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PostPosted: Fri May 11, 2018 9:10 pm 
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My thinking (unencumbered by knowledge) is that the much denser oil would have more inertia and essentially make the not very dense wood float, giving opposite of a check valve effect.

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PostPosted: Sat May 12, 2018 7:16 am 
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James Davies wrote:
If the wood is moving back and forth inside the pushrod, that means the ends of the wood are worn off and are not as originally manufactured. They should fit tight and have a notch in the center so that the hole at either end of the pushrod does not get plugged. See Mike Ruddy's photo above.

I agree with James. Forget the pumping action.

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PostPosted: Sat May 12, 2018 9:00 am 
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Think about valve train movement a moment. The pushrods are stationary for 1.5 rotations of the crank, remember intake, compression, power, exhaust? The cam actuates the pushrod only on it's intended cycle then it's at rest until called upon again, therefore I think the pumping idea doesn't work. Also, liquid is not compressible so once the pushrod is full you will get the same flow out the tip regardless of pushrod inner diameter, the hole in the tip determines the flow. It looks to me that the less reciprocating weight holds the most logical idea for the wood inserts ... my .02$


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PostPosted: Sat May 12, 2018 11:12 am 
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After all the messages listed, my decision for the wood inserts being a "filler" or "check valves" aren't necessary and were eliminated in later pushrods as long as the oil pump supplies the proper output to the rest of the engine.

Yes, 4-cam engines have wood fillers in the camshafts,but they don't bounce back & forth to block any ports feeding the lobes or bearings.


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PostPosted: Tue May 15, 2018 12:25 pm 
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Over the past couple of months, Mike Horton and I have torn down the engine in my '58 A cab to replace the crankshaft. To my knowledge,this is the first time it has been apart since Ray Litz of Competition Engineering rebuilt it in 1975.
One of the things we noticed was that a few of the pushrods had developed a raised "shoulder" on the contacting surface which seemed to be the result of wear against the cups and were the same size as the oil holes.
These pushrods seem to have the wood inserts, so we wonder if the above mentioned deforming of the ends of the inserts might be blocking the flow of oil through the end of those pushrods during the operation of the engine, resulting in wear. Any opinions would be appreciated on whether or not we should remove the inserts.

Thanks,
Spike & Mike

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PostPosted: Tue May 15, 2018 1:11 pm 
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SPIKE JONES wrote:
These pushrods seem to have the wood inserts, so we wonder if the above mentioned deforming of the ends of the inserts might be blocking the flow of oil through the end of those pushrods during the operation of the engine, resulting in wear. Any opinions would be appreciated on whether or not we should remove the inserts.
Thanks,
Spike & Mike


Ken Daugherty (RIP) once posted a photo of a worn wood 'filler', and the end was worn to just the oil hole diameter, effectively plugging any oil flow through that push rod, or at least 99+% of it.

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PostPosted: Tue May 15, 2018 2:03 pm 
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My early, & late '60 Normal engines, the early one wiitgh the small oil pump, the late with the large pump, both had these wood inserts, one can feel the inserts moving inside. My AL S90 pushrods, did not feel like there were inserts inside, nor in the C AL short centered, long tapered steel version, nor, the 912 sets, steel, and hollow. I never had my '57 T1 AL pieces out ?

I agree with Ron's discussion with Ken, and Dick on this one. By now, the '58 N engine, converted to S, by Ray in '75, with the post '61 cast iron Mahle 82.5mm Super cylinders, had little actual wear, except on those ball ends on the pushrods, and only on one end of about 3 or 4 each. Sorry, we caught it on reassembly, not disassembly. My Friend Spike is a custom jeweler, and artfully filed the offending raised shoulders off, and those ball ends, are hardened. I suspect the cause was the loss of the oil film lube, which has historically prevented such wear, which I've not seen before with any other pushrod design. This is an iteresting, and timely discussion.

Back in '68, when I disassembled the then 31,000 mile original late '60 N engine, for conversion to an S, one of the steel pushrod ends, had come loose. As I recall, I slightly ovalled the steel tube, and tapped the end back on, and...had this "to remove, or not to remove", discussion with my then 23 yo self...

My 56 yo S90 engine, had cast iron Mahle cylinders for a C, paired with the original AL pushrods, and about 7 ea. .25mm base shims, thus, it is completely apart, for inspection.

...Oh, Ron's " jewelry", the Pre-Mat billet sump plate, with the drain plug re-engineered, to have a true "low place drain", and his spring loaded pushrod tubes, are true beauty in metal. It's sad, they are unseen, but as I have bought both those pieces, as well, they get my endorsement! I have his centered full flow system too, as I will run a stock muffler,

For Spike & Mike

(We tell our Wives we're working hard. Wasn't it Ken Purdy, an automotive writer who was quoted in a 356B sales brochure for Porsche, who said "just don't tell everyone at the office, it's Fun driving to work..." or something like that...)

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PostPosted: Wed May 16, 2018 3:46 pm 
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Something often overlooked with the focus on later production practice: Porsche used aluminum cylinders with aluminum pushrods from Oct 1953 through at least late 1956 (mid-1957?) on all their pushrod engines, as all these had aluminum cylinders. I believe none of these aluminum pushrods had wood in them. All these engines used the standard VW oil pump of the time. And of course the aluminum-walled pushrods had much thicker walls compared to the steel ones that came before and after, so there was much less empty volume inside the pushrod. These aluminum alloy pushrods were very similar to the ones used on the T2 Supers and the Super 90 later on.

If the purpose of the wood was noise reduction, did Porsche decide they wanted to make noisy cars during this (Oct 1953 through 1957) period? Did they not care about the noise on Super 90 cars? Noise reduction was actually a constant concern in the early 1950s on these cars, if one reads the internal memos reproduced in Conradt's book.

I'll add that the earliest steel pushrods used in the early 1950s had the wood inside them, so when they switched to aluminum pushrods in Oct 1953 on all engines, it was moving from ones with wood to ones without wood.

Anyway, not being a mechanic, just my thoughts.


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PostPosted: Wed May 16, 2018 4:17 pm 
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Mike Horton wrote:
Wasn't it Ken Purdy, an automotive writer who was quoted in a 356B sales brochure for Porsche, who said "just don't tell everyone at the office, it's Fun driving to work..." or something like that...)
Don't forget what he also said about the 356..."the only thing the Porsche shares with other cars is the road".

The one book that Conradt wrote has very interesting memos from the engineering department that cover all sorts of discussion about components that were changed for various reasons. Management often asked "why" and engineering had to give "reasons". They always had reasons for any change. I don't recall one about pushrods but I bet one exists. I do remember management being concerned about the cars gaining weight and how the engineers explained iron cylinders and heavy new carburetors.

The design of pushrods is very complex, at least more complex than it would seem. Aluminum pushrods flex and lose power due to sloppy valve control but are often used for the expansion rate when aluminum cylinders are used. I use LN aluminum cylinders but very robust tapered moly steel pushrods on my race engines. Those engines have seen 9000rpm numerous times without any problems. I wouldn't even attempt that with aluminum pushrods. My race engine valve clearance cold is just greater than zero, the pushrod barely spins, so that the running clearance is not excessive.

As far as wood.... if it ain't used in NASCAR or NHRA it's a dumb idea.

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PostPosted: Wed May 16, 2018 9:11 pm 
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James Davies wrote:
if one reads the internal memos reproduced in Conradt's book.
Sorry James! Apparently I forgot what I read in your post. Now that is a really really bad memory! Anyway, I wish there was a big book detailing all of those internal memos. I find them very interesting. How many times have you asked yourself what the engineers were thinking? It's nice to have some insight into their thoughts.

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PostPosted: Thu May 17, 2018 3:31 am 
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C.J., yes, I have pondered the judgment in those German engineering minds. That justification for the heavier iron cylinders, and heavy Zenith carbs, was one of the best changes they made for long term use, and dependability. The T2 Normals, T6 Supers, and the straight C engines, and their track record are proof of that wise combination.

Spike's '58 Ray Litz, CE built engine, was a true "engine archeology" trip in a great Cab street engine build, by a master. The Intake valves, guides, retainers and keepers, had been updated to the stem seal versions, factory Mahle stock bore cast iron super P/C, steel tappets, stock muffler, and thermostat removal, astute details, were well done. The distributor was replaced with a restored BR 18 unit. I could see the mill machine marks, to return the case bores to standard, and grind marks on the balanced "00", rod set upgrade, and the rod balance confirmed. We replaced the crank, with a 31,000 mile late '60 Normal, new rod & main bearings, clearances confirmed, reset the end clearance at .005", and simply refreshed the low wear, and obvious low use engine. The engine is getting the cosmetics refreshed, and the wood pushrod fillers dealt with, and honing our 616 skills, and most important, renewing an old 356 Friendship, and a Great experience. I can hardly wait to hear it run. Oh, Spike found a local drive train shop, which still relined the 180mm clutch plate, so I had 2 200mm cores done by the same Viet Nam Veteran shop owner, a good find.

Next, is rectifying the errors in my T6 S90, which I stored in '85... just don't tell our Wives we're having a great time, we only refer to it as work...

For Spike & Mike, an update. (This Cab is almost a clone of Franny's)

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