Installing oversized valve guides

[Theichelberger]

Here's a question for all of you machinist out there. Have any of y'all installed a valve guide with a +.002 OD? I was also wondering what the process was, do you bore out the original hole for the guide or do you use a reamer? Any information is useful!

[RCP Phx]

We always just use the size needed for any guide bore that a std size won't go in firmly.

[modok]

The guide should be .0010-.0015" bigger than the hole

Here is a good trivia question...

what was the original size hole?

[Theichelberger]

On one head all four valve guide holes were .4745 inches with the valve guide it's self being .475 inches. Now the other head is a different story, it had 3 valve guide holes measuring at .4755 inches with the valve guide being .476 inches and the last valve guide holes in that same head I measured the valve guide hole at .4775 inches with the valve guide being .477 inches. That last valve guide I could almost pull it out with my fingers. And I triple checked it with 3 different micrometers and they all read the exact same

[modok]

.475 seems to be the original size.
.476 is what PEP's standard size is
I expect a ".003 over" is .478

But you won't know till you get them. I'd get a few big ones just in case in addition to what sizes you think you need.

You can put them between centers and "polish" them to be smaller or turn to be a lot smaller as needed.
A fresh polish will make the lube work better.
Also helps to relieve the press on the first third of the intake guide, that area hangs in the port anyway so no reason for it to have press, instead relieve that and let it pilot itself.

Using more interference than needed you will end up enlarging the hole, tho it's also just unavoidable to a small degree, as engineers sometimes say "aluminum has no lower creep limit".

[Theichelberger]

Ahhhhh I see, I'm having some trouble at the moment finding a .476 valve guide. I have access to a lathe, do you it would be okay to order a .478 valve guide and the turn it down to .476?

[modok]

SURE!
One way I like to do that is chuck up a piece of material of some size, and turn a nub on the end down to exactly the ID of the guide, and stick it on there, then support the other end with a live center.

[Theichelberger]

FANTASTIC!
I'll make a post later down the line showing the end result

[RWK]

If you have access to lathe make your own to fit.
I have a .476 reamer and have reamed the guide holes to clean them up, then make my own guides, .002 oversize of the finished hole. I turn the guides to the plus .002 size or whatever the hole turns out, drill the ID (N size drill) under size press guide in, then ream and hone the ID to finish size.
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73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530

[Chewpapa]

I have first over guides if you are looking still. I think I have all the way up to +.010. OR if you're set on machine the o.d. I have pilots and a drive dog I could maybe ship to you.