Technical Death Rattle!!!!!!

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Technical Death Rattle!!!!!!

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Greetings All, Assistance needed from the engine guru's out there. To cut a rather long story short I have just completed the rebuild post head work. Only changes apart from the Skimming, porting, polishing and valve lapping of the head were fitting of a thicker 1.2mm copper gasket, a new cylinder stud and a change of oil to 10w 60 (mobil 1 older engine performance oil) Engine started on the button, oil pressure as normal, but a loud very alarming metallic rattle or clacking was evident when the revs were raised above 1200 rpm and when the engine was revved it rattled on run down. I have now stripped the engine down and can report that there is now light vertical scoring in the bore sides and on the piston sides (opposite side to gudgeon pin not the forward and rear faces)see pic's. The rings are all intact and clean. Big and little ends are firm and there was only slight contamination of the oil with three small 3 x 1 mm pieces of material on the sump mag plug. I'm so glad I didn't drive the car as it may well have gone bang! So, question time what the hell is going on here???? This noise was not evident prior to rebuild and oil change??? What has caused the markings on the internals - possibly Piston slap but why???? HELP!!!!
 

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Hi, Pistons are 80mm standard not oversize. The bores measure 79.94 and 79,98mm using my vernier. I suspect that 126 (650) barrels have been bored out to suit prior to my ownership. The one thing I cannot fathom is that I was not getting this noise before???????

Ian.
 
Ian, I'm really sorry to hear that news. What pain when you have worked so hard at it.
What is the actual piston diameter? If it is 80mm then surely the barrels would be too tight at 79.**mm. I suppose you have no way of knowing if the barrels were bored out to give clearance fit with the actual pistons used. To me it looks like they have been a bit tight.
How much running of the engine did you do before undertaking the work? Have you any idea where those metallic bits came from?
 
Hi Ian
Do I remember correctly that you had issues removing the crank pulley at some time?
Just wondering wether you have pulled the crank out of alignment somehow.......
 
Ian, I'm really sorry to hear that news. What pain when you have worked so hard at it.
What is the actual piston diameter? If it is 80mm then surely the barrels would be too tight at 79.**mm. I suppose you have no way of knowing if the barrels were bored out to give clearance fit with the actual pistons used. To me it looks like they have been a bit tight.
How much running of the engine did you do before undertaking the work? Have you any idea where those metallic bits came from?

Hi, the measurements are my attempt and may be a bit out, the pistons are marked 80mm std. the indicated Km on the new speedo was at 350, but I have no way of knowing the actual accurate figure. The pistons had not been removed and I think it's difficult to fit them the wrong way round given the instructions that are available??? Having checked with a mechanic friend of mine he thinks it is piston slap and has recommended that I have everything checked and measured accurately to ascertain what fits where and how well. The bores may need a polish too.

Ian.
 
Hi Ian
Do I remember correctly that you had issues removing the crank pulley at some time?
Just wondering wether you have pulled the crank out of alignment somehow.......

Hi Andrew, yep the crank pulley episode has been considered, but I think there would be more indication from the bearings and possibly the big ends if this was the case. I shall remember to mention this to my engine man anyway, thanks.

Ian.
 
Ian;
Been giving the grey cells some severe exercise regarding your problem. Has the cam-shaft been minutely adjusted at some time by elongating the cam-sprocket holes? Is the timing-chain still tight, or have the bolts loosened and the chain become slack? The noise you played me (down the phone!) could be caused by a slack timing-chain. I know a lot of people don't bother, but if the sprocket holes are elongated to fine-tune cam-timing, the sprocket should be locked to the camshaft flange by the simple method of; with the cam and sprocket bolted together in the final position, drilling through the sprocket using the 5th hole in the camshaft flange as a guide, taping the hole in the camshaft flange and then putting a (small, it is only about a 4mm hole) bolt through the sprocket and into the flange.
By the way, crankshaft end-float is between 0.3mm and 0.44mm. This is measured between the crankshaft flange (at the timing-chain end) and the thrust-washer part of the crank bearing (at the timing chain end), with the crank in situ, along with the timing-chain sprocket and oil thrower in place and the crank nut done up TIGHT.
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Ian;
Been giving the grey cells some severe exercise regarding your problem. Has the cam-shaft been minutely adjusted at some time by elongating the cam-sprocket holes? Is the timing-chain still tight, or have the bolts loosened and the chain become slack? The noise you played me (down the phone!) could be caused by a slack timing-chain. I know a lot of people don't bother, but if the sprocket holes are elongated to fine-tune cam-timing, the sprocket should be locked to the camshaft flange by the simple method of; with the cam and sprocket bolted together in the final position, drilling through the sprocket using the 5th hole in the camshaft flange as a guide, taping the hole in the camshaft flange and then putting a (small, it is only about a 4mm hole) bolt through the sprocket and into the flange.
By the way, crankshaft end-float is between 0.3mm and 0.44mm. This is measured between the crankshaft flange (at the timing-chain end) and the thrust-washer part of the crank bearing (at the timing chain end), with the crank in situ, along with the timing-chain sprocket and oil thrower in place and the crank nut done up TIGHT.
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Hi Tom, Thanks for this - appreciated. All of the timing gear is new, the chain was tight and the bolt holes have not been elongated. Your mention of the oil pump bolts coming loose is discounted as I have tell-tale markings on the spin-on filter adaptor and they are all correct, but I wonder if the markings on the bores and pistons is related to the over heating I suffered and caused wear on the piston skirts????

Ian.
 
I would have to agree with Peter; those marks on the pistons are classic 'overheating-scuff' marks. If they are 80mm pistons, new can be obtained from 'Nanni Ricambi' (part number:- ART 0299--made by ASSO). I seem to remember that you go to Italy quite a bit--maybe the people at that address can help you purchase them. If your engine man then hones and carefully measures your bores, it may be 'just' a question of new pistons. Alternatively, maybe ASSO do a 'over-bore' size, and your engine man takes the barrels out to suit.
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Greetings All,

Just heard back from my engine guru with the following news. The cylinder bores are 5 thou oversize - in metric speak that's a bore of 80.13mm. The piston to bore clearance is 10 thou - or 0.26mm. My man says that this is excessive and may be part of the overall problem. There is a distinct possibility that the cylinders have been badly bored out (I suspect from 652) and 80mm pistons put in with a resulting minimum of wear life before trouble. The original pistons are 'Hepolite' and are listed in the catalogue, so after a check and measure of the cylinder wall thickness (rebore?) we may be able to find a piston to fit correctly??? Or it's a new barrel and piston set to purchase?????? I'll get back with news when I know, but it looks like a classic example (bad) of an engine being thrown together rather than built correctly!!!!!!!!!!!!

Ian.
 
Ian , take into consideration that if you go the route of barrels and pistons, you may need to bore the crankcase also.
The 700cc kit I used required this.
I found it difficult to find someone who would undertake a one off job like the awkward shaped 650 crankcase
I ended up working with Tony at MBG.
 
Greetings, have determined that the cylinders are bored-out 77mm (652) and my engine man is confident that we can fit 80.2mm or 80.4mm oversize pistons. As one can imagine the wall thickness is not great but sufficient for my purposes (I have checked if the thickness is affected with the other mods done and it seems that it's all ok) I have found 80.6mm oversize (AxelG) and 80mm oversize (does not say by how much) with Nanni Ricambi. MBG can also get them (from Italy) but everyone is on their hols at the moment so added delay here. My engine man may come up trumps with his searches. If anyone has a good source of pistons to suit let me know please, thanks.

Ian.
 
Been over to the engine machinist's this morning to collect a reground Bis crankshaft and the guy also got me a set of piston rings to fit the 499ccs Abarth pistons and another set of rings to fit the 540ccs Nanni pistons and barrels that I recently acquired.

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I first used these guys in the early 70s for some engine work on a Mk1 Cortina so they have been around for a while. Crank regrind was £48 + vat. The guy to talk to is Paul and I asked him about boring a crankcase to fit larger barrels . He said no problem and about £40 per pot.
 
Greetings,

Question from my engine man - what is the piston to bore clearance with standard and overbored cylinders ???

I have managed to obtain some used 77mm cylinders (thanks Tom) that will fit the bill, I will chat to my man to see what we can do, but I will probably come down to 79.5mm as the pistons are a lot easier to obtain.

Ian.
 
Is this any good to you Ian?
 

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