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V8 Engine - Broken / Cracked Bearing Cap Required !!!!

classiclife
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V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by classiclife »

Hello.

It is assessed that low engine oil pressure can be the result of a cracked intermediate or centre main bearing cap. A phenomenon more common, with the Edward Turner V8 engine, than people realise and there are many references pertaining to the issue.

Has any club member come across this situation and if so, can you provide any photographic evidence of this fact or better still supply me with an actual broken/cracked bearing cap, please.

The request is to allow more research on the subject plus an in-depth analysis of what may be the cause of this situation; the findings will be the subject of a future article in the DLOC journal.

If you can assist, please send me in the first instance a message via the EMAIL option on the Forum and not the PM option.

Thank you in advance.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Ian Slade
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by Ian Slade »

I've heard of this problem via this forum, is it SP or saloon related, having used an SP in competition and frequently ran an SP over 6000 rpm regularly but not since the 1980's I haven't seen this problem nor have any of my SP aquaintances.
Owner since the 70's, Genghis is slightly to my left.

A.N.Other
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by A.N.Other »

Am I getting my stories mixed up hear or was there a problem when Jaguar took over building the engine and knocked the crank forward and backwards with a lead hammer as they did with the XK engine, something to do with checking end float, and it cracked the housings. Sorry if I’m talking male dangly bits.
Colin,
I may be slow but I’m rough as well !

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JohnM
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by JohnM »

I can certainly vouch for the fact it happens, but not why - when my engine was stripped for rebuild it had a replacement machined steel #2 main bearing cap already in place. Russ C seemed unsurprised at the time, simply warning me to check all the others before reusing them, but I'm guessing you've already had chats with Russ about this.
Knowing the history of the car, I suspect this mod was done around 1975 at the previous engine rebuild by the previous owner, sadlly no longer with us.
Hope this helps,
regards,
John
crank 3.jpg
John M in Middlesex, NW London
1962 SP250 "B" Spec
DLOC Herts Region Sec

classiclife
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by classiclife »

Folks,

Thank you for your individual inputs, to date, much appreciated.

John, an additional thank you for the insight along with the accompanying photo; which is going to prove extremely useful as part of the research.

I note your signature flags a SP250, am I correct in saying the photo is the engine from your SP250, please ??

Best wishes.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

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JohnM
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by JohnM »

It is indeed, Richard - as pictured in my avatar on the Cognac Rally in company with a (real) Aston DB4 Zagato GT, an (as-real) XJ13 replica belonging to the same family, and a very knackered Frenchman trying to get his old motorcycle up the hill! (and only in France would you be encouraged to cover up your front number plate with the rally plaque!)

John
John M in Middlesex, NW London
1962 SP250 "B" Spec
DLOC Herts Region Sec

tjt77
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by tjt77 »

As to why the centre main cap cracks:- its due to forces related to running with worn main bearings..when the centre and both intermediate main brings are worn beyond the copper layers, de top wide clearances, the crank 'whips' and puts a LOT for force on the centre cap.. the cure (on top of crank re-grind and polish with new bearings) is a stronger centre main cap.. generally its not a problem on the SP250..but in the saloons the engine has to work hard and spin faster.. most spend their life running long periods at over 4,000 rpms.. btw..Im unsure if good quality main bearings are available again as yet.. I had lot of time and trouble invested in sourcing a few sets of old stock tri metal main bearings a few years back (ended up with several different makes. Vandervell (as original) Glacier and Peter Hepworth) .. King did make the con rod bearings in 'tri metal' format again ..most major suppliers now carry those.. but the mains were only available in bi metal last time I checked.. and load carrying capacity is less than 1/2 that of the original vandervell VP2 lead copper bearings.. plus the harder surface of the tin alloy bearings wears crank along with bearing..necessitating a crank re-grind every time the bearings show wear..

Dart
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Joined: Tue Feb 16, 2016 9:28 am

Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by Dart »

Richard
Just seen this post and I can inform you that cracked/fractured centre 3 mains caps is more common than most owners think. I have now stripped and rebuilt a number of saloon and SP engines and all of them had at least one of the caps in two pieces. My own SP (now owned by chairman Tony Fardoe) had two cracked mains caps and now sports the 3 centre caps as 4 bolt steel mains. I did a number of DM articles and forum posts back in 2009 to 2013 detailing these. I collaborated with Russ Carpenter over these and many other V8 issues over the last 30 years.
John Minchell

classiclife
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Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by classiclife »

Hello John,

Many thanks for your update and at last the true picture of this situation is starting to emerge.

I am in the process of securing a redundant block in order to progress the enquiry. I am also grateful for the additional comments you have added which is of interest.

Best wishes.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Dart
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Joined: Tue Feb 16, 2016 9:28 am

Re: V8 Engine - Broken / Cracked Bearing Cap Required !!!!

Post by Dart »

Richard

Also the thrust wear issue on the centre mains cap is usually most dire in the SP250, because of most cars being manual and most saloons being auto. The auto box does not put any longitudinal pressure on the crankshaft whereas pressing in the clutch does on a manual. Clearly there are exceptions to this with an auto SP and manual saloon but both are rare.

I have read your articles in the DM with interest and Matt Waterhouse and I speak regularly and we have a chat about you re-inventing the wheel on a number of issues which we (and Russ) solved a couple of decades ago. But all are relevant to new owners who will not be aware of the articles in DM back issues or of the technical days we held at Browns Lane and presentations given after various AGM's in the past.
Anything I can do to help out please drop me an email (in the back of the DM)

BR John

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