Opening a Port

A Peaceful and Healthy 2020 to All

A very simple question...I need to enlarge the inlet ports on my Austin Seven exhaust manifold. It's cast iron of course. Would you recommend doing this with an end mill, slot drill or with a stone (perhaps even with a Dremel attachment).

Many thanks in advance.

Martyn

Unless you can clamp it to the mill table don't even think of using an endmill or slot drill, it will be uncontrollable.

A rotary burr or grinding point may work.

Inlet ports on exhaust?

Well the exhaust gasses must go IN one end and out the other

The exhaust and inlet manifold is all one casting so could well be in inlet tract that is being worked on.

Die grinder would be best but Dremel will do, carbide burrs for heavy removal and then smooth with a stone one.

Edited By JasonB on 31/12/2019 10:14:22

Look for a 6mm Foredom on ebay, not cheap but with the correct burrs for ci you will be fine. I always buy Garryson, the cheap ones often don't last long.

There are several questions here;

Why do you want to enlarge the ports? unless you are building a 750 racing engine.

How much metal do you want to remove?

Why mess with prewar components? surly the idea of owning a prewar car is to keep it as original as possible.

Brian

Ian,

It may be worth having a chat with Ian at Oxfordshire Sevens **LINK**. I know that he has been rebuilding and tuning a fair few Austin Seven engines of late and testing them on a dynamometer. He has also built a few successful racing Seven engines. He may be able to give you some suggestions.

Regards,

Jamie.

Simply matching the areas of the ports might be a better term. Matching to the head will not greatly alter the power but may well help the economy. Many manifolds, back then, did not provide a smooth transition to the exhaust.

I suppose many considered the inlet side as the important one - where gases have to find their own way into the engine cylinders (maximum pressure difference of one atmosphere), while the exhaust gases were actively shoved out by the piston (as well as starting at rather higher pressure when the valve opened).

As long as the bit you are going into has a larger hole than the bit you are coming from (e.g. inlet port in head is larger than the hole in the mating face of the inlet manifold), the 'step' is pretty much irrelevant, and on the inlet side can help atomise any fuel droplets. Gasket can be matched to either. Hope I've explained that clearly.

Happy New Year,

Rob

I have just done a port matching exercise on a spare 1098 A series engine for my Morris Minor.

It was surprising just how bad they were when I took templates form each part.

I used a solid carbide burr in a die grinder on mine, and it was very effective and quick to do the job.

**LINK**

Phil

Many thanks everyone.

Inlet.

Dremel

Especial thanks to Grindstone Cowboy. You seem to understand exactly what I want.

By the way Brian...I'm not into 'messing' with pre-War components. That is normally anethema to me. I'm just using conventional (pre-War if you like) engineering methods to try to improve an extremely poor aspiration system as thousands of Austin Seven Special builders have done since pre-War days!

Thanks again everyone. Bonne année from warm and sunny Paris.

Martyn

I would not try and polish the inlet tract, the fuel might not atomise properly, it needs some turbulence to stay suspended in the air flow.

I successfully opened out the inlet ports on my A7 RTC special engine, it had standard inlet valves but very narrow seats.

Phil

Edited By Phil P on 31/12/2019 13:47:42

Opening out the inlet valve throats is well worth doing on an A7 motor. A simple pilot cutter can be made on a lathe very quickly; you can use a reground broken centre drill as the actual cutter. Also, there is no radius on the roof of inlet port where it meets the valve throat. It has been proved again and again that the bulk of the gas flow in an inlet port is in this area -the so-called "short side radius". As it left the factory this area is a sharp right angle rather than a radius. A bit of work here with a burr or mounted grinding point will have good results.

The improvement in the inlet ports can be seen in this photo.

Plus the removal of the sharp corner at the top of the cylinder bore near the valves which I forgot to mention.

Mine had unleaded exhaust seats fitted which precluded fitting larger inlet valves, but enlarging the throats is an excellent way of getting better gas flow.

Phil

Edited By Phil P on 31/12/2019 17:30:16

Try to not take too much material from the inlet ports as they way too big as standard to get optimum gas flow. If you are not competing in VSCC events, dividing the ports into four makes a big improvement.

I used to do all my porting on motorcycles by hand with riffler files. Matching the profiles of bolted together components is best done with the help of thin card cutouts like gaskets, using the stud / bolt holes for alignment. One for each part, and when they are put together, it is easy to see the mismatches, and decide where the metal is to be removed.

You just reminded me that I took a photo of that process.

The red aerosols in the background are a crack detection kit, the A series heads are prone to cracking so I thought it best to check before doing a load of work on it.

Edited By Phil P on 31/12/2019 23:59:38

Again, very many thanks for all the advice and practical guidance. This accords with everything I have read and studied on the subject of enlarging/profiling ports and I will be printing this off and keeping it close as I work. Congratulations to everyone who has already made such a splendid job of the procedure and, above all, thank you for sharing the expertise with me.

Bonne Année

Martyn

If you want to make your Minor go better. Try and get a 1295g head. These were fitted to Austin Princess 1100's. They have bigger valve and better ports. But you have to skim .125" of the head to get the comp ratio back up as these engines used flat topped pistons. I built a genuine 100 mph Minor Pick Up using all BMC parts except the exhaust manifold.

Hi Vintage Engineer.

I think you might be referring to the 12G295 head, I used to run one of those on my Mini van when I was a lad in the 70's. If I used one now I would need a bigger carb and exhaust to take advantage of it as well.

To be honest I am not trying to make the Traveller go a lot faster, I am just taking the opportunity to build the engine to a better standard than they were when mass produced, I am static balancing all the moving parts and being careful with the cam timing, fitting duplex timing set up etc etc. I am after a smoother running reliable engine that I dont need to be spannering in years to come.

Phil

Hi,

Just wondered if after tuning the mechanical parts of your classic engines ,you still use the distributer or you swap to an ECU.