Cam Towers: Rocker shaft bore cleaning

MatthewBrum · 07-23-2008, 07:32 AM

Can I use a 600 grit ball hone to clean the bores for my rocker shaft. There is a corrosion ring where the shaft originally ended and I am concerend about leaks.

88911coupe · 07-23-2008, 07:58 AM

What about the RSR seals as added insurance for leaks? Available from our gracious host but admittedly they are a little pricey. I'm going to roll the dice and not use them on my rebuild since some say they aren't needed if the parts are in spec and I had no leaks (not THERE at least) before the rebuild.
Good Luck!

304065 · 07-23-2008, 08:57 AM

I wouldn't do that. If there is corrosion, remove it with an aviation product.

MatthewBrum · 07-23-2008, 10:45 AM

The corrosion is very hard and cleaning with a brass brush did not remove it. I am skeptical that a cleaning product will remove it. The reason I ask this is I just tore down my engine after rebuilding because 1) Rocker shaft backed out 2) About 8 rocker shafts has visible leakage. The rocker shaft and cam housing bores are in spec. My rocker arm bushings were out of spec (possibly causing excessive friction and rotating the shaft??).

I replaced the rocker arm bushings with new Bunting bearings and ordered new RSR seals. I want to do everything possible to safe guard from leaks. So I think there has to be a way to clean the bores.

My only concern is will the hone remove too much material when using on aluminum and how critical is the surface finish?

Note that I have the 18mm hone on order because the Bunting bearings require some honing to acheive the proper fit with the rocker shaft.

cgarr · cgarr's Garage

Is the "corrosion" just a stain mark or is there pitting in the alum? I have used a ball hone to just brush out the bores before without any problems but you don't want to change the bore size.

So you like those new bushings? are they not slick?

304065 · 07-23-2008, 11:22 AM

If there is so much corrosion that an aviation product like Corrosion-X can't take care of it, then it's probably not a very good wear surface. Used cam boxes aren't expensive.

MatthewBrum · 07-23-2008, 12:15 PM

The "corrosion" is a ring where the ends of the of the rocker shaft originally were. I believe it is from the steel rocker shafts rusting where they are sealed against the cam tower. It may not be corrosion but that is kinda what it looks like. If I run my fingers thru the bore I can feel that ring. It just made me want to hone the bore, especially since I am trying to make an oil tight seal.

I was just concerned about not acheiving the proper surface finish with the hone and possibly oversizing the bore. Craig, if you have passed a hone thru them in the past them I am going to try it (I will make sure I am very careful and take before and aft measurements)

So far I love the bushings, I have them pressed in and just have to drill then hone to fit. I was surprised to see that the factoru bushings were also split, considering the standard practice for rebuilding seems to be to machine the bushings from round stock.

MatthewBrum · 07-31-2008, 05:55 AM

So I purchased a 600-grit flex hone for an 18mm bore. I felt the hone was too rigid so I cut about a third of the balls off. The hone is 20mm OD and to flex 100% of the silicone balls seemed too tight. After removing one third of the balls it felt really good. I honed out my new Bunting bushing to fit and then used the hone to clean the rocker shaft bore.

I think it worked really well and my bores are still in spec. Hopefully I'll have no more leaks!

304065 · 07-31-2008, 07:42 AM

Good to hear. What method did you use to measure the rocker bore?

MatthewBrum · 07-31-2008, 07:54 AM

I used a bore gauge and micrometer. I could not reach the two middle bores in the cam towers. One thing I did notice is that my rocker bushings are not perfectly round. I think it was off a couple tenths. No big deal all within spec.

hcoles · 07-31-2008, 08:14 AM

if the rocker bushings are not round anymore - isn't it a good idea to make and put in new ones? I did that. You can get the bronze material at most any bearing house or try the newer bushing type talked about on another thread... you may not want to be a giuna(sp?) pig. I put in the RSR seals.. seemed like cheap insurance in case I messed up a bit...

MatthewBrum · 07-31-2008, 11:47 AM

These are the newer bushings talked about in other threads. They are a split bushing that are press fit into the rocker arm. Not like solid round stock (by the way, the original bushings were split). If you read above in the thread you'll see I have installed the RSR seal for insurance.

There are three reasons I can think of for the out of round condition 1) rocker bore out of round from factory 2) bearing out of round or became out of round after it was honed 3) I measured wrong.

Either way it does not matter.

hcoles · 07-31-2008, 12:00 PM

ok, I guess I'm not reading well these days..
you are using something like cgarr is testing.. TEFLON LINED, SLEEVE BUSHING ?

MatthewBrum · 07-31-2008, 01:06 PM

Those are the ones, the spec sheet has a much higher pressure and velocity than plain bronze. They seem like they will work fine......only one way to find out

hcoles · 07-31-2008, 01:13 PM

very good - if these are working for people.. could almost be worth pulling the heads and changing... a bit of labor but that's about it. Keep us posted on results...