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MG MGA - Judson Super Charger for MGA

Hi, my name is Rick and I just bought the Judson SC from Andy B. who is located in Canada. I am a little worried that the set up will not function properly so I will provide the details of my current engine, etc.

The car is a 1962 MGA MKII, Stock Motor, valve clearance adjusted to 0.020", plugs Champion N5 gapped to 0.018" per the Judson Manual. I have not installed the SC yet, and I am reading all the past posts from the previous owner and Dominic C and others. The SC was rebuilt by George F last year and looks great. I want to go with the period correct SC vs Moss New SC. But reading the history is making me concerned, confused, or both! :)

So the Questions I have are:

1. Are the plugs and valves mentioned earlier set right?
2. SC Clatter? Is it really that loud?
3. Does the vacuum advance line need to be attached to carb?
4. Champion N5 plugs correct? Hotter or colder is better? Any expirences?
5. Holley 1904 carb rebuilt with .062 jet. Is this a good place to start with my set up? I have 10 other jets ranging from 0.060 to 0.070 jets.

Please feel free to comment on any or all of my questions.

Thanks, Rick
RS Kusy

Hi Rick

I have always left the valves set at the standard factory clearance, plugs too. But I run a bigger valved head and a slightly hotter cam. Try asking Carl Heidemann at Eclectic what he thinks here.

Yes it is loud when you first run it - have you soaked the vanes in a tray of oil first (just unscrew the end cap at the carb end and the vanes slide out) - but it gets quieter in a little bit. It's a lot louder than a standard A, mainly because there is a lot more going out of the exhaust, but the SC makes a fair bit of noise too. Mark the orientation of the end cap first because getting it out of position causes a lot more noise, zero performance, heat and a worn set of vanes. As the instructions say:
"NOISE: The supercharger may sound noisy when iis first started or within the first half hour of operation. This noise is nothing to be concerned about and will disappear completely within the first 20 to 40 miles of hard driving. A slight clicking noise sometimes at idle or after backing off of the throttle after a hard run is characteristic of a vane type supercharger.

Vacuum advance depends on your distributor, but in general you get better economy with it attached. But the Holley is prehistoric to tune, hence the running project to switch to an SU (got the machined tube back tonight, but am now off on holiday for three weeks or so). Just make sure you do not get any pre detonation under power ? acceleration.

N5 is OK according to the factory. I can't be bothered to go down for floors to find what I have in mine, but either BP6 or 7ES I think.

I run the 62 jet too, it runs a bit rich but anything less causes pre detonation. Important is what the service bulletin notes "A flat spot will be encountered at slow speeds or on acceleration if the idle mixture is too lean. The idle adjusting needle valve (brass screw) should be unscrewed until engine slows down appreciably, then the throttle adjusting screw screwed in to provide correct idle speed"

I have run many thousands of kilometers on mine, with one blown engine at the beginning because I didn't realize it was suffering from pre detonation, and one broken crank due to an accident. Set up correctly, it's a very reliable piece of kit. But setting the Holley is a PITA, and I suspect this is the reason they have such a varied reputation, particularly for destroying engines.

There's plenty of information on my site (just about all there is available on this supercharger), so just go delving there.

But relax, if it is tuned correctly and timed correctly, it should be fine. Don't forget to retard from the factory settings because of unleaded fuel.

If you need any more help, I'll be here intermittently this week, then in Asia till the middle of March

Dominic
dominic clancy

Rick, The unit was REALLY noisy when I first started it up after being rebuilt. It did, as Dominic mentioned, quite down considerably after the initial 20 miles or so. You will probably hear a bit of a rattling noise at idle, but that's the nature of the beast and it's not really that noticable once you're in motion. Be sure the oiler is set up to deliver the correct amount of oil as per the Judson instructions.

The .062 jet is what George set the carb up with so I'd assume it should be in the right ball park. I'd suggest checking with him since, as you know, the unit was originally set up for use on my 1800.
Andy Bounsall

This thread was discussed on 19/02/2012

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