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MG MGB Technical - supercharger or cross flow head

I've owned my 74.5 MGB for 30 yrs.and do both city and highway driving. Rebuilding the engine with either the new supercharger or cross flow head. If cross flow head either dual SUs or Webers. Can't make up my mind. Any advice on this decision? Thanks. Mike
Mike Pangia

Mike,
Dollar for dollar the supercharger will give more horsepower.
Bill
Bill Boorse

Believe supercharger easiest way to higher power.

x-flow nice but not cure-all. Dual SU's will yield more tractable power than Weber.

Upgrading innards to handle increase of power wise and equal cost for both.

Turbo a bit harder but more potential.

Money spent on professionally flowed head, matched cam and exhaust will yield dependable power for less.

Mike!
mike!

go on to the net peter burguess , he knows is stuff. he as different heads to suit what you want ,the bottom end of a mgb is very strong ,change the head cam and put some good quality pistons in. as far as carbs go su work well with su air filters and thiner needles.ive spoken to the man and to have a proper sc con you will need a special low comp head cam the full lot then purchase the sc it will cost thousands. my car is standard except for electronic ignit(crane xr 600) falcon 4 branch man ,su air filters and thiner needles. i will be spending money when i need a unleaded con,free flow head and piper cam, you will get 100 bhp plus enough for a mgb thanks daren
daren parker

why do you americans love mgb s ,you have fantastic cars in the usa ,i would love one of those dodge chargers ,or a mustang there great do you know the price of fuel in the uk over 4 pounds a gallon, im sick of it daren
darenparker

i second that daren.

mike,

supercharge a cross flow head, you get the best of both worlds then! and plenty of space in the engine bay to do so.

joe
J P Connor

Sure. If you can cast or mill up a custom manifold!

Why do we like MGBs??? We are up to our armpits in mustangs and chargers and firebirds...yuck!

Something nice about smokin' a late model poser with an old British leaker!

Besides, there are so many of us here in the states that there just appear to be a higher percentage of lunatics.

Mike!
mike!

Sorry for the off-topic post, but...
Daren, man, if you have to ask the question you'll never understand the answer. Aesthetics are like that. The MGB is not big, not fast, not flashy, not even particularly reliable or practical when put against a modern car. I've met lots of car people from the UK, many like MGs, most could understand why we would like, say, Jaguars, but not one could fully understand just how revered the MG brand is on this side of the pond. Why? Who knows. Absence makes the heart grow fonder, I guess. I like the MGB for perhaps the same reason you would like the Mustang - it's a beautiful relic from another place and time.

Sorry to hear about the four-pounds-to-the-gallon thing. Yikes! With the dollar as weak as it is, I could easily buy a decent lunch here for the price of a gallon of petrol over there. Good time to visit the States, you suppose? We're having a nationwide half-price sale. Come on by sometime. :)

Cheers.
Sam

I have the best of both worlds - a fibreglass British car with a big block Chrysler Sixpack in it ;-))
Bill Spohn

I've driven Chargers, Mustangs, etc. THAT'S why I like MGB's! My wife is kicking around the idea of selling her 2002 MINI Cooper S and getting a 2005 Mustang GT. I drove one and it's just like the rest of 'Murican the bunch. Heavy and numb when compared to my B, or my 240SX for that matter. Getting back in the MINI after driving the GT was like strapping on an Formula one car. The Mustang GT does have an awesome engine, though. Heck, the V6 version does 0-60 in 6.9 seconds!
David

Mike,

Supercharger











...and as the British say-

Full stop.

-BMC.
BMC Brian McCullough

I drove a Camaro (as in the same particular Camaro) as my daily driver for nearly twenty years. One day it broke, and I was busy and didn't have time (or money) to fix it for nearly a month. So, I drove the B for that month. I finally fixed the 'maro, and the first thing that I thought after getting back out on the road in it was, "This thing's a pig!" I sold it within a year....

The current stable consists of the B, a MINI Cooper S, and a Honda Wagon. The Honda is the least inspiring of the bunch, and even it handles better than the 'maro did.... Loads better fuel economy, too! ;-)
Rob Edwards

Daren
I'll check out that reference. Thanks.
About your question about why we Americans like the MG so much when we have the Chargers and Mustangs, etc. Those cars have reliable electrical systems, they hardly ever break down and your teeth don't loosen along with the rattling when you hit the slightest bump. Who would want a car like that? Mike
Mike

I'll tell you why I don't like Mustangs, Firebirds, GTOs, etc. They don't turn!
Steve Simmons

I would have to agree with Rob, my other car is an early pontiac TA that looks and goes great but since fitting the SC on my otherwise stock B it hardly leaves the shed. Mike a good stock motor with no more than stock compression is what the sc from Moss and HP were designed for. Other mods may produce a bit more power but the SC is the big difference. The main thing about the SC is the drivability,the power is there from the moment you hit the throttle but docile in traffic. MPG the same as stock, at least mine is. My 69B is 8.8:1CR has done 75000miles 5000 with SC and has never had the head off from new. You find with the SC your only on boost about 1-2% of the time and still cruse about 10*vacuum. All the best Denis
DENIS

Im my humble opinion, the crossflow is the way to go.
So I did ;-)

In the end, you'll have to rebuild your engine anyway.
A SC is quite expensive, and still needs modifications to the (standard) head to be on par with the crossflow.
If you look on Chris Betson't site, you'll see a comparison of the power Phil's B produces (he has a B with a Han Pedersen supercharger and a modified head) against mine (crossflow, 11:1 CR, ...)
Both measurements were taken I believe 2 days apart, in very similar weather conditions, both on the same rolling road and with the same operator (Peter Burgess!).
I can't help but believe that to attain the same power levels, the supercharger setup will be more expensive.

Peter has tested a supercharged car with more horses than mine, it had one of Cameron's cams. To be honest, I was quite impressed by the power figures (check out the archives, Peter posted the results) but, and this one is important to me, below say 3500 rpm, my car has more power.
That may sound unimportant, but I don't pull my car to the redline each and every time I drive it! It's also used in the city and for MGCC outings, and that's the beauty of this setup: it's as docile as a kitten when driven normally but pulls like a train when pushed.
All thanks to Chris Betson and Peter Burgess...

Oh, and YES, it is on Dellorto's (like webers), so please don't just fall for the myths surrounding them. They are fantastic carbs when set up properly (so don't try to be cheap and do it yourself, go to a rolling road, it's the best money spent). And they sound truely amazing too!

And please don't forget to improve your brakes and perhaps your suspension setup as well. These modifications do not have to be expensive, but they are very important when you have more power to play with.
(I installed Mintex 1144 brake pads and shoes, and a 3/4" front anti roll bar, so that's not that expensive especially if you consider having a new engine)

Hope this helps,

Alex
Alexander M

You could always supercharge a cross flow!

I was at Gaydon on Saturday. Next to the display of MG speed record breaking cars the was a supercharged mga twin cam type of engine on a stand. It looked very impressive. Very wide and lop sided as the supercharger is inline with the carbs which are in line with the intake manifold.

Alex your engine might clear 200bhp with a blower as well. Or it might go bang!

David
David Witham

Why don't you get aother MG and do both?

Mike, you have a bit of a dilemma don't you? Do you go high compression with a great head and the biggest carbs you can run on an MGB, or build the engine for low compression and hope the supercharger works out the way you want? I'd build a 9:1 compression engine with an aftermarket aluminum stock-type head, with a great port job. From there, add the supercharger kit. If you don't like it, you can always sell the head and supercharger kit and put on the crossflow, which by the way, is much harder to properly tune.

If you start out with the crossflow at a decent compression ratio, you can't put the material back onto the block to lower the compression ratio later, should you decide to go with the supercharger. Just my thoughts.
Jeff.

Jeff Schlemmer

Where's Vemarooski when you need him? He has both!
Terry

I've owned a few muscle cars in my time, 1970 z28, 1968 442. I remember getting on the freeway and hitting the speed limit (70mph)still in 2nd gear. You just can't go through the gears in those things without racking up tickets and endangering other people.

Also, with all that power, there's no need to plan ahead for turns to make sure you're smooth and exiting in the proper gear. I mean, can a responsible adult ever push a corvette etc to it's limits without being on a racetrack.

It's more fun to drive a slow car fast, than a fast car slow.
Fred H

The Xflow head can with work overcome the problems the 5 port has because of the siemese inlets. When you SC a 5 port motor the inlet pressure also overcomes this problem of uneven cylinder fill. So maybe the gain on a SC Xflow would not be as great as you may expect.
What I like about the SC is that the motor can be stock, with all that goes with it such as, long lasting (dont need hot cams on stronger valve springs)and the like. The power is developed from low revs and its more the torque that you feel. Idle is great and only need to tune one carby. When a hot NA motor with carbys that you can stick your head down is used for traffic or slow conditions they are usually run very rich to overcome flat spots. It would be interesting to compare MPG for both. I just did a trip of 400 miles with a ralle in the middle and got 34MPG on PUL.
fuel.
When we dynoed the car after getting the mixture right it put 102RWHP (up from 65 ) and as I had not used this dyno for a long time I first ran up a commodore v6 (3.8 buick)to get my hand in. The commodore had done less than 10,000KM and the most it would pull uas 108HP so I/m pretty sure those 102horses were not ponies.
It is great that we have so many choices. Denis
DENIS

Good point there Denis,

Last time my car was on a dyno, the operator was very impressed by the A/F-ratio (the picture on the link next to my email address is there and then). It was very stable all over the rev range. It might be worth mentioning that it was actually better than all other cars, and mine was the only non-fuel injection car there!
I am still so surprised with how low fuel consumption is.
All comes down to how it was tuned I guess...

On the other hand, you're absolutely correct when you state that in order to gain horsepower, there is more need for change with a xflow engine. But when torque is the main issue, no mad cams are needed as far as I know.
But generally, yes, in order to have the same power gains all over the rev range, I presume a change in cam would be needed on a xflow engine.

It is indeed great to have so many choices (which is why I'll try to have a go in Phil's car asap :-D)

Alex
Alexander M

Mike
You have not mentioned what type of driving you do.
If you want an MGB that will keep up with today's average motor, is tractible around town, and doing a lot of idling whilst at stops - then an s/c.

If, however you want lots of bhp, but will not be doing much 'town' driving, then a blueprinted 1950 crossflow with full cam.

If you want best of both worlds - then a V8...

regards
Hal Adams

Apologies Mike, you did say what driving you do! I sped read it at first..

My suggestion therefore is the s/c - but please, if you do go down this route - make sure your engine is 100% condition. If not, rebuild it and lower the compression (IMO to 8:1)first. As Denis said above, an s/c is good for a stock engine - I'd go one further and say that any mods to a stock engine will be trouble, and certainly a wide angle cam, or high CR should not be contemplated ...
regards
Hal Adams

Hal,

I take it you didn't read what I posted earlier...

My car has a Piper BP285 cam, but it isn't less usable in and around town, more the opposite! This was one of the first things Chris and I discussed. There's always the possibility of adding hp (Piper 300 cam for instance) but that simply was not my intention.

Secondly, a crossflow head does NOT add hp in the high revs, it improves torque in the midrange. Improving maximum hp can however be attained by modifying the head (valves, porting, ... it's all in Peter Burgess' book).

Most people that have had a drive with my car (most of them in the passenger seat though :-D) were both impressed with the high power it has AND its flexibility.

This doesn't implicate that a SC would be worse, I just can not tell as I haven't driven one (yet).

Alex
Alexander M

Alex
It is hard to be precise about everything in a short note. Yes, it is correct that not every cam will make the engine lumpy, but certainly the cams that are 'generally' fitted to the 'featured' cross flow engines will - I am talking rally/race stuff.

There are tame cams, yes, but pound (or euro) per hp, more will be achieved by the more aggressive ones.

It is a difficult subject to get into, that of s/c versus normally aspirated tuning. There are some serious tuned engines out there that will walk all over supercharged ones.

Using Mike's original question, I take him to be someone not on the race track yet wishing to hold his own against the avearge Nissan Micra... To this end, I advocate the s/c as being the easiest (not cheapest, but he asked the question...)method to get increased power accross the spectrum...

However, I am biased as I, like Mercedes, am a firm believer in the supercharger! My ideal MGB would be a 2L s/c with a 5 speed box - and will be when I can convince myself to hack up my concours GT...

We should have the debate at an MG gathering someday!

regards
Hal Adams

FWIW, on my '66, I have an unmodified MSX crossflow with 45DCOE's set up on Mike Pierce's flow bench. I'm running a tad over 10.5:1 compression and using Pierce's mild cross-flow camshaft with a .060 overbore. I talked to Mike when Bob Thompson built my engine and he told me to stay away from the radical cam that he also sells, the one mentioned in the article in Grassroots Motorsports featuring Mike's 162 BHP, 8500 RPM 'B. I've never had it on a dyno but my G-Tech shows 0-60 in less than 9 seconds. As Alexander said, the mid-range torque is greatly improved over stock. In addition, the engine is still pulling hard at redline. I have driven only one supercharged B so I can't make a valid comparison.
David

Here is a pic of my engine bay.

http://kmnet.demon.co.uk/~arnold/evac1.jpg

David

Dave,
I just have to ask. If your in Florida why is your car Right hand drive? I'll bet you get a lot of strange looks when other motorists see you driving on the WRONG side.
Cool engine though,
Jim
JCR Royal

Take a look at the following webpage on Chris Betson's website. I believe this is Alex's engine that he talks about above. If you scroll all the way to the bottom there are some figures for power of different engines, including x-flow, SC and V8.

http://www.octarine-services.co.uk/alex1950.htm

Iain
I D Cameron

JCR,
Yep, I do get a lot of looks and comments about the car. You should have seen the face of the girl at Taco Bell when I backed through the drive up one window night. It took her a while to figure it out. Thanks for the compliment, too.
David

JCR,
Yep, I do get a lot of looks and comments about the car. You should have seen the face of the girl at Taco Bell when I backed through the drive up window one night. It took her a while to figure it out. Thanks for the compliment, too.
David

I just gotta add to this. My 'Alice' is a 67 GT and on the cusp of being 40 years old. She can't out accelerate a UPS truck.

But.

I have a driveway 3/4 mile from the freeway entrance.
I come out and am immediately tailgated while I try getting up to speed :)

Then... there's a hard left & the entry ramp.

If I don't gain ten car lengths thru the corner, I'm slack or they're better than the usual.

I'm buying a blower. Nice 30's tech and simple, like me and my car.

We're going for 20!!!

Stewart.
stewart

This thread was discussed between 20/01/2005 and 02/02/2005

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