7 replies to this topic

[sr2]

Hi Guys, some sagely advice from the brains trust please.

 

Standard 186 with stage 2 Yella Terra head and a Weber DCD. This is my trusty backup motor that lives in the car while I’ve got my performance motor in pieces on the work bench.

I was pulling the motor to replace the rear crank seal (as you do!) when I noticed oil in the inlet ports. I’m guessing the oil could only have come through the valve seals. The PCV valve is connected to the air filter (which is oil free).

 

The valve guides are in good condition and I had assembled the head with standard square section “O ring” valve seals from a kit I had lying around.

My question is; have I made the right diagnosis and if so are there any modern type seals available that would fit?   

 

Thanks, Simon.

 

 

 

Attached Files

•  Head.jpg   70.06K   4 downloads

[76lxhatch]

If its only a small amount that seems very likely. It can be easy to accidentally damage the o-rings when installing springs, or sometimes they are just crap and will break and disappear.

 

If there's enough meat in the valve guide you can update the seals with a little machining; you can get cutters that locate in the valve guide and work pretty well so can be done on a drill press or potentially even by hand. This is a V8 head that has spring seats done also but you can do just the seal:

 

https://www.summitra...-material/steel

[sr2]

Thanks for that, just the info I need. I've ordering a Comp Cams .530 inch Valve guide cutter with a 11/32 Arbour - wish me luck!               

 

 https://www.amazon.c...r/dp/B00062YEFE

[axistr]

I take the easy road and just fit umbrella seals, more reliable. The square seals can be a bit hit and miss. If you have a hydraulic lifter that bleeds off excessive oil and delivers the oil in a way that floods the valve retainer, then this will cause the same problem and can be on one cylinder only. The seals you currently have will not help in this situation.     

[Bruiser]

A while back I wanted to know wether or not going back to 1.5 rockers on the exhaust could be any better than the full 1.6 roller set,
so fitted stocko stamped ones for a try.
Started getting a good puff of blue smoke on startup, thought I’d buggered it somehow
Asked an engine builder, and he nodded and says that happens.
Didn’t believe him till I put roller rockers back on and it went away.
Still can’t see how extra oil would puddle on top of the valve stem and run down,
But maybe the Viton positive seals don’t play nice with stamped rockers?
The 1.5s didn’t improve anything in my case, by the way

[sr2]

I take the easy road and just fit umbrella seals, more reliable. The square seals can be a bit hit and miss. If you have a hydraulic lifter that bleeds off excessive oil and delivers the oil in a way that floods the valve retainer, then this will cause the same problem and can be on one cylinder only. The seals you currently have will not help in this situation.     

Hi, I'm not sure what you mean by umbrella seals. Do you have to machine the head to fit them?

[axistr]

Umbrella seals are fitted to the valve stem. They look like an open umbrella hence the name. Any oil that run down the valve stem is guided off. They still allow a very small amount of oil mist to give the valve guides lubrication. During my time working at an engine shop, we used to throw all the original stem seals and only fitted umbrella seals. Never had any problems. A few OE engine manufactures during the late seventies moved to Umbrella seals and were very common by the mid eighties.

 

[sr2]

Thanks for all the advice guys. This site has to be be the best informed (with zero keyboard warrior B/S) Holden MB on the internet. 

 

If you're interested a link to my latest/earliest Holden powered build. 

 

https://oldschool.co...”-build-thread/