HO rebuild, need to know what to expect

[Siggers]

Gents,

It's been a while, and the HO is still in my drive way rocker covers off, hoping it was a rocker off, but no.

Seriously considering a rebuild, but what's involved?

All the remove the engine ect out of the way thing is neither here nor there, I have removed the gear box thrice, I get its tight.

I want to know, what's worst case scenario here? A dropped valve seat seems pretty up there in problems, are we talking about a new head and its components? Piatona and a bore? I have read that boring out these engines isn't the best idea? .

Also need to know is there anything special in the HO for a rebuild?

Thanks guys

[skipperau]

Originally Posted by Siggers

I want to know, what's worst case scenario here? A dropped valve seat seems pretty up there in problems, are we talking about a new head and its components? Piatona and a bore? I have read that boring out these engines isn't the best idea? .



Also need to know is there anything special in the HO for a rebuild?



Thanks guys

Hi Siggers, I was thinking about that issue as you know, simply put, you will probably have either a dropped valve or more likely a dropped valve seat as you mentioned.

Either can be sort of bad or very bad, depending on degree. If not too bad a dropped valve can be repaired, reassembled and back on the road for a couple of hundred, if bad, either could require new head and pistons. I doubt if you need new pistons though after our chat, even so the repairs will run approx $2.5K+. You will probably need to find a new head, (I was able to get my existing heads rebuilt with new valve seats after having dropped a couple due to overheating but I'm not sure how many shops are willing to do that work, I've heard of a few shops refusing to do it, not sure why) and they are different to the ordinary heads (a different casting, as well as different cams etc.) You'll most likely to be able to reuse all of the bits from your existing head thus saving $.

Doug


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[skipperau]

It would probably depend on how extensive a rebuild you want to do too. A full rebuild or just the top end to get it running again.?


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[Siggers]

The $$$ at this stage isn't the problem, I am chasing reliability if anything.

Happy to roll with new pistons, they aren't that expensive in the grand scheme of things.

So what your saying is if the head has been munched, there is a possibility of it being no good and it has to be replac d, can't be repaired?

[skipperau]

Originally Posted by Siggers

The $$$ at this stage isn't the problem, I am chasing reliability if anything.



Happy to roll with new pistons, they aren't that expensive in the grand scheme of things.



So what your saying is if the head has been munched, there is a possibility of it being no good and it has to be replac d, can't be repaired?

In theory anything can be repaired, it just depends on how much money you want to throw at it. In my personal opinion your head is probably fine, just needs new seats and then rebuilt. I'm not sure why some shops won't do repairs on jeep heads, I don't see them as being any worse than any other alloy head.

Buy a top end rebuild kit, pull both heads and get the broken one repaired/replaced and you should be good to go.

Refresh my memory, you've replaced the injectors and stuff like that already haven't you?

[skipperau]

Sorry, what I started off saying but left out was that sometimes buying a replacement head can be cheaper than repairing the existing one.

[Classic Boy]

Don't even consider repairing heads that have already dropped a seat they do it because the aluminium has lost its temper (hardness) and although they can fit new seats, but because the aluminium is 'softer' than it needs to be they are not reliable this is why many machine shops don't want to do it.

New bare heads are not that expensive, unless the HO engine uses different castings than std 4.7L that is the route I would go. They are around $400 AUD each delivered for stock 4.7L heads.
Bottom end is nothing unusual and can easily be repaired.
Put a timing chain kit in when you do it too.