Twin HS2 Carb needles

Started by Hercplt, October 27, 2019, 11:14:06 AM

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Hercplt

OK.. Mini is back on the road, but not running well.  For the record I haven't driven it... but the report is that it all seems lacking.  Can't handle loads, lacks power etc...  so... here's the spec.

998+60 (1050?)
12G295 head.  Ported, opened comb chamber, skimmed, int/ext valves from big bore engine (not sure specifics there).
10:1 CR
VP7 cam (270/276)
Elect dist. with vacuum advance.
Twin HS2 carbs.

I was running HIF44, but it never ran perfectly... just too much carb... When it did go, it went like a scalded cat! 2500-6000rpm easy...

Question;  What carb needle should I be starting with??  Not sure what needle was used (investigating now)...

My first guess is too much fuel getting in.

I'm out of country so wasn't involved in the set up.... but seems like the HS2's should work, but the set up might be wrong...

Thanks guys!

Rich
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

You really have to get a wideband hooked up to know. 

Hercplt

1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

MiniDave

You weld a bung into the exhaust right after the header collector, then insert an o2 sensor, then attach a wideband meter to it and you'll know at all times and under all conditions of load and RPM exactly what your mixture is doing.

Complete kits are in the range of $150-200.

Here's an example.....

https://www.summitracing.com/parts/inn-3918?seid=srese1&gclid=Cj0KCQjwgNXtBRC6ARIsAIPP7RuP79Jw8ZGqVNFQ3fZ2yrFsIVT62AhABX66kxj5X6eFQp_CeOFKlW8aApwCEALw_wcB
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jeff10049

#4
What is the timing set at initial and total advance?
Did you find out what needles in the carbs?
You could try gy needles as a starting point they'll probably be lean on the top end though.

94touring

#5
Yeah I think I got mine off Ebay for $125.  You're really just guessing till you either put the car on the dyno or hook up your own wideband.  Dyno really only gives you a full throttle readout whereas in the car you can adjust carbs and needles for cruise.  A lean 15:5:1 cruise air fuel feels perfectly normal, until you richen it down into the low 14s or high 13s air fuel ratios, then you realize how much seat of the pants pep you were giving up at the leaner mixture.  Conversely a full throttle air fuel rich at 11:1 lacks power compared to high 12s to low 13s and is noticable if you have a built engine.  Also lets you know if you're running dangerously lean at full throttle so you don't blow an engine.

Also lets say everything is perfect at full throttle but you have flat spots on throttle driving around town.  We'll say you have blue carb springs and the wideband says on throttle you hit 18:1 briefly then settles in at 15:1.  You now know to add red springs and add a higher viscosity dashpot oil.  You can tune cruise A LOT by changing carb springs. 

Hercplt

Thanks for the thoughts so far... gives me something to start thinking about.

Given the cam, what should I have expected them to set the advance at when they set it up?  or does the cam profile matter for that? 

I've got some investigating to do, but most of this will have to be sorted in the spring.
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

#7
I have an adjustable curve electric dizzy.  Baseline set to 10 at idle, comes on quick, tops out at 32 degrees.  Number 8 on this chart.  It responds well to the quick advance too I might add.  This is on a built 1275/1310 with a 266 cam.   On the dyno it didn't make any more power past 32 degrees either.  Picked up a lot of power by getting air fuel in the 13:1 zone at full throttle.  Cruise you want 14:7:1 in a perfect world, a smidge richer is better than leaner past that number.

94touring

Wideband gauge next to my tach (both must haves on a fast road build in my opinion) and 02 sensor location. 

MiniDave

I set up the Inno we're building for an o2 sensor too, so we could get the carbs dialed in right.....it's an easy thing to do and you can move it from car to car or just leave it in like Dan does. The bung comes with a plug so once you're done you just cap it off.



Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Hercplt

Follow up question to this...

First I haven't done any work on the car... but those that did said that the timing of the dist arm looked like it was anywhere from 35-50 degrees off the number one point while it was at TDC. (static, not running)

Is there a chance that the timing was fine, but they had the wrong TDC?

Apparently they say that they fixed that, but now the car won't run... my math leads me to not having TDC set properly...

Thoughts?
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

BruceK

Sounds very strange.  It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel).  And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1. 
1988 Austin Mini
2002 MINI Cooper S
1992 Toyota LiteAce (JDM)
1997 Jeep Wrangler Sahara

Hercplt

Quote from: BruceK on February 18, 2020, 01:15:39 PM
Sounds very strange.  It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel).  And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.

Right... so... lets presume that they did that properly... any reason why the arm would be pointing so far off?  is it physically possible?

1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

MPlayle

There is one caveat to what Bruce said: cylinders #1 & #4 will both be a TDC at the same time, but only one at a time will be ready to fire.  You need to make sure which it is by looking at the valve rockers.  When #1 is ready to fire, #4's exhaust valve will still be partly open (closing as it is finishing the exhaust stroke), #4's intake will be starting to open, and both #1's valves will be fully closed.

Then you check the rotor is pointing to the correct lead for firing #1.  Also, make sure the rest of the spark plug leads will be in the correct firing order going counter-clockwise (1-3-4-2).

As for your question about the arm pointing being far out of expectation, the distributor drive may have gotten pulled at some point in time and not put back in oriented correctly.

If you are referring to the timing marks (on either the flywheel or crank pulley), they should be as Bruce said: lined up with the pointers when #1 & #4 are at TDC.


John Gervais

Quote from: 94touring on October 27, 2019, 03:46:19 PM
Yeah I think I got mine off Ebay for $125.  You're really just guessing till you either put the car on the dyno or hook up your own wideband.  Dyno really only gives you a full throttle readout whereas in the car you can adjust carbs and needles for cruise.  A lean 15:5:1 cruise air fuel feels perfectly normal, until you richen it down into the low 14s or high 13s air fuel ratios, then you realize how much seat of the pants pep you were giving up at the leaner mixture.  Conversely a full throttle air fuel rich at 11:1 lacks power compared to high 12s to low 13s and is noticable if you have a built engine.  Also lets you know if you're running dangerously lean at full throttle so you don't blow an engine.

Also lets say everything is perfect at full throttle but you have flat spots on throttle driving around town.  We'll say you have blue carb springs and the wideband says on throttle you hit 18:1 briefly then settles in at 15:1.  You now know to add red springs and add a higher viscosity dashpot oil.  You can tune cruise A LOT by changing carb springs.

Wow, I'd love to get into the high 12s or low 13s on full throttle - I'm frequently seeing low-mid 10's, regardless of which oil or spring I try.  I think I've got 10W synthetic in there now.  Cruise and idle seem fine, and with good pick-up on part throttle acceleration - just can't 'floor it', though. 

Quote from: BruceK on February 18, 2020, 01:15:39 PM
Sounds very strange.  It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel).  And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.

And thought I'd add that each timing mark on the crank pulley or the flywheel is 4°.
- Pave the Bay -

94touring

Quote from: John Gervais on February 18, 2020, 10:27:22 PM
Quote from: 94touring on October 27, 2019, 03:46:19 PM
Yeah I think I got mine off Ebay for $125.  You're really just guessing till you either put the car on the dyno or hook up your own wideband.  Dyno really only gives you a full throttle readout whereas in the car you can adjust carbs and needles for cruise.  A lean 15:5:1 cruise air fuel feels perfectly normal, until you richen it down into the low 14s or high 13s air fuel ratios, then you realize how much seat of the pants pep you were giving up at the leaner mixture.  Conversely a full throttle air fuel rich at 11:1 lacks power compared to high 12s to low 13s and is noticable if you have a built engine.  Also lets you know if you're running dangerously lean at full throttle so you don't blow an engine.

Also lets say everything is perfect at full throttle but you have flat spots on throttle driving around town.  We'll say you have blue carb springs and the wideband says on throttle you hit 18:1 briefly then settles in at 15:1.  You now know to add red springs and add a higher viscosity dashpot oil.  You can tune cruise A LOT by changing carb springs.

Wow, I'd love to get into the high 12s or low 13s on full throttle - I'm frequently seeing low-mid 10's, regardless of which oil or spring I try.  I think I've got 10W synthetic in there now.  Cruise and idle seem fine, and with good pick-up on part throttle acceleration - just can't 'floor it', though. 

Quote from: BruceK on February 18, 2020, 01:15:39 PM
Sounds very strange.  It's easy enough to verify you are at TDC with the engine off by looking at your timing marks on the crank pulley (or through the clutch cover window on the flywheel).  And of course then the rotor arm should then generally be pointing to the point on the distributor where the plug wire is connected to cylinder #1.

And thought I'd add that each timing mark on the crank pulley or the flywheel is 4°.

What needle are you using?

John Gervais

Hi - been a long time...

I'm using the AAA needle - KC originally used one on the engine before he sent it to me.  Of course, he used it in a moderately-worn/average HS4 and I've got it in a brand new HIF38.

Have you any ideas that I may have missed?  Oils, HS blue spring (too weak, sputtered like heck); I've even shortened the carb's brass damper (- 1½ mm) in order to get it to rise quicker upon initial acceleration.

Sooo, I've just gotten used to not stomping my foot down for now.
- Pave the Bay -

94touring

If your cruise is good then your cruise stations and spring and oil is good.  You probably just need a leaner needle in the upper stations for WOT.   You can try a much leaner needle over the entire profile and if your cruise becomes too lean, toss in a red or yellow spring to richen cruise back up. 

John Gervais

Not a bad thought - why not, it's worth a shot.  Just need it to stop raining and the wind to die down.  We've had non-stop crappy weather for the past couple o'months - heck, I haven't even done any fishing and there are still those trees I've been wanting to cut down... 
- Pave the Bay -

Hercplt

Update on my original post... would welcome thoughts.

I have had the car running, finally.  I opened up the twins and found that the needles were AH2 and the springs were not marked any colour... I added Blue springs and M needles (leaner).

Granted that I need to strobe the timing in at some point, but its close... and I have not sorted a WB as suggested.

Anyway, it idles ok... revs ok parked, but runs like crap on the road.  Its not pulling much power and misses and faulters under load.  Had to nurse it up a hill in 2nd gear just to get home!  Its also a bit difficult to start when its been warmed up.  It doesn't jump to life like you might think, but lots of cranking and it just sort of sputters to life.

Thats the best I can describe it... any words of wisdom?

Note:  I have 45D type dist, Accuspark Electronic.. new plugs, wires, coil... everything...

1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

#20
Quote from: 94touring on October 27, 2019, 11:21:21 AM
You really have to get a wideband hooked up to know.

I'm going to quote my original reply lol.  My guess is you're lean.  Try pulling the choke when it's barely running under load and see if it improves 

Hercplt

Probably lean like you say.  I have switched back to AH2 needles with the light springs... Last time I was putting along and pulled the choke it wanted to die...
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

Do you have red springs to toss in or double up the unknown springs you pulled out and see if cruise and partial throttle improves. That will effectively richen the mixture at cruise as well as idle.  If it makes it worse then you're too rich.

Hercplt

Ok... so educate me on the springs...  the blue (2.5 oz) spring will do what for me?  I went with that as a starting point as the early 998 Coopers call for it.   The spring that came out was much tighter, just not marked.

The 12G295 head I have has big valves, and was ported... larger combustion chamber with a skim to keep the CR at about 10:1.  So, thinking I just need a richer mixture overall with all that air getting pulled in.  I still have the HIF44 avail to go back on... it has a modified BDL needle for reference.

Rich
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

Blue are lean springs
Red are richer springs
Yellow is very rich springs
Green are turbo and extra rich springs

The leaner the spring the higher the carb piston rides, which alters bernoullis principle.  You get less velocity/pressure differential over the needle port and pull less fuel at that particular needle station.  If you hold the carb piston down using a stiffer spring, you get higher velocity of air and will pull more fuel.

These effect idle and cruise.  WOT isn't effected as much. 

I fine tune my piston cruise ride height by adding 0.7 oz washers to the tops of the pistons where the springs ride.  Blue as a recall is 2.5oz and red 4oz.  With a wideband you can dial it in pretty tight.