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MG MGB Technical - Maniflo Intake Manifold

Has anyone installed one? Feedback? Thanks.
Steve.
Steve Meline

Steve,

' Haven't installed one. I only know of the Maniflo through the engine article written by Steve Strange ("Steve S." from Virginia on these posts). I think Steve knows what he's talking about; I sure learned a lot from him. But he recommends it only as part of the recipe. Carl Heidemen also notes, on the current MGA threads, that the Maniflo works only with a well-ported head, and then only above 6000 rpm. Jeff Schlemmer, who also posts frequently to the BBS is experimenting with a mod to the stock SU manifold that may have a similar effect.

The centerpiece of my own plan is a Burgess fast road head, a Piper 270 (or 285?) cam, removal of the front muffler from the exhaust, possibly a maniflo, and K&Ns.

FWIW,
Allen
Allen Bachelder

I fitted one to my 18V engine, with SU HS6 carbs and K&N air filters, but my engine is very, very uprated, cylinder head ported with big valves, 300 duration camshaft, pistons forged, Carillo conrods, small clutch, ect... I use also Maniflow LCB manifold with one box big bore exhaust system, The result is good.
If you use the Maniflow manifold without mods to the engine, don't expect any thing, in spite of the original manifold it's not very good.
Regards
michel

Allan,

having tried the 270 and 285 in a setup as you are thinking of, i would allways go for the 285 or even better 285/2 and a Peco system again.

BTW with the 285 Piper cams 1 3/4 SU's are further improvement too.

Ralph
Ralph

The Maniflo will be way overkill for most people and most engines. As the engine gets more radical, the effects of the overcapacity manifold get better for top end, but far worse for lower range, aka normal street use. Anyone thinking at this level should look a Vizard's "Tuning the A series" for a very detailed discussion on manifold design for these siameze port engines. It's all been done and figured out, only slight adjustments needed between the A & B series.
FRM
FR Millmore

Thanks for your feed back Guys. I am hoping it will be a good complement to the motor. The almost done 18V, will have a Maniflo intake and exhaust, Harland Sharp 5.1:1 rockers, re-jetted H6's, flowed head, APT seconed stage street cam (270), 9:1 compression, lighened fly wheel...

It will be a street motor. FRM how is the intake a negitive for lower RPM?
Steve Meline

It lowers the gas velocity and lets the charge go backwards out the carbs, especially with drastic cams. With that spec it might not be so bad if the cam is mild, and that engine can probably take advantage on the top end. But my question is, how much are you going to use it above 4000, or maybe I should say 6000 per Carl H's rec via Allen? The same goes for big bore headers, BTW.
FRM
FR Millmore

I am not sure about the over-capacity comments about the Maniflo intake. I have their 1 1/2" manifold and the carb end is 1 1/2" and the head end matches the gasket hole with a nice smooth run between them. The balance tube is much smaller than the stock manifold; this could cause problems at idle. The stock balance tube is very large and where it connects to the runners has a very large cavity that creates turbulence in the air flow. It may be good or bad but the racers that have to use the stock manifold fill that cavity and machine it to smooth out that turbulence.
Leland Bradley

Leland-
I stand corrected, was thinking of a single carb race manifold I saw once. At the sizes you give, it should be fine. I never could figure out why the balance tube is cast the way it is, except as a foundry aid, but you are correct - it's miserably executed. Small balance pipe should not bother the idle, many dual SU cars have small balance pipes with a simple hole drilled into the main throats.
FRM
FR Millmore

Steve-
I replaced the Original Equipment intake manifold on my five-port head in the original engine that I had in my car with a Maniflo intake manifold. Yes, I tried the modifications to the Original Equipment intake manifold, but the Maniflo intake manifold was better yet. Alone it will make for a minor performance increase, but its advantage really comes into its own as other modifications are incorporated. It has high airflow potential coupled with good port velocity, enabling it to take advantage of the inertial effects of the fuel/air charge to better fill the cylinders at high engine speeds with the added benefit of maintaining excellent fuel suspension within the incoming fuel/air charge. In addition, because of the slower heat transference of steel as compared to aluminum alloy, it conducts less heat from the cylinder head into the incoming fuel/air charge, thus making for greater fuel/air charge density and hence more power potential. Polishing and chrome plating the exterior of this steel intake manifold will enable it to reflect away radiant heat emitting from the exhaust manifold, keeping it cooler. Fabricating a simple pair of U-shaped heat shields will also help in this matter. If you elect to use this intake manifold with SU HIF4 carburettors you will need to either use the early version of the UK/European Market SU HIF4 carburettors with the vacuum takeoff fitting on the carburettor body for provision for a ported advance mechanism, or, if you use the North American Market SU HIF4 that lacks provision for a vacuum takeoff, Advanced Performance Technology also offers the option of welding in a nipple on the crossover tube that will allow the use of a manifold-advance distributor. Incidentally, do not let the small diameter of the crossover tube between the runners worry you. Many cars with dual SU carburettors have equally small crossover tubes. If you wish to run an anti-run-on valve and have an earlier car that does not have the carbon canister (Original Equipment Part # 13H 5994) of the 18GK and later engined cars, you will need to use the thinner Advanced Performance Technology’s phenolic carburettor spacers (APT Part # MFA338) that come suitably modified to provide fittings for a vacuum line, as well as the later exhaust manifold (Casting# 3911) as both have a mounting flange thickness of 7/16”. This phenolic spacer with a vacuum takeoff incorporated into its design is a Maniflow item intended to be used with the Maniflow intake manifold that, unlike the Original Equipment intake manifold, has no provision for vacuum takeoff on its crossover balance tube. A companion unported phenolic spacer of the same thickness is also available from Advanced Performance Technology, although a second spacer with a vacuum takeoff may be substituted to allow the use of a vacuum-assisted servo for a power brake system. Because both the angle of this intake manifold is higher (20°) than that of the Original Equipment intake manifold in order to enhance its air flow characteristics, and variances in production tolerances of the bodyshell of the car, in a few cases longer and larger diameter air filters will not allow the installation of an underhood insulation pad, hence the thinner design of the Advanced Performance Technology’s spacers. For the engine that you describe, it should be just the ticket!
Steve S.

This thread was discussed between 21/03/2007 and 30/03/2007

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