Help with Cylinder Head Identification

[MintSprint]

I'm looking at a Twin Cam cylinder head at the moment which came with a story attached to it.

I have a couple of pointers that might help confirm or deny the head's history:

Firstly, the head is stamped at the back (on the face that usually abuts the bulkhead) with the letters VBH70 and GC53.

Secondly, it is fitted with big valves - 1.7" inlet and 1.4" exhaust.

Part of the story is that it was built by Brian Hart and that the 'VBH' stamping is his identification.

Can anyone provide any information that could confirm or deny this suggestion?

[rgh0]

Whats the thickness of the head ? Hart racing heads were very thin as the valves were moved back into the head to prevent them hitting each other and to keep the compression ratio up the head face was heavily machined.

The ports should be very big also with a shallow inside bend on the inlets compared to a stock head- have a look at the inlet port casts I posted a while ago to see hte sort of difference. The inlet spring seat bases may have broken though into the big inlet ports and been sealed or welded up also.

Sorry can help with the VBH number but the other number looks like a normal head number with 2 letters and 2 digits so the story could be true.

cheers
Rohan

[MintSprint]

Head thickness is a few thou under 4.6" (so standard, I think?).

The rumour that came with the car was that it was a factory development prototype for the 'Big Valve' Sprint, with cylinder head work by Brian Hart. Other curiosities include a chassis number that doesn't conform to the normal sequence (it's a 1969 chassis number with a letter suffix written on to the factory records by hand, yet the car was first registered in 1972) and the first two owners were from Norwich and (allegedly) Lotus employees.

[rgh0]

At 4.6 inch thick which is standard sprint thickness it is unlikely to be a Hart racing head. The 1.7 and 1.4 valves are a bit strange as would normally only put these in racing head and then you normally need to sink them in to the head further for the bigger valve heads to clear on overlap with a typical racing cam of the period. Then you need to skim the cylinder head below 4.6 inch thickness to maintain race compression ratio with the larger combustion chamber formed by recessing the valves.

Sounds like your head is set up with very big valves but designed to run on a low overlap road style cam and road compression ratio - Possible that the story is true and Hart did some development work for Lotus around the time of the Big Valve head introduction

cheers
Rohan

[trw99]

I have not got my copy of the excellent Miles Wilkins Twin Cam Engine book to hand. However he devotes a section to the development of an SE engine by two Lotus engineers (again, I can not remember their names - I hate getting old!). This was in around 1968/9 and they apparently got close to 125 BHP from developing the head and changing the carb set up. I do not recall any mention of Hart being involved.

Wilkins then links Tony Rudd's development of the BV head (which he did in 14 days allegedly) in 1970, with the work previously carried out.

Tim

[MintSprint]

Yes, I have the Miles Wilkins book and, as you say, it states that Tony Rudd was responsible for the Big Valve development. I hadn't taken that too much at face value, though... Tony Rudd was in charge of engine development at the time, but that doesn't mean that he would have actually done the work with his own hands - I'm the Design Director for a major housebuilder, so I'm responsible for the whole of my company's design output, but the opportunities I get to put pen to paper myself, instead of merely instructing assistants and external consultants, are few and far between these days!

The dates seem to tally with the 'lost' period between date of manufacture and sale for my car, though, especially as I assume the 'VBH70' stamp would refer to 1970.

[garyeanderson]

Yes, I have the Miles Wilkins book and, as you say, it states that Tony Rudd was responsible for the Big Valve development. I hadn't taken that too much at face value, though... Tony Rudd was in charge of engine development at the time, but that doesn't mean that he would have actually done the work with his own hands - I'm the Design Director for a major housebuilder, so I'm responsible for the whole of my company's design output, but the opportunities I get to put pen to paper myself, instead of merely instructing assistants and external consultants, are few and far between these days!

The dates seem to tally with the 'lost' period between date of manufacture and sale for my car, though, especially as I assume the 'VBH70' stamp would refer to 1970.

Any pictures of the head and numbers?

Gary

[MintSprint]

Any pictures of the head and numbers?

I'll try to upload some tonight. I've taken some - I've now just got to work out how to upload them onto here!

One of the photos did bring out some detail that I couln't read, before: the number stamped on the cylinder head is not VBH70 as I previously thought, but BVBH70. I'm speculating, but does 'Big Valve Brian Hart, 1970' sound plausible?

[MintSprint]

Photos (I hope!):

[trw99]

Martin

Can you let me know the engine number as that may give us a slightly more accurate date for it's manufacture? Thanks

Tim

[MintSprint]

Engine number is K19042

[rgh0]

I have Stromberg Europa cylinder head with the number GR20. So assuming some sort of sequence for the cylinder head numbering and the twin Cam Europas being made from 71 (not sure of their production start) then your head could be from 1970.

Was the cylinder head itself ported or are the ports "as cast" like a standard head?

cheers
Rohan

[trw99]

Engine number is K19042

Martin

Thanks. That K designation would make it originally a Stromberg head for the UK market in 1969. However it is clear from your photos that you have a Weber head. Looking at Frank's records that engine number was allocated to unit 9053B and, from those cars with close numbers, would indicate a June/July 1969 date line.

As you indicated in your second posting, the unit suffix of B is interesting too. Perhaps it indicates a prototype. There are a couple of people with whom I can investigate this further and I shall report back.

Tim

[trw99]

Some immediate feedback from the factory. Martin, you probably have this info already.

9053B has 'Neil Robinson' against it, originally ordered by Geoghegan in Australia, but this has been crossed out. The original single export invoice is also crossed out and two new numbers (indicating a kit) inserted. The engine number is the one you have. The car was originally French blue.

Hopefully more to follow.

Tim

[MintSprint]

Tim,

Thanks; yes I have that information from the factory already, but any further info would obviously be most welcome!

Do you have access to factory personnel records, Tim? I wouldn't want to post names and addresses on a public internet forum, for privacy of the individuals concerned, but rumour has it that the first two owners on DVLA records were Lotus employees and it would be interesting to confirm this (and even more interesting to speak to them, if they are still alive).

Rohan,

The head is heavily ported, but of course it's impossible to say whether this was original or a later modification. It's currently running QED 420 camshafts and QED pistons, but I have no further information to indicate what other work may have been done with previous rebuilds.