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Pair of SP250 or saloon cylinder heads

timmartin
Posts: 50
Joined: Wed Feb 17, 2016 1:37 pm
Location: Berkshire

Re: Pair of SP250 or saloon cylinder heads

Post by timmartin » Thu Jul 11, 2019 10:00 am

Thank you Mike.
I had already discussed this (to me) fairly encouraging head with Russ.

My first reservation was that it looked as if part of it had been fettled using a coal chisel. Russ, of course was more professional. He pointed out that:
1. A piston had broken up in the left hand pictured cylinder, broken pieces of ring having been knocked into the head, and
2. The head had already been skimmed too much for my use. This is liable to cause over-thinned parts to overheat and pre-ignition (pinking). (This is the problem with my own heads)

Thanks again,
Last edited by timmartin on Thu Jul 11, 2019 10:21 am, edited 1 time in total.
Tim
Blue 1964 SP250 in Berkshire

timmartin
Posts: 50
Joined: Wed Feb 17, 2016 1:37 pm
Location: Berkshire

Re: Pair of SP250 or saloon cylinder heads

Post by timmartin » Fri Jul 12, 2019 12:39 pm

Colin and Graham. Just in case this changes your opinion about how much your heads have been skimmed already, this is how Russ checks whether there is enough metal left for him to rework a head. (Measuring the overall thickness of a head can sometimes produce either an over-pessimistic or an over optimistic-conclusion!)

1. Straight edge on the machined face, across the middle of each cylinder.
2. Measure depth to centre of combustion chamber, between the valves.
3. The minimum useable depth is one inch. (When new they are up to one inch and 40 thou. (1.040”)

My posting this does not imply that, unlike me, you need to be told how to suck eggs. Just double checking...

Thank you.
Tim
Blue 1964 SP250 in Berkshire

grahamemmett
Posts: 663
Joined: Mon Feb 08, 2016 8:12 pm
Location: Northwich, Cheshire
Contact:

Re: Pair of SP250 or saloon cylinder heads

Post by grahamemmett » Fri Jul 12, 2019 12:56 pm

Good information as I was to measure the depth of the head being 3.000 inches
Graham Emmett
Northwich, Cheshire
Joint DB18 Registrar (with Marcel Renshaw)
DB18 1949 LCV522 (Yes that one with the P100s)
https://www.db18.org

Warsash 2
Posts: 303
Joined: Sun Feb 28, 2016 1:53 pm

Re: Pair of SP250 or saloon cylinder heads

Post by Warsash 2 » Fri Jul 12, 2019 3:19 pm

Hi
I have been in touch with the SP club and they said that the heads when new the thickness was 3 inches, which indicates that Grahams head have not been skimmed. As such they are hen's teeth.
Regards

Colin

timmartin
Posts: 50
Joined: Wed Feb 17, 2016 1:37 pm
Location: Berkshire

Re: Pair of SP250 or saloon cylinder heads

Post by timmartin » Fri Jul 12, 2019 6:12 pm

Thank you Colin.

I too understood that the nominal overall thickness of a new, machined head was three inches.
But I have heard of thicker ones being seen, up to as much as 3.060”.

It does seem unlikely that one or more of these thicker heads will turn up during my search, but it does suggest to me that measuring the combustion chamber depth may be the more certain way of assessing a used head?
Or have I got it wrong somewhere?
Tim
Blue 1964 SP250 in Berkshire

tjt77
Posts: 502
Joined: Wed Mar 23, 2016 7:01 pm

Re: Pair of SP250 or saloon cylinder heads

Post by tjt77 » Wed Jul 24, 2019 8:03 pm

On the question of head thickness :- 3.0" when new... with std pressed steel gaskets skimming up to .035" can be utilized..
The alternative 'composite' gaskets as supplied today are approx .040" thick.. in practice these allow for a safe skim of +/-.060"

grahamemmett
Posts: 663
Joined: Mon Feb 08, 2016 8:12 pm
Location: Northwich, Cheshire
Contact:

Re: Pair of SP250 or saloon cylinder heads

Post by grahamemmett » Mon Aug 05, 2019 11:03 pm

Tim, are you still after the two heads? I’ve located two which have the required depth, pretty sure never been skimmed and have little visible corrosion around the waterways.
2A7182B6-A41D-491E-A6B5-CBFD4C8EF8A4.jpeg
Graham Emmett
Northwich, Cheshire
Joint DB18 Registrar (with Marcel Renshaw)
DB18 1949 LCV522 (Yes that one with the P100s)
https://www.db18.org

timmartin
Posts: 50
Joined: Wed Feb 17, 2016 1:37 pm
Location: Berkshire

Re: Pair of SP250 or saloon cylinder heads

Post by timmartin » Sun Aug 11, 2019 9:31 am

Thank you Graham. I have replied to you by email and am consulting Russ and Andrew.
Tim
Blue 1964 SP250 in Berkshire

classiclife
Posts: 451
Joined: Wed Sep 05, 2018 9:55 am
Location: Ridgewood - East Sussex
Contact:

Re: Pair of SP250 or saloon cylinder heads

Post by classiclife » Mon Aug 12, 2019 8:59 am

Hello Tim,

I have sent you a PM that may be of interest to you.

All the best.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Area Representative.

Southern Classics Society Events Co-ordinator.
www.southernclassics.org.uk

Ozzsp250
Posts: 196
Joined: Tue Feb 16, 2016 12:35 am
Location: Arizona, USA

Re: Pair of SP250 or saloon cylinder heads

Post by Ozzsp250 » Thu Aug 15, 2019 9:37 pm


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