all original like mom Harley made it

 

Have a look at valve guide seals on this website, he lists all the dimensions for each seal. Look at big lock Chevy seals, 3/8 valve stem.
https://www.alexsparts.com/bb-chevy-...1v-eight-each/

 

great website, all the correct dimensions are indicated
​​​​​​​

The websites in Italy are not so accurate.....James Valve Guide Seal Kit Harley Davidson Big Twin 1948 – 2004not very accurate

 

BIG BLOCK CHEVY, 3/8" X .615"/.625", set of sixteen- eight each

This set fits stock guide diameters of .615" on the exhaust and .625" on the intake.

you use a single size or different sizes on exhaust and intake? with original valve guides

 

The valve guide O.D. on my heads is the same for intake and exhaust so I use the same seal on both. The Alex guy has seals listed by stem size, 3/8.
https://www.alexsparts.com/valve-seals-3-8/
And he lists a pair for Shovelheads, although the guide size of the seals is not .625, Have you measured the O.D. of the guides in your heads?
https://www.alexsparts.com/viton-val...airs-vss-266v/

 

Alez's parts tells me one month for shipping to Italy.
I have found shops in Europe with faster shipping.

I found COMETIC Valve Stem Seal C9424-1 which should be the one you used in fact it is for 1981 models.
COMETIC Valve Stem Seal C9998-1 should be for 1980.The I.D.
it should always be 0.625", I don't know what changes, maybe Overall Height?

Can someone confirm this for me?

I wrote to COMETIC to know the difference between Valve Stem Seal C9424-1 and C9998-1, I'm waiting for the reply.

I have the lower collars available without the first step and also the original and complete ones.
With COMETIC Valve Stem Seal which collars should I fit?

 

Dennis Kirk gives the dimensions of the C9998-1 seal at the bottom of the pic.
https://www.denniskirk.com/cometic/v...prd/266246.sku

 

Mi piace questo negozio, è stato il primo che ho visitato, mi ha fatto capire che il C9998-1 è quello giusto per me.

Purtroppo ha solo 1 disponibile:matto:

 

I like this shop, it was the first one I visited, it made me realize that the C9998-1 is the right one for me.

Unfortunately it only has 1 available

 

BBC today use different diameter stems 7 MM - 5/16 titanium and or cresidium material usually only 11/32 and normal stock 3/8 in a variety or materials over the years like was said the guide has changed in its out side diameter a certati machine is used to set the guide at the correct corrected angles of the seat to set the seal location in its center < this is money to do for a street machine -

the cometic seal is the one to use just use a veneer to check the travel - bottom of the top retainer to the top of the seal installed ( your cam lift is the number ) you must have at least .050 plus your cam lift or the oil will hyd lock on top of the seal and pump oil into the valve guide