MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Falcon Big Bore Exhaust System

Hi Guys -

Just wanted to check with those that have the Falcon Big Bore Exhaust system on their B.

I called Moss and they said this system uses pipes that measure 1 7/8 inches. They stated that the "standard system measures 1 5/8 inches. Is this correct, is the Falcon Big Bore system a 1 and 7/8 inch system?

A difference of 1/4 inch in size over the standard must provide for a large increase in capacity. I just wanted to make sure I ordered the correct clamps. Moss does not list the diameter of any of their exhaust systems - I told them it might help everyone if they did!

Thanks in advance, I am going to order the system today.

Jeff
Jeff Delk

Jeff-
Nope, the OE exhaust manifolds have 1 3/4" diameter runners. Big Bore exhaust manifolds are for Big Bore engines. On a small-bore engine (1868cc or less), you'll have reversion problems. It will result in a bit more power at high engine speeds with the expense of some tractability at low engine speeds. This is due to its greater cross section reducing exhaust gas velocity, which in turn reduces scavenging effect in the combustion chambers at low engine speeds and thus increases “Pumping Losses” while reducing the velocity and hence the quantity of the incoming fuel / air charge. In addition, radiant heat from the tubular steel of the exhaust manifold is much greater, exposing the air in the engine compartment, the intake manifold, and the carburetors, as well as the fuel system, to more heat, thus reducing the density of the fuel / air charge and hence reducing power output. Jet-Hot coating of such exhaust manifolds is therefore highly recommended.
Stephen Strange

I assume your talking about the exhaust system, from the stock cast iron exhaust manifold back. I've had this system on my '67B going on 20 years and have nothing but praise for it. It looks and sounds as it did when I first installed it. Yes, the clamps are 1 7/8". I stuck with the stock '62 to '74 exhaust manifold as it is a hard design to improve on. The sound is great and not as loud as their Tourist Trophy system, which I've installed on a customer's GT. A truly great investment you won't regret. RAY
rjm RAY

Let me clarify my post above and ask again.

I have a 71 B and am using the stock manifold - it has been Jet Hot coated and I am planning on purchasing the Falcon Big Bore exhaust as I plan on having the head work done next year to help the breathing (either through Peter Burgess or here in the US by FlowSpeed).
A super charger is in the picture for a year or two down the line.

I wanted some confirmation on the tube size for the Big Bore - just to confirm what Moss indicated. Is the Falcon Big Bore exhaust piping 1 and 7/8 inches in size?

Thanks for your comments Steve - very informative as always.

Jeff
Jeff Delk

Ray - thanks for your comments - I posted my response above and your post had not yet updated on my computer.

Thanks for the confirmation on the size. Even though I may be using a slightly-too-large system for a year or two, I think I will need it later when I make my other modifications.

Always nice to get the feedback before a $380 purchase!


Thanks again guys,

Jeff
Jeff Delk

Jeff, I've had my cylinder head flowed and have been running a Moss supercharger for over 10 years with no complaints. When you get the supercharger kit, the only problem that you will run into is a proper ignition system. I went with a distributor made by Davis Unified Ignitions in Tennessee. It's based on the GM HEI units from the '70s that incorporate the coil in cap design. I also use an MSD Boost Timing Retard Master system to knock back the ignition timing when the engine is under severe load. It makes for a versatile system that allows me to dial in more initial advance as well as more overall advance. Good luck with your project. It totally transforms the B engine in a way you won't believe. RAY
rjm RAY

Jeff,


Have you ordered the exhaust system from Moss yet? If not, please contact me at bscr@bscr.com. I give discounts off Moss' sale prices.


Ken Lamers
KL Ken

Mine has been on about 20 years, I remain very pleased with it. Its a single box and so it gives a bit more ground clearance.
Stan Best

I'm running a Falcon BB that I installed in 1995. It's got maybe 50k miles on it. It eventually got really loud so I repacked the muffler a la Barney Gaylord:
http://mgaguru.com/mgtech/carbs/ex103.htm

He said it only lasted about 10k miles for him, but based on my current driving patterns that's about 2-3 years for me, so I decided to give it a try. So far, I like it!

Of course 1995 was a long time ago so I've no idea if current production is the same as what I bought, but the one I got fit great, was easy to install (had to modify the rear hanger, though) and has been long-lasting.
Rob Edwards

This thread was discussed between 17/01/2012 and 12/02/2012

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now