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MG MGB Technical - supercharger or crossflow head

Reactivating a 2005 thread. Between the x-flow and the SC....I'd flip a coin. It's like Gwyneth Paltrow and Angelina Jolie: both different but compelling beauties. Vemarooski

vem myers

Vic-
I'll take a crossflow over a supercharger. Simpler, less to go wrong. More room in the engine compartment, too. In theory the supercharger may more power potential, but you'll have to live with the increased downsides to get it.
Stephen Strange

I figure they will cost about the same money, and the supercharger will give more power and a wider power band. True, it does take up more room in the engine bay and it will need service at 100K miles but the cross flow makes the engine harder to work on also since the carbs are now covering up the distributor.

Both will be a lot of fun but personally I'd go with the supercharger kit. Just my opinion.
Steve S

Although you can, "with enough work" and other goodies get a good cross flow to really perform they do need that extra input. Also not all makes of cross flows are equal. To put one on a good "stock" engine will disappoint, were as a supercharger and a days work can make a good "stock" B into a potent little car. Denis
D M HILL

Ilove my Derrington cross flow head, twin 45 DCOE Webers, extractors, side exhaust - so sixties!
Mike

Mike Ellsmore

I would have to vote supercharger. Look if you don't go more than seven pounds per square inch of boost or half an atmosphere, the power will come in early and just about keep going. Surely a crossflow head is just going to breath better but at specific revs, it might even be tempremental? The set up for both can be just as complicated, you may have two carbs to play with, where-as only one big one with the SC. They probably to cost the same but more bag for your buck surely from the sc? Mike
J.M. Doust

Mike: wrong picture, I canīt see the engine!!!
(But what a beauty the car is!!)
Joern-M

Then again, why not drop in the V8 or the V6. Ooops sorry, wrong crowd! Mike
J.M. Doust

Hi Guys,

Why not both Jolie and Paltrow I mean Crossflow and Superharger as on fathers 1938 TA-Special. (Just put some photos on the TD/TF-Page!)

Is it possible to match a SC to an MGA/MGB-engine with Crossflow Head?

Anders/Sweden

T Dahlberg

The supercharger because it has positive pressure (when on boost) at the valves, it to a great extent overcomes the disadvantage of a siamese port. I would be an interesting project though. Denis
D M HILL

Joern - I was just wetting your appetite with the earlier photo - here is the engine!
Mike

Mike Ellsmore

Yeah thats a great looking car and I bet it goes just as well. Denis
D M HILL

I was actually considering the purchase of a crossflow head when Moss first introduced their supercharger system. I quickly realized the ease of installation and access to the carburetor was a big plus over the NA aspects of the crossflow head. The crossflow requires two new manifolds as well as two new carburetors for a proper setup. Changing the oil filter and working on the distributor seemed almost impossible. I've been running the supercharger system for eleven years now and it has transformed my B engine into something to be impressed by. RAY
rjm RAY

Ray- Good points. I went with a remote double cannister oil filter and started an EDIS before I put her down. To this day, I smile thinking about 7000 + RPM and still pulling, well over 100 mph on a balmy summer night in the high plain desert.....and I hadn't shifted into 5th yet..... I went with the side draft SU's and it was all good.
Mike- That is just awe inspring. How long have you been driving that? Vic
vem myers

Vem,
About 6 months - it has been in the MGCC (Victoria) since the restoration in the early 90s. Changed owners 4 times due to father time and health issues.
Mike
Mike Ellsmore

Steve & Ray-
I converted to a remote oil filter as on the Rover V8 model and installed a Crane/Allison breakerless electronic ignition kit, so all that I have to do with the distributor is to clean and lubricate it, usually just once during the winter. Removing the rear carburetor for access is a simple matter of disconnecting the linkage and pulling it off complete with the exhaust manifold, so it's really not all that much work.

The problem that I have with adding a supercharger system is that it still requires the additional expenses inside of the engine that a crossflow cylinder head engenders: manganese silicone bronze valve guides in order to conduct the added heat out of the valves, improved cooling system capacity, etc, etc. Simply bolting on a supercharger to an otherwise bone-stock engine forces a restriction in boost pressure so that the standard-compression pistons won't cause preignition. The result is less power than most people would fantasize that they'll be getting. Of course, it's not in the interests of the vendors of supercharger systems to point these issues out. To get my money's worth out of an investment in a supercharging system would require more money than I would be willing to spend. It would be cheaper to convert to a modest Rover V8, and you'd get more power, too! That's why I'm in the process of building a 4-liter Rover V8 engine at the moment.
Stephen Strange

I have not driven a crossflow, but have a s/c on a stock engine. It transforms the low down torque, making it easier to drive and keeping up with modern traffic. Maybe not so much at the top end but it gets up to 60 odd at roughly the same rate as a modern. The you find a good long straight and get silly and discover the speedo is banging at the end stop...
Michael Beswick

With a little head work, going with silicone bronze guides and a mild camshaft my supercharged engine actually puts out more power than I need. I reduced the maximum boost pressure from 10 psi to 7 psi. To control my HEI ignition's timing, while under boost, I installed an MSD Boost Timing Master that backs the timing off from 0 to 3 degrees per pound of boost. Everything is adjustable from inside the car while you're under way. You can use the maximum amount of ignition timing advance without worrying about harmful detonation. It doesn't matter whether you're driving through long winding hills or flat out across the desert floor, a properly setup ignition system is critical to the performance of a blown engine. RAY
rjm RAY

Ray-
Thanks for mentioning the need for a more complex ignition system that involves manual adjustment from inside the car while you're under way. In my haste, I had failed to mention that additional factor.
Stephen Strange

What Ray said in no way means that a complex ignition system is necessary, as there are many happy SC users sporting nothing more than a properly curved points distributor. From memory Rays engine was first built as a high performance side draft weber equip naturally aspirated engine and the MSD boost master allowed him to cope with higher compression than you would normally build into a SC engine.

Denis
D M HILL

When I first built this engine, to the specifications that Dennis mentions, I was using the car primarily for use on flat ground along the U.S. Alantic coast. Having moved to the mountainous coast of Northern California, I have a greater need to change ignition settings while under way, on steep grades, while under boost. Someday I'd like to give the water injection system a try. It sounds like a great idea. RAY
rjm RAY

Mr Hill is correct - the modern crossflow heads are just starter kits - spend a bunch more money and you may have something, assuming you can find someone to do the work (Sean Brown of Flopwspeed will no longer touch them as they had core shift that meant a significant risk of trashing them, trying to get them to flow as well as the original HRG heads did out of the box).

The supercharger is easy bolt on power - best option for most people.

I've raced with the old HRG like Mike and quite enjoyed it.

Bill Spohn

Mike love your car what colour is that if you dont mind me asking. Also who done the exhaust manifold on the crossflow for you (I take it you are RHD),I also like that rocker cover is it Australian? cheers Cameron
Cameron

Cam, why not share your x-flowed stories. You have some of the best power numbers I recall ever hearing. FWIW, Peter flowed my Pierce fronted MSX almost 10 years ago. Sean got into to it, but then out. I remember Peter's comment on half filling a "coffee tin" with the shaving from the flow work he provided on the MSX. He also corrected a 13k" woopsie in the head surface, and flowed the SU manifold I sent him. I could not have been more pleased with Peter's result and I think he is still doing both the HRG ( if you can find one says Stephen Strange) and the MSX. The 4 years I drove the crossflow at 4-6000 feet above sea level were just very memorable. The car had much broader power then the SC, augmented with a Sierra 5-speed, and my drive enjoyment with that x-flow was special. I've never run or driven the 2xDCOE on a xflow, although Mike Pierce in Gilroy has a DD with the double sidedrafts that he's been driving without issue for at least a decade. He claims it goes like a bat all the time. I hear myself talking myself into resurrecting the ol x-flow gal as I type. Oh what a feeling! Vem
vem myers

Both great ideas. The examples above are works of art.
If you can find a quality cross-flow and don't crave for the much more power, then I would go with the cross flow, have it ported by somone like Peter Burgess and then modify the manifold for port fuel injection and set up the ignition for ECU controlled ignition.
werner haussmann

This thread was discussed between 05/03/2012 and 14/04/2012

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