Brian Eldred Posted July 24, 2019 Report Share Posted July 24, 2019 Hello gurus, Having recently had my cylinder head off (twice - long story), I can't seem to stop oil leaking from the rocker cover hold-down nuts. It had c.25mm cup washers with some sort of rubber washer beneath, but these had deteriorated so I replaced them with nitrile washers. Then thicker nitrile washers, with a fibre washer above the cup washer and a plain washer above that. Still the things leak, unless I tighten them down so tight that the rocker cover distorts even more than it already is (I've tried flattening it a bit with a hammer) If I revert to the standard fibre and plain washer it spews out oil like the Torrey Canyon. The cover is vented to a catch tank so I can't see there would be too much pressure. Any ideas or tips? I need to sort this before taking the car to France next week. Or buy an alloy cover, maybe? Quote Link to post Share on other sites
RogerH Posted July 24, 2019 Report Share Posted July 24, 2019 Hi Brian, as you have tried all the usual ways with no success why not try a different approach. Why not use silicon gasket goo https://www.moss-europe.co.uk/gasket-maker-silicone-sealant-black-200ml-ggl1009.html Clean the stud and all the area, fill the cavity under the cupped washer and screw down lightly. Do NOT distort the cover Roger Quote Link to post Share on other sites
Drewmotty Posted July 24, 2019 Report Share Posted July 24, 2019 Do you by any chance have an external rocker feed line; they can flood the cover if the rocker assembly is worn. Quote Link to post Share on other sites
Brian Eldred Posted July 24, 2019 Author Report Share Posted July 24, 2019 Andrew, no external feed! Roger, yes i have some silicone gasket stuff so I'll give that a try. Btw new cam is performing nicely (apart from lumpy tickover that you experienced I remember). Brian Quote Link to post Share on other sites
Drewmotty Posted July 24, 2019 Report Share Posted July 24, 2019 (edited) Leakage problems in this area are usually caused by overtightening. Dress the cover flat around the stud holes and use fibre washers coated in Welseal or similar under flat washers and back up with Nyloc nuts. Tighten just enough to take up slack and no more. Run it up and let us know how you get on. Edited July 24, 2019 by Drewmotty Quote Link to post Share on other sites
Z320 Posted July 25, 2019 Report Share Posted July 25, 2019 Hi, what about using a "seal" from down under the valve cover? I'm thinking about two short petrol rubber hoses over the bolts, some mm longer than the distance between head and cover. To be compressed when bolding the cover in position? Upper end must be cut accurate for that. Did anyone do that before? Ciao, Marco Quote Link to post Share on other sites
Bfg Posted July 25, 2019 Report Share Posted July 25, 2019 (edited) 1 hour ago, Z320 said: I'm thinking about two short rubber hoses over the bolts, some mm longer than the distance between head and cover. I did this for a Triumph Spitfire MkII in the early 80's. I don't recall further issues, so it must have worked. In any case ; the surround of the rocker cover holes not only need to be flat, clean and very lightly abraded ..as a gasket-face, but also has to be square to the studs. Any gasket goo should be applied smoothly and touch-dry before assembly ..so as to not then be squeezed out, but personally I don't use it around rocker cover studs. Both natural rubber and Nitrile is only good for 100 deg.c. continuous, so somewhat a one shot use with rocker cover temperatures. Viton is good for a little over 200 deg. continuous. Used with a cup washer the seal ought to be very soft and pliable. Natural rubber's shore hardness is around 30 - 90. Nitrile is just a little firmer, and Vitol firmer still ..so perhaps over filling the cup washers with silicon (good for 210 deg, and when set - softer than rubber) and letting those fully set before assembly might work best. This would be the same as moulding your own silicon washers within their cup washer. . Edited July 25, 2019 by Bfg Quote Link to post Share on other sites
Spit_2.5PI Posted July 25, 2019 Report Share Posted July 25, 2019 Brian. I'm no guru, but my after-market aluminium 6-cylinder rocker cover had no sealing at all on the hold down acorn nuts. I selected some suitably sized Dowty washers (aka. bonded seal) and all is good. Maybe a similar solution would work on your (steel?) cover. Cheers, Richard Quote Link to post Share on other sites
Z320 Posted July 25, 2019 Report Share Posted July 25, 2019 Mine is sealed enouht with a POM washer under the nylon nut Quote Link to post Share on other sites
mikej Posted July 25, 2019 Report Share Posted July 25, 2019 Hi Brian, just happens I went through this a few years ago, A not-clean oil -filler cap filter increases pressure and can cause top nut and main gasket leaks. Mine did anyway. I sorted a head where someone had used roll-pins to secure the rocker shaft collars. This caused oil to squirt about and lowered oil feed. Ensure they are Mills pins. Red fiberlite washers under steel washers under both nyloc stud nuts should not normally leak. (I I don't think they need to be red!) Cheers, Mike Quote Link to post Share on other sites
Brian Eldred Posted July 25, 2019 Author Report Share Posted July 25, 2019 Thanks all for the tips. I think I'll try filling the cup washers with silicon first, and maybe rubber tube over the studs for good measure. Will let you know how it goes. Quote Link to post Share on other sites
stuart Posted July 25, 2019 Report Share Posted July 25, 2019 1 hour ago, Brian Eldred said: Thanks all for the tips. I think I'll try filling the cup washers with silicon first, and maybe rubber tube over the studs for good measure. Will let you know how it goes. If your going to use rubber tubes make sure its compatible with oil as some isnt. Stuart. Quote Link to post Share on other sites
Brian Eldred Posted July 26, 2019 Author Report Share Posted July 26, 2019 Well I (over) filled the cup washers with silicon and left overnight. Then cut two pieces of 8mm fuel line 65mm long and fitted them on the studs. SAE J30R9 which I checked is oil and heat resistant. Refitted with fibre and steel washers over the cup washers, then took her for a good thrashing. It seems to have done the trick! Still oil seeping out of various other unknown places of course... Quote Link to post Share on other sites
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