Valve guides

[wondersparrow]

Ok, so the other day I was investigating an oil burning issue on my track 240z and I noticed one of my valve seals was not seated at all. I decided to replace them all with the ford viton ones today. I do have a fairly high lift cam and thought that might have been the issue. Anyway, when I took the springs off the valve in question, I found the top of the guide was actually broken off flush with the surface of the head. bummer.

 

The fsm says to press out the old ones, ream the hole to spec and press in the new valve under heat. Is this something that needs to be done at a machine shop or can it be done in the garage? I have a press and flame at my disposal. Does the head actually need to be reamed out most of the time? Money is tight, but if the knowledge consortium on this site suggests taking it in, I will.

 

What might cause the guide to break? Are there "performance" guides? I have schneider cam and springs, don't know about the valves. Should I bite the bullet and replace them all or is it acceptable to replace just the one broken one? Its an exhaust guide that is broken if that matters.

 

Thanks in advance, you guys are always a big help

[Xnke]

If you have to ask if your tools and experiance are good enough, I'd take it to a shop. I have done lots of valve guides, did mine in the head I'm running now. But I also broke a bunch of them learning how to do it, and it's not fun to remove them once you've broken them down inside the hole.

 

Before I was comfortable doing the job, I probably did three practice heads worth of them. Once you get the new one pressed into place, you have to ream/hone the inner diameter to meet specs, 95% of the time, in my experience.

 

You will need a valve guide removal mandrel, and an air hammer. Make absolutely certain you scrub the head and valve guide really really good, and you need to strip the entire head and heat it in an oven or with a torch very evenly, so as not to warp it. SCRUB the junk off the port side of the guide, anything left on the guide will score the bore that the new guide will seat in. Slip the mandrel into the guide, and carefully let the air hammer knock it out, being sure to not put any side loading on the guide or it WILL break off. Then you're **** out of luck, half the time, and have to take it to the machine shop anyway if you don't have another mandrel specially suited to remove the broken guide.

 

Installation is done the same way, with the air hammer and practice, and then you ream/hone the guide to size.

[wondersparrow]

That is quite the job, and it does sound quite doable, but I think getting some practice on a stock head might be a good idea. This time I run it over the machine shop and have them do it. After doing a lot of research earlier, I decided to go have a really close look at things. I think the intake valve in another cylinder is cracked. Its hard to get the light just right to see it from the side. It does look like there is a little oil in the exhaust port, so I'll have them take a peek at that too.

 

While looking closely at everything I noticed that my valves seem to be a cobbled collection of who knows whats. The markings, shape and even colour of the valves are slightly different. Looks like only a 2 angle valve job. I know that this car has been raced pretty much since it was new and has had a lot of owners. I just wonder if it is worth it at this point to get some new ones. I don't see valves or guides for sale at many of the usual places. Springs and cams are all over the place, hehe. As well, I am pretty sure my guides aren't stock, I have a stock e88 head for comparison purposes.

 

Anyhoo, I guess I got some things to think about. This quickly went from a cheap and easy valve seal job to a serious case of while I'm in there's.