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Old 28-08-2017, 11:06 AM
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Carb Flooding

I had a rare 'breakdown' on the way to the Gold Cup yesterday.

Car began misbehaving and wouldn't tick-over. Then when I smelled fuel I decided to investigate because of the fire risk. I had an extinguisher in the car and also I'd decided to avoid the motorway thank goodness.

Well I soon realised that the needle valve on the rear carb was the problem but 'tapping' the float chamber didn't cure it. Fuel was dripping onto my enlarged heat shield.

Annoyingly on my carbs the cover on the float chamber won't lift off without moving the float chamber sideways. That meant I had to remove the carb to get at the 10mm nut that is hidden behind the linkage to the main-jet. I didn't know about that nut until yesterday.

Undid the air-filter and about a pint of fuel poured out!

So the reason for the post is to highlight the difference between the 3 screw and 4 screw dashpot designs and how to remove the float chamber cover. Mine is the earlier 3 screw carbs. Also carry an extinguisher just in case of fire.

I cleaned the needle (it's not one piece but two and a tiny spring) and then it was sorted.
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Old 28-08-2017, 11:57 AM
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And all this by the roadside - very impressed!

Why do these things suddenly fail to work properly like this? I have the 3-screw as well.

That's a great shelf-cum-heatshield as well!
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Old 28-08-2017, 12:02 PM
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Quote:
Originally Posted by uk66fastback View Post
And all this by the roadside - very impressed!

Why do these things suddenly fail to work properly like this? I have the 3-screw as well.

That's a great shelf-cum-heatshield as well!
Yes why? I went out in the car on Friday to check all was ok. Adjusted tyre pressures including spare, checked oil, water, tools including jack etc etc. All was fine!

Dave Jarman is responsible for the heatshield.
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Old 28-08-2017, 12:40 PM
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Triple Dellortos is the only sensible resolution.
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Old 28-08-2017, 01:11 PM
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Triple Dellortos is the only sensible resolution.


I do have a plan for the winter and I have the hardware.

Simple stuff like this is not the fault of one type of carb though. I need better filtration and more use.
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Last edited by Rob Gaskin; 28-08-2017 at 07:40 PM..
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Old 28-08-2017, 02:43 PM
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You should carry your backup plan with you! Roadside swap over!?
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Old 28-08-2017, 06:07 PM
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4-screw dashpot is the earlier design. Most UK cars had 3-screw version.
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Old 28-08-2017, 06:52 PM
SacCyclone SacCyclone is offline
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Quote:
Originally Posted by Rob Gaskin View Post


I do have a plan for the winter and I have the hardware.

Simple stuff like this is not the fault of one type of car though. I need better filtration and more use.
Hi Rob,

Really sorry that you had that problem but it is not all that uncommon, especially on cars that have been sitting for years....I know yours does not.

I have worked on over 20 early zeds that have been sitting for periods and the sticky needle and seat gives me fits. I have to say that with some fiddling, I have always been able to remove the float lid on both three screw and four screw type SU's. Yes, the four screw is much tighter space wise to get the float lid off but I have managed. Turning the float lid about a 1/4 turn and a slight angle before lifting usually does the trick. Of course, careful not to damage the float and mount tabs. Just wanted to throw that out there to save a bunch of time in carb removal. My mechanic showed me this trick several years ago after I said what a poor design it was.

Thanks for the heads up on the 10mm nut that secures the float bowl.
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Old 28-08-2017, 09:22 PM
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I struggled to fix this same issue on my SU's with the silver car. Lost count on how many times I removed the float lids. As Mike says, it is possible to remove it as he described but takes a bit of fiddling then you have to be careful not to damage the float.

As an alternative to Jon's suggestion of triple, I'll suggest the much safer option of fuel injection
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'76 280z ExLHD Red v8 Lexus powered restomod.
'74 260z LHD Restomod just started.
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Old 28-08-2017, 09:35 PM
franky franky is online now
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Quote:
Originally Posted by johnymd View Post
I struggled to fix this same issue on my SU's with the silver car. Lost count on how many times I removed the float lids. As Mike says, it is possible to remove it as he described but takes a bit of fiddling then you have to be careful not to damage the float.

As an alternative to Jon's suggestion of triple, I'll suggest the totally gay and gender bending option of fuel injection )
Efa
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Old 28-08-2017, 09:51 PM
datsfun datsfun is online now
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Originally Posted by franky View Post
Efa


Like for like, the Initial outlay and set up costs must be the double on EFI set ups compared to carbs ?
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Old 28-08-2017, 09:56 PM
nospark nospark is offline
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My rear su carb was flooding guite often. I took off the fuel rail and after rodding it with lecky cable I had
compressed air blown through it. This has fixed the problem. I added a small in line filter between the rail and the carb as insurance as mine are not hitachis with the small internal fuel filter. Likely that fuel rails corode internally
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Old 28-08-2017, 10:15 PM
franky franky is online now
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Originally Posted by datsfun View Post


Like for like, the Initial outlay and set up costs must be the double on EFI set ups compared to carbs ?
Plus on going costs o high heals.

Yes, it's got to be 3-4 k with mapping and ecu or more?
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Old 28-08-2017, 10:52 PM
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Plus on going costs o high heals.

Yes, it's got to be 3-4 k with mapping and ecu or more?

Its not too bad. Mr Walker does a very nice kit now.


http://www.emeraldm3d.com/generic-th...r-engines.html

RR session would be required for carbs as well of course.
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Old 29-08-2017, 09:34 AM
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That's not a bad price (2900 with an inlet manifold). A set of triples with manifold and linkage is around 2100. Not sure how much a pair of new SU's are but I'm sure a lot cheaper plus no on-going cost of high heals
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'72 240z RHD (4BOA) Painted and waiting assembly.
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'76 280z ExLHD Red v8 Lexus powered restomod.
'74 260z LHD Restomod just started.
'71 240z LHD zg arched. Still in California.

Go to: www.240z.me.uk to checkout the cars.
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