cracks in pre-combustion chambers from Spec...? (2 Viewers)

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No. 3

No. 3

Joined
Dec 13, 2007
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Location
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I have ordered a recon'ed head from a certain supplier of LC parts that we all know. It is for my '87 HJ60 which had a pre-combustion chamber fail. The head was dropped shipped to a mechanic far away (near where my troubles began) and I haven't seen it.

My question is this: each (!) of the pre-combustion chambers has a fracture in it, not a big one as it has been relayed to me but a fracture. All are tight in the head. As I am having a failed chamber and the ensuing damage repaired, I am a leery of the "if they are tight in the head they are fine" answer I got from the supplier.

Should I worry?

Thanks again guys,
Jeff
 
I have seen many that are cracked (I don't recall seeing any used ones that were not) and most, not all, are radially in relation to the piston, those generally are not a problem.

The cracks to be concerned about are the cracks, which if they were to go all the way through, would leave a section of the pre-combustion chamber unsupported and liable to fall into the combustion chamber.

I can relate as I've had an engine lock up due to a falling pre-combustion chamber.
 
Apparently cracks are common.

But if it was me, I'd automatically replace the precups whenever a head is off and such cracks are noticed.

A new set of precups is cheap enough from companies like Engine Australia. (Well at least it is for a B or 3B engine so I assume it'll be the same for you.)

:cheers:
 
No matter who is responsible don't install a head with cracked precups, buy new ones and replace them, if you are this far in and don't replace them it could cost you an engine. If the issuse means that much to you send the head back for a refund it will be cheaper to do this than buying a motor.


Jim
 
I just re-read your post. You say you have a reconditioned head? Then it should have new combustion chambers. A used one is... well... used!!
 
The tightness in the head is definitely not the limiting factor - the cups sit only halfway over the cylinder, the rest is squished against the block, so they're never coming out if they're whole...

... IF they're whole. If they rack all the way through, you'll end up with an engine looking like David's ^^.

Always replace precups.

Here were mine:

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cruiser_guy said:
I just re-read your post. You say you have a reconditioned head? Then it should have new combustion chambers. A used one is... well... used!!
Click to expand...

I just looked at SOR's website and they don't claim to replace pre cups on reconditioned heads. How you can call it "reconditioned" is beyond me, it is still "used" in my book. And just how do you magnaflux a head (which they do claim they do) with the cracked pre cups still in place?

That being said take everyones advice and replace all the pre cups not worth the risk of further failure.

Tony
 
You can buy your precup from the dealer but your probably leave your both arms there !

Check for a AUS supplier like ::: GW Engine parts - INTRO. I have paid around 26$ each for my 3B precup when I rebuild my engine in 2007.
 
a reconditioned head !! Then it should have new combustion chambers.Guides, valves machined / Min for a diesel.. Springs / rotor-cups etc are added.

Always..

VT
 
Thanks for all the responses, my thoughts when hearing that the cups were cracked ran to an "Oh s***". It seems strange to be calling the head reconed without replacing them.

My poor truck has been in Mammoth Lakes (I am in SF) since it broke down on Aug 30. Really. It is my daily driver for work and surfing. There have been a series of SNAFUs with supplying the mechanic in Mammoth with the parts from two suppliers. He finally received everything last Friday. I think that I am going to have him put it together and drive it back here and order the chambers from Cruiser Dan and have them replaced locally. I just need the truck back in my possession even if it means having the head off twice.

I don't know what to say about Specter- the head had the valves reconed, ground, new seals, etc. Maybe they would have redone the chambers if the order had been correct the first time and they hadn't had to rush it out? Regardless they were the only partner to take to this dance. At least for the money and time frame I was looking at.

If I were to have the chambers replaced here in SF how invasive would that be after the head was off the engine? Would I have to have the valve train removed again? I would hope to be in it for merely the machining and a(nother) new head gasket. I could pull the head and deliver it to a shop myself- it can't be that tough.
Thanks again guys,
Jeff
 
Jeff;

Virtually all heads that have been in place for a while will have cracks in the chambers.

I have combustion chambers here, and they can be shipped to your guy in Mammoth to arrive in a few days. For the cost of new ones, I don't think it's worth taking the risk.

As others have said, you should not install a head with cracked chambers on it. They should always get replaced if any cracks are present, and after they go in, the head needs to be lightly machined to bring the depth back into spec.

~John
 
No. 3 said:
Thanks for all the responses, my thoughts when hearing that the cups were cracked ran to an "Oh s***". It seems strange to be calling the head reconed without replacing them.

My poor truck has been in Mammoth Lakes (I am in SF) since it broke down on Aug 30. Really. It is my daily driver for work and surfing. There have been a series of SNAFUs with supplying the mechanic in Mammoth with the parts from two suppliers. He finally received everything last Friday. I think that I am going to have him put it together and drive it back here and order the chambers from Cruiser Dan and have them replaced locally. I just need the truck back in my possession even if it means having the head off twice.

I don't know what to say about Specter- the head had the valves reconed, ground, new seals, etc. Maybe they would have redone the chambers if the order had been correct the first time and they hadn't had to rush it out? Regardless they were the only partner to take to this dance. At least for the money and time frame I was looking at.

If I were to have the chambers replaced here in SF how invasive would that be after the head was off the engine? Would I have to have the valve train removed again? I would hope to be in it for merely the machining and a(nother) new head gasket. I could pull the head and deliver it to a shop myself- it can't be that tough.
Thanks again guys,
Jeff
Click to expand...

You'll need to remove the valvetrain to get the head bolts out, so thats gotta come off no matter what. Manifolds can probably stay on for a quicky job.

Unless you have the SST for pulling the precups (you don't) you'll also have to pull the injectors to hammer the old ones out.

Shouldn't need any machining, just new HG and reinstall.

Its not hard, but pulling the head is never fun.

All that aside, I would wait and have John send you new cups. You never know if they removed what little metal was holding the cups together when they ground the head.
 
Thanks again folks, I have new chambers on the way to a machine shop in Bishop. I wait another week to get her back .....

It is really too bad about the precombustion chamber weak link on this engine, I am looking at the bright side though, the largely rebuilt engine should keep going for buckets more miles (km's I guess for my Canook Cruiser).

Amaurer nailed my hunch that pulling the new-to-me head would be more hassle than it is worth with it being off now.

Can't wait for the next camp out at the beach in the truck!
Jeff
 
I have been reading this thread and thinking about all the replies from everyone saying replace them as if some major destruction is going to happen , while reading this and thinking about every 3b out there that has 400,ooo+ k on them turboed and non turboed and they all have minor to major cracks in their precups and are still going strong.
Is this a case of the sky is falling... if this was a major issue then everyone with 3Bs would be changing their precups after 100,oook like BEBs on the PZs and the 1h motors.
After writing this now I have probably cursed myself and heading for self destruction on one of my engines anyways I take chances.
 
I wouldn't say it's an "the sky is falling" issue, but if you have already had one drop, and you have the engine apart, then it's worth doing them.

There is not much one can do to prevent new ones from cracking just as the old ones have done, but putting somewhat risky parts back into an engine is never a good idea.

The whole reason why the 2H came apart in the first place was due to a dropped cup... we know what going down that road looks like.

As for engines dropping cups, I do see it from time to time, but it is not very common, and usually it follows an over heating episode.


~John

btw, dieseler, any updates on what happened to your HJ61 transmission?
 
Just buttoning up the one you sold me I will be on the island for the next 2 weeks on vacation so will finish it up when I get back.... then I will dive into the broken one.

sorry for the highjack
 
Dieseler said:
I have been reading this thread and thinking about all the replies from everyone saying replace them as if some major destruction is going to happen , while reading this and thinking about every 3b out there that has 400,ooo+ k on them turboed and non turboed and they all have minor to major cracks in their precups and are still going strong.
Is this a case of the sky is falling... if this was a major issue then everyone with 3Bs would be changing their precups after 100,oook like BEBs on the PZs and the 1h motors.
After writing this now I have probably cursed myself and heading for self destruction on one of my engines anyways I take chances.
Click to expand...

The difference between not replacing cracked precups and "the sky is falling", the engine is apart, there are cracks present in the precups of the "reconditioned head". I have read the postings and no one has suggested replacing precups in 3Bs every 100,000k just this engine is at a point where it is the least expensive way to get new precups in the head and it is cheap insurance that the engine won't have a repeat problem.
It would be different if the guy said he already had the engine together and wanted to know should he tear it apart because he found out the precups were cracked, I would say bummer but run it.
If you think the precup problem is no big deal than you haven't had a dropped precup in an engine, my 3B dropped a precup at 260,000k, it seized the engine. As far as Johns comment about they fail because of an overheating issue I owned mine for about 40,000k and never had an overheating issue, it dropped a precup on my daughter in the snow on Mt Hood made for an interesting afternoon. I read in this thread that cracks are common in the precups since it is common it appears to me not to be an issue about the cracks but where and how the precup cracks. My solution which cost me dearly, was to purchase a 13BT no more precups, way better fuel milage.:cheers:
I hope you never have a precup failure in any of your rigs it sucks.

Jim
 
Last edited:
Certainly this was never meant to engender any controversy!

John hit the nail on the head (except in my case with the overheating, at least in my ownership of the truck), the whole of my nearly two months' long travails were due to a cracked precup failing and dropping a chunk on the piston below. It is a bad scene that could have been much worse. To purchase a "reconditioned" head that contains the seeds of the same problem is frustrating at best. Perhaps it would have been fine but perhaps not. While the truck is in pieces it seems prudent to change them out even though it means more time and money.

And incidentally the supplying vendor SOR is unapologetic about this even after initially building and delivering the wrong head. (To their credit on that at least they did ship the right head for the 2H a week and a half later. It would have been hard to spin that though.) At the very least there ought be some explanation on their site about the precup policy they have. Really I think they ought be charging the money to replace them if cracked and subsequently surface the head, neither of which were done on this one.

Don't rip your engines apart to replace the chambers and may this never happen to you, especially hundreds of miles from home. It has been an expensive outer ring of hell.

Jeff

PS: Jan-78FJ40 in the future try John at RADD for parts, I think that you'll be pleased with the value.
 
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