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MG Midget and Sprite Technical - HS2 questions

I did set up the refurbished HS2 pair for the fast road 1310 cc by PB (not Philip Bruhl but Peter Burgess). The frogeye goes like a rocket with lots of torque. I had great help from a book by Des Hamill about SU carburettors and http://www.mintylamb.co.uk/suneedle/. I have 7 pairs of needles. V2 needles work best, V3 needles are a little bit slower in acceleration.
I have a few questions:
Will sub stacks help? The Med engeneering.co.uk are looking good but do not have a “Dutch” price. Are there alternatives?
Why does the piston in the HS2 not reach the top. Is it a fault in design or is there another reason? How much will shortening help?
My Veloce book is published in 2004. A long time after Bernoulli’s published his law in 1738. This law is not mentioned in Des Hamill’s book. Does he mention it in a later edition?


Flip
Flip Brühl

Flip
I believe (or have been told) that some pistons don't actually get right to the top
Every one that I've seen does go right up---
Just a thought--remove plungers from the dashpots and see if they go right up then---They may have the wrong plungers fitted to them
William Revit

Med ship to Holland with no problem.
Their big sub stacks are great but fitting a filter can be slightly challenging, a K&N suited for a 89mm pipe works wel
O K

Careful Flip, Bernoulli introduced Eddy and Flo into the ports and they have never been seen since!
You will have to pop over for a visit to the rollers.
Hi Willy, on some of the larger SUs they were fitted with shortened dashpots to prevent full lift to keep power down. Seen mainly on V8 Rover engines in military vehicles to stop the 'lads' (and lasses) thrashing the bejaizus out of the engines.
I haven't noticed this on the smaller sus but knowing Flip is such an animal with the throttle and always being chased by the law, maybe it is a good thing :)

PS Flip, if you bring some more of those gorgeous chocolates I will make sure your engine is the best it can be! I will even sign the print out :)
Peter Burgess Tuning

Hi Peter
Yeah , the only ones I'd heard of here were the 2"SUs on Rover 2000--4cyl that apparently had restricted travel---?
I was thinking that if Flip has just fitted reco'd carbs that somewhere along the line that the plungers out of larger bore units may have mistakingly been fitted and that they might be too long restricting travel
Don't know, it was just a thought---
William Revit

Hi,
They are alternatives in the Moss and MGOC catalogues. They do look different than the MED ones, but are also cheaper (https://www.mgocspares.co.uk/acatalog/MGOC_SPARES_1275_175.html - item 91)
Hard to know what is the benefit, and which one are more efficient. Vizard does say they give extra air flow.
If you buy those ones, measure them: mines were 1 or 2 mm smaller in diameter than the carb inlet...a bit of the opposite of the effect you are looking for !
Good luck,
CH Hamon

Flip

Any of these stub stacks of interest:

http://www.minispares.com/search/classic/Stub%20stack.aspx

Cheers
Mike
M Wood

I know it is often the case, but for this item, the price is really expensive for some steel and machining...
Also, don't get why the "K&N" ones are different from the other ones... I guess it is flow reasons, but doesn't make sense to me...


CH Hamon

You can pick up the K&N type for under a fiver on eBay - they do require some fettling to match the inlet tract, and if you're so inclined you can also give it a proper radius to improve flow.
f pollock

This thread was discussed between 08/12/2019 and 11/12/2019

MG Midget and Sprite Technical index

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