Help me ditch this smog crap on my 260

[g9m3c]

I really appreciate the help everyone has given me this week! Right now, the car will barely even start, and if it does, you have to keep the accelerator on the floor to keep it idling. If I'm going to start tearing into the carbs and such, I would like to simplify things a bit. What all smog components and hoses can I do away with? I want to rip off everything I possibly can that isn't necessary for the car to run. Thanks!

 

 

-Grant

[JSM]

Which carbs do you have? Post a pic.

[g9m3c]

Flat top su's. Here they are.

 

 

[jasper]

FYI. FLAT TOPS SUCK. MY suggestion.(WHAT I DID) Get a set of round tops. Get a 280 exhaust manifold, headpipe, and manifold heat shield. If you're lucky enough to find a non egr balance tube, you'll also need the 280 throttle link (LONGER). If you can gather these parts, than I can help you make it all work!!!! (EASY) Oh yeah... should be a square port 280 manifold..most likely, assuming currently stock

[g9m3c]

FYI. FLAT TOPS SUCK. MY suggestion.(WHAT I DID) Get a set of round tops. Get a 280 exhaust manifold, headpipe, and manifold heat shield. If you're lucky enough to find a non egr balance tube, you'll also need the 280 throttle link (LONGER). If you can gather these parts, than I can help you make it all work!!!! (EASY) Oh yeah... should be a square port 280 manifold..most likely, assuming currently stock

 

 

Yea, I know they suck. If this was a small block chevy, it'd have been running a week ago. Haha, I'm not familiar with these engines at all. I have a factory service manual, but that's not helping a whole lot. I don't really want to get different carbs and all though. I will be putting an LT1/T56 into this thing before long, so I really just need to get this thing running with the flat tops.

[jasper]

Do yourself a favor. Pick up a set of decent round tops, with air cleaner. this will solve your carb problems. Flat tops are not user friendly. I have no advice on repairing flat tops. Good luck.

[cockerstar]

It might be easiest to buy a set of round tops if you're going to have to rebuild these carbs to get it running. More than likely, you'll be able to sell them for whatever you pay for them, assuming that you get a fair deal

[g9m3c]

So there's no hope for getting this thing running with flat tops?

[240z!!!]

here read this:

http://www.jetlink.net/~okayfine/su/tunacan.html

[waddiejohn]

For what it's worth, I machined the bottom of my 260 carbs and made a couple of parts so that I could adjust the mixture then removed all the smog crap and doubled my fuel milage and the little car ran like a raped ape afterward. It wouldn't pass emission however. I used a friends shop to measure tail pipe emissions and "tweaked" things to get it through. I ended up with the carbs leaned out until it was hardly drivable. Timing at TDC and idle at 1500 RPMs. Every year I made these adjustments to get through emissions then reset it to run good. I finally found a set of carbs from a 240 for $100 and installed them.

The 260 carbs didn't have a remote float bowl and could vapor lock when run hard on a hot day here in southern Arizona. Other than that it ran great. The first thing I did that was really interesting after failing emissions was remove my smog pump. My readings actually improved. Three hours elapsed between tests, so maybe atmospheric conditions may have come into play some, but not a lot I would think.

Oh well, end of my little story.

[g9m3c]

here read this:

http://www.jetlink.net/~okayfine/su/tunacan.html

 

 

 

That's a really good read, but I don't see the triangular piece that it talks about in the desmogging paragraph on my carbs.

[Tony D]

That's a really good read, but I don't see the triangular piece that it talks about in the desmogging paragraph on my carbs.

 

1) the article is about SSS FOUR CYLINDER flat-tops, a different animal than what you have.

 

2) you have the 'triangular piece of metal' I see it in your photos.

 

The Non-USA 38mm SU Flat-Tops were basically Round Tops with additional circuitry for total closure idling. Meaning the throttle plates were totally closed and a separate circuit fed fuel and air to the carbs. What the page does is ham-handedly disable the circuit, and then make the superior later-model carbs act like the earlier round tops.

 

If you understand what those carbs do, altering the idle circuit jet drillings allow for a perfect idle situation, while keeping the needle and jet in the main body rich for best power off-idle.

 

YOUR flat-tops have an integral float bowl below the throat, an FSM is invaluable to understand how to get them set up out of the gate, and then move from there. They have the same advantage that the idle circuit is totaly separate from the transition/main circuit so you can 'lean out the idle' for emissions while still having a decent needle taper for power. It's why so many of these carbs are raped and only their needles taken, they are a different taper and provide nice power when used in earlier roud-top SUs'

 

The power valves as well as some diaphragms on the side of hte carb are suceptible to damage from backfire, and will make them run rich.

 

But all facets of troubleshooting/rehjabilitation is covered in the FSM, start from there and you will get a car that runs decently.

[DCZ]

If you want to keep the flat tops, DO WHAT TONY SAYS regarding the FSM. He helped me get mine running decently a few years back until I could swap in the turbo engine. In my case, the float bowls had a bunch of trash in them and a lot of the hoses were missing or leaking. The float bowls are hard to get to compared to the round tops. I ended up removing the carbs to get to them and just cleaning everything up, then putting as many of the hoses as I could back to the way they are in the manual. It ran a WHOLE lot better. I would hesitate to tear off the "smog crap" without knowing exactly what I was doing because the system is designed as a whole. The manual explainations and drawings can be a bit confusing so stick with it and you should be able to get it running.