wont idle please help

hi everyone i need help i have put the recoed engine in the van looks good and thats about where the excitement finishes i cannot get it to idle have used the same carby and the electronic ingnition off old motor put new cap and rotor on it will rev fine but as soon as you lift the foot off acc it backfires thru the carby it and stalls it starts quite easily all the vac hoses are new and i put new manifold gasket on and this little problem is now keeping it off the road any help would be greatly be appreciated i dont mind swapping and changing things but i am not a good problem solver thanx wizard (now i wished i did have madjic powers ) thanx wizard

Had the same problem with a Ford cleveland once and beleive it or not after checking several time found we had the firing order out of whack Maybe give that a try

if you have a can of aerostart try spraying it around the base of the carb and also the manifold while running and see if the motor picks up it so you have a vacum leak. also try the vancum advance by sucking on it and holding you tonge on it see if the presure drops.

on a holden 6. its easy to put on cap on backwards.

By the sounds of it, I'm with Daz....

Vacuum Leak or incorrectly plumbed hoses...........

Backfire indicates a timing related issue, did you check the timing with the vac line off the dizzy and plugged?????

Also check dizzy vac advance is functioning, diaphrams do get old and leak.... circlip falls off advance arm.
If it has mechanical flyweights inside the dizzy also check they haven't seized or gummed up.

I have to agree with the above comments, triple check the firing order, then timing,etc,once your sure thats OK check the fuel supply, fit a clear style filter between the pump and carbie, if you can see air bubbles going through the outlet side of the filter you pump has gone,sounds strange but had the same symptoms on 2 different motors which ended up being the pumps both times.
This is usually only with mechanical pumps, electric normally either work or they stop dead.
There are many other things that could cause these symptoms,but start with the basics- plugs, leads,timing, fuel.
Let us know how you go.

i would like to thank everyone on their suggestions check firing order last night i got that one right dissy was working on old motor fine and the carby didnt come off the manifold and the carby was brand new when it was on the old engine going to put 2 manifold gaskets on it on the w/end they dont seem to do the thick orange gaskets anymore dam asbestos and lead and i will recheck the timing thanx wizard

Did you change the brake booster or any other vacumm type of parts, you didnt leave off any hoses did you. spray wd40 around the hoses. i had same trouble on mine . it was a cracked hose.

Hey buddy, if your still suck with it, take it to a fellow in Newcastle next time your in this way. He is in Gateshead and is an engine guy called G Force engines. The man is a holden tuning genius. He will charge you an arm and a leg and you'll feel violated when you leave but you'll drive home in your car with a massive smile on your face. He has made my sick puppy into a vicous guard dog...Hes highly recommended. Good luck mate.....

just thought i would let everyone know that after 5 weekends and 4 mechanics later and everyones suggestions it wasnt any of the above problems it was a mechanical fault that the engine builder said there was no way there could have been anything they would have done they had tightened down the rocker arms way too tight and because of that the valves were held open making no vacuum at idle so it couldnt suck the fuel in found it saturday now it runs like a dream now will be putting the electronic ign back in tonite and taking it for a test drive on friday arvo after work thanx wizard

well then, you'd better get your entry form in for the nats then, since it's all good and u can now drive overseas (LOL) to Philip Island Nationals.... looking forward to seeing it.

took the old girl for a bit of a squirt on saturday it was if i was driving a totally different car much better heaps good with the auto all that i need now is for some of the neighbours to leave the area as i got told off by the lesbians not good looking ones 2 houses down and on saturday arvo got told off by the bloke who lives berhind us apprently the van is too loud now havent touched the exhaust from what was on it before only put in straight cut timing gears and put a wider belt on the gilmer drive and it dosent like to idle under about 1400rpm but other than that everything is now great thanx wizard

STUFF the neighbours.. if your happy that all that counts.

here is a small problem i have how do you set the idle when in drive, when driving the car it is fine but when you pull up a the lights or in slow traffic it wants to stall you have to keep tapping the accelerator to keep it running. it has a stall convertor (2500rpm) built to suit the cam, so it doesn't scream its head off when in park or neutral.the van is fitted with electronic ignition, 350cfm holley,cain manifold,had the timing check and it is right.could it be a jetting problem with the carby.thanx wizard

i jetted my 350 holley down to 65 from 70.s idled better, that was on a 202 with headers and 1/4 race cam manual though ,also, if you get your dissy regraphed to the mods it helps too. cheers

i will know in a couple of days time if my idle problem will be fixed as i went to buy a bigger carby (500 instead of the 350) that is on there now when i got talking to carlos at hume performance told him my problem and he said the 350 is more than enough to run it and said send it down to them with the cam specs and they would modify the idle circuit in the metering plate .thats when he asked if the list number on the carby was 7448 well its not it appears to be what he called a reverse idle carby and i will never get it to run on this engine, fine for std motors.my fuel feeds in from the front of the fuel bowl on the left as you look at it and not the side and has a side mount float not a centre pivot.so i have ordered a new 350 with modified idle circuit.he said hopefully the only things i need to touch when i get it is the idle and maybe the mixture screws as the run them on a 350 chev before they send them out.so heres hoping that after a year and a half of driving it like it this fixes it as mrs wizard is really starting to get the s*&ts and if i would have know this before i probably would not have put it thru the end of the shed (by the way still looking for front panels to fix the van) thanx wizard

had to send the new carby back to hume performance car would not even fire with it on i thought i was loosing the plot and could not even fit a carby and i got it back today fitted it when i got home from work and it started first time and also idles in gear (drive/rev) it has been the rotten carby all this time thanx everyone for your help ps now all i have to do is find some front panels to replace the damaged ones thanx wizard

glad you got it sorted mate, nothing is better than a sweet motor ....