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vping

vping

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I have a car show tomorrow so I start up the GT to get her outside to clean her up. Started fine. Found the gears after she warmed up to about 160 and pulled her out. Stepped on the peddle to give it a good burst and blow out some goodies and it's bogging down. No matter how much I floor it, won't rev any higher & wants to stall. Why?
 
3ooo rpms?
 
Hi Vping, Check your timing.---Fwiw--Keoke
 
No higher thatn that, and i've gotta work the throttle a bit to get the revs up a little and then I cannot keep a costant idle. Just wants to die.
 
fuel starvation me thinks...
 
Just some ideas....

Does it belch back smoke(flooding) or none (starving lean)?

Float(s) stuck open/shut? Clogged filter (starving only)?

If its got SU's, maybe a a venturi is hung up.

Timing would do that but unless you have distributor fairies (yes, they ARE real) , I don't know how just sitting would cause it to change.

Adam
 
JUst checked fuel and shes good. It does not belch but I hear some back firing as I try to give it gas.
 
/bcforum/images/%%GRAEMLIN_URL%%/savewave.gif Adam

I have experienced a dizzy actually repositioning itself if the locking bracket is loose and the engine backfires when trying to rev it up.---Keoke
 
I suppose that a loose clamp would do it!

Worse, I had one where the shaft screw came loose causing the rotor to rise up and grab the contacts in the cap and spin the whole dizzy! The vacuum muffin was ripped off and there was not much left to send to Jeff for the rebuild!

If you are geting fuel to the carbs and they are not hung up, timing is a good bet. Also, do you have smog stuff on it? Lots of opportunities for problems there.

Adam
 
Ok here are a few other things that I am not familiar with.

Rear bowl empty (not bone dry) front bowl full.

I have the tops of the carbs off and I'm looking down at the jets. When I manually move the shaft that the choke cable attaches too, the front jet goes down the rear does not. Only when I continue to turn the shaft, does the rear then start to move.

Not sure about the 12 flats .120 thou thing but we'll get to that later.
 
Sounds like 2 things going on at once.

First, to run right, both bowls need to be filled.

Try blowing into the fill tube on the cover the rear carb.
Only when the needle valve is pushed up, should it stop taking air. (That's how the float regulates the fuel level in the bowl.)

If it flows air okay, check the last piece of hose to it for a flap or other blockage.

Once you find out why you are not getting fuel in the rear bowl, you should be able to at least run.

After that, you need to balance the carbs and adjust the linkage to get the jets moving in unison. Follow the Haynes
or get a fried who ACTULLY KNOWS what he/she is doing to help you with it. You will be amazed at how much better it will run when the SUs are working together! If you get really stuck, I can probably talk you through it on the phone.

Adam (I wish I HAD a shade tree to work under so I could be a shade-tree mechanic....)
 
Well I bottomed out the jets. Set them .120" thou down and fired right up. A little tweeking with the unisyn and all is running well. Can't understand why she did this just glad she's running.
 
I'll venture tha the rear float valve was stuck shut. The very act of removing the bowl cover ws enought to free it up. Bowl fills, back 2 cylinders fire, and off you go!

Probably could have gotten it free with a swift whack with a wood tool handle or a dead mallet.

When you were "tweeking," did you loosen, adjust and reclamp the linkage?

Glad you're rolling! Have a great Sunday adventure!

Adam
 
No and I just met with someone that asked me the same question. I need to really learn how to set these carbs up.
 
All you need is a screwdriver, SU nut wrench and a piece of rubber hose. If you're really fancy you can replace the rubber hose with a flow meter.

Use the rubber hose (listening to pitch of air flow) or flow meter to measure air flow into each carb and adjust the set screws with the screwdriver. Once they are equal, use the screwdriver to lift each piston 1/8" and see how the engine reacts. Use the SU wrench to adjust the mixture until you get the proper reaction of a momentary rise in idle. Once that's done, go back to the flow meter and continue moving back and forth until neither flow or mixture needs any adjustment. Done.
 
Steve is right on. I've owned three cars with SU carbs and thats all I did to set the carbs up. My wife is a nurse so I used a stethoscope, but a piece of hose shoved in your ear works just as well. After the initial set up watch the plugs and they should tell you if you have any problems.

All the cars ran just fine. I suppose you could get all technical and buy a bunch of meters and stuff but I really have not seen the need.
 
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