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MG MGA - Derrington Head
|There is a Derrington head on Ebay at the moment that has me sort of interested. Item No. 111465944301|
Can I ask for your thoughts before I consider entering a bid.
|The fabricated manifold looks kind of hokey. I suspect it is not port matched, so it may not flow well. You might be looking for a different intake manifold.|
In the head itself, there appears to be a weld repair in #2 chamber between the intake and exhaust valve seats. Aside form not being polished smooth, it looks like a good repair.
|Steve, I agree with Barney: the manifold is a bit of a muddle. I had a much more straightforward one on the one I sold last year. All depends on the price... Shane|
Last winter I was talking to Cameron who rebuilt my engine about these (and the modern replicas) of which he has handled several. In summary great if they work but some are in a dreadful state. He had one on the bench that he had abandoned trying to repair after much effort so a bid on ebay is a gamble. The modern ones have a bad name but he reckoned he can usually sort these.
I have the original HRG Derrington catalogue which gives lots of performance data on various cars including As I can scan this if required.
I always used to fancy one.
I bought one a few years ago with 1 3/4" manifold.
The manifold on the ebay one looks strange and the mounting studs for the carbs seem to be canted over at an angle so not sure if standard 1 1/2" carbs will work.
I have had real difficulty getting the 1 3/4" carbs and filters to fit under the bonnet with the manifold that came with mine even with the cut out in the bonnet for the twin cam arrangement which I think became standard post twin cam introduction and using twin cam filters.
So far I have not fitted the head because it was not straightforward. The car highlighted a few weeks ago on the bbs gave me more enthusiasm to have another go although it had 1.5 carbs.
|Thanks all. Going to give it a miss.|
If you have time to scan the catalogue, I would be very interested in a copy.
(wellardm - optusnetdotcomdotau)
As you are aware I have a HRG-Derrington head on my coupe with twin 45 DCOE Webers. I love the period look of this set up plus the umph it gives so would not part with it. While my engine does have a lot of mid range torque, it will also rev to 7000 okay. But I am of similar belief to Peter Burgess that if you are looking for outright power a well worked standard configuration is best (there are comparison figures and comment in his book "How to power tune a 4 cylinder MGB") .
If I was you I would look at buying it and fitting it with the Weber set up - you are the type of person that "doesn't do standard"!
One thing with these heads is that they have become soft over time this could cause the head gasket to fail prematurely. Mine was deemed soft when last overhauled but I opted to take a chance with it rather than have it heat treated and so far so good - I also have larger diameter head studs than standard. I have also heard of soft alloy heads being hardened by pad welding the face and machining back - seems radical but have been assured it works!
Could you please send me a copy of the HRG - Derrington brochure at firstname.lastname@example.org
For those who haven't seen it before there is a lot of HRG Derrington info on Bill Spohn's web site
|Intake looks very similar to mine other than mine having 1 3/4 SU's and what looks to me PO added tubes
Yes I can send you the scan of the Derrington Catalogue but what is your email address?
|Paul, -- If you are scanning the catalogs, please send me a copy. I can post it on my web site. Email to email@example.com|
|Guys, I keep a fair bit of HRG info on my site at |
Including the HRG dyno info and fitment instructions at
|The trouble with these cross flow heads is that with the carbs on the other side practically all the electrics are obscured.How people check points is a mystery to me. Also the fresh air intake to the heater cuts across the carb air filters. Any one got a twin cam heater box with intake on the other side? Last month the thing I dreaded most occurred, the hydraulic brake pressure switch failed. You can't even see it with the carbs and filters onthe RH side. (easy with a minor - straight down on RH side of radiator.) I did manage to change it with lovely son in law lying underneath holding the fixing on by feel. Yuk.|
|H L Davy|
|Could you could turn the heater around and swap the motor to the other side after drilling holes for the heater matrix? This would allow you to route the cardboard hose on the left of the motor. It would not work on a LHD car (hence the repositioning for the twin cam heater).|
I found a heater box from a Triumph Herald, which is already in the reverse orientation. It just needed mounting brackets (pop-riveted if you don't have welding skills).
|It isn't really that hard to work on the distributor - I just remove the rear Weber and manifold (3 bolts - do not need to disconnect throttle cable or drive to the second carby, just slips apart, you then lay the assembly on the heater shelf). You can then work on the distributor - I normally remove the distributor from the engine which makes it even easier to work on (same with standard cylinder head cars). I generally have to make a new paper manifold gasket each time. To adjust the timing I have a custom made long spanner that goes down through the gap in the manifold to loosen/tighten the distributor clamp ring - you can get your hand down the back to turn the distributor.|
I have also had to replace the hydraulic brake pressure switch - remove the rear carby as above, blocked the 5 way brake pipe union against the starter motor (hi torque type) with a piece of wood, and use a long socket and couple of extensions to loosen the switch from above.
Similarly to remove the alternator it is easier to remove the front Weber.
(The above is small price to pay for the omph from this setup and the looks you get when you open the bonnet).
My car originally had a heater fitted by cutting and mitering the heater inlet pipe stub so the intake tube ran on the exhaust side (you can see where it rubbed through the insulation on the exhaust header pipe). The water pick up was a plug hole on the exhaust side of the HRG head - there are 2 of these plugs on the exhaust side). While this setup worked fine we don't have much call for heaters in Oz so it is now in storage box.
Its looks like you have managed to get the 1 3/4" carbs to fit under the bonnet but without the normal twin cam filters. Do I see some spacers between the manifold and the carbs? I'd be interested in some other photos of the installation from low front and close ups just to see how it all fits and how close the top of the carbs are in relation to the shroud. I think I have the same manifold as you have as in Gary's photo.
I was thinking that I would have to reduce the angle of the manifold very slightly to make it all fit with the filters and avoid fouling the starter switch.
Your comments would be helpful.
The manifold is the one suipplied by derrington with my head when I bought it, so it's not surprising that others have the same manifold.
I don't have any angle on the spacers and the HS6s don't fit with both twin cam filters so I have a pair of trumpets with oiled foam filters. Because I have long trumpets, I had to cut a small chamfer on the top of one (the front?) to clear the shroud. This doesn't alter the filtering because the foam sock hides the trimming.
I will try to take some pictures this weekend.
Pictures attached, as requested. I hope they show what you need to see, if not, let me know and I will try again.
My manifold came with mounting flanges for HS4 MGB carbies. I had these altered to take the H6. I expect that with the right angle, the twin cam air filters may fit (I have a pair that I was hoping to use and may try again if you succeed).
It seems that I can only attach one picture at a time so the others will follow.
This shows the ram tube trimmed to give clearance for the inner guard. It's pretty dark but hopefully good enough.
|Last one, showing the foam filters in place.|
This thread was discussed between 20/09/2014 and 05/10/2014
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