How to install 351W (74-92) Valve Stem Seals on 351M/400 Heads.


We decide to use stock rubber seals for the 351W. They are available at most auto parts stores at a reasonable cost. Rubber seals are more forgiving IMHO and can be used on stock or oversize valve stems.
At any rate we decided to use Clevite 216-1067 positive valve seals for 351W (1974-1992). They are only .160 thick as opposed to stock umbrella seals that can be as much as .215 - .265 thick pictured below. Using the Clevite 216-1067 seals requires the valve guides to be cut to .562 OD.
To cut the valve guides to .562 OD you will either need a cutter (Approx $60) or have them machined at your local machine shop (Approx $40 to $???).
We decided to use the tool pictured below with a reamer:
The heads we had were 1978 Reman head that has both single & multiple groove valve stems. Both Intake and Exhaust valve stems were .015 over size.
Because of the oversize valves the cutter’s arbor for 11/32 stems needs to be + .015. So we had to purchase a 3/8 arbor ( $14 ) and cut it down. This tool has changeable arbors so you can cut with different size valve stems.

The machine shop near us didn’t have an arbor for their tool to fit oversize valve stems. They were going to use the 11/32 arbor. I tried this in a junk head reamed for 11/32 + .015 and discovered the wobble ( .015 too small of arbor ) made the final OD uneven with approx OD of .545. That was another reason for doing this operation ourselves.
Here is a pic of the tool and a cheap reamer.
Tool Pic 1
Tool Pic 2

Here is what the guide looks like after being cut by the tool
Cut Guide Pic

Remember to ream out the top of the guide!!

Now, we need to check and see if we also need to cut down the guide height to get clearance for the cam lift. The stock D5AE-A2A head pictured above measured .730 between the guide and the crane retainer. We planned on using a .560 lift.
With a .560 lift + .160 seal + .060 safety = .780
Thus we had to cut down the height by at least .050
This pic shows the final height
Cut Guide Final Height Pic

To install the seal, use a little oil on the seal surface that touches the stem. Oil the stem. Put on the plastic protector that came in the box. Carefully !! slide the seal on the stem over the grooves (Protected by the plastic sleeve) and press on to the newly cut guide. I usually push the seal on the guide just a bit and then grab the seal with a clean shop rag and twist while pushing. It usually goes right on. You can also purchase a tool to install the seals.

The seals are installed in the pics below
Installed Seals 1
Installed Seals 2

I am sure there are other and possibly better ways to accomplish this task. This is how we did it…


Now why would you not want to use the umbrella seals?

Well if you plan on running a cam with a lift of .530 or greater you maybe getting close to running the stock retainers into the umbrella seals especially if you have heads with replaced guides.
Here is a pic of a stock guide and a replaced guide.
Stock Guide Pic
Replaced Guide Pic

The replaced guide in the head above is definitely taller by at least .50

Here is an example of a combination that will NOT work using a .530 lift cam.
D5AE-A2A – Stock Valve guides.
Intake Single Groove
Stock Retainer – Measures .782 between Valve Guide and Retainer.
Add stock plastic umbrella seal on left in picture below that measures .265 thick. Seal on Right measures .215
Umbrella Seal Pic 1
Umbrella Seal Pic 2

So,
.782 - .265 = .517
Installing a .530 lift cam with these seals in place will just be plain ugly!!!

Using the one on the right:
.782 - .215 = .567
Most spring suppliers say add .060 for safety.
.567 - .060 = .507 safe lift.

Get the picture??? You just have to check to be sure… And check each valve!!!

Note: Rocker Arms and Coil bind are other issues that MUST be considered and are not discussed here.

Or maybe you just don’t want that puff of smoke on startup or that trail behind you. This can be caused by using the small umbrella seal on the exhaust valve. The .530 lift will uncover the stem enough to get excessive oil down the guide.
There are other types with longer sides and thin at the top.
Like this one positioned on the stem at approx .530 lift:
Red Seal Pic
It is .140 thick so there is lots of room; however note how much of the stem is uncovered at max lift!

Or you maybe you just want positive valve seals!
So why not just use the Teflon Seals?
You could and the process of instillation is essentially the same except you will most likely use a .530 cutter.
There is much information on Teflon vs Rubber seals that can be found with a little searching on the net… We are impartial as to which is better. We have used them both over the years.

Hope this helps anyone planning on converting to positive valve seals on the 400.


David

 

You should write this up as a tech paper and submit it to the webmaster. There is a whole section here with tech papers. The link is to the right or you can use the one below:
https://www.ford-trucks.com/articles/index.html

 

Eric,
Thanks I could use a new t-shirt ...
David