At 8:13 PM +1000 23/6/98, Chris Leah wrote:
>With regard to the recent thread on the rocker oil feed kit,I have one of
>these kits from Moss UK fitted to my Spitfire. Runs from a union on the oil
>pressure switch to a threaded hole at the back left corner of the head.
>I fitted this as is and have experienced some oil leakage from the push rod
>tubes as fitted to the Mk1/Mk2 heads. Our local club expert told me that the
>unit allows too much oil to be delivered to the rockers as the oil passage
>via this feed kit is about 4mm diameter up to the hole in the head. He feels
>that there is also a danger of reducing the oil supply to the main bearings
>with all this oil flowing to the rockers via this feed. He did feel that the
>rockers need additional oil and recommended filling the 4mm hole in the
>banjo bolt that fits to the head by brazing a brass plug into the hole and
>then redrilling it to 1mm diameter hole.
>I have done this and certainly the amount of leakage at the push rod tubes
>has been reduced.
>Whether or not this modification that I've done has eliminated any benefits
>of the oil feed kit, I wouldn't know. My gut feel says no, but I am not an
>engine expert. Maybe some of the guru's out there would like to comment?
>Chris Leah
>Durban, South Africa
>1966 Spitfire Mk2
>1960 Herald (Newly acquired)
Chris
I fitted an oil line to my TR6 at the beginning of the year. The first
banjo bolt broke when I tightened it and Moss sent a replacement. The
first bolt was bored about 3.18 mm while the replacement was bored 1.98 mm
(sorry about the measurements but I used imperial drill bits to establish
the size of the holes).
This does not sound like much, but the cross sectional area of the hole
varies by a factor of 2.6. While this might explain why the first bolt
snapped (it could not have been my clumsiness), it might also explain the
comments about the amount of oil that flows to the head and runs down the
valve guides, etc.
There has obviously been a significant change in the design of this part
(or the manufacturing tolerances/quality control are woeful), so it might
be worth checking this part with the various suppliers. In my case, both
came from Moss US, but the original line came from their New Jersey branch
and the replacement bolt from their Goleta branch.
Can these banjo bolts be purchased from independent sources (such as brake
line suppliers) with a range of bore sizes? This would enable the oil flow
to be optimized.
Trevor Jordan
74 TR6 CF29281U
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