Engine only runs with starter fluid

[siteunseen]

Mine have or had rubber nipples to align the dome to the body. I broke them off after watching the DVD. Steve says to loosely tighten the screws and find the smoothest spot then tighten them down. Ignoring those things. He says most are gone anyway if they've been apart.

[hatepotholez]

2 hours ago, Patcon said:

That was a good idea. I had never thought of running them with out the screws

Thanks!

1 hour ago, Captain Obvious said:

Earlier you said that you have a 3 pot. (I'm assuming that means you have three screws holding the suction chamber to the carb body?)

I've not messed with those personally and am wondering...  Does that version have the little epoxy alignment nubbies sticking up into suction chamber to align the chamber to the body? If that's the case, then there's no guarantee that a replacement suction chamber will align correctly onto your existing body. It's a surmountable issue, but something to watch out for.

Yes, I have those. It was suggested before to remove those alignment tabs. I would prefer not to do this until I am out of choices.

1 hour ago, siteunseen said:

Mine have or had rubber nipples to align the dome to the body. I broke them off after watching the DVD. Steve says to loosely tighten the screws and find the smoothest spot then tighten them down. Ignoring those things. He says most are gone anyway if they've been apart.

Were you also having sticking issue with the piston and damper?

[siteunseen]

I honestly don't know, I watched the DVD a couple of times then rebuilt the two carbs.  They were original to the car and it had been sitting for 10 years.  During the rebuilding I found the nozzles weren't dropping down and the float chambers were crudded up, the float valves were sticking too.  Now they're nice and shiny and work like new (I'm guessing-I was 3 years old when they were new). 

[Captain Obvious]

Well there's no guarantee that those alignment nubbies will line up with your replacement suction chamber, but certainly TRY them first before you remove them. You might get lucky and have a temporary local relaxation of Murphy's Law. Doesn't hurt to try first.

When you think about the geometry, you really need to be very close. You're trying to stick a 95 thousandths diameter pin into a 100 thousandths diameter hole and (in a perfect world) have it not contact anywhere around the perimeter. They couldn't hold the necessary tolerances at the factory, so they resorted to characterizing every carb instead by fixturing them and using "cast in place" alignment pins instead.

And if you do cut the alignment pins off, remember that you're going to have to realign those suction chambers each and every time you ever take them off again in the future. (Same goes for you Cliff!)

 

 

 

[hatepotholez]

4 hours ago, siteunseen said:

I honestly don't know, I watched the DVD a couple of times then rebuilt the two carbs.  They were original to the car and it had been sitting for 10 years.  During the rebuilding I found the nozzles weren't dropping down and the float chambers were crudded up, the float valves were sticking too.  Now they're nice and shiny and work like new (I'm guessing-I was 3 years old when they were new). 

 which reminds me, I have to watch the SU DVD in it's entirety.

4 hours ago, Captain Obvious said:

Well there's no guarantee that those alignment nubbies will line up with your replacement suction chamber, but certainly TRY them first before you remove them. You might get lucky and have a temporary local relaxation of Murphy's Law. Doesn't hurt to try first.

When you think about the geometry, you really need to be very close. You're trying to stick a 95 thousandths diameter pin into a 100 thousandths diameter hole and (in a perfect world) have it not contact anywhere around the perimeter. They couldn't hold the necessary tolerances at the factory, so they resorted to characterizing every carb instead by fixturing them and using "cast in place" alignment pins instead.

And if you do cut the alignment pins off, remember that you're going to have to realign those suction chambers each and every time you ever take them off again in the future. (Same goes for you Cliff!)

 

 

 

This is true. Hopefully the replacement parts work. 

[Captain Obvious]

Best of luck with the replacement parts. Hope that fixes your carb issues.

While you're waiting for parts to arrive, can you take a couple close-up shots of the suction chambers and the top of the carb bodies where the nubbies stick up? I've never seen those alignment pins on anything other than the flat top carbs. Sounds like they started that process in 72 and went on like that through 74.

So your carbs don't have any provision for aligning the nozzle underneath? Sounds like (unlike the previous years) your nozzle position is fixed and the suction chamber is (was) the movable entity?

[siteunseen]

I had my spares down today and was going to post some pics!

I'll do it in the a.m.

Mine are 3 screws with the nubbies on the front 2 screws.  The rear screw has nothing. The way the nubbies are positioned, one side is above the screw hole and the other side it's below. The suction chamber can only go on one way. If you slightly tighten the screws, get the piston dropping smoothly then tighten them down it's super simple.

The nozzles have to have their angled "leg" pointing to the float chamber and that's it. 

I won't disagree with you but the nubbies are no big deal on the 3 screws I have. They're all crumbly anyway.

I'm too comfortable to go downstairs at the moment but will in the morning for pictures. 

I can't understand why his are fine without screws but bind with screws? I'm too frugal to buy new parts but everybody's not like me and you.

Goodnight Sir.

 

 

 

[siteunseen]

Maybe the body screw holes are cross threaded? Maybe the screws are wrong? Seems like there would be scratches if something needed replacing? 

[hatepotholez]

11 hours ago, Captain Obvious said:

Best of luck with the replacement parts. Hope that fixes your carb issues.

While you're waiting for parts to arrive, can you take a couple close-up shots of the suction chambers and the top of the carb bodies where the nubbies stick up? I've never seen those alignment pins on anything other than the flat top carbs. Sounds like they started that process in 72 and went on like that through 74.

So your carbs don't have any provision for aligning the nozzle underneath? Sounds like (unlike the previous years) your nozzle position is fixed and the suction chamber is (was) the movable entity?

Thanks. I will take some photos on Sunday. I haven't actually seen the bottom of the carbs as they are installed. The nozzle goes up and down into a bronze tube.

10 hours ago, siteunseen said:

I had my spares down today and was going to post some pics!

I'll do it in the a.m.

Mine are 3 screws with the nubbies on the front 2 screws.  The rear screw has nothing. The way the nubbies are positioned, one side is above the screw hole and the other side it's below. The suction chamber can only go on one way. If you slightly tighten the screws, get the piston dropping smoothly then tighten them down it's super simple.

The nozzles have to have their angled "leg" pointing to the float chamber and that's it. 

I won't disagree with you but the nubbies are no big deal on the 3 screws I have. They're all crumbly anyway.

I'm too comfortable to go downstairs at the moment but will in the morning for pictures. 

I can't understand why his are fine without screws but bind with screws? I'm too frugal to buy new parts but everybody's not like me and you.

Goodnight Sir.

 

 

 

I'm not sure either. Honestly I don't think it's from dropping it and was probably an issue from before I even purchased the car. This was another owners project that I took on so I am not sure if the carbs were rebuilt thoroughly. 

I agree on being frugal, I have two projects and do not like spending money if I have to, unfortunately this is something I don't think I could avoid as I really do not want to remove those alignment tabs until I have tried all avenues. 

 

 

[Captain Obvious]

Without seeing the parts myself, I can't tell you where the interference is, but dropping it sure doesn't help. It doesn't have to be bent much. A thousandth in the wrong spot would probably be enough to cause the binding you're experiencing. Think about it this way... The only "seal" between the upper side and the lower side of that suction piston is the close fitting (but non-contact) dimensions of the OD of the piston in the ID of the suction chamber. Doesn't take much distortion to cause interference. Out of round chamber. Out of round piston. Bent damper tube, Bent needle. Bent mounting tab on chamber.

The reason the binding goes away with the screws not installed is that the chamber and piston can squirm around just enough in whatever direction it wants to in order to move without binding. Doesn't have to be a lot of interference, and doesn't have to be a lot of squirm.

You'll figure it out, and hopefully it's as easy as swapping out the piston and chamber. Maybe you'll have to remove the nubbies, maybe you'll get lucky.

As for the alignment pins.... You really only need two alignment pins to establish repeatable positioning. That's why a third pin on the rear screw is unnecessary. On the flat tops, the nubbies are actually cone shaped and that shape does a better job of establishing position than a straight sided cylinder. Are the 72's cone shaped or straight sided?

[Jarvo2]

'72 are cone shaped.  Agree with everything that Capn' Obvious stated.  On several sets that I've rebuilt I've had to knock off the nubs as well as tighten/loosen the dome screws at different intervals to get it to line up correctly to prevent interference. 

[siteunseen]

9 minutes ago, Jarvo2 said:

'72 are cone shaped.  Agree with everything that Capn' Obvious stated.  On several sets that I've rebuilt I've had to knock off the nubs as well as tighten/loosen the dome screws at different intervals to get it to line up correctly to prevent interference. 

That's what I'm trying to say without making anybody mad or sounding like a know-it-all.  If he cut the cones off and maybe tapped the suction chamber with a rubber hammer until everything was smooth then tightened the screws?

We'll see soon enough, can't have too many Z parts.