appreciate any help , 440 has a smooth idle during warm up , once warmed up , 180 to 190 degrees , after idleing for a while , the motor seems to load up & rev drop slowly 3 to 400 revs from 800 rpm , black /blueish smoke out tail pipes blip the throttle be ok , then it might do it again teo or three times , then next time i go for a run & let it idle , its perfect , carbs recent , new fuel lines & filter new pump & pump push rod , heat cross over blocked off , manual choke , there is no set pattern for doing this , if it dont do it one day , if it does it the next day it will do it two or three times
appreciate any ideas , feed back etc

What carb? Good filter between mech pump & carb? I'd check & maybe replace the needle/seat assy & make sure the float ain't hanging up anywhere thru its' travel nor taking on fuel (waterlogged). Idle fuel psi not close to the edge (eddy). might fix a thin red straw to a can of starting fluid & blast a 2 second shot into each idle mixture xrew port tho with it going rich like that I'd be more inclined to think that it's a needle/seat issue rather than dirt in the idle circuit which that usually just makes it die. IF no luck you might check all the carbs' gaskets (correct ones/ correct side up or down/screw tightness. EDIT & blast out all the passages with starting fluid or brake kleen. Holler how it goes

thanks for the quick reply , its a elelbrock carb , will have a look into it the weekend ,see where the fuel pressure is at first , then go from there , & i'll report back
thanks again

I had a worn out timing chain/gears cause similar symptoms before.

thanks for the reply worn timing chain , thats interesting , don't think this is the case , not long replaced mine about 2 thousand miles ago , but will bare that in mind , & if nothing is found with fuel pressure & floats needles carb etc will have a check ,
thats whats got me scratching my head , its random , might not do it for days , then bam will do it ,

thanks again for the imput

just up dating , fuel presure , is just under 6 psi at hot idle , went through the carburettor , no sign on anything , dismantled it , had a rebuild kit on the shelf so put new float needles & seats in , re adjusted the float levels , but were spot on from the last time i adjusted them , blew eveything out with compressed air , new fuel filter , even though the other was only a few months old , putit all back together , with new gaskets , fired it up , set idle mixture , let it run for half hour , all ok , but we will see what happens ,

Check the ignition timing when cold versus hot and see if it retards more when hot if it does try advancing the timing another two or three degrees, make sure to check the total timing after that. Don't run anymore than 36 to 38 on pump gas at or above 3500 RPM . I weld up the advance slots in the distributor to limit the mechaical advance so I can increase the inital timing at idle, I like and use 14 to 18 initial and 34 to 36 total No vacume advnce on my toys IHTHs

thanks for your reply , appreciated

will have a look at the timing , never gave it a thought , i set it up , 20 degrees inital & 34 degrees total , all in by 35 hundred , vacume advance set up to 50 degrees at part throttle opening at max engine vacume ,
will have a look the weekend ,

.

just another up date guys , , checked timing & advance hot & cold , went for a 50 mile drive , plenty of idling , perfect , got back home , let it run , strong idle at 800 rpm , coolent tempreture 185 degrees thinking ha , problem gone on its own , with in two minutes
started sort of loading up revs started to drop to 300 , black blue smoke , blip the gas cleared ,
i'm wondering now , under certain conditions , the step up springs lift the meetering rods at idle ,
any idea on color for a idle in gear of 9 to 10 hgs of vacume , still have orange 5 hg in there i think , i forget , was playing about before with this carb on another motor , will have to check

any feed back would be appreciated

I'm not thinking of anything that would make/let the piston assy rise up to get you into the power circuit (if that's what happened) especially with you idling & not doing anything but you might check in there. I'd more suspect a saturated float or float/float linkage/needle/seat issue. Holler how it goes. EDIT Unless something is randomly blocking the vacuum to the power piston(s)

I would recommend checking your distributor advance weights for sticking/ binding . I have seen them hang up a little,you set the idle,eventually they go back in place and the idle speed drops.
When yoyo blip the throttle it sticks again and the idle is back.
Keith

How sure are you the tank is not rusty/cruddy? I see you went through the carb and put a new filter on. It was fine for a time and then it returned. I know you said you didn't see anything, but you did clean it. An idle circuit can get a little junk in it and cause fits.

On my 360, I had to get the fuel pressure down to 4.5# to 5# to keep the Eddy from idling rich. Not sure if that translates to a big block. But that was my experience.

hi guys , sorry for the late reply to your posts , apprecate your time ,
timing is inital 20 * & total of 34* .
idle at 800 , with about 580 -600 in drive still 20* degrees BTDC , dont start advancing till about 1500 rpm all in by 3500 rpm ,
tell you what i have noticed now , that wernt apparent before , soon as the coolent tempreture stays 185 -190 for any length of time , sometimes the idle will act up like i mentioned in first post too ,
went of for a 30 mile blast yesterday evening & let it idle was ok , like i say its random , did think it may be really hot under hood temps & the hot air rising up in the unsilenced air cleaner , i'm out of ideas , like i say was perfect yersterday , going for a nother run tomorrow ,

Do you have another carb to try to see if the carb is your issue? Possibly if your vacuum level is low that your metering rod plunger springs may be boarderline and certain idle conditions may let them lift and throw the rods up and then you will have a load condition. What cam are you running?

How big is the cam.

I would try lighter springs in the dizzy to get and keep more idle advance

bet that helps a lot!

since you are on the verge of and bouncing the step up springs more idle advance and slightly higher idle will cure things. 38 total is good so maybe try 24 initial right away.

I like to see mechanical timing all in by 2500 (or less) and a bit less vacuum total.


try 4 more degrees and 950 idle 750 in gear!

you have he chugging!