 Which goes to show that crying poverty does have it's advantages on occasion. My valvesprings and retainers were in a bag, in the box, and they even cleaned all that stuff up, leaving me only the task of assembling the valves and valvetrain. On assembly of the rocker arms, I noticed that one of the lash adjusters was eroded/munched, on a Sunday night, no less. I went to one auto parts store, then another, no luck, other than a price quote of $23.00+ for ONE. Last resort was Auto-zone, who happened to have a box of four on the shelf, and they sold me one for ten bucks, plus tax. So, heads assembled and ready to bolt up, I looked at the block, and, I thought to myself "if you don't clean up ALL the pistons, you're going to have trouble". I made the decision, and spent the majority of an evening, removing all 6 pistons, and the crank, stripping the block to bare. This allowed me to break the glaze on all 6 cylinders and properly clean the block, crank, and remove all the carbon and gunk that had accumulated over the miles around the ring grooves. I know a little about engines, but what I don't get is whether or not the rings get "stuck" in place, and whether the heat generated frees them up so they can work, or just how they do what they do with all that crap around them. What I do know is that now I have all 6 pistons as clean as new, and all 6 sets of rings measured well within the .012-.018 factory gap, and all 6 have newly honed surfaces to re-seat onto. So, we'll see just how it all goes. I will treat this like a new build, as far as oil changes at 50, 150, 500, and 1000 miles before I consider it "broken in". I've used this plan for every 4 stroke engine I've ever built from lawnmovers to hotrods to class 7 diesels, and never had a failure, ever. I have the heads bolted on and torqued. So, all that remains is the timing assembly, water pump, and peripherals. I noticed that some of the plastic timing belt enclosures, and the dented oil pan are going to require donation from the original engine, so, I'm putting the project on hold, as I will be focusing on the arrival and commissioning of my new 250EX in four short days!!!! Once I have that all ironed out, I'll pull the van in, pull the engine, swap the necessary componentry, and get that little gas-sipper on the road. More (including photos) in the near future.

[Cippee]

I've been a mechanic for a long time and you know your stuff good job. The ring question about the gunk. I think sometimes all the carbon seals the piston better. I had a car that I gave a intake cleaning to. You hook a machine up that sprays cleaner into the intake while it runs and it cleans the intake, valves, and pistons. The car never burned oil until I did this. I would bet it cleaned the gunk off the rings and made it start to get oil blow by. I just have to say one thing dingleberries!!!