You're Fired!

I decided to pulled the spark plugs to make it easier to rotate the crankshaft while I was replacing the push rod guide plates. It's a good thing I did, mainly because one of them was loose.

Cylinder number 4 couldn't have been firing too well with some of the exhaust gases blowing out around the plug. The entire plug is covered with soot except the part covered by the boot. The rest of the plugs look pretty good with a nice healthy tan color, although 1 and 3 are kinda light. A few of them have fresh oil around the base and threads which means the valve cover gaskets are leaking a little so I ordered new gaskets along with new plugs.

My new push rod guide plates arrived; they're the correct 5/16" instead of the the 3/8" somebody else installed. You can read my previous post concerning the push rod guides here. I set one on top of an existing one to check the fit (yes it's upside down).

Looks much better. If I centered one rocker over the valve stem the other rocker aligned almost perfectly, something that couldn't happen with the bigger guides. Here's what the oversized guides look like:

It's a bit of work to replace the 8 guide plates, mainly because you have to adjust the rocker arms, which in turn requires you to rotate the crankshaft until each cylinder is at top-dead-center. The harmonic balancer has a marking for TDC but that only works for cylinder #1 (and also #6). I needed markings for the other six cylinders.

The firing order for the Ford 289 Windsor is 1-5-4-2-6-3-7-8. Being a four-stroke engine each cylinder fires once for every two revolutions of the crankshaft. With all eight cylinders firing once every 720 degrees of revolution you get a single cylinder firing every 90 degrees. So I needed markings on the balancer for 90, 180, and 270, measured from TDC. The balancer has a diameter of 6.375" (ok, I looked it up) giving a circumference of almost exactly 20". Wow, that makes things easy. All I needed were marks every 5" around the balancer. I even labeled them so I could be certain I had the right cylinder.

Just turning the crankshaft to TDC for cylinder #1 doesn't mean it's in the correct position to adjust the rocker arms. It could be 360 degrees off. To ensure both the intake and exhaust valves are closed the distributor rotor needs to be pointing at the #1 spark plug wire.

Since replacing the guide plates was going to be tedious I set up a little routine so I wouldn't overlook anything.

1. Start at TDC for cylinder #1.

2. Remove the rocker arm retaining nuts and then lift off the rocker arm for the two valves. I set the left rocker arm on the left side of my parts tray and the right one on the right side so they would go back on the original side.

3. Use a breaker bar to remove the rocker arm studs. They must have been installed with thread locker instead of thread sealant. I kept the left stud on the left...

4. Clean the threads on the studs where they go into the head.

5. Remove the old guide plate.

6. Clean the threads in the head (as best as I could).

7. Place the new guide plate in position.

8. Coat the stud threads with Teflon (PTFE) paste thread sealant before hand tightening each stud. When I removed the studs most of them came out with dry threads but a few were wet. You can see in the picture that these studs do indeed screw into a water jacket so thread sealant, not thread locker, is required.

9. Torque the studs to 60-70 ft.lbs. Before tightening I pulled down on the guide so it wouldn't be cocked to one side since there is some play.

10. Oil the push rod end, stud threads, and valve stems in case you wiped them clean.

11. Install the respective rocker arms and retaining nuts.

12. Adjust each rocker arm. Tighten the retaining nut until the rocker arm becomes snug on the push rod. Then add 1/2 to 3/4 of a turn more to set the pre-load on the lifter.

13. Squirt some oil on both ends of both rocker arms as down around the pivot areas.

14. Rotate the crankshaft clockwise 90 degrees and repeat the steps for the next cylinder in the firing order.

The rocker arms on the right have the new plate installed and align with the valves nicely. The two on the left still have the wrong guides. Yikes.

While I was doing all this work I also wanted to check the rocker arm geometry to make sure the push rods were the correct length. This is easily done by coloring the top of a valve stem with a marker, assembling the rocker arm, and cranking the engine a few turns to check were the rocker touches the valve stem.

Above is a closeup off the #1 exhaust valve stem. After I adjusted all of the rocker arms I turned the crankshaft another 90 degrees to put the #1 cylinder back at TDC. When I had first adjusted #1 I had colored the valve stem tip with a marker before assembly. You can just barely see the horizontal line where the rocker arm contacted the valve stem while I was hand-cranking the engine through 2 revolutions. It's not super important that the wear pattern is centered on the valve stem as long as it's close. What is important is that the thickness of the line is as small as possible, meaning the minimum amount of friction. If the push rods weren't the correct length the wear pattern would have been wider.

Miss Alignment of the Roller Rockers

They say a picture is worth a thousand words...

At first glance everything looks good; a 6B23 (23 Feb 1966) date casting, Comp Cams Magnum Roller Rocker Arms, Erson Cams Guide Plates, all nice and clean. Then I see the poor wear patterns on the roller tips, and how the leftmost rocker is slipping off the center of the valve stem. 

I had a similar problem with my stock 289 heads back in high school. The factory mills a rectangular slot in the head to guide the pushrod and thus keep the rocker arm aligned with the valve stem. The problem with that is if things don't line up perfectly then there's no adjustment. If the rocker isn't centered over the valve stem then it wants to slip off the side, putting unwanted side forces on the pushrod and rocker fulcrum. The solution it to open up the factory pushrod guide which is milled in the head and install aftermarket guide plates that mount under the rocker arm studs. This, unfortunately, requires removing the head so the factory press-in rocker arm mounting studs can be pulled out. Then the heads are drilled and tapped for screw-in studs.

Fortunately for me this has already been done, and yet, my rockers are still crooked. Normally, you would loosen the rocker arm studs, slide the guide plates around until the rockers are aligned, and then tighten the studs. But in my case I can actually push the rockers into alignment by hand since there is way too much side play. The roller tip on the rocker can shift side-to-side by around 3/16". Looking at the 4th rocker arm above, the pushrod is nearly touching the left side of the guide, while the 3rd rocker has a large gap between the pushrod and the guide plate.

I twisted a rocker arm to push the pushrod to one side of the guide plate so I could measure the clearance on the other side.

I didn't have a feeler gauge big enough so I had to stack 4 together to fill the gap. Its hard to find an exact figure on what the clearance should be but 0.012" seems like a safe minimum. In my case I have (at least) 0.078" which is 0.066" too much. I measured the width of the guide plate and it looks to be 0.391" which just happens to be 0.016" wider than a 3/8" pushrod, but way too wide for my stock size 5/16" pushrods. So I need to buy either fatter pushrods or skinnier guide plates. Guide plates it is.

I am concerned that the correct size guide plates may not entirely solved my rocker alignment issues. Yes, they are adjustable, but the slots are still a fixed distance apart so both rockers get adjusted the same amount. The intake rocker could end up perfectly aligned while the exhaust is off by a little. They do make 2-piece guide plates that let you align each rocker independently, but they need to be welded together to maintain their alignment.

I'll try the 5/16" one-piece guide plates first before I resort to the bikini (two-piece, get it?)

UPDATE: This problem has been corrected in my post You're Fired!