The .002" camshaft endfloat is achieved by the lapping of the camshaft gear onto the camshaft or by facing the camshaft bush. If the camshaft now moves .004", either things have worn to increase the clearance between camshaft and bush or the bush is moving axially in the crankcase. This is a photograph of my square headed camshaft bolt which had worn the retaining hole in the bush oval and bent over due to the axial pressure on the camshaft. There are several threads on here about replacing this square headed bolt by drilling and tapping crankcase and bush 5/16" BSF and sealing with a Dowty seal. Whether or not this is the cause of your knocking I would suggest this is an easy and useful modification. Not necessarily any need for a new bush, just turn it through 120° and redrill both holes.
Realise this thread has drifted away from engine knocking to heavy deposits on pistons but as it all part of trying to get answers….
I purchased an internal bore gauge with a DTI and having checked numerous times now the bores have no more than 0.0015” deviation anywhere within the bores with all four being 2.198” max.
The pistons are all 2.188” in the area of the three top rings and on the split skirt there is a slight step up where they are all 2.196”.
The 2 upper rings have 0.001” gap in their grooves in which the ring sits and are all free to move.
The 2 lower rings (scrapper?) have a gap of 0.002” within their grooves in which they sit again are all free to move.
The ring gaps taken with the rings set 1” down from the top of the bores show a gap of 0.009” for the top two plain rings and 0.010” and 0.014” for the two lower rings.
The bores are all polished (glazed?) with no sign of any honing marks anywhere in the bores, even in areas where the rings would not contact the bores.
Would any of these dimensions be a concern and likely to be the cause of the oily carbon deposits?
If so what remedial work would be considered necessary?
With regards honing what is considered to be the best way to achieve the a satisfactory result, the three legged type honing tool or the Flex-hone type?
Answers on a post card please to the Balls Pond Road Care Home for Austineers
Cheers Denis S
26-10-2022, 06:56 PM (This post was last modified: 26-10-2022, 06:57 PM by Charles P.)
(26-10-2022, 04:24 PM)Ruairidh Dunford Wrote: I would get it professionally honed.
I second that.
Unless your bore measurements are way off a proper honing (not a simple egg whisk glaze buster job) should sort it.
I'd also contemplate a new set of rings, whilst you are in there. Easier and cheaper to do it now.
And run it it carefully, with cheap oil or running in oil. Definitely nothing fancy
An update, following advice from more learned fellows, the block, head, pistons and rings have been delivered to Southern Rebore Services to check everything out for me.
They report that there is insufficient wear in the bores that would require a rebore and new pistons.
The head has a slight bow, again nothing significant but they will lightly dress this to rectify the bow, the block is ok.
The valves/seats have all been vacuum tested and no issues found and they believe the block to be surprisingly good condition.
So they are going to hone the bores and provide new rings and set the gaps accordingly.
I have rectified the end float on the camshaft, despite having the engine stripped, I really do not want to disturb the bottom end of the engine and remove the cam unless it was absolutely necessary. And so I have made a new peg bolt with a larger peg diameter than the original which was constantly trial fitted until it fitted into the bearing and now eliminates the end float. I realise this may not follow learned council but considering the mileage I am likely to do, it does follow the original design (albeit that was somewhat flawed) it will probably see me out!!
As for Ruby running rich I now realise that the original carburettor had a gasket at the top of the float bowl. When the carb was originally cleaned and put back on the engine a new gasket was made that was an identical replica to that removed (I still have the original). However what I have now come to realise is that there is no hole in the gasket that sits directly above the slow running jet and so would stop any flow between the hole in the cover and the jet in the float bowl.
Having done a little research it appears there is not normally a gasket fitted at the top of the float bowl?
So if this is correct the question is: would this be the cause of the engine always running rich or should I be looking elsewhere??
Again all comments welcome.
Cheers
