valve guides

[vugbug68]

I ordered a few different oversized valve guides to replace one that came loose on my Tims Stage 1's. CB had .002" and .005" so I ordered 2 of each, the valve would not slide into the .002" guide at all, but it fit perfect in the .005" guide, tried a few different valves with the same results, I dont understand nothing was said about the inside diameter being different. Anyone else have this issue?
_________________
71 Super - Backroad Thrasher
66 Corvair - Weekend Cruiser
90 4 Runner - Muddin

[modok]

If the diameter is extra small you may have to ream it in two, or possibly even three steps.
My preferred method is one pass diamond hones, but you can only take out about .0007-.001 per pass, so if the ID was extra small I'd have to start with a .313-.314 HSS reamer, then pass both my diamond hones through it, so, three steps.
And, so, what's the difference between two steps and three? well, not much.
What's the issue?

the issue is.... if you have the right reamer for the hole, or the right hole for the reamer.

[modok]

That's what I'd say if you walked into the shop.

Did I nail it? who knows.
You don't have to have mastery, or even proficiency, just to make it work, nor do I expect everybody to be an expert. If you want to start at the stone age or whatever....that would be fun too. But.....it's going to be hard if you go back so far that you don't have a 0-1 micrometer. So, tell me you do?

[FreeBug]

[Q-Dog]

I suppose if one didn't know that guides have to be reamed to size, one might also try to hammer a new guide in there and possibly crack the boss too! We all have to start somewhere, right? But, still, expensive lesson if it all goes bad, no?

Any machine shop should be able to install them, and ream to size. But a shop not familiar with air cooled heads might also muck up the job.

So, I suppose if I spent good money on parts from a shop that does almost exclusively one type of part, I would most likely call that shop for info, or more likely just have them fix a problem.

So, why not send them to Tim's and have them fixed correctly?
_________________
Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[Coyotemutt]

[[email protected]]

[Type 5 Joe]

The 1st issue to address would be the loose guide.

The guide boss most likely is ovalled / Galled / oversize / inconsistent in size... If it was run that way for awhile.

You need to set the head up in a mill and "dial in" on the guide boss hole. Obviously it must be positioned with truest part of the existing hole aligned with the ram (or quill) of the machine.

Do a "kiss cut" with an end mill to establish location and a land for an oversize reamer.... Ream the hole and check it visually and with measuring tools for a full "clean up".

Then determine the size (outside diameter) of the guide you need... Often I just make the guide a custom size on a the lathe. Finish it on the O.D. with the interference fit you desire... Make the I.D. slightly undersize for final finishing.

Then address the inside diameter / valve stem clearance after its installed.

You'll need to re-cut the seat once the guide installation / valve stem fit issue is repaired... I would recommend having both heads gone through.

I'm sure Steve Tims could do all this for you... And maybe work with you on price a little (maybe) as they were his heads.
_________________
If you would like to contact me, just email through one of my ads on here...

I don't use the P.M. service on here.

[FeelthySanchez]

Another nudge to suggest contacting/sending it off to Tims, as it could be a native goof. If so, repairs might even be gratis.
Also maybe ask yourself how well did ya wish this engine to run:
So far, only a couple gents here have mentioned that valve guide R&R also requires that the corresponding valve seat be reconditioned to maintain concentricity (ref: Head Reconditioning 101, 2 Units)
_________________

[vugbug68]

I understand that they have to be reamed to size once installed, but I’m confused why the difference in size (it’s like .004”) I might just take them down to CB or Tim’s, the heads have 30-35k on them so I’d hate to have another one come loose, might be time for a refresh anyway.
_________________
71 Super - Backroad Thrasher
66 Corvair - Weekend Cruiser
90 4 Runner - Muddin

[mark tucker]

VALVE GUIDES NEED SIZING !!!!! they are not put in and run items.

[FeelthySanchez]

Difference in their OD sizes is to CYA as much as possible: we know that 1 guide fell out, so at the least - the new guide going in there needs a larger OD.
Generally best left to the gent whom performs the valve job, but here's the basics of it: If a +.002" OS guide doesn't stick fast, knock-out the +.002 & try the +.005" size.
Guide IDs are normally & deliberately furnished a trifle undersize because they will distort/upset slightly when pressed into the head's guide boss. Think of it as a simple math equation: undersized ID as furnished + slight compression when installed = more undersized ID due to the press fit. Hence the "crush" that Roy noted, & need for the subsequent ream-to-fit operation.

Bottom line is @ 30-35K, she may be about due for a valve job anyway, so let the machinist sweat the gory details
_________________

[mark tucker]

so... why did the guide fall out china head?

[modok]

[nsracing]

Are you trying the guides and valve stem outside the head? or installed? Before you install the guides, you need to figure out the dimensions of that g guide boss. Is the bore oval? Is the bore tapered? You need and inside mic to see that. How much press will the new guide get?

This is machining shit. Care must be taken when removing the old guide. Most shops will just chatter gun the guide out. Sometimes it will mushroom and broach the guide boss.

On installing guides, i found the only guides that need resizing are the ones hammered in with sledgehammers.

If you install the proper size guides and they go in straight, the valve stem should fit. If you do not heat the heads when you install the new guides it will sometimes get mushroomed if you hammer the shit out of it.

I have done many rebuilds on heads before when I did big-valve conversions and that has been my experience w/ installing guides.

It is not as simple as it seems.

[vugbug68]

[nsracing]

When the intakeare missing the guide bosses, the guides will walk. That is why i do not use heads that have been chopped like that. I like the 040 castings as they remain to have these intake bosses.

The 113 bosses have been chopped too-