3B Pre cups

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BJ70/85

BJ70/85

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Joined
Oct 5, 2004
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16
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62
Location
Nova Scotia
I just finished a teardown of a 250,000k 3b, measured all tolerances and to my surprise everything is still within "new" spec according to the factory manual Although some of the"max" specs seem to be a little fat to me, I trust Toyota. The only thing that was bad was the 4 pre-cups had cracks.
The dealer wants 285.00 each :censor:(their cost is 156.00), I've searched here to find 4-wheel auto at 100.00 each, but I do remember reading someone here got a set in Aus. for something like 180? but I can't find it, or the place.
Toyota wants over 240.00 for a head gasket, I realize OEM is best but NAPA has a complete engine gasket kit for less than 190.00. Has anyone used these, or are they a waste of time. Also is there a way to keep the new precups in tight? I would like to machine the head for a clean surface, even thought its within spec. I was thinking about using a hi-temp epoxy and center punching the edges to the head. Any thoughts or comments would be appreciated.

Thanks,

Doug
 
I have pre-cups in stock - call for pricing (you'll be pleased you did). Engine gasket kits in stock.

The new cups will fit well. When you pull out the old ones, they don't go back in with any kind of proper fit.

~John
 
Eric Winkworth said:
I'm curious, did you run an EGT?
Click to expand...

No, this engine came from a parted out 70 that sat for 10 years, my engine has 500,000k and I want to turbo this one. What are the advantages to checking EGT in a 3b. As I said this is my first diesel, If this rebuild cost too much I'll build a small block chevy for it;)

Thanks Radd, I'll contact you this week.
 
EGT - Exhaust gas temperature

With one of these gauges you can monitor your exhaust temps. The way I look at it, typically in a metal foundary aluminum furnaces are around 1400 degrees (thats molten metal) this of course will be a bit different with different aluminum alloys...

That being said a 3b has no trouble at all making exhaust temps that high or higher when working up a decent size hill at speed, or just maintaining 100kmph plus on the highway... An EGT is critical in maintaining maximum engine life...

Every time I see someone talking about cracked precups I'm always curious if they were running an EGT... Although others have much more long term and intimate experience with the 3B, I have a funny feeling that if you were to keep EGT's just below 1400 degrees for the life of the engine you would find precups still in tacked!

others may disagree, but I know myself before getting an EGT I definitaly was HARD on my 3B!
 
Eric Winkworth said:
EGT - Exhaust gas temperature

With one of these gauges you can monitor your exhaust temps. The way I look at it, typically in a metal foundary aluminum furnaces are around 1400 degrees (thats molten metal) this of course will be a bit different with different aluminum alloys...

That being said a 3b has no trouble at all making exhaust temps that high or higher when working up a decent size hill at speed, or just maintaining 100kmph plus on the highway... An EGT is critical in maintaining maximum engine life...

Every time I see someone talking about cracked precups I'm always curious if they were running an EGT... Although others have much more long term and intimate experience with the 3B, I have a funny feeling that if you were to keep EGT's just below 1400 degrees for the life of the engine you would find precups still in tacked!

others may disagree, but I know myself before getting an EGT I definitaly was HARD on my 3B!
Click to expand...


I have a 3B in a 1985 BJ70 308,000 KM with a Turbo Glide turbo kit installed at 260,000 KM. The EGT gauge was installed pre turbo, max boost set at 13psi, fuel adjusted so the EGT would not go over 1200F pre turbo. A precup cracked fell down into engine seized engine. I noticed your max EGT is 1400f but you don't state pre or post turbo. I think 1400f is to high a temp either pre or post turbo. The max EGT of 1250f pre turbo is a temp that is safe for short duration runs with a max of 1100f pre turbo for sustained runs.
My 2 cents worth.

Jim
 
Q. How much boost and power do you set up for along with Max EGT?


A. We use 9lb and a torque gain of no more than 30% and an EGT of no more than 500°Celcius under prolonged full throttle usage. My staff and I have seen many turbo kits installed exceeding these parameters resulting in severe engine damage. Use of chassis dyno is mandatory before and after fitment of turbo.
Turbo-Glide: Q. How much boost and power do you set up for along with Max EGT?

This statement is from Turbo Glide web site FAQ, they state 500C as the max temp, in this answer they do not specify pre or post turbo but in other answers they reference post turbo so I assume this is post turbo. 500C is 932F a general rule is post turbo equals 200F less than pre turbo so 1132F.

So the big question is, what constitutes excessive EGT? If everything is working properly, 1250º to 1300º F. is a safe turbine inlet temperature, even for sustained running, mile after mile. Above 1300º F. things can start to get edgy. Remember, excessive EGT damage is cumulative. Over 1400º F., you're usually gambling against a stacked deck and it's only a matter of time until you lose. The higher the EGT, the shorter that time will be.

Banks Power | Why EGT is Important

This is an answer that Banks posts on their FAQ web page it is long so I copied a short quote if you want the rest follow the link.
They address the pre post turbo EGT fairly well in this FAQ.
I hope this helps.

Jim
 
I was talking to the local machinist about pre-ignition chambers and he said that droppong a cup was a common problem with Ford diesels. I don't know if the 3B is bad for loose pre-cups, but he says that he epoxies them in place with great success. Exactly what kind of epoxy he uses, I don't know I can find out though.
 
That would be great.
The precup interface is partially over the cylinder and the rest is over the block in order for the precup to fall into the cylinder it must first break into pieces, I am not sure if the epoxy would help with a precup failure of this nature?
The interesting part of your comment is what epoxy could survive at the temps present in the precup area, I would really like to know what epoxy was used.
Thank you

Jim
 
I'll have to find out. There are dozens, if not hundreds of different kinds of epoxy I'm sure there's one that fits the bill. It's probably not JB weld... Epoxy seems to be a blanket term for any 2 part thermoset plastic.
 
Just curious how do you get the pre-cups out if they were to crack again if you epoxy them in place,I know a motor will probably only be rebuilt once in it's life time.
 
Chang-kuao-lo said:
Probably a bit of heat along with punching out with a drift? Another good question.
Click to expand...

My point exactly "a bit of heat" is what I think is going on in the precup area, how will an expoxy hold up to 1000F heat or more? I am not aware of any expoxy that can sustain really high heat/vibration/diesel fuel/heat and cold contraction. I really and I mean this without any sort of sarcasm want to know what they use because I can think of alot of other things I could use it for.

Jim
 
I'll make it a point to find out. Perhaps the pre-cup would have to be machined out? Then again, when the engine is running there is no downward force (drift pin) on the chamber. Is it always the case that the chamber cracks then falls into the cylinder, or is it the other way around in some cases? I remember having a defunct (cracked) 2LT head where one chamber dropped out, and two of the other three were loose with no cracks in them.
 
Generally the pre-cups crack radially in relation to the cylinders. Occasionally they will crack in such a way that they fall into the cylinder (don't ask how I know, it wasn't cheap). Generally they are a little loose. One shop that did a head for me used a punch to try to hold the pre-cups in place.
 
BTW, does excess heat cause the head precup cylinders to open up to wide, causeing it to fall? Some one said if they crack, they will drop into the cylinder in pieces. Epoxy could carbonize and take up and slack or grip onto the pre-cups preventing the precup pieces from dropping into the cylinder. I now have 460,000 km on my original engine and never had a precup drop yet.
 
Radd Cruisers said:
I have pre-cups in stock - call for pricing (you'll be pleased you did). Engine gasket kits in stock.

The new cups will fit well. When you pull out the old ones, they don't go back in with any kind of proper fit.

~John
Click to expand...
You still carry precup?need for a 77 b series

IMG_20160526_093248.webp
 
Yes, I have pre-cups in stock but it looks like you might need a new cylinder head. If you can't source either the cups of the head locally, I can assist you with those parts.

~John
 
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