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Oz34
United Kingdom
2543 Posts |
 Posted - 30/06/2014 : 18:45:02
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Some will remember that OS 3678, "Oz", returned early on day one and I diagnosed a blown head gasket. There were those who, on the basis of the symptoms agreed, while at the same time saying that they had never heard of a solid gasket failing. They still haven't!
On my despondent return home I decided to put the car in the garage and catch up with the hedges and all the similar things postponed in order to get ready(?!) for Scotland.
On removing the head I was presented with an intact gasket but, on turning the head over, was greeted with a dropped exhaust valve seat; the cause of my woes. Moral; don't be a cheapskate, buy a new head as it's cheaper in the long run! Rather than gamble again I have now got one coming courtesy of Mike and Jamie.
Older and wiser,
Dave
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O.Thomas
United Kingdom
755 Posts |
Posted - 30/06/2014 : 18:49:55
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| Can't have been fitted properly then!! |
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Oz34
United Kingdom
2543 Posts |
Posted - 30/06/2014 : 18:59:04
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They'd been there a long time Ollie. I think in earlier times they had a reputation for dropping?
Dave |
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Mike Allison
United Kingdom
196 Posts |
Posted - 30/06/2014 : 19:27:25
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With some sixty years running these cars I can only say that I am inclined to agree with Oliver here. I must have fitted seats to more than 100 heads over the years, and not known of any failures. It is more likely that you were trying to run with too lean a mixture, in my experience a common fault of latter day drivers, who rely on settings by those more used to tuning modern lean-burn engines.
When I started running these cars we always ran on the rich side, and when I eventually worked for Reg Jackson, he told me that they used to get the idle mixture dead right according to the SU set up guide, and then richen three flats on each carb for competition work, or hard driving, otherwise the engines would run too hot and burn valves... and that from the man tuning the cars when they were new!
Admittedly if you have a new head, it wont lose valve seats, but it will not stand up to prolonged running on unleaded fuel either, and you will get burnt seats and valves! |
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Colin McLachlan
United Kingdom
991 Posts |
Posted - 01/07/2014 : 11:46:40
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Glad to hear you're getting it sorted, Dave. Are you having the new head fitted with hardened seats? I've been running an S&V head with hardened seats for quite a few years now, doing a bit of hill climbing and using up to 6500 (+!), with no problems so far. I may take Mike's advice and richen the mixture a bit, to be on the safe side.
Colin
PA 0613
MG3242
Register No. 2591 |
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Oz34
United Kingdom
2543 Posts |
Posted - 02/07/2014 : 12:06:08
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Perhaps Mike I have to plead guilty. I used a Gunson's Coloutune with PA standard needles & couldn't get anything other than a yellow flame, so I fitted the weak needles & managed to get a vaguely blue one. Should I have accepted the yellow & still now be a happy bunny?
Thanks Colin. Armed with both Mike's comments & your own, Perhaps I will have inserts in the new head & go richer.
Cheers,
Dave |
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Mike Allison
United Kingdom
196 Posts |
Posted - 02/07/2014 : 16:23:23
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Dave, I have never used "Colortune" so cannot comment about that. Set the jets at 11 flats (down) from the bridge. If you can get to a smooth idle, lift each piston about 1/32" and the revs should drop a little, not falter. If revs rise, then you are too rich. If the engine cuts or stalls, you are too weak. With a PA I would used M5 needles.
When you have achieved the smooth idle, richen three flats from there. The engine will hunt a little (revs rise and fall, about 100/200rpm. Set idle speed at 750-ish, and the car should perform well under all condition.
Hope you get it sorted soon: summer is rushing by, and there is too good a weather spell to miss!!
Best wishes,
Mike |
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Oz34
United Kingdom
2543 Posts |
Posted - 02/07/2014 : 16:57:25
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Thanks Mike & I am going to have inserts in the new head.
Cheers,
Dave |
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Bob Clare
United Kingdom
278 Posts |
Posted - 08/07/2014 : 00:15:38
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Dave,
You may be comforted (and Mike A perhaps discomforted - add one to your list Mike!) by my reporting that I had the selfsame problem on PA 1028 (BPG 994). I had the seat replaced and have run the car with no further problems over the last 5 years. Mike's mate did the job originally as I'm sure he did yours and 7 out of the 8 seats remain intact. I reckon the failure rate is quite small and the cost of replacing the seat provided nothing major had happened in consequence and it hadn't in this case, was VERY MUCH LESS than buying a new head!
Bob Clare
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Bob Clare
United Kingdom
278 Posts |
Posted - 08/07/2014 : 00:26:35
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Whoops!! Just re-read your original post and obviously I mistakenly assumed that Mike Allison had been involved in the engine rebuild for your car. Nothing in your posting says that so apologies all round.
Mike, nontheless you now know of one failure on a P engine you rebuilt but at a seat failure frequency of <1% that ain't bad!!
Cheers.
Bob |
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