Lotus Twin Cam 681F "L" cylinder block by OED

[lotslow]

Hi all,

obviously a brand new 681 F "L" block is now available from QED promised to be far stronger than the original block or the american kent and good for a 90mm bore. Do anyone know details concering quality and source?

Peter

[rgh0]

another new "good for 90mm bore block coming out" ???? I will like to see some details on that

cheers
Rohan

[bcmc33]

Hi all,

obviously a brand new 681 F "L" block is now available from QED promised to be far stronger than the original block or the american kent and good for a 90mm bore. Do anyone know details concering quality and source?

Peter

I have no knowledge of the QED block, but it is four times the price that I paid for a new Ford Racing 711M block. A new 701M block is the same price as the 711M.

However, I would like to know how the QED block can be far stronger than the Ford Racing blocks that are made from 40.000psi cast iron with beefed-up main caps.

[lotslow]

Hi Brian and Rohan,

if you look at QEDs internet page there is only limited information.
Brian, I thought the Ford Racing 711 block costs less than the 701, where did you buy yours?

Cheers Peter

[garyeanderson]

ok

[CBUEB1771]

Price (each): ?3,300.00 (Excl. VAT)

Close to four times what I paid for a Ford Racing 711 block? Gulp.

[qedmotorsport]

Hi guys,

We've made some changes to the product page to answer your questions:

http://qedmotorsport.co.uk/qed-shop/lot ... nder-block

Please note that at no point have we made any direct comparisons to the new American 711m blocks.

@piss-ant: Please can you remove the picture and description from your post. A link is all that is needed. (thank you)

[rgh0]

Fantastic that they have made the mods and increased the bore casting outside diameter resulting in siamesed the bores to enable you to truely and safely go to 90mm bores - will make a really nice high torque road engine if you dont mind the cost.

The eligibility officiers will need to start more closely checking twin cam capacities in the future !!!!

cheers
Rohan

[elansprint71]

Apologies in advance for my ignorance (I'm a time-served Toolmaker, not an automotive engineer ) if you put 4 x 90mm bores into a standard-length casting, would there not be some danger of cylinder overlap?
Assuming that I'm correct (unusual, I know) would the required longer block casting not also dictate a different spacing between the con-rods, in other words a different (longer) crank-shaft?
If any of the above is correct, how would one get it past the scrutineers?

Just off to check the dimensions of the Bentley W12.

[rgh0]

The nominal bore spacing is 96.5 mm so a 90mm bore leaves 6.5mm between each bore. If the bore cylinder casting OD is greater than 96.5mm then the bore castings join together and the result is a section of solid metal with siamesed bores like QED have done and you are fine. On the original blocks you had a 5mm water jacket between each cylinder bore so not enough metal to go to anywhere near 90mm bores.

No need to change the bore spacing themselves
cheers
Rohan

[CBUEB1771]

We've made some changes to the product page to answer you questions:

So the cross-block oil feed from the oil pump side to the main gallery on the exhaust side has been removed. A good idea if you want 90mm bores. I guess this means you need a dry sump style system and route a line externally to the main gallery to feed the crankshaft.

[qedmotorsport]

this is true of bores over 85mm, yes. any bore size below that, the cross drilling remains. (updated the product page to clarify that)

[nebogipfel]

Close to four times what I paid for a Ford Racing 711 block? Gulp.

Gulp indeed

[EnfoKen]

You either need it or you don't. It's a reasonable price for a low volume product from a small manufacture like QED or Gathercole.
http://www.davidgathercole.co.uk/engines.html
Considering tooling costs are many $$$$$ it's a wonder that smaller companies like QED take the risk. I am sure there are many racers
that thank them for producing it.


QED, is there internal clearance for a longer stroke crank? When I installed the 77.6mm crank in my TC block, I had to clearance for the rods at the bottom of the bores. 2.2L Twin cam...

KA

[qedmotorsport]

77.6mm stroke should be fine