Camshaft Oil Spray Bar Redesign and Rebuild

[Captain Obvious]

I pulled my valve cover to adjust my valves and discovered that my oil spray bar was in bad shape. The distribution blocks were bent a little and weren't sealing against the cam journals and the short tubes at front and rear were no longer parallel to the cam. Did a little searching and discovered that this is a very common problem. Clogged, leaking, bent, falling apart.

After studying the factory design, I believe it is a misapplication of materials. The steel tubes are "soldered" into the aluminum distribution blocks at one end, and are brazed to the steel center mounting bracket at the middle. Not only does solder not stick to aluminum in the first place, but the thermal expansion rates of the steel tubes is different than the aluminum head that it's bolted to.

This means that as the head grows in length when heated, the original tubes must pull out of the aluminum distribution blocks. And when the head shrinks back to room temperature length, the tubes will try to squeeze themselves back into the blocks, but cannot. This creates pressure pushing the end mounting blocks away from the center mounting point resulting in all of the stress and strain problems that occur with the original spray bar.

My answer is to redesign the bar with two major improvements:

1) Seal the tubes to the distribution block in a means compatible with the materials used. In other words, soldering steel tubes to an aluminum block is not the answer.

2) There has to be some "give" in the system somewhere to account for the differences in thermal expansion of the materials used. Since the two end mounting points must be fixed, then the CENTER mounting point has to float in order to account for expansion and contraction length of the head. This is opposite of what the factory did. I also wanted to retain the same geometry of the tube with respect to the cam which means a straight bar down the side of the cam would not work because it would be farther away from the cam than the original design.

My redesign project turned out very well and I figure that other Z owners might like to see what I did to fix the problems. Not taking anything away from the other solutions that are out there, but here's what I did:

Pulled the tubes out of the aluminum distribution blocks and cut them free from the center support bracket with a hacksaw:

Took some "billet" aluminum bar, cut off some sections, and machined them into oil distribution blocks including threaded holes where the tubes are inserted. Made some lids to seal off the oil distribution blocks and cut some gaskets to go between:

Machined some threaded brass collars for the tubes and soldered them to the ends of the tubes. Solder doesn't stick to aluminum, but it sticks fine to brass and steel:

Made some brass plugs for two ends of the short tubes and soldered them into place:

Made a new center bracket with tight slip fit holes to accept the inboard ends of the tubes. This slip fit allows the non threaded ends of the tubes to float and account for the changes in length as things change temperature:

Cut some gaskets to seal against the cam journals:

New design done and ready to be installed on the engine:

Once I was all done, I wanted to check the bar to make sure everything worked properly, so I pulled my spark plugs and coil wire and cranked the motor over (props to Blue for the idea) by shorting the starter solenoid terminal to the battery connection on the starter. Not the best pic because I'm doing the shorting with one hand and trying to work the camera with the other, but you can see streams of oil shooting out of the bar onto the cam lobes. I was surprised how far the oil shot out, even at cranking speed:

Much better than the original design. Oil doesn't leak out anywhere you don't want it to, and it shouldn't have the same mismatched thermal issues of the stock bar. And I used "billet" aluminum, so it's got to be good, right?

I've also got a bunch of other pics, so if there's a different angle that you would like to see or any questions about the project, just let me know.

[Randalla]

Nice clean job on the spray bar. Seems like it works as good as it looks. A couple of questions. Did you enlarge the holes that spay the cam? Looks like a very steady stream of oil now, which should enhance lubrication. Any thought of producing these for sale at some point?

[Captain Obvious]

Thanks! I'm very pleased with the way it turned out. I was a little apprehensive about tooting my own horn, but I'm just so durn happy with the results!

I tried to keep the geometry of the tubes the same as stock. To that end, the tubes are the same distance from the cam as stock. The tubes are the same height up the journals as stock, the angle that the holes spray is the same slightly downward direction as stock, and to your question... No, I did not enlarge the holes.

In other words, my new bar functions the way the original one was supposed to, but probably never did.

As for availability for sale, I hadn't thought about it. At the amount of time I put into the first one, there's no way anyone would want to buy them! But now that the learning curve is over and the design bugs have been worked out, the second one should take a whole lot less time, right?

Haha. Maybe I need to make a second one and see how long it takes now that I sorta know what I'm doing?

[SteveJ]

Question: How tight is the fit on the center bracket? I could see some possible issues in the future with vibration if there is any play. Sorry if you've already accounted for that, but I can see how that might have influenced the soldering of the original design.

[Reverend]

Nice!

[Captain Obvious]

Question: How tight is the fit on the center bracket? I could see some possible issues in the future with vibration if there is any play. Sorry if you've already accounted for that, but I can see how that might have influenced the soldering of the original design.

Steve, good question. The short answer is "as tight as I could make it and still allow the tubes to slide in and out".

I was concerned about vibration and play on that center mounting bracket. I thought about using some sort of flexible vibration absorbing "bushing" at that center support. Something like rubber grommets or a piece of fuel hose tubing pressed onto the tube ends that fit into a snug hole in the center bracket. However, I was worried that anything electrometric I used there would eventually fail and fall apart. And once it failed, not only would you have a very sloppy fit, but you would also have rubber chunks loose up in the valve train area.

In the end, I decided that a "no play" all metal slip fit would be the best option. I figured that if there was no play, then there could be no velocity, and hence, no energy to cause wear of the surfaces. So I drilled those holes undersized and then carefully reamed them to fit the tube ends. The intention was that there would be no lateral movement but still allow for axial growth.

I don't know how long it will last, but I can guarantee that it will last a whole lot longer than the :stupid: stock design!

[Captain Obvious]

Oh yeah. One other thing...

CHECK THE CONDITION OF YOUR CAM SPRAY BARS!!

After studying the original factory spray bar design, I believe they can be placed into one of two categories:

1) Those which have already failed, or

2) Those which are very close to failing.

CHECK THE CONDITION OF YOUR CAM SPRAY BARS!!

[EhlersRS]

Richard,

Thanks for the information and you did a great job on the redesigned spray bar. I've just begun the long process of restoration and would like to get the motor running before dismantling the car. I pulled the valve cover off and everything looks good, except the short spray tube and distribution block in the rear were bent inward. I'm wondering, could this process be done to the original oil distribution blocks? For instance, rather than making new billet distribution blocks, could threaded holes be added to the original distribution blocks and then threaded brass collars added to the tubes? Also, a new center support bracket would be needed. Considering the short spray tube in the rear is already "loose", I know this will eventually need attention.

Thanks,

Robert S.

[5thhorsemann]

Captain, first let me say beautiful job, it does my heart good to see that there are still people out there that know how to turn handels. I had to sell my Brigeport EZtrack 5 years ago for lack of shop space at the new location, and I miss it very much.

I think you could produce these things in lots of 100 or so (50 sets) in rapid fasion if you make the tooling blocks based on the prototype parts. I have been looking for a decent replacement for the spray bar since I bought the car with no luck. I would be very intrested in a "Rebuild kit" that would contain the blocks and fittings.

A slight design modification suggestion, if I may be so bold. Replace the steel slip bracket with an aluminum block that accepts the end of the tube and supports the last 1/2 to 3/4 inch of the tube. Of course you will have to machine the cam side face of the tube boar open to allow oil to spray the close lobes,(create a "C" profile as viewed from the end) That would allow you to open the tolerance at the slip conection, and the larger interface section will hold oil which will dampen the vibration and allow for smooth, stress free sliding of the floating ends durring thermal cycles.

Your thoughts.....

[Captain Obvious]

I'm wondering, could this process be done to the original oil distribution blocks? For instance, rather than making new billet distribution blocks, could threaded holes be added to the original distribution blocks and then threaded brass collars added to the tubes?

Robert, I understand completely, and I looked at the original distribution blocks for a good long time trying to decide if I could reuse them. In the end I decided that it would just be better to start fresh. To answer your question... There probably is enough meat on the original blocks to thread them, but my blocks had other issues as well. The rear block itself was bent and that was what was causing my rear tube to slant inwards (like yours). Also the mating surfaces of both blocks where they seat onto the cam tower was gouged, probably from the temperature related squirming.

Your blocks might be in better shape than mine, but with all my block's issues in mind, I cut the cord. The new from scratch blocks also allowed me to include larger seating surfaces on both sides... One side onto the tower which keeps the distribution blocks square to the tower, and the other side for the lid which ensures a much better seal than the original one.

So, in the end, I think it's possible to thread and re-use the original blocks, but you'd be missing out on some of the improvements. Is it worth the time savings? It wasn't to me.

[EhlersRS]

Richard,

Thanks for your input. I haven't taken the oil spray bar off, so I don't know the condition of the mating surfaces on the distribution blocks. The rear tube is slanted inwards because the rear block is bent inward (as you mentioned). The car was well maintained as displayed by the records that came with the car. I can only assume someone "bumped" into the bar and bent it when the valve cover was off. If I attempt to resdesign an original spray bar, I would look for a straight one to start with. Since this design flaw is well documented, it's suprising one of the vendors like MSA don't offer a reproduction unit. The only one I've seen so far was posted by Gerry "30 Ounce" and it's basically a billet rectangle tube that replaces the original and the cost is $150. I would definitely be interested in purchasing a redesigned spray bar that more closely matches the orginal design.

Robert S.

[Captain Obvious]

5thhorsemann, Thanks for the encouragement and input.

I've made three of these things to date and each one has been easier than the first, but even even after three of them, there is STILL no way anyone would want to pay what these things really cost. As I'm sure you can tell, it's all labor. A CNC shop could whip the basic parts out at quantity at a reasonable price, but like you said... I'm turning handles! Very old handles.

Thanks also for the input on the center mount. That's the one part of my design that I'm still not thrilled with. I've been struggling with a way to improve the design and I'm toying with a few ideas on that center bracket to use on the next one.

I had considered making a thicker center mount out of aluminum blocks, but I hadn't thought about extending it farther and cutting a slot for the oil holes closest to the center mount.

One of the other non-obvious things that I get with the thin center bracket is that it allows for significant misalignment of the tubes. By that, I mean, I want the distribution blocks to establish the locations of the tubes, and the center bracket is there simply to keep the cantilevered tubes from flopping around in the wind. With that long length between mounting points, I wouldn't want the tubes to be tightly constrained at both ends (axially OR radially). One end or the other.

My current thoughts on that center bracket is to leave it stock, and then let the long tubes (the two center ones) float into the distribution blocks on O-rings. The O-rings would seal while still allowing the tubes to move in and out as their lengths changed. The two short tubes would still thread in, but the longer ones would slide. I would have to put sleeves onto the tubes to block the original oil feed hole and clean up the uneven surface, but that would still be easier than turning the threaded couplers.

Bummer about the Bridgeport. That hurts.