428 Valve Guide Seal Replacement

[The Real McCoy]

So, it's my first day of retirement and I decided to ease into replacing valve seal guides on my brothers 66 Thunderbird 428.  What could go wrong.....  He bought it a few years back and it tends to smoke after idling awhile and in general is rather tired.  History on the engine is not known other than casting dates, casting numbers, and engine build tag seem to dictate it is all original and all there.  I am doing this in frame and took the #1 exhaust valve spring off just to make sure what was involved.  It had the old umbrella valve guide seal which was very brittle but intact.  The valve stem measures (with a caliper)  about .383 above the keepers and a little less down by the top of the guide.  The valve guide O.D. is about .668.  The shop manual I have says stem diameter should be .3741 to .3748 (3/8 I guess) and also says they come in .015 (.3861 to .3868) and .030 (.4011 to .4018) Oversize.  None of these dimensions really match up with what I measured other than the .015 oversize is close, but even that does not seem right.  While looking for a source for the valve guide seals I note that Survival lists the Viton seals for either 11/32 (.3437) or 3/8 (.3750) with either .530 or .562 OD for the valve guides.  I haven't looked else where other than the local Car Quest said they would have to special order them.  I was hoping someone could give me some direction on where to locate some seals that will fit and explain why my measurements don't seem logical.  This is obviously not a performance engine and am only trying to eliminate some smoking.  You will note I am a Newbie so let me down easy.

What I would really like to do is swap a really good running Z code 390 from my Galaxie in to the Tbird and make the 428 something to be proud of and put in my Galaxie.  Big Brother seems to think original is nice which I don't disagree with, so I doubt that will happen.

Thanks for any feed back you can give me.

[My427stang]

Here you go

http://www.alexsparts.com/3-8-x-625-660-valve-seals-viton-flex-body-type-bbc-fe-ford/

I get them directly from US Seal, but Alex's packaging and web site makes it easy to find stuff.  Look at his notes, good enough to help you make sure they'll fit inside your springs

[Barry_R]

We also get the 3/8 stem seals in .650ish guide diameters.  Its ostensibly a Chrysler item..
They fit a lot of OE heads OK, but there is variability in the OE guide diameters so its a "maybe" deal.
They are pretty big in diameter, so they'll only work with single springs - won't clear doubles.

[The Real McCoy]

Thanks for both replies.  The springs are single with a damper spring on the inside, not a double spring, so I assume either suggestion would work.

I noticed no one offered a solution to why my stem and guide measurement seemed to be off so I made an assumption that was a polite way of telling me I better go check my measurements again.  I am not in my own shop and only had access to a caliper I had never used before and found that it had not been "zeroed"....., once that was done I am very close to 3/8.  Retirement just got a little better.

Barry, are those seals shown on your site or do I need to contact you?  I only seen the one offering that I mentioned on my original post for the .530 to .562 OD.

[Joe-JDC]

I will let you down easy by suggesting that if there is that much variation in the stem-to-guide clearances, you need to remove the heads and have guides refurbished.  Have them cut the guide bosses for PC seals of whatever diameter seal you wish to use, and get a fresh valve job, and new springs/seals.  Your valves may be reusable, but a valve job will do wonders for making the engine run better and not smoke.  Just changing the seals will not stop the smoking if you don't address the guide clearance issue.  Joe-JDC