4.0 head assy
- Thread starter DarthMole18
- Start date
Yep. I've never done it, and I probably never will.... I'd let the machine shop do it when they do everything else to the head. 
Part number has been superseded a few times:
ERR3648 --> LGJ100900 --> LGJ000030
Part number has been superseded a few times:
ERR3648 --> LGJ100900 --> LGJ000030
I'll probably just let the machine shop do it. I have so many spare head assemblies, but not a good spare drivers side. Want you to just tell me I can take a valve guide out and replace the cracked one and it will be ok. Not the case though. What are those big 3/8 hex screws for in the head?
Yes, you can.
You can also use bronze guide liners to give worn guides a new lease on life. (look at www.cylinderheadsupply.com).
Excellent. Greatly appreciated. Only additional question is, how do I remove and replace a cracked valve guide?
The professional route is a safe bet. But this is an exploratory mission. If the valve guide were to be replaced, would it be pressed in, threaded in, or some other way?
Old one pressed out, new one pressed in, reamed and trimmed if needed. I think there is a section in rave about it.
I've seen some service manuals for Japanese cars that had instructions along the lines of put the new guides in the freezer, put the head on a hot plate and heat to X degrees, press the old out and press the new in.... all using special drivers of course.
Doesn't look too difficult, 8.70mm or 0.342" reamer after installation.
You could do that with an adjustable reamer and a bore gauge (gage)
Peter
You could do that with an adjustable reamer and a bore gauge (gage)
Peter
Thanks for the support. I'm gonna try it on a spare head assy and see how it pans out. Is that diagram from the BL factory manual?
It isn't difficult but it is important to have a right size driver on hand so it goes in straight.
It can be done cold but heating the head and chilling the new guides can make it very easy.
Yes, the diagram is in the 4.0/4.6 Engine Overhaul guide in the section Valve Guides - Renew
I'd turn up a spigotted drift to knock the old one out with and then knock the new one in. If you have access to a decent press, that is possibly a nicer way of doing it.
We've never needed to do this yet as we have spare used heads to recycle.
None of ours seem to wear much, they are all pretty good after 100k+ miles.
Peter
We've never needed to do this yet as we have spare used heads to recycle.
None of ours seem to wear much, they are all pretty good after 100k+ miles.
Peter
I cracked a guide stripping out a parts truck. Valve wasn't moving, so after I pulled the head I gave the valve a good hit with a sand mallet to bang it out. Valve guide cracked.
