LATE G12 OIL leaking engine bolt.

[Les Howard]

Hi All. On my recent restoration of a G12 I noticed a small amount of oil oozing out of the behind the head of the front bolt at the neck of the crankcase left side. I removed the bolt to see an angled oil way drilled down to the oil "modulator" on the exhaust camshaft end. I don't know what this drilling is for so any suggestions please. It seemed obvious to now fit a red fibre washer behind the bolt head instead of the flat steel one I had fitted and I was wondering if it was standard factory fit to have a fibre washer here? I show the drawing and a photo for the position (not my engine). The red arrow shows the drilling and the green arrow is the end of the bolt (top of crankcase neck) and also where it leaked. Thanks for any insight on what I discuss here.

G12 LEAKING BOLT.jpg

G12 OIL LEAK.jpg

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[1608]

__That crankcase bolt is either wasted or the left hand crankcase bolt hole is slightly larger ( can't remember which). But the drilling leads from the oil distributor bypassing the bolt and lubes the rocker gear._There should be either a copper or fiber washer under the bolt head.

[g80csp11]

Using a dowty seal is best for this location

www.ebay.co.uk/itm/353856013351

[Les Howard]

Thanks very much to both of you for your speedy replies. Re: 1608: The 3x bolts that are at the front of the engine are all the same size and they are standard originals. I didn't notice when doing the original rebuild, but removing the leaking bolt a little while ago I thought the actual through hole did look as if it had a very slight extra amount of clearance (bigger hole) which would easily allow oil to flow past the bolt on its route. Taking this fact a touch further, is this the main route to the oilway channel at the top of the crankcase neck centre joint that feeds the rockers.... both inlet and exhaust? Re G80csp11: Thanks very much showing me the best washers to use and where to buy them. Although the fibre washer is OK after a very quick test, I'm sure the Dowty type will be a better long term seal. I did not notice what washers the engine had when I stripped it, maybe they were copper ones?...Thanks again all.

[1608]

Yes, the only route. This oil channel is a common oil leak point where the c/case halves meet.

[Les Howard]

Thanks very much for confirming this 1608. I had imagined that there was an oil-way hole direct up from the crankcases into that cross channel. I hadn't realised it used a "dual-usage" bolt-hole, I wished I had studied the oil routes more when it was stripped down. At least the pressure here is somewhat lower than the full flow from the oil filter as the rotating regulator/modulator creates pulses of pressure that the rocker supplies bleeds off. Then again, the peak pressure of those pulses might equate to the same crankshaft pressure but the average pressure will be lower. This is the second complete rebuild as the first time I had a leak at the dreaded oil filter crankcase join! I hate to tempt fate but at the moment it doesn't leak but as said, don't want to say too much, I'm for ever the worlds biggest pessimist