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MG MGA - Derrington Installation Finished

At last I think I have finished the installation of the Derrington cylinder head on my car. It has only taken just over a year! It started with a rear crankshaft seal modification and then I had to get a custom inlet manifold made. There was a period of 4 months when I hoped that Maniflow would make it but they had other priorities so I had to find another source. Lucky I did as I have a really nicely made manifold in stainless that fits.

Then it has taken my 6 months of fiddling to get the engine to run nicely, mostly my own fault for setting the static timing on the wrong edge of the switched light!

There were other challenges on the way, including the distributor and vacuum unit, the mounting flange alignment on the manifold for the carbs and the leaking stud in the head for the rocker assembly.

Things to note are the heater valve is now mounted on the bulkhead, the brackets for the throttle (custom bracket on the carburettor mounting bolt) and choke (early MGB arm on the air filter), the clamps for the exhaust bolts and the brass heater pipe (custom brackets made)(the front and rear studs in the head are a bit short but I couldn't get them out), the shortened fuel pipe, a la twin cam, and the revised trunking for the heater. I was hoping to fit a twin cam heater in the same hole as the original but the fan motor interfered with the regulator. The trunking is from a twin cam courtesy of Jim Alcorn and actually fits quite nicely round the back of the rocker box using a twin cam inlet to the heater box. The water pipes with sharp bends to go to the water valve and under the trunking are from an Austin Healey. They were very hard to find with long tails.

The carburettors and air filters just miss the bonnet stay and the starter switch by about 8mm. There may be occasions when they hit but most of the time I think they are OK.

I took it for a test drive yesterday and was very pleasantly surprised. Lots more mid range torque I think. It also runs a lot cooler than before so another solution for Steve Gyles and the overheating topic perhaps. Maybe a bit complicated and expensive though.

The water pump was I think leaking a few weeks ago but it seems to have stopped now. I know it's likely to fail again sooner or later though.

I loaded the first picture in the other orientation but the site seems to have rotated it which is a pity.







John Francis

Well done John,
If you had done this and described it so well a few years ago, I might have followed suit. I had a Derrington Head and inlet manifold but chickened out and sold it. I saved myself a lot of trouble but envy you the mid-range boost that I, too, was looking for.
Shane
Shanerj

Well done John.

Have this as a reward. -


Nigel Atkins

Hi Nigel Thanks. Was that easy to do?
John Francis

Download, open, rotate, save, upload (delete). Probably works as I'm not doing it on a phone or i-can't device and/or I'm using a different program (MS 2010 for photos as I prefer the old version).

Nigel Atkins

John
What carburetors are you using H4 or 6s? Distributor access has been an issue for me (Derrington head and Webers) solved with a 123 distributor.
Nice job by the way!
Mike
Mike Ellsmore

Mike. Thanks for the compliment.

I'm using the original H4s on the advice of Peter Burgess. He thought for road use the H4s would be best. Also I couldn't get a pair of H6s I bought to fit with twin cam filters. The front filter hit the inner shroud.

I have taken the distributor in and out more times than I care to remember! I got a dab hand at removing the rear carb to extract the distributor. It really helps to remove the throttle shaft link bar with the wavy concentric spring links and using a very short spanner for the carb nuts.

I have a pertonix which I have had for ten years and is fit and forget unless it fails. I have read that some people think it will fail! I'm not of that persuasion as I used to design and develop sensors for engine management systems at Lucas (The Prince of Darkness). John
John Francis

Looking good John - nice work
William Revit

Nice work John.
Nothing wrong with a pertronix on a sound distributor. Had one on my twin cam for many years and no problems, even though some say the distributor can get hot it has never complained. Good luck and stay safe.
Bruce.
Bruce Mayo

This thread was discussed between 23/02/2021 and 24/02/2021

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