26 replies to this topic

[PACINO]

MG 1300S engine bored 0'10. Cylinder head with big valves and double springs. Twin carburettor S.u. Hs2, blue springs. Ignition electronic 123.



The car runs less than years ago. I don't know why.

Regards!

[MiNiKiN]

Hi guys! Reading a old post trying to get an information to improve my carbs I see this; "You have proved a single HS2 with a modified head produces virtually the same as the Twin HS2's". What do they mean with "head" ? (I'm sorry but english is only my third languaje).

Definitely, and after writing rivers of ink, is it really possible to improve the performance of a double Hs2 by following the Vizard method or not?

Regards, Luis

MG 1300S engine bored 0'10. Cylinder head with big valves and double springs. Twin carburettor S.u. Hs2, blue springs. Ignition electronic 123.



The car runs less than years ago. I don't know why.

Regards!

You can of course modify the twin HS2's (call it the Vizard or whomever method) by optimising the throttle butterfly and spindle and the piston. By optimising I mean improving flow, i.e. A) reducing the cross sectional area of the flap and spindle that stands in the way of the air and B) by improving the shape of the piston to reduce turbulences.
By doing so you increase the gas speed, hence you get more AF-mixture into your engine - provided the engine demands more (i.e. is modified accordingly) and ther eis no other bottle necks (get to this latter).

Once the carbs are flow-optimised you shall of course re-tune them (different needles and likely a different spring rate too).

Looking at your photo and rather fundamental engine description, I'd suggest to bin the Coopers filters and replace them with K&N's in a standard twin filter housing (hard to get - I know).
I have also read that the 123-ignition isn't the best choice - so this may as well be your bottle neck.
What about the double valve springs? What spring rate are they? Too hard and rather your push rods bend than your valves open, too soft and at higher revs your valves start a life on their own - in both cases independent of what the cam timing wants them to do.

At last: 3 illustrations from "Minis heißer machen" that show how to modify the spindle and piston.

Drosselklappe = throttle flap
Drosselklappenwelle = throttle spindle
modifiziert = modified

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Edited by MiNiKiN, 14 July 2020 - 02:45 PM.

[gazza82]

Those air filters are going to be sucking in warm air once the engine gets to temp and that isn't the most efficient way either.

 

 

They are designed to go in a case too!

 

 

The car runs less than years ago. I don't know why

 

So what has changed?

[PACINO]

Hi MINIKIN, and thank you very much for your help. Fantastic answer. Thanks Gazza too.

3 QUESTIONS

First. When you say; "improving the shape of the piston to reduce turbulences".. I guess you mean to this:




Second. Do you think double valve springs are not good for my engine? I can change it without getting up the cylinder head.

Third. Lately I haven't heard anything positive about 123ignition. No one seems to like it. The problem is that with my old Points Distributor the car turned on very badly. I tried everything.. I changed the coil, sparks and renew many things, but it was all useless. The engine did not deliver its full potential and didn't start well. At least with the 123 the ignition is good, but when you get 4000revolutions the engine says NO more. Years ago, I reached 7000rvpm in an open road. Perhaps having replaced the Dynamo with an alternator is more important than it seems? This has been one of the modifications in recent years along with putting a Servo.


# as for the air filters, I know this is not the best way to carry them, but my problem is that I have the metal box, but I DO NOT have the cover. I've been thinking to make one in another material or ask in this Forum if someone sells me one.

Regards, Luis

[MiNiKiN]

Hi Luis, see my replies below in >bold<

generally, If I was you I would check the engine for any parts that have worn or broken and hence cause the reduced "pulling power".
Then concentrate on fitting modified or different parts. Because by swapping parts you only put more variables into your equation.
 

Hi MINIKIN, and thank you very much for your help. Fantastic answer. Thanks Gazza too.

3 QUESTIONS

First. When you say; "improving the shape of the piston to reduce turbulences".. I guess you mean to this:

exactly, by reducing turbulence you improve flow capacity. AND: by removing excess material from the throttle flap you increase the effective area (i.e. same as if you fitted a slightly bigger carb)


Second. Do you think double valve springs are not good for my engine? I can change it without getting up the cylinder head.

Depends what double springs you have and what the valve lift and cam profile are like - it is meant to go hand in hand and be adjusted to each other.

Also consider that something in your valve train is not right any more (a valve may not fully close, a burnt valve or a crack in the head, just to name a few other mechanical reasons)

Third. Lately I haven't heard anything positive about 123ignition. No one seems to like it. The problem is that with my old Points Distributor the car turned on very badly. I tried everything.. I changed the coil, sparks and renew many things, but it was all useless. The engine did not deliver its full potential and didn't start well. At least with the 123 the ignition is good, but when you get 4000revolutions the engine says NO more.

 

Can't contruibute anything about the 123 ign appart from what I read myself.

 

Years ago, I reached 7000rvpm in an open road. Perhaps having replaced the Dynamo with an alternator is more important than it seems? This has been one of the modifications in recent years along with putting a Servo.

 

I dare say, that the change from dyno to alternator shouldn't have any big adverse effects - except you fitted some 30kW alternator to power your ICE    

# as for the air filters, I know this is not the best way to carry them, but my problem is that I have the metal box, but I DO NOT have the cover. I've been thinking to make one in another material or ask in this Forum if someone sells me one.

Regards, Luis

Cheer

Marcus
 

Edited by MiNiKiN, 14 July 2020 - 02:40 PM.

[PACINO]

Hi Marcus, cheers man! je je the alternator is the correct for this car, from Minispares, but I don't know where I read that with the alternator you're loosing power. Around 1-2 horses.


Another thing that I do not know if it could be negatively influencing the carburetor flow, is NOT having the crankcase outlet tube connected by a Y to the carburettor.



Regards, Luis

[timmy850]

If it used to drive well, and now it has less power most likely it’s a tuning issue, or the engine is getting tired. The engine is designed to get air from near the exhaust (even more so with the factory airbox) as the early cars used to ice up during the winter. This is not your problem

Having the crankcase tubes connected to each other may be your issue. Try plugging both the holes instead , or connecting again to the crankcase. These are meant to be sucking in air and will affect the mixture

Try:
Full service
Check rocker clearances
Check timing advance is correct
Check the compression across all cylinders

There was a guy making the lids for the airbox, I’ll try and find the details

Edited by timmy850, 14 July 2020 - 05:16 PM.

[PACINO]

Thanks a lot Timmy. Should be nice about the airbox lid.

As for how worn or aged the engine is, I must say that in 2004 I completely rebuilt it. Ovebored 0.10, new pistons, con rods, crankshaft ... and everything. Since 2004 I will have done about 30,000kms. The compression readings from just a few months ago are 135 PSI in the four cylinders. And although a couple of people told me that it was not bad, it seems to me very little for a 1275 engine. And more when five years ago I did the measurement and it gave 180PSI in all four.



The only explanation I can give you is that in these last five years, the Distributor has been very advanced and has caused a premature deterioration of the piston rings.

I don't want the Millers oil anymore. The other day talking to Keith Calver he told me about the problems he has had with engines that carry this oil. Now for a year, I put Valvoline.


Best regards!

[PACINO]

[PACINO]

nothing ?

[timmy850]

Contact Nippycars on Facebook about the lid

When you did the compression check did you have the throttle fully open? Did you try again with a squirt Of oil in the cylinders?

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[PACINO]

Hi Timmy! I just saw this post. Thank you very much for your answer. I had already seen that Facebook link a couple of months ago. I appreciate the notice, but those lids have a prohibitive price for me. That is around 100 euros with shipping.

As for the compression test, I did it with the accelerator fully depressed, that is, the throttle valve open. Tomorrow I will do it again. Let's see what it gives me.

Kind regards, Luis