Idle speed problem - Holley Carb specialist needed

[T5GRF]

The idle speed on my can am is running way too high (2k rpm) and it is a pig to drive.

I think we have established that it is probably the Holley carb that needs adjusting, could any one recommend a good specialist in the Herts area?

Cheers for your help in advance

[gtr-gaz]

Try www.bob2000.com/carb.htm

You may even be able to do it yourself.

Gary

[bluesatin]

Very easy to do yourself. Should find instructions on the holley web site. Are you sure it is not the throttle cable keeping the butterfly open when hot- common problem that is easy to sort.

[steve_D]

I'm told the most important thing to start with is to get the fuel bowl levels correct.
Steve

[andycanam]

I've tried the idle adjustment screw and it was sitting at 700rpm when the throttle returns to it... I'm no expert on the holley carb but I think the accelerator pump things are whats keeping the idle too high by not allowing the throttle to fully return.

Trouble is it was alright for a while after I've adjusted it even at full operating temperature but then after a few days (or his long journey home) it started playing up again.

Neither Mark nor myself feel we know enough about the holley to mess around with it too much hence the seeking of a local specialist.

Andy

[j-k]

[redacted]

[rjneville]

Had the same problem on my GTR. Took it to Peter Knight Racing (in Daventry, Northants)who easily fixed it. The car was totally different afterwards and did not cost me much.

[methodwares]

first, ensure the throttle plates close completely. disconnect the throttle cable and look down the carb throat.

second, the throttle cable needs just a touch of slack when connected to the carb, so as not to bind or hold the throttle open.

third, check the float level. Assuming you have electric fuel pumps, turn the pumps on for a bit to fill the float bowls and turn them off. Remove the float bowl plugs. Fuel should just barely trickle out. Adust your float level until this happens. You may need to turn the pumps on a few times, replacing the plugs before you do. It's not the easiest, but if you have clear plugs, its easier as you adjust the float level until you can just see the fuel

once all this is done, adjust your idle. also, make sure that the fast-idle cam is not sticking anywhere.

the accel pumb, unless adjusted horribly wrong, shouldn't affect your idle, it is only used for when the throttle is stabbed to give an extra burst of fuel so the engine doesn't dog

[t5grf]

thanks for your comments, unfortunately I am sadly lacking in the spanner weilding dept, I therefore need somebody that can look at this on my behalf.

Does anybody know of a specialist close to Herts/Middx?

[andycanam]

Just to clarify.
The throttle plates are closed fully when on the idle screw (and it idles there at 700rpm happily).
There is slack on the throttle cable (hot & cold) and its not binding.

The carb has float level clear plugs and it seems correct level when I've looked at it.

The reason I suspect accel pump as they were holding the throttle open too long when the car was in my garage.... but they were returning eventually.....
I don't think they are pumping fuel in I just think they may be getting stuck and not allowing the throttle to return to the idle screw.
Could they stick when very hot?


Whatever the problem is it needs to go to a local specialist to get sorted, as an Ultima idling at 2000rpm is not fun.

[Stig]

I have the same problem and I'm not convinced that you need to touch the carb at all providing the initial hot-idle was correctly set.

My idle plays up when the engine bay gets hot. I think this is a result of the throttle cable sticking. I'm going to replace it (the factory replaced it when they SVA'd the car saying mine was snapped? The one in there looks as if it came from a MKII Escort!) with a teflon lined job.

On which not, does anyone know where I can source such a cable and what length would be needed?

Ta

[andycanam]

CJ
actually even if this proved not to be the problem it's probably a worthwhile mod anyhow.

[Boosted LS1]

I'm near j24 of the M1 and have used/adjusted plenty of Holley carbs. I've also converted them to 4 corner idle. What you have should be simple to sort out but I would need the car here so as to look into the chokes to see what's happening. Does it smoke at idle, blown power valve, flooding float bowls etc. You also don't say which Holley it is and there are important differences. I suspect the throttles are to far open and air is getting in somewhere. You need to have some clearance on the accell pump adjuster. If they are fuelling at idle then you will see the nozzles dribbling fuel into the choke area (use a mirror). If you bring it here I'll look at it for free apart from a trip round the block

[Stig]

andycanam said:

CJ actually even if this proved not to be the problem it's probably a worthwhile mod anyhow.

You're not wrong mate. Any idea where I can get teflon lined cables (before I get started on Google )

[methodwares]

Ah, forgot about power valves. Silly things, one healthy backfire through the carb and there's a pretty good chance it's gone. Also, look for vaccuum leaks. Can't really help more than that unless I see it.

[Boosted LS1]

Well if it's over fuelling it will be rich and probably sooty out the tail pipe. More I think about it I suspect an air leak. I'd look at the throttle spindle seals and spray some carb start onto them. I'd also check the vacuum pipe to the distributor is plugged onto the carb properly. Check any unused pipes have plugs over them and also look at the brake servo pipe (carb end). Has it got a check valve in the servo pipe? Also check the secondary throttle plates are being closed properly by the primary linkage. Look again at the primary plates. If they are closed as you say they are you will see a transition slot in each bore just above the plate. It's a tiny groove that allows air to bypass the plate as you come off the idle jets. Some people adjust the plates open to far so you don't get smooth transition. Make sure the accellerator pump cam isn't squirting the pump jets prematurely, if it is you will see the fuel dribbling from the jet nozzles. If it's not the above it could be a gasket but that's doubtful unless the carb has been taken apart.

Finally, it may not be the carb. Have you checked the timing and centrifugal advance? It may be over advanced.

[davefiddes]

Stig said:

You're not wrong mate. Any idea where I can get teflon lined cables (before I get started on Google )

Clive mentioned this lot do most types of fancy throttle, clutch, control cable: www.speedycables.com/

[davefiddes]

Oone tip I've seen mentioned before is that you can use an unlit propane torch to check for vacuum leaks. Just waft it about the joints, vacuum tubes, etc with the engine idling. If the revs rise then you've just found your leak!

[Stig]

davefiddes said:

Stig said: You're not wrong mate. Any idea where I can get teflon lined cables (before I get started on Google ) Clive mentioned this lot do most types of fancy throttle, clutch, control cable: www.speedycables.com/

Thanks mate, but Speedy don't do Teflon lined cables

Here's their reply to an email enquiry I sent:

"We do not supply cables that are teflon lined cables. Our throttle cable outer has acetal liner which is fine for normal applications. If the cable is very close to a very high heat source you could look at fitting heat protective sleeving that is available from people like Demon Tweeks. At the same time try to keep as much of the cable as possible away from the heat source."

[Boosted LS1]

Speedograph Richfield or richmond of Arnold, Nottingham do teflon lined cables or they used to