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MG MGB GT V8 Factory Originals Technical - Hot air/cold air induction?

My injected V8 takes its air from within the engine compartment. I was wondering if it would be better to move the filter and intake out into the front next to the rad. It occurs to me that colder air would be denser and contain more oxygen and might produce more BHP.
I think that intercoolers work on the principle of cooling the air as much as possible for the same reason.
Also I suppose that the air might be forced in a litle more if the intake is exposed to the oncoming airstream.
On the other hand, every V8 I have ever looked at seems to take its air from inside the engine bay and I can't possibly be the first person to have thought about this.

Any comments

That's what i'm doing. Since I had to make new radiator brackets, I cut 2.5" holes in each one and ran some ducting through them.

I've made 2 filters that sit in front of each brackets and am still working on a carbon fiber intake plenum for the carb.

It's gotta be better than sucking in all that hot air.
Michael Hartwig

That's right, Marc, the engine intake does need the cooler air, for all the reasons that you stated. I've seen a few conversions where a corrugated tube is snaked from the air cleaner to up front near the grill. Great idea if you can find the room.

Best, Joe
Joe Ullman

I have taken twin induction from ahead of the radiator, to take advantage of reduced temperature and slight increase in atmoospheric pressure.
Nick Smallwood

Woops wrong link.
Try this one!
Nick Smallwood

Great idea. consider that the tubes (air intake) will also be inside the engine bay. If tubes are going to be used then used alloy flex tube,they radiate heat. If not, they should be insulated to avoid heating the air going in. It would be much better to rush the air in, this aids in the cooling of the air. Big intake smaller delibery end, the intake should be oval and larger than the tube. it's just like a funnel effect.
The shorter the track going into the intake the better.
Also used the largest air cleaner and container possible to get the volume. Raming air in is good if good if the vehicle can travel at 100 mph to get 1 to 2 psi depending on the design.
Bill Guzman

I see this remote air intake and filter on lots of modern fuel injected cars. Has anyone tried this on a carburated induction. I'm planning on a ducted intake to the carter afb on my 67 conversion, with the intake in front of the radiator cowl and an in line filter of the flat sort. Has it been done with success?
Chris Jones

Here in Australia this is a very popular mod for all types (ie Fuel injected and carbs)of vehicles due to the elevated Summer temps of high 30's and low 40's.

The usual method is as you suggest keeping the duct runs as straight and smooth as possible.
Place the duct as high as possible to avoid water ingestion and use the pick up point just in front of the radiator as Nick Smallwood mentions.
BTW a good material is ducting ued in fan boosted wall ovens. It is about the right size, self supporting and insulated. Usually cheap too. Try builders supply places.
Local performance mags here report little if any direct gain from the increased pressure but all report gains from the engine by the power not falling away as temps go up especially in traffic.
Good Luck. Pete, Sudney, Australia.
Peter Thomas

I have not done this but I helped a friend put a 3.5 into a B using this arrangement

The carb was a Holley (390 I think but don't quote me here since this was few years ago!)
The snorkel attaching the carb to the filter box was from a 4WD (Range Rover I think) and the filter was a standard K&N aftermarket foam panel type fitted into a box from a locally made GM car normally fitted with a 5.7 lte V8.
All in all the change was a success.
One minor bonus was the decreased noise levels from the induction side at least.

The big plus was taking air from a cooler part of the car not directly from on top of the engine beneath the hood / bonnet
The intake was fitted through the round hole in the radiator support panel and held in place ahead of the radiator with a cable tie attached to the underside of the hood lock panel.
Cheers, Pete Sydney, Australia.
Peter Thomas

I did that on one of my cars many years ago (OK OK, it was a Marina) and always reckoned it gave very good results. You would probably get away with it with the EFI but with carbs could have problems in winter with a long warmup needing choke. Like many factory V8s mine came with K&Ns presumably 'cos the cast manifolds broke long ago, and hence the temperature compensator intakes are missing. Takes several miles to run smoothly with no choke if I drive off from cold, but if I go about 3/4 mile and buy a paper it runs perfectly when I start off again.
Paul Hunt

Sounds really good, I have thought about this for some time. My GT conversion is std. Vitesse 3.5 with Weber/Edel. current air cleaner is Mr. Gasket low rider, 14" dia with 1.5" height. Plan to have 3" pipe up from side of rad fitted with a K&N (RE-0930) behind grille. The pipe would run up to carb and terminate onto a closed ally box (plenum), perhaps 10"diax2". Is this plenum size OK? How much air does a 3.5 need? How does the 'ram effect' effect things? What size filter is best? The K&N list gives the RE-0930, size: neck dia 76mm, body size dia 117-152mm, length 152mm, capacity 340BHP!! Any help on sizes etc and words of wisdom, greatly appreciated Thanks

I've done it with mine, fixed a Pipercross cone filter on the end of the airflow meter low down on the inner wing, and boxed in at right angles at the side of the radiator, and cut a triangular hole in the lower valance from the bumper mounting to the inner wing and made a scoop from the spoiler up into this.

I think I have a pic of the engine bay which may show it.
Car has just been rebuilt and goes on road at the end of the month, so I do'nt know how effective it will be

Mike Barnfather
Michael barnfather

This thread was discussed between 06/03/2002 and 08/03/2002

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