Here is the dilemma. I have a H2AD that uses one quart of oil in 5hrs. I have had all cylinders of twice and top overhauled by two different shops now and have the same somewhat high oil usage both times. The first shop measured the bores to be well within serviceable limits, replaced the exhaust guides,checked the inlets but did not replace them and re-cut the valve seats, honed the bores and fitted new rings to the serviceable pistons. Still high oil usage after 100hrs so of they came again and went to a different shop. Cleaned and checked again but still within limits and no new inlet guides fitted. ( Didn't need them they told me) honed and new rings fitted again. Same oil consumption after 55 hrs I realize that 5hrs/qrt is within consumption limits but is very annoying.
The cylinders are standard nitrited and now at 3000 hrs since new(second life). This thing starts easy, idles well and makes heaps of power( my RV6 trues at 163kts at altitude) but uses oil!. The latest leakdowns are all 78 or 79.
The H2AD has the barrel type cam followers and pressed steel type rocker arms similar to the Ford top end set up. It also has heaps more oil circulating in the rocker boxes than a "normal" Lycoming because of that.
This all gets me thinking the oil is being sucked down the inlet guides and burned as well as leaked into the combustion chambers before the rocker boxes can drain when stopped.
My question is this, has anyone fitted "mushroom" type valve stem seals on the inlet valves of these engines (or any other Lycoming for that matter)?. What do you engine Gurus out there think?
Cars use them to stop this from happening why not aircraft?
Cheers
Graham
Last edited: