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MG MGA - MGA 1600 with Judson and SU HIF

Dominic and I did this mod. some time ago ..fitting the Judson with a new inlet manifold and a larger SU HIF. It performed well for me after some fiddling to get the right variable needle and tune. I have driven the car often but only on 50 to 150 km runs since the mod..and general seemed to get about 30mpg but never measured precisely . I spent a few days last week giving the car detailed maintenance, tune check (and renewing the brake fluid) for a long drive from Narooma NSW to Melbourne, a distance of 690km along just one road , the A1 Princes Highway. I just got to Melbourne and I used the journey to check precisely what the fuel consumption fig was for the Judson/SU combination. I filled before starting and then twice ..last time 1km from home in Melbourne .Total 98 octane fuel consumed was 52.96 litres...making the fuel consumption rate 7.7 litres per 100km, 36.5 mpg ( imperial) or 29.2 mpg (US) . I was quite amazed and have checked the figs a few times. I recollect reading the fig for the original Judson/Holley fixed jet combination was around 21 to 23 mpg( US) so the SU seems a massive improvement..which is why Dominic and I ventured down the path. ..very pleasing!!
Neil Ferguson

I support what Neil reports. The Holley is agricultural compared to the SU, and also impossible to set so it has the correct fuel mixture across the whole power range. To avoid pre-detonation you have to select the fixed jet of the Holley to deliver enough fuel at high speed, which means that it runs rich across all other conditions. With the correct needle, the SU delivers the right mixture all the time. The only drawback is that the exhaust is *significantly* louder, which is something I will look at in the new year.

The Judson is much improved by the change, and I have a unit available for sale with this mod if anyone is interested. Holley and SU are with the kit, but it has a canister oiler instead of the correct valve cover.
dominic clancy

Dominic..My exhaust is louder as well especially when the boost kicks in on a long climb. I did think maybe it was time to repack the silencer with glass fibre ( last time 3 years ago ) and will do so anyway ..but your comment is valid. I had to put sponge plugs in my ear for the drive.
engine seems to be running slightly hotter as well...but then I went through a temp of 36c for a long time so maybe that had an affect..... also drove through a heavy thunderstorm but no stops so the waves went over my head ( most of it!).
Neil Ferguson

Dominic,
How am I able to install this in the US. I presume it is a new SU carb and a NEW hand made manifold. Please send me more information. Also, why would the engine run hotter if not pushing it hard but getting more economy. Too lean on fuel?

Jeff Becker
Long Beach, California USA
JEFF BECKER

Jeff...my comment about the coolant temp may well be a furphy ie irrelevant. I made it immediately post the long drive. My coolant level was down when I checked later ...took about 1.5 litres to top up so I have embarked on a total check of the cooling system. I also mentioned it was hot day ..36c ie 97F.
I also just pulled out 2 of the 4 Bosch plugs and they are a very healthy brown ...good and certainly not lean . I originally set up the system and chose the SU variable needle using my Gunston scope.

Dominic started the idea off as a thread on this site after someone set up an SU on a Judson in US I recollect . We both designed our manifolds independently ( his steering is on opposite side to mine here in Oz) and we got them fabricated locally but used the same 1.75in SU HIF6/44 carbs.. which are available fairly easily.
Great mod.. very pleased .
Neil Ferguson

Jeff

I will mail you the drawing for the manifold separately. I also wrote a guide which I believe is on my website. The carb that needs no modification can be bought new from Burlen for around 100 GBP and is for a Sherpa van! I haven't measured my MPG, but rich ending the mix will reduce temperature a little. In any case it is a much better solution than the Holley.

If you are interested in a kit of manifold and carb (used but modified and serviced with a kit) one of my friends has a set for sale. I am a bit tight on time before I go on vacation next week, but can organize very thing when I am back from vacation in mid Jamuary or put you in direct contact - he is American living in Switzerland, so communication will be no problem.

The reason it runs with better MPG is that the Holley is a piec of junk!

Dominic
dominic clancy

Further to previous comment on engine heat and Judson/SU. I drained out old coolant and used a chemical flusher to clean out system. Filled it up with a premix ( inhib.,glycol etc ) ..also reset electric fans to kick in at 180oF (same as thermo. and lower than previous 190oF setting) to give extra transient time for the cooling during condition changes .Off on a drive and coolant temp hovered between 185 to 190oF. All seems fine...
Think I may also replace front grill slats with stainless mesh in the near future to allow extra air on really hot days.
Neil Ferguson

And because I mailed Stuart Mumby some pictures for the new edition of "Call it MGA" here's what the SU setup looks like - this Betson engine / Burgess SC Head and SU Judson setup will be going in my car in January. I just have to order up a much more effective exhaust to cope with the extra exhaust gas volume that is created and which completely overwhelms the standard silencer / muffler.

The second tappet vent tube is fitted to help reduce crankcase pressures as much as possible (and it will be painted when it has been cleaned up). It is going to be a pain fitting the exhaust to the manifold and the tacho cable is just possible with nimble fingers. The braided hose is the float chamber overflow.

The HIF44 is one that is specified for a Sherpa Van, and requires no modification and is cheaper new than the junk sold used on eBay!


dominic clancy

Dominic

Are you going to add an extension pipe to that braided overflow pipe to take it below the exhaust pipe?

Steve
Steve Gyles

This thread was discussed between 30/11/2014 and 13/12/2014

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