MAIN
Carburetor
Previous Page | Next Page
Robert Thanks, that's interesting. I wonder what it's doing in my twin SU HS2's then ! As they are on a 1275 Midget Mk3! And by the AUD markings on the dashpots they are the correct carbs for that car, ruling out someone simply swopping over some from the 1100. I'll ponder this a bit more, but will probably swop back to the AN needles. Nigel "amukdigiphoto" 33164... MORE
My book says that the D3 was the std needle in 62-68 MG 1100 (1098 cc) using 2 HS2 carbs. The numbers are as follows: AN D3 1 .089 .089 2 .0855 .085 3 .0827 .083 4 .0807 .081 5 .0787 .080 6 .077 .0794 7 .0753 .0785 8 .074 .0778 9 .073 .0745 10 .072 .0764 11 .071 .0721 12 .070 .075 13 .069 - Bob Troutdale, OR "Robert Webb" 33161... MORE
Hi guys I was cleaning and reassembling my carb's today and noticed the needle was a D3, yet for normal mixture the standard needle is meant to be a AN. Can anyone shed any light or explain why this needle might be a D3 and not an AN and should I switch back to an AN needle? The engine is not modified in any way. Tia Nigel "amukdigiphoto" 33149... MORE
Nigel... This needle does not show up anywhere in any of my literature on Series A engines, for rich, normal or lean categories, stock or modified. If your stock motor calls for an AN, then that is what I would use unless you've got logical good reason to use the recommended more rich or lean one for the application. Cap'n. Bob '60 :{) PilotRob@... 33156... MORE
Royce, an aftermarket SU carb kit manufacturer, has needles with letter/numbers like this in their kits. I suspect other kit makers do also. So far, I've found them to be pretty much what's needed in the cars that get these kits. Paul A "Paul Asgeirsson" 33157... MORE
Nigel, I don't remember what your car is, But FWIW... I had a similar problem with my Bugeye, My car came disassembled and the fuel tank fiting was not included. By trial and leak, I found that (USA terms) a standard tubing thread, copper compression fitting works. V.B. says that the same fits 65-74, and that the same pipe nut also fits 75-79, so I would assume that this should work in your car. I used copper tubbing from gas tank to carbs, (1 1/2" :() ), which is not stock, but is easier to bend and doesn't rust.... MORE
Aw c'mon, "Pacbell" Bob! What was Bush gonna do in the next 5-10 minutes that wasn't already being done by the FAA and appropriate government agencies? Our president is not a king or a dictator, no matter what certain others might want you to think and our president isn't personally carrying flak guns or SAMS! Besides, like the SU carbs on our LBC, our government works interdependantly to a great extent. There exists reason to believe the appropriate Government agencies MIGHT have failed to respond in a timely and/or appropriate manner. This is being addressed. By the time Bush... MORE
Well it's official. I'm a frustrated MG owner! I've had "Chloe' for almost two months and haven't really driven her yet. First, we fixed the brakes...then I went to drive her and she wouldn't start...cleaned the carb and adjusted it...hubby drove her out to test her and the clutch went out...pulled the clutch slave cylinder and bought a kit to fix it...still had clutch issue. Bought a new master cylinder today...STILL didn't work. WAAAAAaaaaaaa!! Yep, I'm whinin'. Summer is a'wastin' and I want to drive! Any ideas, guys? (I just had major surgery and my doctor doesn't want me... MORE
Yep.... You got it big guy!!!! Of course, this assumes a reasonably healthy engine pulling decent vacuum. TWO CAVEATS.... 1) If the engine's clapped out and is pullin' lousy vacuum, the pistons will never "top out", spring tension and fully open butterflies notwithstanding and thus....it follows, that.... 2) the entire induction system has got to be "air tight" as well. You don't need a midget under the hood. You need an SU carb tool kit!!! It comes with a little jet centering tool along with "rods" you place within the piston tubes which temporarily take the place of the... MORE
Rob, That helps. So let me get more clear. The spring rate (color) determines how high the piston will rise in relation to redline under load, for example if it will not reach the top under load or it reaches the top way before red line under load, it is a function of the spring/color and how fast the piston reacts (not how high it goes) is a function of the viscosity of the oil in the damper. Is that close? Now all we need is a midget to curl up in the engine bay and peer into the... MORE
Guys... Can't help but believe we are losing something in the translation, here. A faster rising of the piston (as Duncan points out) can be counterproducive to acceleration in terms of low end torque not only because of the "ramming affect" of a "smaller" venturi at the low end, but also because of the "leaning out" of the mixture on acceleration caused by "too great a rate". The thing is, the "proper weight" oil is "correct" for "rate of rise" in accordance with the maker's design of the application to begin with. The spring controls wherein the needle will... MORE
"venturi", Bob! :):) Call it whatever you will...as long as we're all on the same page in the same book! :) I like Alan's suggestion as to the British MG Metro SU carb. set-up alternative to Jen's carb. problem. The stock Metro needle would probably be right in the ballpark as well, considering the Metro is an 80hp Series A. Good one, this...methinks. Cap'n. Bob '60 :{) PilotRob@... 32727... MORE
What effect was this mod supposed to have? I would have thought the hole towards the mouth of the carb would allow more air to enter the space above the piston, and reduce the amount of depression, giving less piston lift? David "David Jacobs" 32716... MORE
Cap'n , Personally I've never heard it called an air valve - always a piston. I have a dim recollection that one of the tuning mods for improved acceleration was to drill two 1/82 (3.125 mm) holes in the piston at 90 degrees to the keyway. The existing hole in the side of the piston would be tapped and an aluminium plug screwed in .That was for the HS2 1 1/4" carb for minis though - might work on the midgets also. Somebody will prolly have an SU tuning book and confirm or deny the above. Just my tuppenyworth... MORE
From: David Jacobs [mailto: mail@... ] Sent: Wednesday, June 23, 2004 13:39 To: midgetsprite@yahoogroups.com Subject: Re: [midgetsprite] Re: misunderstand???? What effect was this mod supposed to have? I would have thought the hole towards the mouth of the carb would allow more air to enter the space above the piston, and reduce the amount of depression, giving less piston lift? David "Duncan Sinclair" 32719... MORE
I just opened my SU book and it calls it the piston and the butterfly close to the head is called the throttle valve. The piston is more of a variable venture and the butterfly is more of a valve that turns on and off the air/fuel flow. FYI, Bob "Robert D. Gardner" 32714... MORE
OH...and Jens...I forgot!!! Before you get started on a compression check, DO check the throttle cable hookup and be sure when you put the accelerator pedal fully to the floor the BUTTERFLY is FULLY open! :):) Cap'n. Bob '60 :{) PilotRob@... 32706... MORE
Ah HAH.... You may have hit the nail right on the head here, Jens... "If (my engine...tuned or not) cannot SUCK (produce enough vacuum) to open a pair of HS2's....." EXACTLY!!!! It is time to "begin at the beginning", Jens. As in MAJOR tune-up. Step one is checking engine "mechanical health".... with valves properly adjusted...time for a basic compression & leakdown check. Considering recency of engine work, you're looking for 150 or better on compression check and leak-down rates of less than 10%. Remember to hold the butterflies fully open (accelerator pedal fully to the floor) during the compression... MORE
Jens... ...the air valve is the largest moveable part of the SU carb and holds the needle. I have heard people refer to the air valve as a "piston". The butterfly (or it's position) is controlled by your foot and the accelerator cable and is the closest moveable part of the carb closest to the intake manifold. :):) Cap'n. Bob '60 :{) PilotRob@... 32704... MORE
Jens Fixed and 'spring loaded' needles are not interchangeable, as the spring loaded needle has a collar attached and is longer than the fixed type. My SU Needle Sizes chart shows me that AAV is indeed a 'spring loaded' needle for a .090" jet. I'm not even sure any HS2's used 'spring loaded' needles, but I'm not sure on that one. N "amukdigiphoto" 32691... MORE
Jens, Fixed needles are held rigidly by a grub screw into the piston, but swinging (or biased spring) needles are retained by a separate collar, they are forced by a light spring so that they contact one side of the jet, so no centering is needed, but the jet and needle both wear more than the fixed type. They're not interchangeable because of the retaining ring on the spring type. HS2s used both types, depending on the year. You can check which yours is by the tag number on the carb float bowl (what do you mean, it's not... MORE
I'm looking at buying a 1976 MG Midget special 57K with the 1500cc engine it has the Webber carb upgrade new starter and alternator but the connecting rod bolt came out and trashed the lower end of the engine they said it need a crank connecting rod and the block needed to be machined. How much would it cost to rebuild vs. replace with new/used engines???? also what are the specs for this engine stock and with the Webber carb kit??? besides that the car is decent shape minor rust (not bad surface only on seams)and there are a... MORE
The replacement jets arrived this afternoon. My son installed them and measured the gap, right in the middle of the range. The lids were put on the float bowls and the pump turned on..... NO leaks. The engine was started again no leaks. Now I just need to tweek the carbs a little. I believe the car will be running on the road this weekend. Thanks to all who suggested going back to SU jets. I should have know! Martyn "Martyn Eastwood" 32656... MORE
I've just fited a 73 Midget motor into my 67 Morris Minor. The smog rails etc have been removed and the ports plugged. Curently, the induction is the stock Minor setup, this will chnage in time, but I want to get the car finished before I go dual carbs and a larger bore exhaust. Anyway, I have 4 distributors, the stock 41400 25D unit, the stock 67 Minor unit, opne from a 64 TR4 and a DM2 from God know what. As far as I can tell *none* of the 4 vacuum advances work. I have removed each and... MORE
Thanks to all for the responses. I had considered hairline cracking around the jet but I was able to get a jet to work so it must be the *&^%*(()_) Grose jets. I've got new jets on order so I'll report back when they are in. Martyn "Martyn Eastwood" 32610... MORE
