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Author Topic: aurelia B20 2nd series pistons  (Read 630 times)
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Dikappa
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« on: 27 May, 2018, 08:22:18 PM »

Long shot but one never knows...

Today took the aurelia B21 out for a short trip, alas it became a very short one indeed...I didn't even make the end of my street before it suddenly had an urge to drop a valve...
As one can expect the result isn't pretty, and unlas a small miracle happens there will be one aurelia less on de Sliding Pillar.

Anyway, since this B21 (ex Christo) is equipped with a B20 2nd series engine, I'm now on the lookout for parts.
On dismantling I found that it has normal 72 flat head pistons fitted, and this should have been domed pistons (this explains the very low compression measured, which always puzzled me, although it was starting and running very well)

So now looking for a preferably new or very good std size 72 mm domed set of pistons, new valves, one liner, the lot...

Any help most appreciated!

Koen
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GG
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B20 s.2, Appia C10 unrestored


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« Reply #1 on: 28 May, 2018, 01:47:30 AM »

Jorn -
When we rebuilt the s,2 engine here in the states, we had pistons made to match the standard CR (unless we raised it to 9:1, canít remember offhand). The ringset used is important (surprisingly a point of failure), so we worked hard to ensure these were a good combination. I think the pistons were J&E, the rings Deves. If you want, I can look up the order number when back home. Also Sergio Alais makes pistons.
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B20 s.2, Appia C10 unrestored
chriswgawne
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« Reply #2 on: 28 May, 2018, 10:07:44 AM »

Hello Koen,
What a shame to have this problem however I expect the rebuilt engine will run better with more power so something to look forward to.
I think I may have a set of new standard 72mm domed head S2 pistons in England and maybe a used liner or two as well but I will not be next back there until the end of w/c June 11th.
If you are not sorted out by then tell me and I will have a look for you.
Kind regards
Chris
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Chris Gawne
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Dikappa
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« Reply #3 on: 28 May, 2018, 10:44:26 AM »

Hi Chris,

In an attempt to still make the Sliding Pillar with the car I decided to go the fast way and order parts with Cavalitto.  Not cheap but not overly expensive either in my opinion.
Will keep you all posted of the progress, currently engine is out and both heads dismanteled (I will renew all valves/springs for safety...)

This afternoon the heads will go to the engine shop for new seats where necessary (one for certain!)

Indeed I wonder how big a difference the new pistons will make...already now it was a swift car, last outing with the club I seem to have outrun a thema 8.32, the guy came to me afterwards asking what engine I had in it....now that was all small roads ideal for the aurelia!
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Parisien
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« Reply #4 on: 28 May, 2018, 11:44:21 AM »

Less than ideal Koen, but hoping everything goes to plan and the B21 is back on the road as speedily as possible and still holding off those Ferrari engined Themas!

P
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Frank Gallagher
chriswgawne
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« Reply #5 on: 30 May, 2018, 01:28:19 PM »

Koen,
I wonder why you dropped a valve? It cant have been anything to do with the incorrect pistons of course.
About 12 years ago my 1st Srs B20 dropped a valve in the fast lane of the M3 doing about 80 mph and this wrecked the corresponding piston and did some damage to the head.
I had new pistons and valves on my shelves and the head was repairable but what had happened to cause it? In my case, it was a bad batch of springs as the one fitted to the offending valve had cracked and there were several other cracked ones as well. The cracks looked due to corrosion although the springs themselves looked fine and were new when I had built that engine about 6 years earlier.
So I bought a complete new set of springs from Cavalitto and all has been well since re-assembly.

BUT, with one B20 engine I have built up from bits from several engines, I inadvertently used incorrect valve collets. There are at least 2 types and at a casual glance they look very similar but on close inspection one design fits the valve much better than the other. I spotted the difference before I tried to start the engine thank goodness.
Could this be your problem if it wasn't a broken spring?
It would be interesting to know.
Chris
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Chris Gawne
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Dikappa
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« Reply #6 on: 30 May, 2018, 03:38:06 PM »

Hi Chris (and hi to all other readers off course!)

Maybe I did not express myself very well, the whole head of the valve snapped of from the shaft.  From examining the shaft (on the valve head side was not much left to examine) the engine man thinks the material just was tired.
There was also too much play on the valve guides, allowing the valves to be out of centre and get 'tilted' a bit every time when closing.

Now yesterday I noticed one of the pistons is not perfectly centered and seems to 'rub' the side of the liner, so tonight the whole block will go to the engine man as I have a feeling this can only be caused by a conrod out of true.  I fear this will mean no sliding pillar with this engine, but now it's appart so far it can better all be correct IMO.

Luckily I can loan a B10 block, that might be a solution...

Will keep you posted!
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GG
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« Reply #7 on: 30 May, 2018, 04:11:07 PM »

S.2 block may be different from B10. Stud location revised for different heads.
« Last Edit: 30 May, 2018, 04:18:32 PM by GG » Logged

B20 s.2, Appia C10 unrestored
chriswgawne
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« Reply #8 on: 30 May, 2018, 04:46:54 PM »

Oh dear. Its getting complicated isn't it?
Aurelia pistons don't always have the gudgeon pin dead centre in the piston don't forget - it can be offset. NOS pistons often have an arrow on the crown at 90 deg to the pin to ensure the engine builder gets the pistons all facing the correct way.
I would be surprised to hear that you have a bent conrod if the engine was vibration free but funnily enough I do recall the previous owner grumbling about vibration.
Chris
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Chris Gawne
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Dikappa
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« Reply #9 on: 30 May, 2018, 07:45:41 PM »

Hi Chris,

Indeed when I got it is was hell, it felt like it was trying to shake out the floors at 70km/hour....
But after my last year pre-sliding-pillar stress action, replacing all drive train, oily clutch, rear suspension and dampers etc, it was running like a dream.

The engine has always performed well IMO, which now puzzles me the more.  I just returned from the engine man, he'll take it further appart tomorrow.  I'll inform him about your remarks, that might indeed be a possibility...thanks!

We sort of decided do do it properly now, so complete engine will be stripped down and inspected properly. 

Might install a loaner B10 engine, and otherwise we'll take the Gamma....
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GG
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« Reply #10 on: 30 May, 2018, 07:51:24 PM »

I had a similar valve failure on my s.2 a few years back. Head just broke off - I think it was also fatigue after many years, snapped right at the head meets shank part of the valve. All was fine, but we never found the head. We had new ones made up (I think titanium, might have been SS) to replace them, and they have been fine since.

Years later, driving the car, there is this odd vibration noise, clearly coming from the engine area (or so we thought). Seemed to be fan blades ticking against the radiator, only on deceleration. Couldn't find any marks on the radiator. Could it possibly be the starter solenoid moving around? Nope. We were stumped. Totally confounded.

Then clever friend opened up the exhaust on one side, and found the valve head inside! It was well situated under power but would rattle in the pipe when slowing down. Funny, these cars.  
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Dikappa
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« Reply #11 on: 31 May, 2018, 05:14:04 PM »

Engine was further dismanteled today.  The verdict: one bent conrod, crank no good, bearings no good.

Sounds a bit silly for an engine that was recently rebuilt...little bit frustrating I must admit.
« Last Edit: 05 June, 2018, 04:52:09 PM by Dikappa » Logged
DavidLaver
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« Reply #12 on: 31 May, 2018, 10:23:06 PM »


Might not feel so at the moment but it is good to know what you're dealing with.

Have been watching some Horizon documentaries testing with Williams as ground effects and turbos came in.  There was a nice demonstration with a slinky how valve springs hit harmonics, fail, followed by valve contact, bent over, punched by the piston, bent rod, thrash the block to bits. 

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David Laver, Lewisham.
Dikappa
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« Reply #13 on: 01 June, 2018, 06:00:06 AM »

Well, in my case the bent rod is on the opposite side of the engine (RH-side of car), were I noticed the piston to be rubbing the cylinder...which then led me to bring the complete block to the engine man.
  
« Last Edit: 05 June, 2018, 04:51:23 PM by Dikappa » Logged
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