faulter on accelleration

[my8thholden]

good morning gents ..I have done only a few miles since registering my FC restoration ..The car so far is fine ,however when moving off from standing ,ie traffic lights ,there is a faulter ,feels like its about to stall ,then quickly picks up again ,its is getting slightly worse ,and yesterday a small backfire in the air cleaner ,my memory tells me this is not all that uncommon in greys ,but my memory doesn't tell me the answer , I am thinking float level ,condensor ,carby butterfly,but perhaps better to use your memories ,and knowledge ..i'll look forward to that enlightenment ..thx Vern ..

[ardiesse]

Vern,

Mixture is too lean.  Retarded ignition timing makes the effect worse.

When the engine's warmed up, reset your idle mixture.  If the car still leans out, then it's possible you have gunk in the main jet: take the air cleaner off, rev the engine up and clap your hand over the air intake.  Gunk in the fuel is common with newly completed restorations.

If that doesn't work, you might have an intake leak.  With the engine idling, spray WD-40 around the carburettor base and the legs of the inlet manifold.  If the idle changes, you've found the leak.

Rob

[Harv]

Either that, or the accelerator pump is not pumping.

Engine off, air filter off, pump the throttle linkage - should get a nice mist of fuel into the carb throat.

If there is no or little mist, air horn off the carb (without dropping the screws down the carb throat), disconnect the pump plunger and look at the washer. If it’s a leather one, soak in fuel overnight, then condition by flexing it with a screwdriver. Plastic ones are less malleable, and may need replacing.

Cheers,
Harv

[my8thholden]

ok ..I am also thinking fuel , the memories of the procedure are coming back ,even though I don't recall a hand clap over the carby Rob ,I elected to put the carby straight on the engine as it was brand new ,came from BMC Zetland 1961 ,that was pretty optomistic ,all I know is it has a .051 main jet ...so i'm about to find out about the throttle pump ..the car seems very rich ,after a few short runs ,put finger in exhaust pipe ,it is sooty black ,black powder ,that's unburnt fuel ..thanks fellas ,i'll post results ...Vern

[mcl1959]

I agree, if the carb is that old since reco, then the fuel plunger will be dried out and not pumping correctly when you push the accelerator
Ken

[my8thholden]

Gents ..Thanks Ken ,its looking that way ,that will be my first job after this long w/e ,and i'll have another hour in the day , I have posted elsewhere on here the origin of the carby ,I volunteer with a guy who was a development engineer with Leyland Aust ,in the 50's and 60's ..he still drives to this day the prototype of the Austin Freeway he worked on ..he tells me they used buy 3 Holdens and 3 Ford Falcons and pull them apart ,to test their components against their ever evolving development ,the carby I have came off one of those cars ,Allan says its done about 50 miles ...he also has a beautiful Leyland Force 7V ...what are your thoughts on the black soot in exhaust tail pipe ? ...Vern .

[mcl1959]

Vern, unfortunately the good old days of super petrol when you could tune your car by how grey the exhaust pipe was are gone. Unleaded fuel gives a very black exhaust. Hard to tell from a description, but an overly sooty exhaust would generally be a sign of burning oil. Be best to compare your exhaust with other older cars (Not modern cars with catalytic converters) to see whether yours is comparatively the same, better or worse.

Ken

[graham_fuller]

Hi Vern,
There is a good guy that reco's carbies in Campbelltown (extreme fuel systems) and its not that expensive. He recolours them at the same time. My car use to do similar things and the reco fixed it.
Cheers
Graham

[my8thholden]

gentlemen ...Ken ..Thanks for your input ,I have a few too many things on my mind , yes the days of looking in your tail pipe for that clean grey look are gone ,the engine does blow a bit of white smoke on start up when hot ,thats oil ,and hopefully new rings still bedding in, valve guides passed inspection when head done ,stem seals are the ring type not cup type , spark plug examination might be warranted ..Graham ,thanks for your carby info ,i'll see how the accelerator pump is ,I would certainly want a quality one if I need to replace ..stay well Vern .

[my8thholden]

gents ..I took the air horn off the carby as suggested Harv ,very carefully ,and removed the pump plunger ,steel shaft ,leather cup ,brass spreader inside and alloy keeper ,it looked in good condition ,some powdery residue on the plunger shaft spring ,so gave it all a good clean ,then wet the leather with petrol as suggested and carefully eased the brass spreader out a little all round then reinstalled ,nice squirt of fuel into carby throat when pumped ,whilst working noticed something bright just briefly and then tinkle down side of engine ,pushed the car back to reveal a blanking plug came out of the carby body adjacent to the plunger ,just sitting there ,how lucky it was there so delicately ,at 3pm on a Saturday arvo ,two tiny little centre pop marks and a smear of Stag and back in ..put it all back together ,started and running nicely and could rev it no probs ..time for a test drive ..The doctor says the neck brace can come off in 3 weeks ..cheers Vern ..

[Harv]

Good result 

When I first started playing with carbs, I took one in to Carburettor Service Company in Lidcombe. It had a loose plug, and I wanted to buy another one. The gentleman put the carb onto the bench, and laid into it with a ballpein hammer. Only one belt, but really hard. My eyes nearly fell out of my head. I mentioned that I would never be game enough to smack a carb that hard.

"Yes... that's why I did it for you".

Third generation carburettor fiddlers. They really know their stuff.

Cheers,
Harv

[Errol62]

What do you think the issue was Vern, loose plug? Sounds like the plunger was ok.

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[my8thholden]

Clay ..Having the co incidence of the plug at the same time does add a new possibility ,and the plug is a through hole ,so if it was sucking air it would have a effect ,the plunger is in good shape and came out easily ,after I expanded the little brass spreader it was bit harder to put back ,the bottom line is ,so far so good ...cheers Vern .

[Errol62]

Thanks Vern. I'm having a similar issue. Improved when I put a kit through the carb and now seems to go away when engine is well and truly warmed up. It seems to amount to misfiring at throttle crack say 650rpm.

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[Harv]

The little leather washers look OK, but after sitting idle for a while (a few months) they lose their "spring" and need to be soaked/stretched back into suppleness.

If you've got mist in the carb throat Clay then the washer is generally doing it's job.
a) Check the pump link is on the middle hole of the pump arm - the wrong hole will only give a little pump squirt.
b) Pull the pump check valve out, put it in your lips and breathe in and out through the valve (don't accidently swallow it  ). Make sure the little ball in the check valve is doing it's job. If it is passing, it will push fuel out of the pump and back into the float bowl.
c) Check the spring on the pump plunger. Too stiff a spring and the mist comes out too fast, too weak a spring and the mist is too slow.

Can send you a check valve and spring if needs be.

Cheers,
Harv

[Errol62]

Done all that thanks Harv. Seems not to be an acceleration lean out but a miss at static fast idle throttle valve position.

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[Harv]

Could be the transition holes in the throttle body are blocked. They help the carb perform in that mid range where the idle system is maxed out, but the main jets are not really flowing. . Remove the throttle body, and see if you can see the holes (just above the throttle plate level). There should be three holes - the lower one is below the throttle plate, and the other two are above the throttle plate. It's hard to feel the air flowing out of them if you test with compressed air (especially if you have fat fingers like me), so use water and look for it piddling. Once you are done, blow dry with air and run some metho through to get rid of the water. The holes are a bugger to get to, and are very fine. Cut up a length of low-amp copper wire, and use one of the strands to clean them out.

Could be a main jet (try a bigger size), but that normally gives a miss at higher revs (cruise mode on the highway).

Cheers,
Harv

[Errol62]

Thanks Harv I’ll give it a go at some stage. I thought about investing in a cheap sonic cleaner but wasn’t sure it would be big enough to fit larger carb parts in.


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[my8thholden]

gents ..whilst we are on carbys and fuel ,in this day and age ,what fuel octane do you run in your standard or close to standard grey motors ,and any additives you add , cheers Vern ..

[Harv]

I bought a cheap ultrasonic unit for carbs. It did nothing, and is still in the naughty corner  Tried all the internet tricks (put parts in a bag of solvent, higher temp, isolate part from basket etc) but nothing helped. Still find thinners is best for the task.

I normally run V-Power in everything. Doesn't have ethanol in it, so easier on seals. Higher octane lets me wind in a little more timing. Good fuel density, and good acceleration due to the blend.

I don't run any additives. I've done a lot of miles in the FB before it got hardened valve seats, and saw no valve seat recession. Have never seen anyone experience valve recession in a grey, but would love to hear from anyone who has.

Cheers,
Harv