Ooops, I dropped a valve

MALDI
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Ooops, I dropped a valve

Post by MALDI » Sat Apr 23, 2011 1:17 pm

My '84 2.5L stock engine with 82,000 miles on it dropped the #2 cylinder exhaust valve.

I was at a track day. The engine was fully warmed up (I had been on track about 20 minutes). The valve dropped while at about 1/2 throttle exiting a turn at about 5000 rpm.

So we all know that these are sodium cooled valves and, being hollow, are prone to fail.

We also all know that going to solid stems valves solves this.

But, nevertheless, could I have prevented this?

Could I have been running too lean and the valve overheated? But there were no (large) air leaks in the (stock) intake system, and after the fact testing showed that the injectors all flowed close to normal values. In general, the engine ran well throughout its rev range.

Could the valve lash have been mis-set? It was set professionally by someone who has worked on Alfas for a long time about 10,000 miles before this happened. Is 10,000 miles too long between valve settings?

Or was it just my bad luck?

The coda to the story is that I now have a used 3.0L bought from a good friend. (This is the engine the GTV6 should have had all along.) This used engine has about the same mileage as the dear departed 2.5L. How can I keep the exhaust valves where they belong?
Attachments
P1010017a.jpg
Probably repairable, but not worth it.
P1010017a.jpg (53.5 KiB) Viewed 4747 times
P1010016a.jpg
Not much useful info here.
P1010016a.jpg (14.12 KiB) Viewed 4747 times
P1010003a.jpg
Is the rod even salvageable?
P1010003a.jpg (48.55 KiB) Viewed 4747 times
'84 GTV6 3.0L
'81 X1/9
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fedezyl
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Re: Ooops, I dropped a valve

Post by fedezyl » Sat Apr 23, 2011 3:30 pm

Interesting! :shock:

Rod in my opinion isn't salvageable, head probably is, but the easiest solution is to drop that 3L in.
As far as the valve failing, I don't know really...
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scott.venables
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Re: Ooops, I dropped a valve

Post by scott.venables » Sat Apr 23, 2011 6:52 pm

If the valve clearances were set too tight the hot exhaust valve won't get enough 'seat time' to transfer heat into the head. Lean mixture and detonation wouldn't help either.

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Re: Ooops, I dropped a valve

Post by kterkkila » Sat Apr 23, 2011 10:29 pm

How typical failure that is on Alfa V6 engines? Have someone else had similar valve snapping? If it's really rare, then maybe it's just bad luck.
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MALDI
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Re: Ooops, I dropped a valve

Post by MALDI » Sun Apr 24, 2011 5:33 am

Definitely not preignition since I heard nothing and was running high octane gas at the time.

I usually use Shell V-Power mostly for the detergents. Its octane rating here in the US is 93 which is the average of the research octane number and the motor octane number. Could I have been using too HIGH octane gas?

Before anyone comments remember that octane numbers are calculated differently depending on your country: http://en.wikipedia.org/wiki/Octane_rating
'84 GTV6 3.0L
'81 X1/9
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Re: Ooops, I dropped a valve

Post by JohnGTA » Thu Apr 28, 2011 5:54 am

MALDI wrote:Definitely not preignition since I heard nothing and was running high octane gas at the time.

I usually use Shell V-Power mostly for the detergents. Its octane rating here in the US is 93 which is the average of the research octane number and the motor octane number. Could I have been using too HIGH octane gas?

Before anyone comments remember that octane numbers are calculated differently depending on your country: http://en.wikipedia.org/wiki/Octane_rating

It is definitely pre-ignition & 93RON is definitely poor quality fuel. From 98RON onwards we are definitely OK.
Only way to stop that from happening is to recalibrate the distributor from 31 degrees max advance at 5000rpm down to 26 degrees.
Do that even on the 3L version, trust me, I blew up 2Xsets of heads on 98RON with 11.2:1CR before I learnt my lesson.
Good luck :)
85' 3L GTV6(White) number 197off 212, 3.5L
83' 3L GTV6 (Red) number 46 off 212
03' 156GTA(Red)3.7L Turbo
06' 147GTA(Blue)3.8L+6XITB's
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Re: Ooops, I dropped a valve

Post by scott.venables » Fri Apr 29, 2011 2:18 am

You shouldn't need 98 octane fuel for a standard engine with 9:1 CR. I doubt 98 would have been readily available in the mid eighties anyhow.
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Re: Ooops, I dropped a valve

Post by Zagato » Fri Apr 29, 2011 8:58 am

Of course it was!
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Re: Ooops, I dropped a valve

Post by SimonB » Sat Apr 30, 2011 12:49 am

US calculates octane number differently to most other countries.
http://www.csgnetwork.com/octaneratecalc.html
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Re: Ooops, I dropped a valve

Post by WhizzMan » Wed May 04, 2011 12:55 pm

Older sodium filled valves sometimes break at the fuse point. If this was caused by overheating or not is hard to tell from just these pictures. Because the valve ended rattling around, it's hard to say even if you have close ups of the break surfaces. The breaking is a combination of weak design, fatigue and lesser quality of manufacture and of alloys used. One or more of these could very well have been a contributing factor.

I'd keep the 2.5 and rebuild that, just in case the 3.0 you are going to put in now isn't what you expect from it. A 3.0 is a nice engine, but over here in Europe, a lot of people say they want the 2.5 back in their car because it revs so much easier and sounds so much better.

93 USA octane is over 95 Europe octane. That should be fine, providing the car is otherwise standard and in good condition.

As already mentioned, too tight valve clearance could have caused overheating on the track. If you have not driven the car "in anger" since the tune-up it's had 10.000 miles before, this may well be the first time you would notice valve timing being too tight.
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Re: Ooops, I dropped a valve

Post by MD » Wed May 04, 2011 1:17 pm

in Europe, a lot of people say they want the 2.5 back in their car because it revs so much easier and sounds so much better.
Forget the music. Three litres is what Alfa should have built these cars with in the first place. When they went head to head in South Africa with BMW, they realised the foul up and finally came up with the goods.Torque is where its at. Music is for the Ipod.
Transaxle Alfas Haul More Arse
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Re: Ooops, I dropped a valve

Post by MALDI » Wed May 04, 2011 4:18 pm

The 2.5L engine had many hours of track time after the valves were adjusted. If anything I would think the valves would be out of adjustment.

The 3L is in already and it is wonderful. :D The 2.5L does sound better but the 3L is more fun. It is very unlikely I'll go back. It does surprise me how much difference there is from the additional ~30hp.
'84 GTV6 3.0L
'81 X1/9
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Re: Ooops, I dropped a valve

Post by kevin » Thu May 05, 2011 1:08 pm

Whizzmann, that's good info there. Hey what's better music than the 2.5 is wait for it " the carbi 3.0" . You can hear all those carbs sucking just like the 4 cal without an air box and then at high revs it has deep roaring sound ( md like our lions that roam our neighbourhood :D )
Sorry back to thread again. Were all inserts still in?
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Re: Ooops, I dropped a valve

Post by MALDI » Thu May 05, 2011 4:15 pm

kevin wrote: Were all inserts still in?
Do you mean the valve seats?
'84 GTV6 3.0L
'81 X1/9
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Re: Ooops, I dropped a valve

Post by kevin » Fri May 06, 2011 8:45 am

Yes , seats. Also a common cause of failure ( not common failure)
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