Builds 1988 BJ74 “Number 1” (4 Viewers)

[FJBen]

Block work.


The block was shaved down 2 thousandths so that the liner protusion would be correct as 2 of the cylinders were out of spec and sitting too low.
From there you have to set the counterbore so that the liners are the correct depth and equal.
The liner protusion (not the ridge) needs to be .4~.39 of a thousandths ( close to 1/2 a thousandths) or about the thickness of a piece of paper.


Liner protusion is how far the liner (not ridge of liner) sticks above the block. This is important because if the liner is too low, the liner can actually move up and down causing the liner to break, and most likely a failed headgasket. Too much is bad as well as you won't get a good seal, which pretty much guarantees a leak and failure. Both are bad and don't allow the headgasket to crush seal correctly.



New freeze plugs were also made for back of the block as they are no longer available.

The machine shop guy works on a ton of isuzu 4B/4BT 6B 6BT and says they are very very similar. A lot of the specs are the same. He doesn't like much foreign stuff, but he said this is a really nicely made engine so I think he is kind of enjoying working on this.

 

[ceylonfj40nut]

Good tech here! Did not realize that liners install has to be within that close tolerance. Do you have a close up that shows difference between liner ridge and liner you refer to?

 

[FJBen]

Good tech here! Did not realize that liners install has to be within that close tolerance. Do you have a close up that shows difference between liner ridge and liner you refer to?

I try and get a better picture when I get back to the machine shop, but this is the best I have for now.

In this picture you can see basically the outside circle of the liner just barely sits above the block surface. That measurement is the protrusion. The ridge you can see on the inside circle and it sticks up for lack of a better word.

 

[ceylonfj40nut]

I try and get a better picture when I get back to the machine shop, but this is the best I have for now.

In this picture you can see basically the outside circle of the liner just barely sits above the block surface. That measurement is the protrusion. The ridge you can see on the inside circle and it sticks up for lack of a better word.

View attachment 1885463

Crystal clear. I have another 2H sleeved that I will be inspecting and putting into my 40. Need to check 2H FSM if same applies.

 

[FJBen]

Not much work getting done by me, block still at machine shop, Injection Pump getting looked at $$$

Newest job is picking up broken branches from the ice storm the other night.

 

[ceylonfj40nut]

I try and get a better picture when I get back to the machine shop, but this is the best I have for now.

In this picture you can see basically the outside circle of the liner just barely sits above the block surface. That measurement is the protrusion. The ridge you can see on the inside circle and it sticks up for lack of a better word.

View attachment 1885463

Did they have a shim of that thickness in place to stop the “press” at the right height?

 

[FJBen]

Did they have a shim of that thickness in place to stop the “press” at the right height?

As far as I know, by decking the block and making sure the counterbore was cut to the correct depth, no shims were needed. When he presses the sleeve in, it should be at the correct height. Mine weren't that far off, but he wanted to make sure the protrusion was even and in spec per FSM.

I had 2 cylinders that were too low. It wasn't really bad, but enough for him to say we should make it right. I agree.

My understanding from him is that you can deck most blocks regardless of what a FSM says, as long as all other components are measured and taken account of as they all effect each other.

 

[FJBen]

Just some measuring today.

My clutch disc is showing .8mm rivet head depth. The FSM states .3mm as the limit. I don't know exactly the new rivet depth for an Aisin clutch, but I found some FJ40 specs at 2mm new. That would put me around high 30%~low 40% overall life left on the clutch disc.

Not terrible, but combine it with the pressure plate burn spots (which you can't resurface, the fact I already resurfaced the flywheel and the fact that it will never be easier than now; it's time to do it. Only $$$ right?

hot spots

No idea if this is original clutch.

 

[FJBen]

I park in my shop so I get to look at the cruiser everyday. it's motivation to get it going!

 

[FJBen]

Almost on the home stretch of machine work.

Lathe work cleanup on the rocker arm shaft.

rocker arms cleaned up

 

[FJBen]

Tech Time from the Machine shop: Con-Rod Con Job.

When the machine shop looked a lot of the machine work that was previously done to this engine, he was less than impressed, and a lot of it he said was junk work. Case in point, lets look at the con-rods and bearings. These were done by a prior shop in california.

Issue number 1.

When you press the conrod bearings into the con rod, make sure you have the right tools. It's an extremely precise fit number 1, and number 2 it's a tapered bearing so it's not just an easy/simple push in. You have to either make or buy the tool and press it all in straight. The previous shop didn't have the right tool and you can tell it was pushed/forced in crooked.

Scoring/marking all over the outside of the bearing.

More tell tale evidence of a wrongly installed bearing. The actual nick on the end is less problematic, than the grooves outside the whole bushing. You can grind/file/chamfer the ends to get rid of the sharp ends.

So what happens in these situations where the bearing outside is messed up by getting pressed in wrong?
Spun bearing. Would have happened. I wouldn't have known this and installed away. Bearing spins, no oil and teardown.

 

[cruiserdan]

Just some measuring today.

My clutch disc is showing .8mm rivet head depth. The FSM states .3mm as the limit. I don't know exactly the new rivet depth for an Aisin clutch, but I found some FJ40 specs at 2mm new. That would put me around high 30%~low 40% overall life left on the clutch disc.

Not terrible, but combine it with the pressure plate burn spots (which you can't resurface, the fact I already resurfaced the flywheel and the fact that it will never be easier than now; it's time to do it. Only $$$ right?

hot spots

No idea if this is original clutch.

Reusing a clutch for a job this in-depth is like taking a shower an then putting your dirty shorts back on

 

[FJBen]

Part 2 of bearing issues. This was the initial issue that raised some red flags with the machinist instantly. As soon as he saw this, he said we have a problem here.

Inside the conrod bushing you see the oil hole, and the oil ridge. If you look on this first picture, that oil ridge is rounded over and not straight. This tells him right away that the wrong tool was used to hone out the bearing to fit the wrist pin (or grudgeon)

Contrast that picture, with the picture below of the correctly installed and honed con-rod bushing. See how square the oil path is? Pictures isn't the best but you can see square edges if you click on the picture.

By using a brake hone hand tool, the whole bearing was out of round and the piston wrist pin was loose and wobbled slightly. It measured differently all the way across. It also was sticky/binding in spots as well. This can result in a spun bearing again, along with bad heat transfer that can destroy a bearing, piston and score the walls. Joy, more rebuilds.

The factory spec has a min-max difference of .019 or basically 2 thousandths. He set the clearance at 1 thousandths as he has done on other engines then showed me how it fit in there and how well the wrist pin worked with the bushing. This was eye opening. Any sharp outer edge was cleaned up with a small hand file as to not dig or wear incorrectly.

next up, large con rod bearings.

 

[FJBen]

Multiple problems on the Big End Bearings.

A lot of hard work went into screwing these up. Again, this is just using the wrong tool for the job, or using the tool wrong for the job. On a bearing and bearing cap, the are a pair. you don't change those as they are chamfered (beveled) as a pair for clearance around the crankshaft. The shop had labeled and wrongly joined 2 of them. That means there is no smooth surface on the chamfer which leads to spun bearings on the Big End to start.

He noticed this right away, matched and numbered the bearings and caps as correct pairs. However, that was not the extent of bad work performed. Again, we are talking very precise measurements across the Big End so that the bearings fit correctly and it all connects to crank precisely for oil clearance. This is basically a straight as measurement across the con-rod as you can get.

By using the wrong tool, or tool wrong, the other shop had 1&1/2 thousands of variance machined across the big end of the con rod. Again, bearing issues, spun bearing, heat transfer would have happened. By the time my machinist was done, it was at 1/8th of a thousandths out from straight.

The correct honing machine. The measuring gauge is in the upper right corner.

But wait!! There's more.....wrong.

The bearing end caps are usually cleaned up/ground/filed after honing. Previous shop again wrong tooled/job sanding the top surface where it left sharp edges that can interfere and bind the cap fitting correctly on con-rod bolts. This is the correct way to grind stone the top, the clean up the hole to make sure there is nothing interfering with the con-rod bolt.

There is a machined surface that tightly fits the cap as you see in this picture. You can also see where he stamped the con-rod and bearing cap to end any confusion.

When all of this is straight and in spec, you get check your bearings. This fit very nicely (taiho bearings from Engine Australia).
You will notice the bearing sticks up a little just over the cap and over the con-rod. When you tighten and torque it down, this is called "crush"

Here's a paragraph to explain better than me about crush, and why it's important that all these parts are machined to correct specs:

The term “crush” refers to the outward force created by the portion of the bearing that extends above the housing bore when the bearing halves are set into place. This “extra” material holds the outside diameter of the bearings firmly against the housing bore when the assembly is torqued to specification.

By increasing the surface contact between the bearing and connecting rod housing bore, crush minimizes bearing movement, helps to compensate for bore distortion and aids in heat transfer.

In simple terms, bearing crush is what holds the bearing in place.




I'm learning a whole lot on this build. I would have went about my merry way and installed all this, and then probably in no short time been having all sorts of issues. He again stated how well built and designed of an engine it was. There are a lot of shops out there doing things the wrong way because they don't care or don't know how to do it correctly. hopefully this will help someone learn what to look for in the future.

 

[cruiserdan]

Where did you find this guy? A true Craftsman.

 

[FJBen]

Reusing a clutch for a job this in-depth is like taking a shower an then putting your dirty shorts back on

Yep, new clutch going in. If the pressure plate was in good shape, I might have just put in a new disc, but at this point it's replace it all.

Where did you find this guy? A true Craftsman.

Yeah, I lucked out finding him here in my town of 4,500. He does all the machine work for the farming/ag community, tractor dealerships, and most parts stores. Gets a bit shipped in as he does a lot of head work on Isuzu and large diesel.

almost 40 years in the business, A little crotchety, hates shortcuts and shoddy work and doesn't want his work coming back again...sounds a little familiar eh Dan?

He's building a file on engine so that he know everything he did, specs and everything about it. I'll try and get a copy of that once he's done.

 

[cruiserdan]

That file and his gained experience on the engine platform will both be valuable.


Very familiar.......wait, whut?

 

[FJBen]

Dropped off the valve seals from the Engine Australia kit. They are different from the seals that were put on from the previous shop's rebuild. My guess is that they sourced/used whatever they had available. They might have worked, I don't know, but we decided since I already had them in the kit, to put the seals that came in the kit on.

He was measuring the crank to big end bearing specs.

He also spent some time double checking the clearance on the spec and felt it was too tight. The specs he found in a book, (which he literally has books from the 20's) show that wrist pin clearance as 1 - 3 thousandths. He went back and changed it to 2 thousandths and said he liked that better. Felt 1 thousandths was a little tight. Good with me.


@Cowboy45 @ceylonfj40nut tagged you, the last couple of posts here could be valuable in your rebuild. This one I thought was very interesting given your big measuring post earlier.

Also in interesting news that I wouldn't have thought "that" much about. You can see on the above table he has the parts all sitting together. Pretty standard for most of us. He does that to make sure the temperatures are very close. It's a bigger deal in the winter where you might have some parts on a counter, some on the floor, some in a box, etc...and when measuring these close specs they can be off.
He was just dressing up the bushing on the con-rod and could feel the temp difference. He stated temperatures could affect measurements up to a 1/4 of a thousandth so he likes the make sure all the parts are as close in temperature as possible when measuring critical clearances out.

I don't know if or how much of a difference this would make, but it sure makes me feel better about his attention to detail. The term I've come to hear it called is temperature induced drift. It makes sense as we heat/cool things to get them to fit. I guess add this to a list of things I never would have thought of doing this myself.

 

[FJBen]

More lessons learned.


So during this build, I'm replacing the headgasket obviously. With the Engine Australia kit, they give you a composite head gasket.

Composite Head Gaskets can be the following...(and what the 13BT came with originally)
A. Thin gasket sheeting bonded to a steel core with a fire ring at the cylinder bore and various kinds of coatings to seal fluids.
B. Perforated metal with a compressible core such as flexible graphite again with a coating for sealing and a fire ring around the bores.
C. Perforated metal core with facing material such as flexible graphite mechanically “clinched” to the core and fire rings around the bores.

Toyota has updated to MLS style gaskets as they have determined they are better.

MLS gasket:
MLS is short for Multi-Layer-Steel. Several sheets of stainless steel are layered to give the desired thickness. An MLS gasket's ability to protect against blow-out in high cylinder-pressure situations is due to the embossed layers acting as a "spring" to account for increased head lift.

All engines have a certain amount of head lift...head lift is how much the head lifts off the block during combustion and cylinder pressure. The head gasket is supposed to take up that space so no leakage occurs. You don't really want leakage anywhere in your life. The MLS style gasket is better suited to maintain that. The MLS is the newest technology an improvement and just the way to go.

HOWEVER...this is the facts I didn't know about. The machine shop was glad we ended up machining the head and block because thats required to get the best seal out of an MLS gasket. He said we would have had to machined that to get the best seal, so good thing we had to do work.

According to a few sites I found this info:

Due to the hardness of stainless steel MLS gaskets require a very smooth finish surface or leaks may result.

MLS gaskets can be very forgiving, but only under strict circumstances. The surfaces of both the block and heads must be sufficient to allow the previously-mentioned outer coating to properly seal. The tolerance for roughness of the sealing surfaces is much lower – almost half of what you can get away with if using a composite gasket, and the smoother the better.

This become MUCH more important once you start talking about aluminum heads and cast blocks. The dissimilar metals can create all sorts of problems. Thankfully the 13BT is all steel.

Well thats interesting. He went on to say, you usually don't have much choice if you are doing a headgasket repair in the vehicle, but you want to make sure the block or head aren't warped either. That obviously would require pulling the engine. There have been a few people on here that have replaced the headgasket with the MLS replacement. I'm guessing there is a point where the surface area is too rough for an MLS causing leakage, but a composite would stay sealed. I'm definitely not suggesting removing the block and machining it for every head gasket either, neither was the machine shop recommending that.


Just some information to know and think about when rebuilding these old diesel engines. Trying to share some knowledge.

 

[FJBen]

Yet another update, and more steps backwards.

The cam bearings don't fit the block. They fit the cam but they are too small for the block. Upon researching on the web, I found my answer here on the web by @Brewsterfire describing the same issue I have. Turns out there are 2 available cam bearing sets from Taiho that you can get from Engine Australia.

The cam bearings I have are: BCTO700A. These are too small for the block. I need to order BCTO700B which has a larger OD but still fits the cam.

Somewhere there is a change in the block or an error in parts land. The block changed from 3 to 5 cam bearings, and it's possible they got larger in OD size as well. I don't know how to confirm that.

The front bearing measures 2.264, and the rear 2.254. Someone with a bare older block would have to measure to see if thats when the change occurred. Curious if the 700A size is the same thats in the 3B.

At least I will have some parts to sell...