Push rod tubes

karlp · 10-21-2002, 07:48 AM

I think mine are too short.
I've had a chronic leaking problem at the head end of the push rod tube.
Granted I used Bus o-rings about a year ago, but they had not leaked until I switched to Mobil 1, at least not much.
When I look at them from underneath I can see the inner ridge for the o-ring groove. They are all about the same length, within ~1/16". On some of them that ridge is even with the underside of the head. If the tubes were all 3/16 or so longer, I would think they would work better. On some of them, I can see the o-ring!

I installed them with a little copper permatex aound the block end o-ring. Pushed them in with a wooden dowl until they popped in. Completely dry down there.
I used a Dow Corning vacuum grease on the head end o-rings.

Where am I going wrong?

'74 1.8, stock as far as I can tell.

Thanks, Karl

karlp · 10-21-2002, 12:48 PM

I was hoping for something like:
"Karl- The 1.7 tubes are 6 7/8 from o-ring groove to o-ring groove. The 1.8 are 7 1/16 from groove to groove. It is possible that a P.O. used 1.7's in your engine. The o-ring should sit ____ up in the head"

Don't make me go over to that other forum!!

Thanks
Karl P

Dave at Pelican Parts · Dave at Pelican Parts's Garage

All the pushrod tubes are the same length. The only differences that I know of are the early-early 1.7s, which have pushrods that are a different (smaller?) diameter on the head end.

Perhaps your engine has been "worked", and they needed to space things out further?? This can happen with long-stroke motors...

--DD

Jake Raby · 10-21-2002, 05:20 PM

Use permatex liquid thread sealant on them, and install into deburred bores, polished with steel wool.... All tubes were the same length, but a 1.7 early Porche engine had 1mm undersize pushrod tube ends on the large end.

karlp · 10-23-2002, 01:42 PM

Thanks Dave and Jake. I had a feeling..... I guess I'll get the right O-Rings and valve cover gaskets and combine with a valve adjustment.
They still look too short to me, I can't imagine this engine was "stroked"

Karl P.

Kenny Powell · 10-23-2002, 03:13 PM

I inquired of my mechanic after a engine rebuild about using synthetic oil, and was told that in air-oil cooled engines that it would promote leaks especially from push rod tubes, But I believe eventually all Porsches develope oil leaks of some type. allthough
I had a 74' 1.8 that was as dry as a bone underneath the engine not a sign of oil never leaked. just an answer to your comments about synthetic oil.