QED Twin Cam Cylinders Heads

[CBUEB1771]

Does anyone have recent experience with the QED Twin Cam Heads I really don't like the idea of SAS head not using replaceable cam bearings.

[TBG]

I am saving up for a QED head as my engine builder states that if you have no bearing shells to begin with you will need them down the line. So QED gets our vote. D

[englishmaninwales]

I understand it is to do with modern alloys, casting process and oil being superior to that of the 1960s that enables the cams to run directly in the cylinder head with minimal wear. Certainly the Rover twin cam cylinder head in my Caterham 7, with this type of cam bearing arrangement, is 27 years old and having spent most of the 80k miles of its life on the limit, is still within cam bearing tolerance.
Malcolm

[Foxie]

I am on my third TC head supplied by QED. In principle would prefer replaceable cam bearing shells as an option, although I have never had worn cam bearing shells.

However, I am at present rebuilding my 1978 Ferrari 308 GTS, and the cam bearings are directly machined into the caps. From research, these engines are capable of high mileage without trouble, so it seems that this system works.

[fatboyoz]

Hi Foxie,
Any other comments you can make in regard to any aspect of the QED head?
E.g. any extra machining required, quality etc.
Cheers,
Colin.







quote="Foxie"]I am on my third TC head supplied by QED. In principle would prefer replaceable cam bearing shells as an option, although I have never had worn cam bearing shells.

However, I am at present rebuilding my 1978 Ferrari 308 GTS, and the cam bearings are directly machined unrecorded into the caps. From research, these engines are capable of high mileage without trouble, so it seems that this system works.

[/quote]

[gjz30075]

Foxie, are you on your third head because you had to return two of them? Or are they
for other twin cam vehicles?

[el-saturn]

same question: 3 heads sounds like quality issues!!?? sandy

[Foxie]

Head No. 1 was the original Lotus 1970 head, when I bought the car in 1985.

This head was later converted to QED 420 spec by QED and became Head no. 2.

Six years ago it became clear the original cam bucket bores were worn. These were replaced by Phil Price at Connacht Engines. ( QED were not doing any machine work at the time )

Engine capacity increases (It's now at 1862cc ) and head service skims meant the compression had now gotten to the point it was blowing head gaskets.

So a competely new QED large port race valve head with 48cc combustion chambers was fitted 4 years ago.

This is now Head No. 3

I have always got very good service from QED, and never had a problem with any of the heads.

I never had to do any extra modifications or machining to the 420 and 450 heads.

I have done a total of 55,000 miles over 20 years in Europe with the MSA Euroclassic, taking in places from Trondheim, Budapest, Rome Valencia, and Lisbon and most places in between. We always got home.

I have been circuit racing and hillclimbing in the past 14 years, and won the Irish Hillclimb Championship Historic Class in 2018 and 2019. Two head gasket retirements, and one dropped valve, caused by the valve cut-outs in the new Dave Bean pistons being marginal for the big valves. Very fortunately the valve head immediately jammed in the port, so there was minimal damage.

[bitsobrits]

Am interested to know your route to the 1862cc displacement, particularly which crank did you use and what other mods were required?

[Foxie]

I built my first high capacity engine 20 years ago using the tall block and crank, 83.5 Omega pistons, and 5.05" rods.

Along the way I fitted an 82mm crank.

The con-rod bottom ends hd to be ground off a little, as did the inner walls of the block adjacent.

After a number of rebores the tall block was out to 84mm and was retired, replaced with the new 681 block from QED.

This block can be bored to 90mm, and there is plenty of room for the conrod ends.

I thought this would be a tall block, but it was the standard Lotus height, Doh !

However I sourced a set of 85mm low compression-height (1.13" ) pistons from Dave Bean in California.
4.926 rods got the height right, and the piston domes were machined to give a 10.57 comp ratio.

Ken Gray there was very helpful, I could chat to him late in the evening while he was still only on afternoon tea.

I'm slowing down a bit on the competitions now, so it should last out a while.

[RichardHawkins]

Roxie,

Just general interest, how do you get a tall block ngoni under the bonnet? I have only two to three mm clearance wit a standard block.

Richard Hawkins

[RichardHawkins]

Foxie,

Sorry about getting your name wrong, did not notice until after I pressed send.

Richard Hawkins

[Foxie]

Roxie,

Just general interest, how do you get a tall block ngoni under the bonnet? I have only two to three mm clearance wit a standard block.

Richard Hawkins

I have a Spyder chassis, where the engine mount rubbers are reversed and bolted to the chassis, not the block. There are two legs bolted to the mounting holes in the block, which bolt to the "wings" of the engine mounts

I welded up the mounting holes and drilled them higher to drop the engine the required amount,