Couple questions for the engine rebuilders (1 Viewer)

[dkyuss]

To the wise and experienced members of MUD, I am starting my first engine rebuild and hope you can shed some light on some of the finer details. Thanks in advance!
Turbo'd 1981 Bj60, 3B. 495,000kms, unknown history but (I think) non oem head gasket so has seen some work in the past.

Engine was running fine, compression was decent, 390-425 psi, but a small bubbling leak at head gasket above the water pump got me investigating and maybe the OCD took over a bit. I took it all apart!

Little bit of cleaning (scotch brite and oven cleaner)... got me here.

The cam shaft and lifters are in pretty rough shape, with only one lobe measuring at limit, the rest undersize.
So... I found a seized bottom end for cheap (<300,000kms) and robbed the Cam shaft and lifters, which are in much better shape. Not perfect either, but way better!

I was then concerned that I probably lost some abrasive particles on the top ring, so might as well keep going.

The plan is to rebuild this current motor with new (to me) camshaft and timing gear set. I hope to go inexpensive, not cheap on this.

Then while im driving around on this minor rebuild, my new to me seized bottom end can slowly be properly rebuilt. New sleeves, pistons, bearings etc. Probably new camshaft and lifters too. Eventually get another head and rebuild it so all ready to drop in one day. This is a good winter project, but now I want to be and too much $$$ to do the whole she bang at the moment.

I enjoy these kinds of projects, and partly why I bought the truck in the first place.

So Questions;

If I read the FSM correctly, the cylinders are allowed 0.012" wear to the liner to be within the 'wear limit'

Yet further on, piston oil clearances are tight (0.0008 between max/min)! and even differences in piston/liner 'mark' sizes are tiny (0.0004" difference between marks) compared to the 0.012" wear. Not sure what to make of these numbers. Why so tight tolerances if 12 thou wear is allowed?

So this is what I am measuring on my rig. I am hoping to give the cylinders a kiss with a flex-hone (a couple tenths of a thou), new rings, and reinstall. I will measure cam/crank bearings... was planning to replace, but so far everything measures/looks near new.

I need some plastigage to measure oil clearances, or can I just pry on the shafts with a dial indicator to measure??

Cylinder measurements are in thrust direction (wider of two numbers) at top of cylinder. MAx 0.002" taper and out of round. My bore #'s have some room for error as I am using (cheap Chinese set) telescoping gauges, and then measuring with a micrometer. I would say +/- 0.0005"

CYL# | MARK | Cyl MEASURE | Piston MEASURE |Oil Clearance
____________________________________________________
1 | 2 | 4.0172 | 4.0114 | .0058
2 | 3 | 4.0168 | 4.0119 | .0049
3 | 1 | 4.0159 | 4.0119 | .0040
4 | 2 | 4.0167 | 4.0111 | .0056

I think this looks healthy and a good candidate for a quick hone and re ring. But I have never taken an engine apart before, not sure what is normal or not.

What say ye wise Mud members?

If this is feasible? would I replace standard rings matched to the piston/cyl mark#? Oversize and file to fit?
Or is this a plan for disaster?

Cheers!

 

[ozcrusier]

I would go with your plan with new rings on those pistons as they look good with zero blow-by then flex hone the cylinders with new standard slippers and mains bearings if yours look good.

 

[roscoFJ73]

Not sure what to make of these numbers. Why so tight tolerances if 12 thou wear is allowed?

My guess would be that its to do with heat expansion. The pistons would expand more than the block. Someone at the factory has calculated the amount of expansion between 20c and operating temperatures.

 

[dkyuss]

I would go with your plan with new rings on those pistons as they look good with zero blow-by then flex hone the cylinders with new standard slippers and mains bearings if yours look good.

Thanks for the feedback. Like I say, I think it looks/measures good but I have no experience inside an engine, thus my caution and questions. Thankfully we have excellent FSM's to follow.

My guess would be that its to do with heat expansion. The pistons would expand more than the block. Someone at the factory has calculated the amount of expansion between 20c and operating temperatures.

I do understand that. This is the oil clearance measurement and would ensure clearance at operating temperatures. My question was more to do with if pistons and cylinders are measured in 0.01 mm but cylinder is allowed to wear 0.30mm which negates any tight tolerance left. If cylinder has worn .25mm it is within limit but obviusly the oil clearance would be too great once the cylinder has worn this much. I guess this could make sense now that I read it all again in that the FSM is specifying new conditions for the engine, and that it should run to 'spec' for .30mm of cylinder wear.

 

[ozcrusier]

At the stage your at I would go with new alfin pistons for the minimal cost the engine may last another 500.000 K + with good service but if left as is you will need to go back in as the top ring lands will fail eventually.

 

[gerg]

The 3b has reinforced ring lands from the factory. As far as I know the entire B series does. No need to upgrade. They are not the weak point if the engine. It's easy to see if you look closely or shoot a pic up close of the piston.

 

[dkyuss]

Not sure I see reinforcing rings?
I still need some piston ring pliers.....

 

[gerg]

The top ring has two distinct bands of different metal imediately above and below it. It is reinfiorced. Another good indicator is that its not completely hammered out like most 2hs would be with the same miles of your 3B

 

[ozcrusier]

Lucky 3b owners why didn't they run them on all the Hino engines.

 

[gerg]

3Bs are not free of issues, but they are designed for turboing. Piston injectors and reinforced ring lands make it quite suitable. 2Hs on the other hand make up for it with displacement. Sort of. Why Toyota didn't use reinforced ring lands on the 12ht is a good question though. They knew better.
g

 

[dkyuss]

Question on the camshaft.
I have read it recommended to grind or polish these sharp (like a blade) edges worn into the lobes.

Comments? How best to achieve? Grinding bit on a dremel? Emery by hand? Or just a file?

 

[dkyuss]

So I am getting close to thinking about starting up. Trying to educate myself on startup procedures after rebuild. Cam shaft is newly ground, cylinders honed/new rings and head is almost complete.

I found this though some searching here and seems like a good starting point.
http://www.dieselduck.info/machine/01 prime movers/1999 engine rebuild start up.pdf

Anyone have any pointers or tips? Break in oil?
Thanks

 

[dkyuss]

So I am getting close to thinking about starting up. Trying to educate myself on startup procedures after rebuild. Cam shaft is newly ground, cylinders honed/new rings and head is almost complete.

I found this though some searching here and seems like a good starting point.
http://www.dieselduck.info/machine/01 prime movers/1999 engine rebuild start up.pdf

Anyone have any pointers or tips? Break in oil?
Thanks

Quoting my own stuff..... but really would love some opinions. @gerg @ozcrusier
Clarify also cam shaft was professionally ground, not as per my prior question. More details and pics in my build thread in signature.




Also my new stainless precups have this internal ridge. My instincts want to grind/buff this smooth. But maybe I should just leave alone?

Thanks in advance.

 

[ozcrusier]

I would use plenty off assembly lube on the cam and lifters for first start up. I left the injectors out off my 12ht so I could spin the engine over fast to build oil pressure before starting. I also filled the oil filter. I seated the rings on the first drive by finding a good size hill and laboured the engine in a high gear I done this twice and just took it easy for the next 500 K. I'm just over 1000 K now oil is still like new so no blow by getting past the rings. This week I plan on warming the engine and re-torquing the head by backing each stud back half turn then torque to factory spec again.
I have no experience fitting pre-cups but have read there a tight fit and take some getting in
Good luck hope this helps.

 

[gerg]

You can clean up the casting, that would be a good idea. I would hesitate to advise you to do more unless you do a lot if reading on the precup piston relationship and how it relates to the air fuel jet. Disturbing that flow can result in majorly decreased effeciency as it's designed to keep the fuel off of the cylinder walls. I ported my cups lots, but left the piston side mostly unaltered. If you take good care cleaning all the carbon out of the precup seat in the head the cups will just tap in easily with a rubber mallet. If they are dirty then it could be quite difficult. Make sure you Check protrusion off the head once the cup is in. I think it's .1 mm max last if I remember correctly. Perhaps someone can verify thsat.

 

[gerg]

Here are my last cups. Pretty happy with them. Burn very clean at all rpms. Can't say how much of a difference they made as I always change so many things at once, but burning clean is always a plus.

 

[gerg]

Don't know what's up with the tiny pics, but here is the thread. Scroll to the bottom.
PreCup temp ..
g

 

[dkyuss]

Thanks for the link and details guys. I will polish the internal casting ridge, sharp edges in the 'throat' and put a small radius to the sharp edge on the piston side on these stainless precups reducing any stress risers. Also could set this up on the cnc at work and produce some nice dimpling patterns (Not sure my hand ground cups would look as nice as yours) to minimize heat transfer. I would think the dimpling would also provide some relief that would minimize induced stress at elevated temperatures and differences in thermal expansion, especially stainless vs cast.

I have access to a large surface grinder so will deck the head to ensure all is nice and flat.

The precups appear to locate and contact the head at only 2 locations, the upper ring on OD and the very base, both locations dimpled would allow fuel air to pass on backside of the precup as well?

And I will look more closely.... but I think the flash is showing a piece of lint or casting line that almost looks like a crack on the bore of the throat?



Also, @ozcrusier the link I posted RE seating rings suggests a 3 hour process..... Thats one hell of a long hill! Basically get it out on the highway and go hard but not too hard?

 

[gerg]

Any gaps between the cup and the head get filled completely with carbon. I too thought about dimpling the gasket contact surface area, but only after I had installed it all.

 

[dkyuss]

Ive since assembled, ran a few thousand kms and with symptoms of low compression high blow by, torn apart to do it correct this time.
Typical bores

Wear on piston skirt

I think I may have me some ol piston slap due to too large of oil clearance.
Pistons are all undersized and cylinders oversize. Bores are listed in the thrust direction (90º measures much closer to spec). All cylinders have at least 1 thou taper. Pushing .0060" piston oil clearance (spec is .0035-.0046")

Options from here?
My preference to save $$$ would be to replace cyl liners, bore and hone to suit my undersized pistons, reuse existing pistons and rings.

Alternatively knurl pistons?? Anyone do this?



Now I have more
Questions ???

Stamped # on the piston rods crank ends do not match.
Cylinder
#1 #2 #3 #4
1-2 1-2 1-1 1-1.

Can anyone enlighten what the stamps mean?

Piston oilers are supposed to be 10-30 degrees from vertical. Mine appear 5-8 degrees at most!
Another piece of the puzzle?

Now on cyl 2 and 3 with low compression, I coincidentally have heat like marks on the crank pin. Caused by blow by? Should I check crankshaft for straightness? Be concerned about annealing/heat treatment effects?

I know lots of questions..... Hope someone can shed come light on this.
Thanks!