Many people ring and ask "why should I buy a billet sheet metal manifold?" & "what can I gain by buying a manifold?"
Obviously the answer has many variables.  So on this page we will give a few examples

Before giving you 2 very good examples there are a number of questions you need to answer before your purchase:

Does your manifold maker have years of experience in the design of manifolds?
Does he have a flow bench and engine dyno for development and testing of ideas and theories?
Does he have years of racing experience?
Does he have an engineering degree?
Does he understand Fluid dynamics?
Does he understand wet flow vs dry flow design differences?
Can he design your manifold to work with other harmonics if  runner length is compromised by design requirements?

At BG Engines we are Engine builders. racers and  Engineers.

Runner length, taper and plenum size is designed to work with the specific combo in your engine.
While we do have off the shelf manifolds available for common engine packages;
we prefer to consult with you and produce a manifold that will meet or exceed your expectations.

All of our manifold development starts with basic principles of fluid mechanics and CFD in conjunction with actual testing via flow bench, the engine dyno, and track data. . Analyzing all of these variables carefully is where product refinement, knowledge, and experience increases with each manifold we produce. We base the foundation of products and applications around these principles.

Our small team is made up of  someone who has been building race and street engines for 30 years, and who has been designing and building manifolds since 1991. A CNC machinist and programmer with a degree in Engineering, specialising in Fluid Mechanics and computational fluid dynamics. Fabricator and welder with many years experience. We have Flow benches, Fuel flow bench, Superflow 902 dyno and CNC machining centres. We have years of experience in Drag, circuit and boat racing, with our own cars  and as crew chiefs, mechanics and engine builders for  both factory and private teams.

Back to a few real world examples

427 Small block Chev with AFR 227 heads.
These heads flow 309cfm which equates to 636 HP

Both engines were the same compression, had the same camshaft and used the same exhaust for dyno purposes
Both Engines used ICE 7 amp ignition systems (ICE
and ran on BP Ultimate 98 Octane pump fuel

Engine Number one
Edelbrock Victor Senior and Pro Systems dominator carb  628HP

427 Victor senior pro systems dominator

Engine Number 2
BG Custom billet runner sheet metal manifold and 2 holley HP carbs 684 HP

BG Sheet metal manifold NA on 427 SBC

You can see why it is referred to accoustic supercharging, as the engine makes more HP than the potential of the cylinder heads due to the ram effect of high pressure waves. A properly designed manifold  can make a huge difference. In this case 56HP, and just as importantly 15 foot pounds of torque.

Overlaying The 2 graphs illustrates this difference. Some people are concerned about losing bottom end power, but as can be seen the BG manifold NEVER makes less power than the Edelbrock

BG Manifold is superior to Edelbrock

Adding a small shot of nitrous this same engine

nitrous plumbed BG Manifold

427 with Nitrous

Overlaying the 2 graphs

Nitrous oxide

Independent testing confirms and exceeds these figures

460 cubic Inch Big Paw Holden engine

Torquepower Big Paw 460

Craig Bennett from Torque-Power engaged us to build a manifold for twin 1150cfm throttle bodies on a 460 cubic inch Big Paw  Engine.

The reults with a  cast manifold and a 1450 cfm dominator Dambest carb were:

768HP @ 6300 rpm
665 ft lb
Impressive figures for the big paw dominator single plane manifold

With the BG Billet intake and 2 1150 cfm throttle bodies the same engine made

840HP @ 7200
700 ft lb

Craig's Big Paw Engine, blocks, heads and manifolds combinations are available at