I'm working on a prototype set of stainless pushrod tubes.
Advantages:
Precision machined heavy duty ends for greatly improved o-ring retention
Stop using paste sealants to keep oil from leaking at pr tube seals
Lower heat transfer than mild steel
Slightly smaller (3/4" od) tubes for better stub pipe clearance without need to dimple the pr tubes
Available in custom lengths, longer or shorter
Never rust out - never need replacement

I'm also considering using separate oil return hoses from both rocker boxes so that the pr tubes no longer have to handle that function.
That would allow the smallest possible tubes without the p-rods rubbing.
Machining the ends would be simplified, thereby lowering the cost of production.


Your thoughts?

Edit 09/12/14: These are in Production. Go to Post #26 for add'l information.

I wish you would have come out with these back when I still had my -4.....

I love the idea though. When I get another 914 with a -4, I'll buy a set.

God yes!

I would be interested; especially if you could eliminate those wire thingies that are a PITA whenever I adjust the valves. I can't get my finger past them to feel is the stainless pushrod will spin (zero lash cold but the pushrod should spin is what I'm told to aim for).

I'm still working on that part.

I'd be interested in that!

Any estimate of cost? I'm interested.

I haven't done any pricing yet.
I made CAD drawings yesterday.
My machinist started turning chips from a piece of round bar this afternoon.
I got lucky and found a piece of the exact tubing I had in mind, already in my shop.
We'll have a full set made up for testing by next week sometime.

Sound like a go for me. Appx production time ?

I would be up for at least two sets if priced fair.

Interesting

i would go for two sets, depending on price of coarse.

Sounds good!

Add something to ease PR tube removal. Grabbing them with pliers is effective, but damaging.

What an excellent idea! Thanks.
We're already on it. And the feature will make installation easier as well, since the o-rings will be a little tighter.

Now I just have to figure out how to replace the wire bales with something more convenient.

I've always thought something welded to the valve cover would do the trick. I hate setting my valve lash and spinning the pushrods (for a loose "0") with the wired bales...

Then again, a simple clamp device at the head side of the pushrod tube would also keep it from sliding out.

Here's the first crude prototype.
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Installed in our exhaust assembly fixture.
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The flange is there for easier removal.
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I'm not sure the flange is necessary. This thing is a lot sturdier than the stock pieces.
With just a little motor oil on the o-rings the tube presses in without much difficulty, and the shoulder on the large end may be exposed enough to push against for removal.

There's plenty of compression on the o-ring but the correctly shaped groove does an excellent job of supporting it.
I've pushed this tube in and out many times already, without being all that careful, and no sign of damage to the o-rings.

I was thinking a snap ring on the back side of the head might be suitable for retention, but there are too many engine variations possible. A small change in engine dimension might make that feature unusable.
Another idea was safety wire from the flange to the case but there's no good place on the crankcase for all the wires.
I also considered some kind of bar screwed to the case which overlaps the edge of all 4 holes at the small end of the tubes.
The wire bales will still work with these tubes.
Not sure what's best yet. Trying to keep it simple.

We're building a 2.5L track engine right now and the customer doesn't want any oil leaks,
so I've ordered material to make a pilot run.

Rather than make them all 3/4" od, part of each set will be 7/8" od.
The smaller tubes clear the exhaust stubs better and the larger tubes flow more oil.
My materials cost is within $0.05 per tube assembly between the two sizes so this doesn't have any effect on final price.

They will be initially priced at $240 per set of 8.
Custom lengths will be available for $20 more.

Click to view attachment

Great work! Those look really nice and will be a great upgrade for anyone.

Good evening Chris,

Is that $20 additional for the set, or each? BTW they look very nice.

Thanks

David

for the set

They won't be on the shelf, but as long as I keep some of the pieces in stock, unassembled, I can build a custom set without too much trouble.

"Upgrade". There's that pesky word again. I like the idea, and I like the product and the first rate execution (like everything else Chris does), but I would hesitate to call it an "upgrade". Improvement, maybe. Personally, I have had limited P/R tube leaking issues over the last 41 years of servicing 914s on a weekly, if not daily, basis. In the case of headers as shown, I'm sure the diameter is probably an improvement, unless you figure in the OE tubes that are already necked down to about 3/4". As for rust, maybe I'm spoiled here in California, but I've yet to see a P/R tube rusted through or even weakened.


The Cap'n

I think the section where the seal rides would certainly be considered an upgrade. The stamped and formed tubes seem very inconsistent in the old tubes.

Nice job Chris

The later oe style is .790 dia., so a little further clearance added with the .75 SS tubes.
Since we make some rather large exhaust stub pipes for performance applications, the smallest diameter PR tube is a significant benefit.

We've actually had to replace tubes which were leaking thru pinholes from rust.

The biggest improvement, as Bartlett914 noted, is the proper o-ring support.
It takes more effort to install our tubes because the o-ring is compressed more, but the sides of the groove are tall enough that the o-ring won't tear.

I would buy a set.....

i like the idea, and can see the benefit. unfortunately i just put in brand new ones, and i installed them per advice from the crusty one, just use a bit of motor oil on the viton seals to give some lube when installing them. installation seemed to go good, but if i have leaking issues i might consider it. and when i do my rebuild, this will be on the short list of things to do.

These are now available.
For details see my Whats New at Tangerine Racing Products thread in the Member Vendors section

Click to view attachment