Sticking dashpot

[Z-Luke]

This weekend I took the dashpots and float bowl lids off the carbs to give them a cleaning. Upon dis-assembly I noticed the rear needle was visibly bent, so I will have to get a new one. However, once the carbs were descuzzied I noticed that the rear vacuum plunger in the dashpot was sticking and not falling freely. When just the needle w/plunger was put in, it would fall freely, but once I put the domes on it would stick.

This is causing massive drivability issues of course. I'm wondering what i could have messed up that would lead to the dashpot sticking like that. It does it with or without oil dampening or the dipstick in. Maybe I bent the needle even worse and its causing a mis-alignment.

Thanks for the help...

[Bruce Palmer]

You're talking about the piston hanging up in the dome right? Sounds like some interior "descuzzying" may be in order......

Bent needle - Is the needle showing any shiney areas? As is often the case a bent needle will wear the fuel nozzle oriifice egg shaped (oversize) giving a metering situation with an undersized needle and an over sized nozzle. You may need needles and nozzles.... depending on what they look like.

Sounds like new carbs are your only way out of this situation...... It's Monday morning and I just had to say that to kick the week off right!!

[Pop's Z]

IMHO. Save yourself time, money and grief, and send them to Bruce at ZTherapy. One of the best things I did for my Z.

Cheers, Mike

[Bruce Palmer]

IMHO. Save yourself time' date=' money and grief, and send them to Bruce at ZTherapy. One of the best things I did for my Z.

Cheers, Mike[/quote']

Mike,

There'll be a little something extra in your pay envelope at the end of the week..... nyuck nyuck

[Z-Luke]

While I fully intend on getting the Ztherapy treatment, I can't afford it just yet. It was either that or the suspension for the time being, and I decided the car smashing on the ground on every bump was a greater hindrance to driveability at the moment. That is, until I started messing with the carbs...

The needle is not polished. You really have to look carefully to see its bent, but you can see it under careful scrutiny. The piston was NOT sticking at all in the dome before I took it apart and messed with it, leading me to believe it is a re-assembly error. It just doesn't fall freely - I was really careful in keeping the piston matched with the dome. I think it might be a mis-alignment of the piston to the dome. I can only think thats caused by the bent needle?

[Bruce Palmer]

HMmmmm. There really isn't any way to mis-align the piston in the dome. It either slides up the tube or it doesn't. No place for either to move to some other "outta whack" location. Try a good finger wipe up inside the dome and see if you can feel any "scuzzies"..... We keep this up with the "scuzzy" thing and it'll become a new industry standard for techno-speak.

[tlorber]

Is it possible that the dashpot plunger rod is bent?

[Bruskiz]

With 4 screws the nozzle can be adjusted by loosening nut underneath the carb. If you take the needle from the front carb and place it in the rear, does it still stick?

- Mike

[Z-Luke]

Hello again gents,

I believe my problem is indeed the needle. That thing is so ****ed I think it's throwing the whole works off. Since its so beyond recovery, I decided to try and bend it with my fingers into at least somewhat of a straighter angle. In doing this, combined with a super secret handshake special order of tightening the dome down, I was able to get the plunger to drop. Not perfectly, not quite with a thunk, but more of a 'tink'.

The results in drivability are stunning. Now it drives like a car. With the vacuum advance working again, and the carbs reasonably balanced I can drive from a stop with gunning it and making the clutch do all the work. 3rd and 4th pull really well, and it was roaring past 95 mph and climbing before I let off because the whole car was shaking.

It's nowhere near perfect, but it's now driveable. Thanks for all the help up to this point. Until I can get all the other upgrades to go on this will do.

The only weird thing is that both 3rd and even 4th gear seem to pull harder than 2nd. 2nd just sort of feels lazy and I'm not sure why. It could be that the bent needle is holding back how quickly the dynamics of the fuel delivery adapt to the demands of the engine.

Edited April 20, 2010 by Z-Luke