23 replies to this topic

[finch661]

i finally got round to reading vidards book on tuning the a series engine. i was really interested in the carb mods, like filing down the throttle spindle. has anyone attempted these mods and if so how sis you get on?


thanks

[Ethel]

The mods are easy enough. Don't expect massive gains & be very careful if you touch the piston, definitely a case of less is more - test run it frequently.

[Dave33]

Yep,have done these mods on my 1380,hif44,streamline butterfly,thin down spindle,replace screws so as no protrusion,
chamfer edge on piston,and square off bore.
motor will now pull a higher gear up hills etc than before mods,i suppose it depends if the engine needs more cfm,might not be noticeable on standard motor,but havent tried on one myself.
You will have to alter the needle profile after you do mods though,its all in the vizard book.
by the way,take note of vizards comments on streamlining the bridge,its no good on a road used motor.
hth
dave

[bmcecosse]

Yes -well worth doing - although I haven't gone to the extreme of thining the throttle spindle right down. A good bell-mouth on the air entry to the carb is well worth doing - as is rounding off the leading edge of the piston at it's base.

[Retro_10s]

Watch out when you slim the throttle shaft right down etc - you can run into trouble getting your idle down (on mine it wouldn't go lower than 1k...

i would personally only smooth the middle out and leave the area around the screws that hold the butterfly in place - obviously smooth into it so that you get good flow.

Flowing the carb elbow (if using a standard airbox like i am) is also a well worth mod.

[finch661]

Yes -well worth doing - although I haven't gone to the extreme of thining the throttle spindle right down. A good bell-mouth on the air entry to the carb is well worth doing - as is rounding off the leading edge of the piston at it's base.

regarding the bell mouth, when exactly is that? i cant seem to find it in vizard (cant see the wood for the trees_

[Boothy]

Not trying to hijack topic but what pages are these mods on i can never seem to find them?

[Turbo Nick]

every little bit helps

Edited by bud666, 19 June 2010 - 09:27 PM.

[Ethel]

Bell mouth refers to the air inlet. It depends on what type of filter you have. K&N produce a "stub stack" for their filters, and some will have something similar built in. Otherwise, just radius all the edges smoothly, sharp edges create shock waves and ruin airflow.

[Burnard]

No points, its a total waste of time and would never work
























ok, thats a lie, the mods work great

Edited by Burnard, 19 June 2010 - 09:45 PM.

[finch661]

the changes are on p115. i am about to fit a hs4 to my mini, might spend a bit of time and make some of these changes

[mini-geek]

anyone got any pictures? not got my bible with me at the moment, may try this on my twins....

[finch661]

anyone got any pictures? not got my bible with me at the moment, may try this on my twins....

i am thinking the same, got a set of hs2's for my project, i have to rebuild them any way... some pictures would be nice as well though, the pictures in the book are a wee bit small. (i know most of you will have your carbs on your car lol)

[Retro_10s]

my project thread has pictures somewhere

[Big_Adam]

I've done the spindle mod, but differently.

Mr Vizard says to slim it down, its quicker to cut the top half (thredless half) away and file it down flat. Takes 1/8th the time and give the same results. Makes the carb much perkier but you will need a new needle.