New valve guides, ID too tight - help please
 

I ordered valve guides 930-104-321-50-M105 from our host for my 83 SC 3.0. I tested several before installation and the valve stems fit perfectly. I machined off a couple of hundredths from the OD, cooled the guides, heated the heads and they tapped in with what felt like just the right interference fit.

However, the valves won't fit now that they are in the heads. They feel about like I could tap them in. I know better, but use that analogy as a reference. The heads, guides and valves have been at the same temp for two weeks since installation of the guides.

Did I order the wrong ones, or is it normal to have to ream them after installation? If so, what's the technique? I hope I don't have to take them out and start over!

Thanks folks,
Steve

Anytime there is an interference (press or shrink) fit the id will be smaller after installation, so if the guide to stem radial clearance was not enough before installation then they could bind after installation. Sounds like you need to ream it a bit.

The guides need to be reamed after install. There is a reamer made for this task.

all guides need to be fitted to the valve stem after installing them. the quick and dirty way is to ream them. the best way is hone to fit. intake and exhaust stems are one to two 100ths different from each other. what are you planning to do about machining the valve seats?

I wasn't planning on machining the seats, as the leakdown numbers on this engine were excellent, but it showed signs of bad stem seals. There was a little bit of play in the guides, so I thought it would be an easy and cheap "while your in there" to replace them.

Now I think I'm beyond my skill, or just tool, level. I don't see the logic in buying a $350 hone for something I may only do once or twice. Do the flex-hone tools work well? If so, what abrasive do you recommend? They jump from 8 to 9mm. Do they flex enough to put a 9mm down the bore carefully, or do you use an 8 and move it around evenly (this seems to risk introducing an out-of-round to the bore)

We are lacking in quality machine shops where I live and I'm trying to avoid shipping them off to someone, but that is looking like a reality now.

Thanks,
Steve

The new guides will mean the valve will be seating slightly differently than with the worn guides which allowed it to seat however it wanted. Now the new guides will restrict the movement more so your leak down numbers may not be as good as before.

you ABSOLUTELY need to cut the seats after new guides. no way around it. period, end of story. your leakdown would be off the charts if you didn't. that's why i asked.

as for the guides, what did the new ones measure originally on the OD, and what did you end up with? 13.08mm is standard and they go in fine with some crush. if you took a couple of 100ths off them, they may now be on the loose side. they can't go in too easy.

Darn, I got this far before making a rookie mistake, not bad I guess :)

The OD was 13.08, but even after heating the heads to 400 and freezing the guides, they would not go in. I actually ruined the first two that I tried. After turning them they still took decent hits to get them in. By no means did they tap right in. I think (hope) the fact that the stems won't go in would indicate pretty good crush, I just didn't expect that but it makes sense.

John, I'll send you a PM later to discuss your services. I appreciate the help here. I think it's time to let a pro take over.