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MG Midget and Sprite Technical - HS4 for 1275

Eventually I plan on running an HS4 setup with a hopped up 1275 engine. However currently my engine is still pretty stock.
What is the minimum changes that I would need to make in order to switch to HS4 now (I did not want to spend time spiffing up the HS2).

Is it possible to adjust the HS4 so that it is not running too rich for this stock engine?. I read somewhere that running headers and performance exhaust would help? Eventually I will build an engine that can use the extra fuel mixture but that is not going to happen this summer. However, if it is possible to run HS4s now I want to change my intake manifold now and spend my effort with the HS4 instead of wasting time rebuilding the on the old ones (I think that my throttle shafts are worn).

Is this just not going to work for me now (rebuild the HS2 for now)?

thanks,
Rebecca
R Harvey

HS4 a complete waste of time and effort, especially on a US spec late 1275. You will spend far more time and $$ trying to set up the HS4 than it is worth, and then need to do it all again when you mod it. OTOH, you can replace the HS2 throttle shafts in an hour for the price of the parts. IF they really are badly worn. The HS2 are good for double what the US spec 1275 will make in stock + wore out form.
Compression, headwork, cam, exhaust - then carb change.

Get your car right and learn to drive it before you do all that.

You DO have Vizard's book and you HAVE investigated MGExperience Motorsports board as I suggested a year or so ago?
<<<Readin' is cheaper and faster than parts>>>

FRM
FR Millmore

thanks for the advice. I am not going to have time to change the engine until next winter. I will do as you suggest (stick with HS2). This was just a sanity check before I go ahead. I am spending most of my time on the body (engine will be an side show until next winter).

thanks,
Rebecca
R Harvey

These are the books that I have:
MG midget A-H Sprite High performance manual - Daniel Stapelton
the 1275cc A-Series High-Performance manual - Des Hammil
The SU Carburetor High-Performance manual - Des Hammil

Rebecca
R Harvey

the mini crowd have been using a single HS4 in place of a pair of HS2s, but for a midget the hard part is getting a manifold that will hold it at an angle that will allow it to clear under the bonnet

I agree with FRM, a pair of HS2s are not hard to rebuild, maybe less work than trying to get a whole different one to work right



Norm
Norm Kerr

Page 36 -37. All a twin HS4 has to really recommend to it is that it looks stock/ish and is bigger than a pair of HS2s. But a single HS6/HIF6/HIF44 is more of a performance option.

Getting the mixture right is just down to the correct needle and dashpot spring.

Probably fitting a pair of HS4s and getting them correctly calibrated and set up will be a lot more work than rebuilding the HS2s.

However, fitting a single HS6/HIF6/HIF44 might be a quicker solution, but not necesarily cheaper than rebuilding the HS2s.
Daniel Thirteen-Twelve

thanks Daniel, you are exactly right! "single HS6", is what I should have said (meant to say), or, even better, HIF44.

Norm 'spell check" Kerr
Norm Kerr

Does anyone know of a book that talks about this stuff.?


prop
Prop

I made the swap to a single HS6 (NOS carby off Ebay) on my 1275. Very easy mod and works great (I also fitted a dashpot damper rod that had a flat brass cap to lower overall height). Now I have found a good condition HIF44 which I will be putting on soon (once 5 speed installation sorted). Will be getting it dyno tuned to get the sep-up right though. Just as well I have a partly dismantled mini in the drive which I can donate the HS6 to.

Murray
MK McIntosh

This thread was discussed between 02/05/2011 and 04/05/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.