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4GC mystery...
Just can't stay away
Just can't stay away

Dave Harrison
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Due to poor running and that I had a rebuild kit on hand I have removed and disassembled my 55 400, 4GC carb. Found several issues with dirt but main problem appeared to be the accelerator pump seal to be partially disintegrated and both primary and secondary float heights set too low which I have now corrected. The carb is still disassembled as I now have another issue that the accelerator pump inlet check ball is stuck in it's seat, no amount of soaking in various solutions or trying to blow out with compressed air or tapping seems to help, as everything else came apart so easily I am now of the opinion this has been driven hard into the seat during a previous rebuild. This makes me wonder how it ever worked properly in the past...?
The carb is the correct model 7007230 though almost definitely has been replaced or rebuilt at some time due to general good condition and still fresh looking gold anodising.
I have read back through several posts where the same problem has been encountered, does anyone have any opinion as to if I definitely have to get this out as I am now tempted to reassemble as it is and see what happens...
Makes me wonder if one of the professional carb rebuilders is doing this for some unknown reason...?

Regards, Dave.

Posted on: 2018/6/28 4:55
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Re: 4GC mystery...
Home away from home
Home away from home

Craig Hendrickson
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It's been a while since I've had my 4GC apart, but IIRC it's like most carbs of the era,i.e., there's a well under the accel pump seat that is sealed with a pressed-in & staked plug. Drill out the plug and punch out the accel pump ball from below. If the seat is deformed, they a bigger OD ball is called for (there are specialty carb shops that have 'em). When done, seal the old well plug with an aftermarket (same shops as above) screw/press-in plug. Problem solved.


P.S. The accel pump probably still "worked" because it can get fuel from the float chamber IIRC through both a slot and pin hole.

Posted on: 2018/6/28 12:17
Nuke them from orbit, it's the only way to be sure! Ellen Ripley "Aliens"
Time flies like an arrow. Frui
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Re: 4GC mystery...
Just can't stay away
Just can't stay away

Dave Harrison
See User information
Hi Craig, Cheers for the reply. I thought about drilling the bottom out as its about the only option however as it had ran OK up until recently I decided to re-assemble it as it was. I checked the adjustments as per the manual, well best as I could figure them out anyway and all seemed OK so I reinstalled the carb and soon as the fuel got through she fired up and ran smoothly and sounds great. Revs freely with no splutter or hesitation and the choke came right off correctly on warming up...
Haven't had chance for a road test with some load as yet as I have a slight weep from the filter bowl gasket to rectify first. If all is OK then I'm going to leave well alone. As you say fuel must be getting in somehow probably from the long slot in the side of the accelerator pump section...
Im getting a vac gauge this week to set up the idle mixtures as per the procedure I think previously posted by Owen. Will let you know if it runs OK...

Thanks, Dave.

Posted on: 2018/6/29 5:37
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Re: 4GC mystery...
Just can't stay away
Just can't stay away

Dave Harrison
See User information
Update: I made a new gasket which fixed the inlet glass filter bowl weep and took her out for a spin. She ran nice and smooth and accelerated well from any speed with no hesitation or spluttering, got up to 75 MPH on the motorway with the modern traffic just sailing along... So I'm gonna have a go at setting the idle mixtures next week and then leave this alone now as the stuck check ball doesn't seem to make much or if any difference. Maybe a thought for anyone else who encounters the same problem.

Cheers, Dave.

Posted on: 2018/6/29 8:47
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