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Carbs 2.0

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Cujo

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Okay - got the correct needles for the carbs finally (original non tapered were wrong) and had the shop check the throttle linkage shafts - which they said were fine. Have also replaced all gaskets again (including manifold) and here are the symptoms now (with 8 degrees before TDC timing and correct gap on the points and car to regular operating temperature).

Idle is still high (about 1200 rpm when it is supposed to be 1000) to get the Uni-Syn to mid gauge (with the center twisted in)
Also, when I place the Uni-Syn on the front carb the idle increases, but not on the rear one (but when check all suspect areas with propane for vacuum leak I get no increased idle.
Once I get the same air flow and go to adjust the mixture (I had to turn both jets down another six flats to start with - past the standard 12 - just get the car to stay running) the rear carb has to be turned down another six flats to get it not to stumble when the piston is raised slightly.
The end result is still a car that is missing and I am getting ready to drive it off the local cliff (never had this issue with any of my cars before) :wall:

Any ideas at all are welcome.

Thanks again
 
Have you checked engine compression? Had a similiar mess and turned out to be leaking head gasket. Cheap and easy--what could it hurt.

Kurt.
 
Give the jets a little push upwards I had a rear carb that would hang the jet when the choke_ fast idle was used.
 
How about butterflys, they both closed at idle or at least the same. Do you seperate them in the tuneing process.

Just ideas
 
Okies you going to have to go in side. Follow The Leak.

Again, the whole needle valve seat assy can be taken out without removeing the carb. Out and in easy once you see the how of it.
 
Lets sort out a couple of these issues.

First, if the idle speed changes when you place the unisyn onto the carb, it's restricting the air flow too much--you need to open it up a bit until this doesn't happen. Unfortunately, there's a narrow range of adjustment where you can get a reading but it still doesn't affect the tuning. I find that, on my bugeye, I can't put the float in the center of the range. Just not enough air moving through it.

Second, the standard 12 flats is just an initial adjustment. Lots of things will affect the final adjustment--like how far the needle is inserted into the piston, the float level, and minor dimensional differences in the jet assembly. If you reach a limit to the adjustment range and it still isn't right, then you have a problem. A turn or two more or less past the initial adjustment is not a problem.

Third, if the car is missing, it's probably not carb adjustment. In my experience, at least, the adjustment can be pretty far off and it won't miss. If you have a miss, I'd look for something in the ignition system; or, at least, make sure--really sure--that the ignition system is OK before going on to the carbs. You can't get a good carb adjustment with an imperfect ignition system.
 
So I tracked it all through again and I have made a huge jump forward by discovering one of my valve to rocker gaps was way off - must have come a drift after initial setting with the engine out. Once that was right gap then the carbs balanced out fine with a good idle at 1000 rpm. Only issue now is a seeming hesitation to accelerate - not a miss just a bit of a dead feeling. what is the difference between having the needles biased towards the air cleaner vs the intake manifold
 
No idea what you mean by needles biased??

Check points gap again unless you did.

Check plug gaps.

Check timeing.

Something is just a bit off, and I also now think it is not carbs.
 
all of that checks out to specified tolerances.
On these SU's the needle is "floating" on a spring at the bottom of the damper. The whole assembly is held in by a setting that has a slight ridge on one side - this either biases the needle in the jet off center slightly - either towards the air cleaners or towards the butterfly.
Based on my manuals I think someone has put later carbs on the car
 
Cujo said:
So I tracked it all through again and I have made a huge jump forward by discovering one of my valve to rocker gaps was way off - must have come a drift after initial setting with the engine out. Once that was right gap then the carbs balanced out fine with a good idle at 1000 rpm. Only issue now is a seeming hesitation to accelerate - not a miss just a bit of a dead feeling. what is the difference between having the needles biased towards the air cleaner vs the intake manifold
Click to expand...

what oil are you using in the pots? I had 20-50 and replaced with ATF - eliminated that bog completely.
 
The damper oil is to richen the mixture briefly during initial acceleration. The thicker the oil, the longer that enrichment lasts and to some extent, the richer it will be. Of course, over rich could cause that stumble too but lean is the more likely cause. The other likely cause of an acdceleration stumble or hesitation is the vacuum advance.
 
Ahh, guess what, you have H2 carbs.
 
I think bias of needle makes no difference.

However, I am going to shut up now as I can really only speek to H1 carbs with authority.
 
jlaird said:
I think bias of needle makes no difference.

However, I am going to shut up now as I can really only speek to H1 carbs with authority.
Click to expand...

I have switched the needles to bias towards the air cleaners and the car definitely runs better.
 
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