AC Owners Club Forum
AC Owners Club Forum => Ace, Aceca & Greyhound Forum => Topic started by: Gus Meyjes on September 07, 2007, 15:12:46
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HELP!
Mt car is all done. I took car of the brakes, clutch and oil leak issues. With a brand new pedal box assembly. The pedals operate smooth like a new car.
Brakes are fantastic with the front Disc conversion. Steering is super tight and precise with the steering rack conversion. The car looks fantastic!.
But, in spite of the engine rebuild with upgrades such as a mild comp cam, new pistons and con rods, a ported head, new sleeves, gaskets etc and an increase in compression from stock to 9:1 ratio (according to Robin Woolmer) I can't seem to get power out of this engine.
I've had various widely ranging suggestions on timing with the new cam.
It is now set at 12 degrees advance and 36 total. the carbs are problematic. They have been completely rebuilt by professional SU guys. But they mostly do twin set ups for MG's. The plugs look good, it's not running lean or rich. But power feels flat. Synchronizing these carbs is problematic, largely I think due to the spring-linkage. The first carb always leads out before the others follow and open up.
Can anyone offer me any suggestions on tuning these SU's?
(http://i129.photobucket.com/albums/p222/AEX674/IMG_4380.jpg)
Thanks,
Gus
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Gus,
The carb set looks great, nice clean set-up. I’m no expert on AC’s with SU’s, but here are some thoughts.
The timing values seem in the right range. Compared with other performance engines, 33 to 38 degrees of total advance is normal. I’d be surprised if timing was the source of low power.
I would not think the first carb leads the other two. The throttle butterflies are a “balanced” design. There is equal butterfly area on each side of the shaft so it takes almost zero torque to open or close.
If the return spring is on the opposite end of the shaft from the throttle linkage, leading could occur. I don’t see that in the picture.
I use a Syncrotune to tune my Solex’s on the Bristol engine. It’s available from Moss Motors (PN 386-200) at $29.95. I disconnect the linkage from each carb and balance the individual carbs very accurately at an idle ensuring all three are on the stops. I then reconnect the linkage and recheck the balance. I assume they stay balanced through out the range of throttle openings.
How many miles are on the engine since the rebuild? My Bristol had similar timing and carb problems but also seemed a little down until about 300 miles. Around 300, the rings seemed to seat and power improved. Have you checked compression?
Peter Stanwicks
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Thanks Peter,
The engine is brand new after rebuild, only 25 miles, so that may be part of it. I did balance the carbs out the way you mentioned, but that was to no avail. The engine is much happier with the choke on, which makes me think I am starved for fuel, even though the plugs had a nice although light, color.
I hear about people sanding down the needles to get them to allow more fuel in the mixture. I just don't know where and how to sand or even how much.
Do you or anyone have any experience with that?
Gus
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Gus
I have sent you information From Midel in Australia & Burlen Fuels in UK both are SU experts, Midel web is ' www.sumidel.com ' & Burlen is ' www.burlen.co.uk ' They can supply you a range of needles but more inportantly give suggestions as to the original needles & perhaps what you should consider now with your set up.
The needles have a very precise shape & i doubt you could reproduce this consistantly on three needles.
The other issue is are you now using the correct choke size? my racing special was set up with 1&3/8'' choke carbs, it would be worth some discussion with other racers!
I asked Burlen yesterday if they had a formula to size carbs to engines & the various detail parts & they said NO, you could however talk to there experts though!
It looks as though some level of developement is needed.
I did send quite a bit of info to Ron Mack on timing etc.
Regards
Robin
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Gus,
If the engine runs better with the choke, fuel starvation is a possibility or maybe a vacuum leak. If the engine idles poorly, a vacuum leak is more possible.
Peter
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Hello!
anybody would know wich is the correct fuel level for a H2 AUC 700 Carb? (1959 car).
i have found different sources in referecne to the float fork setting.
Should it be set with a 7/16, 3/4 or 3/8 rod across the underside of the lid?
Thanks!
Eddie
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According to the instructions supplied with Burlen rebuild kits for AUC 700 carbs,
a 7/16 (11mm) diameter rod should be used. This measurement is for when the
needle valve is on it's seat.
Regards, Luke.
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I had the same problem with my Healey some time ago (only 2 carbs). He asked for a slightly pulled choke to run equally. At the end it was a loosened screw wich fix the needle in the piston. The shoulder of the needle should be flush with the bottom of the piston. It was about 2-3 mm the needle had come out. Easy to control or to fix - just open the bell housing on the carb and pull the piston.
Regards, Chris
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Hello Gus,
I have been running AEX 31 with an engine that sounds similar to the specification you have, for 7 years.
Ignition setting also sounds the same.
I have also experimented with a number of needle sizes but have found that the engine runs best with the
standard DW needle and the top of the jet adjusted 1,5 mm down from the bridge.
Which needles do you use?
Please let us know how it goes.
Regards Jonas
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According to the instructions supplied with Burlen rebuild kits for AUC 700 carbs,
a 7/16 (11mm) diameter rod should be used. This measurement is for when the
needle valve is on it's seat.
Regards, Luke.
Tahnk you Luke,
I set them up as you suggested. and then tried to tune them, but i dont seems to be able to get them right.\
They remain quite rich, and very strangerly the first two pistons work at 200 degree less then the other 4... (100' vs 300).
And this dont change even by changing the carburettor settings to the extremes. very strage. may be there is a leak.
Also despite the cylinder work, when i disconnect the plug of it, it doesnt seems to badly affect the engine running.
i can see it works as when pulling the plug out you can see there is combustion.
On another note, when checking the igition with a strobo light, i can not see any sign on the flywheel.
The maual says 1/6 should be seen. I will try again and eventualy alter the timing.
Best,
Eddie
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Hi,
I've read through the posts with intetest and can see you've had lots of great advice, just a thought though as it's easy overlook some the basics and assume you've got carb problems. A quick check with a vacuum gauge will give you some good indications of what's going on, expect steady reading of approx 18 to 20 inches of mercury, a fluctuating reading would indicate a mechanical fault, e.g. valve clearances, seats, etc, a steady low reading might indicate ign timing or valve timing etc. As a test you could even try rotating the distributor with the vacuum gauge connected to see if this improves your reading.
If you suspect you've got an induction air leak have a Google of a tool called smoke pro. I've used a snap on version of this for years and it is unbeatable for finding induction leaks.
Hope this helps a bit.
Kind regards Nick
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Hello Nick,
thank you!!
it is the first time i work on a car, but i come from motorcycles and with my firends we always say that 80% of Carburetor issues are electrical!
i was able to get a rough carburation yesterday, the car doenst smoke or miss beats. As well after cleanign the jet (and the rusted spring!) of the first carburator, al the cylinders run around the same temperautre.So despite the mixture skrew completely open it was running lean. Now it should be ok.
As well, this time instead of starting tunign them from one turn and and half out, i started the tuning procedures with the mixture skrew completely in. The standard one and an half turn out was already too rich.
Today will try to check the timing. But still not to sure what i should see on the flyweel as marks. now i dont see any, so i am definitely out.
I will consider that Smoke Pro, and unfortunately the syncorniser i bought never arrived! so i am using the hiss method for alligning them.
i am considering as well and exhaust gas analyser.
And defintely a full rebuild kit for the carbs!!!!! i dont know i will get any closer to a good carburation with these worn parts.
Eddie
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Hello!
anybody would know what i should see with a strobo light for a Weller engine?
I can see three markings on the flywheel: a "5", a bar "I", and a "1 I 6"
With the strobo lamp i can see the "I" with the motor running very slow, then it disappear...
At what should i aim?
Thanks! and sorry the manual is not very helpful on this!
Eddie
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I had exactly this problem last year! just going out now, but give me a shout and I can talk you through our process of resolving the issue which may help
Regards
Chris
07557 304376
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The bar "I" is just a few centimiters before the "1 I 6".
"1 I 6" should be the TDC for Cylinders 1 and 6, so i belive that the bar "I" is the firing point at 12.5 degree before TDC.
Anybody can confirm this? what's are your flywheels marking on a CLB engine?
Thanks!
And Thanks Chris for your availability and time at the phone today!
Hello!
anybody would know what i should see with a strobo light for a Weller engine?
I can see three markings on the flywheel: a "5", a bar "I", and a "1 I 6"
With the strobo lamp i can see the "I" with the motor running very slow, then it disappear...
At what should i aim?
Thanks! and sorry the manual is not very helpful on this!
Eddie
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Hello,
I have measured the distance between "I" and "1 I 6", the mark "I" is 1 1/4 before the mark "1 I 6", so i can confirm that the mark "I" is the firing point.
Hopefully this can help 1959 CLB owners (in case these are factory markings!)
Eddie
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Hello!
I am not still able to get the engine running right...
I am unable to get a stable idle. after a while it goes down to a point that then the engine goes off as is it too low.
As well it is very difficult to get the engine revving. I have to give little hits to the pedal to not flood the engine. if i push the pedal down the engine drowns and stops.
At times the idle seems fine, but then it goes down and the engine stops. This even if I set the idle speed higher.
To keep the engine running i need to keep give small trottle strokes, untill a point the engine finally is able to take the throttle and revs up. But then shortly after it goes down again.
Any suggestion on what should be the issue??
- I have between 95 and 110 PSI in all Cylinders.
- New Lodge NH Plugs with gap set as per Manual
- New Distributor Cap and Rotor Arm
- Distributor Points set as per manual
- Ignition timing set as per manual (no indicaiton on the revs on the book, i set it at 2500 RPM)
- New connections on the spark cables
- Foat Chamber level set as per manual
- New float chambers needle valves
- Few drops of SU Oil in the damper pistons
- needles centered in the Jets
- Approximative carburarion done ( 1,5 turn out and then adjusted from there)
- Approximative syncoronisation done (Hiss method, not very precise as per below i am not able to get the idle stable)
Thank you all in advance in case you have any suggestion!
Eddie
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Have you checked if you have an air leak in the induction manifolds between the carbs & the head? this may account why you cannot get stable running setting up the carbs!
Robin
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Hello Robin,
no! i didnt! i will try to buy an air leak detector spray anche check.
Eddie
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i bought a can of ether starter. will try later.
I was thinking that may be is just fuel starving? may be the new needle valve are different? i didnt measure them, as i tought these were standard.
Or may be the float level too low? but then if set higher i belive it overflow into the carbs.
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Hello,
After this last winter I’ve had great problems getting AEX 31 to run nicely, or run at all! What you have described sounds very similar to what I experienced. I tried loads of different things until I emptied the tank and put some new fuel in the car. As strange as that might sound that actually seemed to have solve the problems.
So I’m wondering if you have fresh fuel? The fuel in 31 was 5-6 months old. I’m in Sweden and 98 octane here has a 5% ethanol mix.
Maybe be worth a try getting new fuel?
Best Jonas
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Thank you Jonas,
the fuel is fresh.. so i dont think is that.
Yestarday I tried to spry some ether around the carbs and i was not able to find any leak. May be there are, but i was not able to detect any.
As well, i tought that the issue could have been float bowls venting as i changes a well the 3 slotted fiber gaskets, but i tested the carbs without retaing nut so fully open to the atmosphere and no visible change, so i belive the floats breath normally.
may be the issue in the end is just that i am doing long static tests, and never did any tuning on the road as the car has no papework yet so can not go out.
And may be this flood the engine after a while. may be some soot builds up etc etc as the mixture is a bit rich, and in the end the engine stalls.
I will try to do the MOT techincal inspectio as is. and then try to fine tune it.
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Eddie
I think your ignition timing is wrong. You tell us you set the AC figure (12.5 degrees btdc ?) at 2,500 rpm. But this is a static setting (we didn't have strobe lights in the '50's). Don't know anything about the centrifugal advance curve but I think it is running too retarded. Suggest you try the old trick of slackening the clamp bolt and turning the distributor in the advance direction with the engine running to see what that does. You don't mention evidence from the appearance of the plugs. Get it up to temperature, switch off and take the plugs out. Are they nice light grey/sooty black/oily black/petrol wet?
Hope this helps.
Michael
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Hello Michael,
Thank you. Indeed this is one of the possibility, in fact part of the issues started after i touched the distributor :-\ ...
so instead of dinamic timing, i will do it static and thake if from there...
The plugs are a black, no oily no wet, just a bit rich i belive.
Thanks,
Edmondo
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Dear Micheal and all,
I time it statically and it runs fine!
So it was definitely out of time. I did the static timing with a Lamp.
i took the plugs off, rolled the car over in 4th and set the points to open on the "I" mark on the flywheel (12.5 degree advance as per the manual).
I disconnected the condenser, and used a lamp. It goes off, exactly when the timing mark goes trought the hole in the clutch bell.
Now the car keeps the idle, and i have set it around 1000RPM.
As well the engine runs about 100 degrees cooler! so there was surely something wrong with the timing.
I will now tackle carb tuning again.
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hello,
Are the carbs from a saloon 1 1/8 diameter or fron an ace/aceca with 1 1/4 diameter. You definately need at least 1 1/4 chokes and even 1 1/2 dia for racers.
I remember having your problem with the third carb lagging opening compared to the first and so used a piece of 5/16 inch solid brass rod instead of the spring. Later i realised that the spring needed reversing because the coil was wanting to unwind itself and creating lag.
The weller engine is not about power but smooth torque which makes it a great engine and 9 to 1 compression should increase the torque unless the modified head has destroyed it !
Regards
Tony