Cracked Head

Technical MGB discussion
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Hazza1190
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Forename: Harry
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Cracked Head

Post by Hazza1190 » Mon Apr 27, 2020 4:41 pm

Hi Guys,

Hope everyone's doing well.
Unfortunately upon cleaning the head up this weekend to send off the Peter Burgess (for the ecotune work), I have noticed a crack between cyl 1 and 2 (see pics below). I emailed some pics to Peter himself and he thinks the head is toast. This wouldn't worry that much usually but its a 12H2708 large valve head which seem more expensive and rare, so i was happy that I had one in the first place. Is it worth my time and money trying to source another large valve head? Or is the performance gains negligible, even after Peter has worked his magic?

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Thanks!
Harry.

Ian Fozzard
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Re: Cracked Head

Post by Ian Fozzard » Mon Apr 27, 2020 6:23 pm

I would say that whatever Peter advises is the advice to be accepted!!

I think there may be folk out there who could weld the head, but again I would defer to Peter.

B series heads are still reasonably easy to come by, so your best bet is probably to get another and let Peter do his work on it. I would have thought that Peter could bring most head castings up to a similar level of efficiency. He may even be able to supply a suitable one for you?

The reason that some heads may be more expensive is perhaps due to competition regs which limit what work can be done, therefore a good "standard" head may be worth seeking out.
Peter could perhaps confirm whether this is the case?

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear

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Peter Cresswell
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Re: Cracked Head

Post by Peter Cresswell » Mon Apr 27, 2020 9:23 pm

Hi Harry,
Although you could get the head repaired, the process is time consuming and quite costly and you would still need to persuade Peter Burgess to work on it. If you source another second hand one, there is no guarantee that it will not be cracked as well. Best bet I think is to ask Peter Burgess if he can supply a head, and work on that or sell you a modified head off the shelf. In his book he tells readers not to worry if they don't have one of the better castings like the 12H2709 as they can all be modified to the same spec.
The 12H2709 heads are rare because they were only fitted to MGBs for 2 years and the Austin 1800S for the same period. The people racing in the standard spec classes like to use them, as the class regulation specify the head can't be polished, only grit blasted to clean them and as the have the best gas flow they are quite sought after.
Pete
1969 MGB Roadster
2011 MG 6 TSE Magnette
2007 Mercedes SLK
Plus 32 other cars since 1965

ChargedAutoGT
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Surname: Moore

Re: Cracked Head

Post by ChargedAutoGT » Wed Apr 29, 2020 10:35 pm

It's toast.

There is another consideration. did this come off your car? And if not does your car have an 18V engine as the 2709 head requires cutouts for the exhaust valves which are only present on 18V?

A 12H1326 or 4736 can be retro-fitted with larger valves. I have had my 1326 done by Peter But it's not on the car yet so cannot report on differences.

Lastly - I read from someone who went out and bought a new head from County - then sent it to Peter for Econotune job . He said Peter had to return it saying it was NOT suitable for Econotune modification and most other mods. Now this is what I rear - but if that is a thought in your mins I would double check with him first.

I also bought a 2709 ... same issue. then another - different crack. But then I found a good one which is one my car now. a numbers game.....

The larger valves will have a positive effect in the higher RPM ranges, difficult to say exactly where - or if the seat-o-the-pants-meter can tell. but it's nice to have the correct head.
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cracked head.jpg

Ian Fozzard
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Re: Cracked Head

Post by Ian Fozzard » Thu Apr 30, 2020 8:25 am

I haven't had any direct experience of County cylinder heads, but understand (from a reliable source) that they are very poor castings. A lot of irregularities in the ports, casting flashings etc.

I would agree with Peter (Cresswell) that if you can find any good uncracked head, Peter (Burgess) should be able to make it into a good-un for you😊.

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear

Vic Butler
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Location: North West Hampshire

Re: Cracked Head

Post by Vic Butler » Thu Apr 30, 2020 6:43 pm

A few years ago I was looking for a replacement cylinder head and a mate let me rummage through the ones he had. One was a 12H 2709. I took it to Slark Racing Engineering (then in Amesbury) and Brian Slark said he'd work on it over the winter. After a while he phoned me to tell me that one of the inlet valve seats was damaged, likely by ingesting something but he could get round it by fitting MGC inlet valves. Brian used to be the ace cylinder head man at Downton Engineering and he told me this was a "Downton Dodge." It goes really well and as Downton cylinder heads were renowned for flexibility the engine pulls well from low revs bearing in mind the 1.75 inch inlet valves and the HS6 SU's which are genuine British Leyland Special Tuning which I bought in 1981 with the matching inlet manifold.
Unfortunately I fitted the head then realised I hadn't photographed the combustion chambers.
The head it replaced was a "back door Downton" according to Brian when he converted it to unleaded last century as it had been welded but was a genuine Downton. I swapped it for the 12H 2709 head. The old head developed a crack but my mate was happy to swap. At the time he didn't know about the damage to the 12H 2709.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

Hazza1190
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Forename: Harry
Surname: Bukin
Location: Devon

Re: Cracked Head

Post by Hazza1190 » Mon May 04, 2020 12:45 am

Hi Guys,

Thanks for the replies! After a lot of arguing with myself i have decided that i want to embark on a V8 conversion as its what i have always wanted. The current 1800 is toast (block is utterly worn and the head, well, you know about that!) so would need over a grand putting into it to get it where id want.
I understand that the later Rubber Bumper cars are easier to convert but I am going to convert my current project (1973 B GT). Any of you guys done a V8 swap, specifically on a chrome bumper? Im obviously going to go for a rover V8 (either the 3.5 or 3.9 im not too bothered). Any resources that you guys may have on this would be of great help!

Cheers,
Harry.

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George Wilder
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Location: North West Essex

Re: Cracked Head

Post by George Wilder » Mon May 04, 2020 12:57 pm

Harry
Search the V8 site https://www.v8register.net/ lots of info if you search - complete projects documented
George
George Wilder
1965 MG MGB Mk1
1995 MG RV8
2005 MG TF 135
1959 BSA D7 Bantam

ChargedAutoGT
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Joined: Wed Nov 21, 2018 9:37 pm
Forename: Graham
Surname: Moore

Re: Cracked Head

Post by ChargedAutoGT » Sat May 09, 2020 10:53 pm

Join MGEXP and check out engine swaps. Hundreds of them and lots of Rover V8's
G

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