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MG MGB Technical - Performance intake manifold???

Hi again. I'm researching possible performance intake manifolds for my 73B. First, what are the pros and cons of the stock intake? Second, can anybody recommend a good performance intake? I know about the Maniflow by APT Fast. Does anybody run this manifold and/or have any useful information on this intake? I will keep my stock HIF-4 carbs so I would like to learn what advantage I will gain with the Maniflow. Also, I intend on installing K&N 6" round filters, but have no idea what depth to use. If anybody runs this arrangement, can you tell me on my 73B what depth of filter will fit comfortably under the hood? Thanks for all the help.
Brian

Please refer to the archive in addition to whatever is added here. I inquired about this intake a while back and recieved some good information, including the fit and sizing. I've heard pretty much all good so far.
Luke Staley

Brian,

I can't guarantee that you will see improvements with the manifold. That is because the other components of your engine may or may not be matched to it. I will say with certainty that what is written about the stock manifold on the APT web site is correct.

Due to the sudden cross sectional change from the inlet side of the manifold, through the area where the balance pipe intersects, and then back to the port side, the gas flow is markedly disrupted. This causes the mixture quality to go down, and is also an impediment to airflow quantity. Now proper port work inside the manifold can help, but it cannot take the place of a better design.

Hopefully this will help you some, there is a lot written about these manifolds in the archives so have a look.

Sean
Sean Brown

Thanks for the comments and yes, I always research the archives before making a post. I see the Maniflow gets high marks, but there are more (I hope) manifolds out there in use and was hoping to get a concensus of what people are using and like. In addition to the intake, what size K&N's will fit under the hood of my 73B? I can see that they are also very popular, but sizes are not discussed in the archives. The bigger the better is all I know right now. Thanks again.
Brian

I know that Steve S. frequently recommends the 3" K&N filters for non brake boosted applications. And, obviously your right, for the most part bigger is almost always better, this is not a place that vacuum is helpful. K&N keeps flow numbers on their filters and can help in finding the necessary filter surface area for your flow requirements.

I was interested in a related topic, in the possibility of using a filter "box" and remote filter like many newer cars. Being burdened by the booster box, and not over excited to follow Steve's recommendations of switching out the pedal boxes (I'd rather rebuild an engine than lie under a dash), I would love an alternative to the pancaked K&N's for this application.
Luke Staley

Luke:

It would take some work but a cold air induction box would be a plus. I know at least one guy who is looking at this for his C. I run 1.5" K&N's on my C and I have no problem anymore of getting air to the carbs. I've been tempted to hook up a duct like is on my A and direct it at my carbs just to see if it does any good. When I do it, I'll make a run before and after with the G-Tech just to see what it says.
Probably won't get this done in the next week but hope to have some results. I know that the tests for cold air induction on the dyno show as much as a 5 hp improvement on V8's but suspect its one or two on a MG.
Steve
Steve Vandal

This thread was discussed between 18/12/2001 and 22/12/2001

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.