So now we come to the cold air intake. I first proposed this many moons ago in my "Not going Holbay" series in the Horn. Having read what David Vizard has to say about this I feel somewhat vindicated since this idea met with some resistance then due to the very real likelihood that the engine would experience a high speed lean out.

I never found a problem with this happening but that doesn't mean it didn't occur either, just that I wasn't aware of it. For those people that didn't read that series my idea was to build an induction ram air system that picked up just behind the grille and feed this pressurized cold air straight into the carburettor after passing through a wire packed cartridge which was housed in the ducting. This is something for nothing, because instead of picking up warm low pressure air that's heated by the radiator we can pick up cold air pressurized by a static head as the car moves forward.

The net effect of static head and colder air provides a 12% increase in hp available at the rear wheels. This is the sort of improvement expected from 1.77 pounds per square inch of boost from a supercharger.
These figures are substantiated in the book and agree with my extrapolations back in the Horn.

The good news is that David explains how to overcome the high speed loss of calibration and the answer is so simple I could have cried.

All you need is a balance pipe running from the airbox to the float chamber of your carb. This provides the same static head above the fuel as that found in the airbox, hence more fuel is metered into the engine according to pressure levels. Brilliant.

Even better is that the Apollo CIS system marketed by K&N even features a range of pipe adaptors that screw into the Airbox so you can do just this.
And if that isn't enough for you, the Weber 32/36 DGAV has a blank plug that you can drill and tap into the float chamber. This is a very neat setup indeed. Unfortunately none of this works with DCOE's so you'll need to acquire a 32/36 DGAV and a 1592 manifold to put it on.

Remember you don't want water heating so you will not need the dreaded water elbow.

This mod will cost in the region of £360 plus the manifold ( unless you are lucky enough to own a Series 3 or 4 ), but you'll never get as much hp for that sort of outlay anywhere else.

Best Regards Ed

Hi Eddie, although extreemly happy with my Holbay, twin 40 set up, I'm always open to new Ideas. I bought the vizzard book - "How to build horsepower" and can see where your coming from. Is this the best book to get? Any way I've just bought a manifold for a donndraught webber off ebay. I was thinking of going down the road of porting it to a spare Holbay head I'v got. With the manifold came a 24/26 down draught webber in need o some TLC. Its supposedly jetted for a 2.0 litre twin cam, Is this worth working with?

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Hi Dave, if you have found another Vizard book then get it, because the man is a genius. The book which inspired me to new heights is actually called "Tuning the A Series Engine " 3rd edition available from Amazon

Here's a link

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The price is a lot higher than it was when I first recommended it at the beginning of this thread, but it's worth every penny.

Today we tested the new 32/36 DGAV Weber Progressive Twin Choke downdraught on a Series 3 fitted with a rebuilt 1725 motor fitted with a Chris Draycott large ported head and Piper Fast Road cam.
Even though the timing wasn't set up properly according to the engine's needs the results were breathtaking. This is arguably the definitive carburation and induction system for an Alpine, certainly an order of magnitude better than our old friend the 28/36 DCD. The induction system is neat, functions superbly and has made the installation of the DGAV carb an essential must for anyone with the Solex 4 branch manifold.

Dave, forget the 28/36, get a 32/36 DGAV from Fast road cars.
Once fitted you'll need to invest in the K&N Apollo CIS as well,
You'll see the whole installation at Warwick where I'll have a list of part no's to obtain to finish it all off neatly.

I did take some nice photos of the set up but haven't got my website up yet so can't display them, sorry about that, but it all looks very professional and fits the Alpine engine bay as though it was designed for it, and clears the bonnet by a mile.
Peter is going to replace the fast road cam with a milder street one to strengthen the bottom end a bit, but for a first time out of the box carb the results were fantastic.
Best Regards
Eddie

Well from that I take it I should junk the 24/26 carb, But as for the manifold. the 2 holes are 32mm dia. I assume these could be machined to match the 32/36 carb.

Absolutely, the best way to do this is to use the 32/36 DGAV baseblock as a template to open out the manifold port. Remove any bridging between the two chokes ports. You should end up with an exact copy of the shape of the baseblock. You will need to buy the baseblock separately, although Anthony may throw one in gratis if you phone him. We tested the Mexico 1600cc jetted version and it is the one to go for. The 2 litre Pinto jetted one could be too much, although experimentation with jet sizes is in the end the best way to go. Time will tell.
Be aware the choke cable may need rerouting through the bulkhead, but there are already some convenient grommetted holes.
Also there is no need for a balancing pipe to the airbox, the DGAV vents it's float chamber directly into the plenum ensuring full calibration of the fuel supply even at maximum high speed static head. Neat.

Don't forget NO water heating...............................good luck and see you at Warwick.

Best Regards Eddie

Would this be the carb that is listed as Weber 32/36 DGV 5A carburettor, part number 22680.005

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Hi Eddie,

Just wanted to thank you for a very informative thread. I think I'm now completely sold on the 32/36 DGAV. Loads of US owners have gone down this road already and there are loads of threads on the SAOCA forums hailing these carbs as the ultimate for the Rootes 4-banger.

I know you said earlier that you've got some pics of the installation and you're going to put them on your website, but is there any chance you can post a couple here? A few pics would be great, then everyone can see how it all fits together. I'm a regular poster on the retro-rides.org forum and if you were to post such a wonderfully detailed thread as this over there, everyone would be really pleased, but most of them would reply in big capitals 'NEED PICS!'. I'm really interested in the cold-air ducting etc and how all that fits together etc.

Anyway, thanks and please keep us informed of the developments!

Nick

OK guys, A couple of replies in order here, First Mackem, yes that is the carb, and it is the right size jetting for the 1725 and probably the 1600 too if it has been breathed on. It's a bargain really, a steal.

Now to Nick's post: I'd love to display those pics on here, and as I understood it they have to be uploaded to any other site and be linked from there with a URL. Can anyone explain how to get those JPG's on display? I haven't got a photo bucket or anything like it yet.

Willing to have a crack!!!!!!!!!
best regards Eddie

Right, let's see if this works.............................

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OK I sussed it, this is the Plenum I pointed out earlier in the thread linking to a K&N Apollo CIS Universal Cold air intake.

Fitted to Peter Pescud's beautiful Series 3.

Eddie.

And for a slightly different look.

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CUSTOM PLENUM
Cast aluminum plenum, beautifully finished with black powder coating and natural aluminum highlights. The plenum is designed to fit most American 4 barrel carb that have a 5-1/8" flange. Also will fit the Weber DGV carburetor when used with K&N adapter 85-1061. Designed for cold air intake, plenum has a single snorkel outlet that can be fitted with a 4" I.D. hose running to a remote air filter. A K&N universal filter with a 4" flange can also be clamped directly on the snorkel as well. See the Universal pages for filters that will fit onto the inlet. The outside diameter of the plenum is 9" and the snorkel sticks out 6" from the center of the plenum. Minimum clearance required above the carburetor flange is 3-1/8". Customer must provide 1/4"-20 hold down stud.
K&N Custom Plenum
Note: The custom plenum is recommended for small displacement engines (less than 200 C.I.) or low revving V6-V8 engines. If the engine requires more than 45 sq. in. of filter area then the plenum should not be used because the carburetor would have to be re-jetted and a loss of high R.P.M. power will be the result.

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Brilliant, thanks for posting those pics Eddie . It' nice to see exactly how it all fits together. When I saw the K&N Apollo intake on their website I thought it would be quite a tight fit, but it seems to fit quite well with plenty of space left. RE: the support brackets, I'm guessing you made those up yourself? This is the one point where I might have trouble as I can't weld or fabricate.

All I need to do now is look at for the manifold and linkage!

Thanks for the encouragement and compliments Nick, as you can see a fair bit of thought and research has gone into sourcing this system's components. Yes, I did consider the cast custom K&N Plenum but the height of this unit will take it into bonnet hitting country.Also it has a fairly large footprint because it was primarily meant to be used as an airbox with filter inside. This means that it will make adjusting the jets, cables and screws "on the fly" difficult.

In the end the Fast road cars plenum won the " will it fit " contest, due to it's slim functional design. I tried to do this looking through David Vizard's eyes and using his expertise, not mine. Bigger is definitely not what you want here.

Of course now I have the pictures up I can include the part no's of the various components and explain what else you need to do or make.
Those nice neat brackets were made by Peter Pescud himself and as Mr Buff and Polish, he may be persuaded to manufacture some more.
( I already asked........hehe ) But obviously you will need to grease his palm a bit.

So without more ado let's look at what you need to order.

1. RC-5052AS K&N Apollo Silver ( you could also have red or blue )

This comes with the Airbox and K&N filter element, a cast ally trumpet intake and a fair length of black ally ducting.
After much thought both Peter and I came to the conclusion that the mounting of this kit needed extra care to maintain it's clean appearance but more importantly to be able to dismount it easily and without cosmetic damage to the ducting.
Therefore you will need the following parts as well......................
2. 85-6004 Saddle Bracket. X 1

This picks up on the intake adaptor ring which pushes onto the front of the airbox. Some inner tubing gasket is needed to protect the chrome adaptor from the metal of the saddle bracket. This is then mounted onto the top radiator fixing and supports the front of the airbox.

In order to make dismountable but tight connections you will need to order the 85-6002 adaptor kit X 3 .

This contains a length of correct high quality rubber hose, a steel tube of correct diameter and 2 jubilee clips of the right size. In the pictures the ducting going straight onto the airbox is not correct, there should be a rubber hose and steel sleeve making the connection to the airbox and ducting, in all instances. Here we were short of 1 kit unfortunately but now it's arrived it will be fitted in due course.
This lot will cost in the region of £200, more than the carb, I know, but equally important I'm afraid.
Hope that anwers any queries you may have had. I ordered all the parts from Southern Carburettors of Wimbledon, although you may have a dealer a lot closer. Check the K&N website for dealer locations.
Best Regards Eddie

Firstly you should ensure you get trade discount when you pay for these parts. Buying from an outlet like Southern Carburettors affords you this privilege. Buy off the internet and you could pay anything up tp £200 just for the Apollo ( which costs £125 Trade ) so Caveat Emptor.

Also there are a few improvements to be made to the installation as this was just a trial first time exercise. From David's book we know that any sharp 90 deg edges anywhere in the airflow will detract from the flow capability. The Fast Road plenum needs to have a radiused edge on the mouth section inside. and further in is another right angled edge that needs chamfering.

Also when porting the manifold you can greatly improve the flow into it from the carb by opening the outlet away downwards into the main plenum cavity of the manifold. In other words from the baseblock down grind material away at an oblique angle greater than vertical. Be careful you don't grind into the studs though, don't go silly, just ease it out to help the flow. Reading the book will help you to understand how to tackle this.

A further refinement is to align the plenum on the carb so that it points straight ahead, not to the side as in the pictures above. The reason for this is that as the plenum rotates, the support bracket which holds the plenum lid begins to baffle the flow into the carb. This bracket presents the least profile in the straight ahead position. If you also chamfer all the square edges it has ie form a wing profile then it will interfere even less.
The ally ducting will then take a slight S bend to the airbox.

All these tweaks will help enormously to let the engine breathe to it's absolute best potential which is the true object of the exercise after all.
Best Regards Eddie

One last thing to point out as we near the conclusion of this thread is that for that last bit of performance it is necessary to alter the way the engine vents the crankcase.

As we are not hampered by emission regulations the very best thing you can do is to rid yourself of any positive crankcase ventlation valves or pipework. For eg. on my Series 4 there is a vent feed from the Oil filler tube which used to connect via a separator into the pancake air filter as well as a PCV valve on the inlet manifold connecting to the side tappet cover.

The ingestion of oil fumes into the carb will contaminate the fuel charge entering the combustion chamber and cause a loss of octane rating which will adversely affect the timing and ultimately the performance potential will deteriorate. Oily fumes are A BAD THING.If you are running a high compression ratio like me of about 10.5 to 1 then they are AN EXTREMELY BAD THING.

Pinking from this is a great way to blow holes in your pistons................

To eliminate this we need to fit a couple of these :

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You can get these at Halfords and they are cleanable and reusable after re-oiling like K&N ones.. They should also help to minimise the amout of oil blown out of the timing cover.

Best Regards Eddie

HI EDDIE MY FRIEND

No idea what these postings are all about, WAY above my head, but a joy to hear from you, if you see what I mean.
Hope we can catch up at the National - will be there for the Saturday, probably trying to flog off a few mags. and books and stuff.


Bill