I failed to find the contact information for the Austin guy.  He had two Mk1 S cars, one was Aussie if I recall.  Maybe Playle knows him?

Aside from that, I have a question:  when you tested in the driveway, where you under the hood or in the driver's seat?  I ask this because watching a full fuel filter when the missing/cutting out occurs is almost as good as installing a temporary inline fuel pressure gauge like the Honda dude suggested.  If the pressure drops, the issue is upstream.  If it doesn't drop, then I would suspect the needle and seat has closed up.  Would a restricted vent tube allow vacuum to keep the needle sucked up against the seat?  Or manifold vacuum? I don't know.  The SU experts can shoot down my theory, no offense will be taken.

The other question I had is in regard to the fuel pipe under the car.  You replaced all fuel lines, I recall that.  Have you visually checked the hard line along it's path under the car?  Minis tend to get "rallied" a lot... a crimp in the hard line would restrict volume.

I'm pretty sure I saw you'd done that; which is why I suggested you try one that you know is good...

I've had new ones ..and ones tested as good (by my Father-In-law's shop) that turned out to less than completely healthy..

Do you have another vehicle that you can use to confirm that the one that you bought is actually working properly??

Cheers, Ian

I replaced the coil with a brand new one.  but i suppose it could be bad off the shelf.

I'm sure this has been suggested before (i.e. can't be bothered to read all the posts)... but it sounds like a classic case of an ailing coil to me.

I suppose you've already tried a known good coil???

I do know that a dyno session has been suggested before... that would take away all the guess work.  Doesn't take long ..or much specialised (oooppps knowledge to do  power run and check the fueling and electrical system operation.  A simple data logging setup would work as well.. 

Cheers, Ian

I know that we have already discussed a blockage in the tank vent but it bears repeating.

Since you can re-create the problem by revving the car on the driveway, make the problem happen, then remove the gas cap and rev the engine again to see if the problem reoccurs. 

Specialist: if you are going through inlet needles you're doing something very wrong. My first guess would be all the weird chemicals you like to add to fuel.

If you bothered to read all those posts, you'd know we have already covered fueling, ignition, carbs, valves...

Steve's (MLM) problem is probably something relatively simple but not obvious and needs a systematic review by someone more familiar with these quirks.


It still seems to be a fueling issue - loss of power or flat spot above a certain speed under load (an unloaded engine would rev higher on less fuel).
I found a brass foreign object inside a brand new HIF44 inside the inlet seat filter. But ultimately, my issue was with the inlet needle - it looked and worked fine cool, but once it expanded, it stuck. A wee bit of gentle filing and no more problems.

yes, i'm telling you guys, the most i can suspect on the fuel delivery department is a worn out Float valve tip,nothing else... my Primary bet is more on electrical, the ignition timing at high speed to be specific. This is probably the longest active problem that has ever been UN-resolved for the longest time in the history of all forums across the world wide web,, it's got 4 pages and 2.5K+views, aaaand counting. i like Trump, btw 

Thanks for keeping up and all the advice.  I cleaned the tank a few weeks ago.  blew out the screen the best i could.  seems clear. 
I'll let you guys know about the carb.
I've seen the same problem I'm having posted many times across the internet.  very few actually post once the problem is resolved.  if it is resolved that is.  
If i ever cure this I'll be sure to post it!

I'm not too sure about the timing chain diagnosis i got from the local guy. (neither was he).  sitting still the engine will run smooth and strong for a full minute at 4000rpm before it starts falling apart.  

I just re read this Loooong thread and you have basically covered everything fuel wise except a different HIF carb.
I did notice that you had not checked the screen in the tank but with the gas can set up you by passed that. FWIW i would still check it.
Good luck with the carb.

Cool.  Give me a day or two to track down his name and contact. 

Seems the overwhelming consensus is fuel starvation, huh?  If it turns out to be anything but, wow, we'll have to nominate Specialist to Trump's cabinet.

Yes. I am in Austin.  I'm borrowing a hif44 form a fella here in town.  If that doesn't do the trick I'd really like to talk to the guy.
please shoot me his info if it's free to give out.
Thanks!
Steve

Are you in Austin, TX?  I recall you mentioned Austin and 38th st...
If so, there is an Austin fellow who's restored a few Cooper S's and I'm sure he would be willing to lend a hand.  Or ear.  I met him at a British car day in Dallas.

Check the float valve  inside the carb reservoir, sometimes if the fuel pressure is high, it overpowers the worn out float valve ,in turn it allows too much gas to enter the combustion chamber until it floods the spark plug and it sputters.  replace the float valve  if worn,,i use Grose  float valve ., stay away from Viton tip it wear quite easily , ive used 4 of them already... Gosh!!

When it starts to splutter imediatly shut it down and check the float bowl - bowls it is probably running out of fuel if so it is a supply issue go buy a pump.

I'll ask a race mechanic buddy of mine if he knows a good one.  Surprisingly not many shops around here are interested in looking at these old cars.  

Do you have a rolling road/dyno in your area somewhere? I'm sure you'd solve this with one session on the rollers!

It's a new electronic dizzy. new cap rotor and wires.  replaced the old one.  issue remained. 

MML, arent you considering an electrical issue? here's the thing, your car revs at 3k, 4k then bogs, there might be an ignition timing issue, that's what first came to my mind. it's either you have a bad Vaccum advance or a bad mechanical advance, (one of the two tiny springs might got loose). let me tell you how the distributor works, the thing in the middle spins(rotor) and it will throw arc to each of the terminals inside the distributor cap(normally 4), the spark SHOULD detonate exactly when the rotor and the terminal meets face to face., IF your dizzy components are worn out, then arc-ing will occur, means the arc goes somewhere else, not to the terminal, and if ARC-ing occurs, the RPM is not syncronized, then hiccups will occur. this is called the Arc-ing phenomenon. NOW, take off your distributor and inspect for burnt surfaces inside.

I did try the tank is the front seat.  although if i had to guess the problem might have slightly worsened.  I was using an old generic pump i had under the hood. It might have been worse than the facet.  although both pumps appear to put out a steady stream of fuel. 

Have you tried "fitting" the 5 gallon gas can i suggested ? With these issues you have to eliminate one possible problem at a time so keep the pump you have in place and re route the fuel line to the gas can and see what it does. If the problem persists then try a different fuel pump.