Knocking Sound under Acceleration

[PSL184]

Yes my thoughts too. That centre main had only just started to wear so no need for a regrind based on the pics as far as can see

[bmcecosse]

Stephen - you should check out the exchange crank from Bull Motif which seems good value for money. I know I can't get a crank ground and new bearings supplied for that money, although obviously there could be carriage both ways.

[stephenpolhill]

Hello again. Yesterday I booked the engine and crankshaft into the *very* local engine specialist. He is going to regrind the crankshaft and get the suitable sized bearing, and also replace the camshaft bearings (just to be sure). However having just read your post BMC and looking at BM's site, it seems cheaper to get mine exchanged. Is this a good idea or should I keep mine with the original engine and just get it reground?
Thanks
Steve

[bmcecosse]

The BM crank will be fine! And I suggest the cam bearings will NOT need replacing! This is a very unusual (and possibly expensive) thing to do - only necessary where an engine has ground to a halt with zero oil pressure due to complete loss of oil. There is no suggestion off this with your engine. just take into account any carriage charges with the BM carnk -unless you are near enough to do the swap ? It certainly seems to be quite a 'bargain'.

[stephenpolhill]

Having counted it up, getting the man to regrind and order new parts for my crankshaft works out a few pounds more than this swap (inc. P&P) but I still have originality, so I will stick with the plan (regrinding).
As for the camshaft, we thought it necessary while the engine is out, but do you recommend it being changed or not. Precautions etc etc?

[bmcecosse]

No - I would leave them alone! I've never changed cam bearings - and I've rebuilt a good few engines.

[stephenpolhill]

Thanks for that. I'll pass it on, could save me some money

[Mogwai]

Just had a look at your pictures & No4 piston has had it, it looks oil starved to me. The noise you were getting would have been piston slap by the looks of things, do you have any photos of the bores. The crank doesn't look too bad but difficult to tell in the pictures your machine shop should be able to measure them & advise further. cam bearings rarely wear so you'll probably get away with them (having said that I have just had to change mine)

[linearaudio]

[quote="Mogwai"]Just had a look at your pictures & No4 piston has had it, it looks oil starved to me. The noise you were getting would have been piston slap by the looks of things........quote]

Thats what I said, but was shot down for it He initially said the oil light was flickering and he put 1 LITRE of oil in, so a fair guess that no 4 took the hammering!

[bmcecosse]

I didn't shoot you down! I agree - #4 piston is a mess - but - if the rings are ok and the marks can be polished off it should be ok. Normally the piston doesn't touch the walls of the cylinder - it simply glides up and down on the rings - which make the contact due to their natural springiness - but also due to gas pressure holding them out against the walls. I would say (and did suggest earlier) that a rebore and new pistons may be the way forward - certainly that's a much better idea than worrying about the cam bearings! But again - it depends what the 'local' machine shop charges for a rebore. BM do pistons for £85 and an exchange crank for £ 75 (which seems a REAL bargain) - and I would expect to have the reboring of the block done for ~ £50 max. Used to be ~£10/bore standard charge - maybe a bit more these days. It would be virtually a NEW engine if bored and ground. That would be my way forward.

[stephenpolhill]

Hello. With Xmas and New Years getting in the way, I haven't had chance to work on the car. However now we're back to normal, progress should resume.
I got the engine back on Tuesday with a reground crankshaft and new oversized bearings and newly fitted camshaft bearings and finally some new thrust washers.
Total costs were:
-Regrind (£60)
-Bearings and washers (£90)
-Cam bearings fitted (£30)
The engine man also said that the piston has had it and it would be better to replace all 4 as a set as I can't find just one piston for sale at the right size. Unless anyone has one ?

[stephenpolhill]

Looking at buying a set now. What do I do with the old ones? Should I sell them on because they could be some use, or what?

[bmcecosse]

If buying a new set of pistons - best to have the block rebored and then it will be like 'new'. I did say this before - it would have been a FAR better investment than having cam bearings fitted! And I hope they did that correctly - it's NOT easy to get it right! Have you tried a camshaft in the bearings ? Otherwise - just fit a single piston - what size is it ?

[stephenpolhill]

Helo again. Been a long time since the last post. In short the engines in, and we attempted the timing although after head scratching it didn't manage to run well. We took it to the garage for tuning, MOT and final bits to do and they reported that it was a quarter turn out and was being funny but its running like a dream now. Just running in to do. I miss it.
thanks so much for all your help

[bmcecosse]

If it was 'quarter turn' out - it wouldn't run at all........ I suspect bullsh..... However - great it's going now - and presume it passed MOT too? Do you now have an oil pressure gauge connected and working ?? If it's not been rebored - it doesn't need any 'Running In' - just don't hammer it for the first few miles!!

[nigelbainbridge]

dear bmcecosse i am only new on this forum and agree with what you said 100% knowlege is a great thing to have.

[newagetraveller]

Consider replacing your oil filter if it has not been changed recently.
A blocked filter will result in the symptoms that you have described and replacing it is relatively easy.