Knuckle Seat Install

As I mentioned previously, one of the items I would like to cover on my blog this year is installation of big intake valves in a set of Knuckle heads. If you are dealing with stock heads, it is quite likely that you will find good reason to give the exhaust seat inserts attention also. Sometimes the stock exhaust seat is simply sunk too deeply from multiple valve jobs. Often the seat will be pitted so badly as to be unusable. But even if those two items are not an issue, you may want to consider replacing them because they have become extremely "work hardened" from 60+ years of use. While this extreme hardness is not an issue while in service, it makes the seats very hard to work with. Modern seat cutting equipment will invariably chatter, and stone type seat grinders will require lots of time and constant dressing if there are any misalignment issues to be corrected.

So, as part one of this series on installing bigger intake valves in a Knuckle, we will look at replacing the exhaust seats, though if you are planning to use stock size intakes, the same procedure can be used for those seats.

ABOVE: Removing the old seat inserts is pretty simple on a Knuck. With the guide removed, a slim punch will fit though the guide hole and can be angled to catch the back side of the insert. A few taps and your heads should now look like this. (both intake and exhaust seats removed)

ABOVE: Once the seat recess has been cleaned, carefully measure the bore in multiple places to determine how much press fit the new insert will have. You want a minimum of .004" interference, though I prefer .005"-.006".

ABOVE: A home made tool will work for seat installation. This one is made using an old valve with a collar welded just below the face to keep the new insert centered, and a piece of scrap for a handle. Shown here with new insert not seated on collar.

ABOVE: Tool with new seat insert seated on collar. A "dummy" guide will have to be installed temporarily in head to keep everything aligned so that the seat goes in straight. You can always use your old guide (you didn't throw it away did you?), sanded down a bit so it is only about a half thousandth press in the head.

ABOVE: Prior to actual installation, put the head in your oven at 500 degrees (that is the head in your oven, not your head in the oven) and the seat insert in your freezer. If the head is clean, it should not stink up the kitchen, but if it isn't and your wife catches you, you may want to go back to putting your head in the oven. Unlike with an aluminum head, even with a heated head and frozen guide, you will have to use moderate blows with a hammer to install the seats.

ABOVE: Here is the head with new exhaust seat insert installed. Now you can remove the dummy guide and proceed with the valve job, which will be covered in a future post.

One last thing, if you are having trouble finding suitable valve seat inserts, you can follow the link at the bottom of the left hand column of this blog to my eBay store. I will generally have what you need in stock.