new pushrod tube issues

[ekacpuc]

Is it possible for a pushrod to flex enough to wear through a tube? When they flex and you have that ring on the pushrod a few inches from where it goes into the case is that from the billows on the tube?

I've lost two new CB pushrod tubes.. There's a slight ring where the pushrod was rubbing somewhere and it seems about in the billow area (where both failed)...

Using HD Alum. Might try chromoly. Just using beehives so not a huge amount of spring pressure.

I got lucky and saved my scat spring loaded pushrod tubes but I don't want to loose another pushrod tube..

[QRP]

Anything is possible but the ring forming on rhe pushrod usually means it's flexing.

Some more engine specs would help us out.

What brand pushrods?
What RPM you been pulling?

[ekacpuc]

[QRP]

If there were no marks on the pushrods before start up and enough clearance from the tube to start with then my guess is the PRs are flexing.

The PR tube doesn't move so something is hitting it to cause the damage.

Maybe coil bind ???

[ekacpuc]

[QRP]

Personally I like the spring loaded PR tubes.
And yes you may need some stiffer pushrods.

[ekacpuc]

I like the spring loaded ones way more now... I've never had them leak but I thought a one piece design would be a good idea.


I'm gonna order a single standard HD alum pushrod from ACN and check for signs of flex. If its good I'll order a set. If not I'll go dual taper, I forgot about those.

Crazy.. I figured with the beehive being slightly less spring pressure (lots less without lift) than even the standard VW duals I'd be alright. After reading what CB says about their PRs the description does say up to 400lbs pressure and I have less... ACN version says 400-500. We'll see.

[txoval]

How long are your pushrods? I have a set of ACN’s HD aluminum rods I can send you. I believe mine are 277mm in length

Also have a set of Manton Chromoly rods, 281mm in length. They are slightly used, but in good condition.

[Dan Ruddock]

There is no such thing as a 3/8 aluminum pushrod that does not flex, they might not fail but they sure do flex. The answer is in link below.


https://www.thesamba.com/vw/classifieds/detail.php?id=2159797

[ekacpuc]

Dan I actually almost used your pushrods. I already had a set of CB pushrods and life throws twists..


I appreciate the offer from txoval. Waiting for work to start up again so I'm on a super tight budget. Mine are a touch long @ 11"



I'll likely contact you dan in a couple weeks when work starts up again.


Right at the end of the build my Jeep Cherokee caught on fire (lights melted, rims are bare..), unfortunately I was shuffling parts to/from work to clean up and paint so I lost quite a bit. Had to get my old ladies 2002 vw bug going and BAM the oil pump failed and took the turbo with it.


Anyways... Thanks for the answers guys.

[db69]

I had similar problem i went from the thin wall chromoly pr’s to the thick wall chrom pr’s. But I have cb650 springs. Problem went away for me. You may have to zoom in to see the damage but sounds like what you are experiencing.

[mark tucker]

rocker side play, rocker aliginement,pushrods,tube moving as many do if they are not fully seated when assembled. dieing lifter bore...many things can cause it.as well as spring pressures, camshaft,spring coilbind or too close to coil bind,keeper to guide clearance,valve float...and probably more. some springs can start getting coil bind quite far from total coil bind/stack up.rong geo or tubes that are the rong size.... find the issue and fix it. or throw $$ at it
guessing and wish for the best.. even wonkey pushrod tubes can do it....

[ekacpuc]