I’m rebuilding my 1955 XK140’s engine, and have a question regarding the aluminium intermediate timing chain sprocket support.
The eccentric spindle for the intermediate gear on my car is a little worn. The car’s been in storage since 1982 so hasn’t run for years, but when dismantling the engine I noted that all the oil holes on the eccentric spindle were completely blocked with old, dried oil.
I have a later intermediate timing gear, bought on ebay, with the aluminium housing parts and another spindle. This is obviously from a later car. The eccentric spindle on this looks to be the same dimensions, but has large chamfers for the oil holes which the older original one does not have. Can I use this on the earlier engine? The aluminium plate the spindle mounts to (NOT the side with the fine-toothed gear) has a lot more reliefs for oil passages etc. on it, but all dimensions of the aluminium parts and the spindle look to be the same. Is it worth using the later aluminium mount panel as well, maybe to improve lubrication of these parts? Or better to stick with the originals?
Also, I’m fitting new sprockets with new bushes throughout. I’ve been advised that I should ream the new bushes to ensure a correct fit on their respective spindles. Can anyone tell me what the reamed clearance should be?
I don’t believe there was any dimensional changes to that area of the timing gear so I don’t see a problem with using the less-worn parts…others should chime in. On my engine, G5752-8S, there is a collection “cup” above the adjuster eccentric to allow oil to run down to the spinning gear/spindle, but I believe your engine is earlier than mine so I can’t say for sure that you have this feature.
Bear in mind that any new sprockets will not have the 5 drilled holes thru them, as your original sprockets do, that allow oil to lubricate the chain-to-sprocket interface. In this case, you might as well go with the later (4-bolt) serrated plates which were slightly larger in circumference and slightly thicker than your originals.
Thanks Lee - my engine is G3736-8S (from memory), and it does have the rectangular ‘cup’ to feed the eccentric shaft so no change there.
Thanks for the heads-up on the chain lubrication. Not sure what you mean by serrated plates - although I don’t have the parts here at the moment. What are these attached to, and how many are there?
Edit - just checked the actual parts (sorry, should have done that earlier) and presume you mean the fine-toothed plates that the cam sprockets fit over, Lee. The new cam sprockets I have from SNG Barratt do indeed have the same holes between the sprocket teeth that the originals did, so I presume just assembling as before will work OK.
Oh my goodness, never thought the new sprockets would have the oil pass-through holes which were dropped from the design way back in the early 60’s (near as I can determine)…good on SNG! So now you need to make sure the serrated plate’s oil feed grooves are clear…mine were NOT…before reassembly. Look at the plates edge-on and you will see 4 triangle-shaped passages running from the center of the plate to the outer circumference. Then, grab a small gauge wire to clear those passages, followed by lotsa brake clean.