Prepping Knuck Heads for Big Valves

I intended to post something entirely different, but at the moment, Blogger is not letting me cut and paste, so rather than rewriting something I have saved in another program, I will do something fresh.

Some time ago I started a series on installing bigger intake valves in a Knuckle head. This will be the second part of that series. When I left off, I had finished installing new exhaust seats. The seats from Rowe machine nicely (something that cannot be said for the 60+ year work hardened original seats. This also allows you to set the stem protrusion of the new valves, avoiding mis-matched depths.

If the intake nipples were removed for replacement (and in most cases they should be), now is the time to re-install them. I like to use JB Weld on the threads of the nipples, along with a stock type rivet. The epoxy is particularly important when porting, since some of the inner threads inevitably will be ground away. Here's a tip: from here on out, keep a set of used intake nuts screwed on to the nipples to protect those nice new threads.

Now that the new seats and intake nipples are installed, it is time for porting work, if you plan to do so. Doing this before new guides are installed allows you to do the best possible job. Disregarding the area just below the seat and the short side radius, the remainder of both ports should be shaped and finished as per the final product. I like a 50 grit on the intake, and a polished exhaust. However if the exhaust port is to get a thermal barrier coating, there is no point in spending extra time doing a fine polish.

With the majority of the porting work done, it is time to paint the heads. This needs to happen before guide installation, since the spring cups are held in by the valve guides. For a stock look, I use a semi-gloss black, and bake it on at about 200 degrees. Many of the hi temp paints available need this heat cycle to enable them to stand up to standard parts wash fluid. Nothing worse than keeping the new paint looking good through the whole process, only to have it get sticky and wipe off during the final wash prior to final assembly.

While the paint is drying on the heads, it is a good time to make sure the spring cups are ready to go. Often you will find a small crack just below the return tube. Be sure to weld these before going any further. Next, all of the gasket surfaces on the cups should be attended to. I use several purpose built forms along with a small hammer to return them to their original shapes. Don't forget to re-flatten the bottom portion that the guide will seal against. Once the cups are all in shape, they can be Parkerized if you are going for a stock look.

Guide installation, cutting the seats, and final porting work will be covered in the next installment.

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.