Tell me about the Eaton M112 Supercharger and using on carbs

Not really answering your questions, but a bit of out-of-the-box thinking for you....

How about running the twin SU's blow-thru? It's a well known and proven MG/Austin/Rover SU carb setup, and the standard HIF44's can be rebuilt with turbo spec parts.

What I'm thinking is that you're planning on fitting the Eaton in the middle on top (so any excuse to justify cutting a hole in the bonnet ), why not use a standard twin SU manifold, space the carbs outwards enough to mount the supercharger between them with the outlet pointing down and the nose/pulley lined up to run off a belt on the front of the crank pulley. From the outlet the air-charge can be ducted either side then directed into both of the carb intakes/plenums. The intake to the charger out the back can be a simple 180 degree elbow to point forwards from above, giving you the classic supercharger scoop, completely functional and bolt on

The plenum/manifold on the outlet of the charger would probably only need to be 1.5"-2" deep, as long as it allows the air to flow freely out to each carb the shape shouldn't matter too much. A bypass valve on each side of some description would probably be the biggest challenge. I plan on using a simple mechanically controlled bypass system on my supercharger build, basically another small throttle plate that is open at idle and shut at what.

I really think you should reconsider the HIF44, the parts are available to rebuild them to near turbo spec, main difference is that you won't have the o-ringed dash top (mine started leaking close to 10psi). It could work with the 2" SU's, I've not seen it done but doesn't mean they wouldn't work under pressure?

There you go, no excuses to start bolting the supercharger on

Haaaaaang on a minute. On my old setup (crudely sat on the engine in the pic above) - isn't the charger basically upside down?

If that's the case, why can I not simply use the Jag XKR V8 elbow like this one. In fact, either way round it's supposed to be, can I not use an "off the shelf" part?

What is stopping me using the jag outlet as above? If the outlet was underneath, would the charger not be upside down and spinning the wrong way? Wouldn't it make more sense for the outlet to be on-top?

As for spacing the carbs it makes me wonder how much I can space them before it starts to have a detrimental effect.

Do you have the Jaguar outlet then? If you have, bolt it on and lay the blower over the engine to see how it could fit

I reckon you could space the carbs a few inches and not notice any difference, bonnet clearance could be an issue, function over form and all that! Make the throttle and choke linkages and fuel lines longer, new throttle control to replace the P6 rod arrangement, I don't see it needing any specialist or highly skilled know-how or tools doing it the way I've described. A pair of Metro turbo plenums or fabricate your own carb plenums (don't bother with any 'restrictor plates', they're a bodge and not how the factory setup runs).

Tell a lie - there is a 1/2" 2" SU Spacer available - part #c33059

www.bighealey.co.uk/austin-healey-parts/fuel-3/under-the-bonnet-1004-large/spacer-carb-to-heatshield-hd8-c33059 although they list it as 1/2" where everyone else lists that part as 1/4".

I was thinking if I turn it upside down then it's rotating the wrong way but of course it does't so that's a pretty stupid thing to say! Yep you are right - I'll get the car back together first (head gasket failure) and then start working it out. The pulley is the next thing - I think I have something kicking around that was modified, I'll have to dig it if I can find it - and that will decide where the charger sits, really. Unless someone makes a pulley for the Rover V8. My charger seems to have lost it's pulley looking at the pics, too!

I think outlet on the bottom makes makes it get in the way of other things and was also thinking it would be better a bit further away from the heat of the engine?

You don't have any 2" carb spacers kicking around in your vast array of bits do you?

Yep, still in the stone age with a dizzy The carb tower is about the height of the distributor anyway, and would have to clear that, so it'll sit quite high regardless. Triangular lump will probably get in the way of something but will only know when I start mocking it up. *if* I can buy an elbow off-the-shelf no doubt it will point upwards for the standard orientation - that might decide where it goes as it beats trying to make an elbow.

My experience of blow vs draw through is limited to air cooled VW's and stuff I've mucked about with for friends, however it translates to the Rover anyway, as it's a 4 stroke engine... usually that draw is fine, if you don't mind driving flat out all the time. you do get flat spots, even with an SU, which is a lovely progressive natured carb, blow through is far nicer, it just feels like you're driving a bigger engine, and it's the reason it gets used for production vehicles everywhere . You want a nice linear power progression, that's why you've gone super over turbo.

I remember having this discussion with Pete when the two of you first made a start on this project.

If you're serious about boosting it, save yourself a whole load of pain and just get the front wheel cut for 36-1, get a megasquirt and figure out a way to go EFi on it, simplify it with a single TB (72mm will flow enough) and have the manifold drilled and tapped for injector placement. I know you wanted to keep it low tech, but you'll only end up disapointed with the results.


Boosting it runs into a whole heap of issues, draw through on that charger isn't ideal anyway, the teflon coated ones you really don't want to go that way with either because you'll end up breaking apart of the coating and it's really nasty stuff to have going through the head and into the bore, basically it'll damage the engine.

If you go down the blow through route, you can just run boost from the charger outlet to the carbs, but you'll need to mount the charger somewhere other than in the valley and run pipework from that, as your carbs will have to sit in the valley on the heads. You can convert SU's to run boost, they used to do it for the metro ones, it's relatively simple.

The second issue you're going to have is retarding your timing for boost.

How does the dizzy advance on the P6?, if it's vacumm you're going to want to change that to a centrafugal advance or find a way to modify the can so it doesn't do funny things when it gets a positive rather than negative signal.

If you insist on keeping it carb, then at least find a way to lock the distributor when it advances, otherwise you're going to melt pistons, if it's centrafugal, you can usually drill and tap the body to add an advance lock which will prevent that.

Don't be tempted to knock the timing back static, because by doing that, you'll have an engine that performs badly off boost, floods with fuel as it's not buring the mixture and you'll see some nasty burps. It'll also be very hard to start.

With regards to fuel supply, if you do boost it and go blow through, depending on your fuel pump, you'll need something to regulate fuel pressure, otherwise the boost will stop the carb from filling with fuel as the floats get pressurised.

You'll want a variable rate FPR that's boost sensitive, the R5 Turbo's used to run carb and blow through and used a malpassi (sp) unit for this that took a reference feed from the inlet manifold.

The the car still running bosh in line pumps with a holley feeding it? , they should be up to the task, but install a swirl pot as well if you haven't already. Last thing you want is to loose fuel mid boost.