View Full Version : carb tunning and timing

01-11-2011, 03:24 PM
hey i got a 460 that was running, its got a 750cfm 4160 holley carb. im not sure if the timing was right on before i had to tare my carb apart and now im trying to slap it all back together. its getting the odd back fire through the top but it idals okay.. i drove it down the road and its deff running rich and only seem to backfire up the top when i step on it... is there a way to find where the timing is sposto sit (it hasent been out so its at tdc and is in the right gear set..) i donno how to tell if its the carb that needs ajusting or the timing...:dontknow:

01-11-2011, 05:25 PM
I'm a mechanic and this post confuses me.

Dirka.. Perhaps you can translate this post into english and we may be able to assist this poor person.

01-11-2011, 06:41 PM
i dont even know if the timing changes when the carb is out... when i have the light on and im watching the mark it moves as the idel increases.... so i geuss get it to barley idel and then do the timing? and then tune the carb..

01-11-2011, 06:55 PM
so i did some more tinkering, marked where my timing was then shifted it but its ideling a little high, and the the idel screw is all the way out.. the choke is off, and ive checked for vacumme leaks... it doesnt seem to be back firing now though... i tried to turn the mixture screws all the way in and nothing... i have the vacume gauge on it and i ajusted them till i got the highest vacume, so they are a half turn out..

01-11-2011, 07:50 PM
oh and i dont think its a vacume leak cause its holding at 17".. and one of the original problems was the spark plugs looked like cake...

01-12-2011, 02:22 AM
as the rpm increases the mechanical advance increases timeing
you need to disconect vacume advance and plug hose to set timing
the poping could be caused by a lean condition does the acelerator pump work?

Punk in Drublic
01-12-2011, 07:28 AM
if youve fucked with timing and carb adjustments itll take a while to get it all back to happy. i did a similiar thing when i was younger and dumber. couldnt get the truck to run worth a shit, took alot of tinkering to get it rrally get it runnin tight,

01-12-2011, 09:33 AM
sounds like the accelorator pump is fucked, and set your timing without your vacume advance

01-12-2011, 10:19 AM
oh yea set your timing then carb

01-12-2011, 01:46 PM
wrong jet for the secondarys? i belive the timming should be 7-13 BTDC depending on the year

Mud Slinging Dumb Fawker
01-12-2011, 05:41 PM
make sure the wires are in the correct place

01-12-2011, 06:38 PM
4skin called it... i didnt know about the vacume advance but had a buddy over this mornin.. the metering block wasnt doing its job, the accelorater pump was ajusted backwards and the timing was a little out..... oh and the sleves in the throtle body were woren out to crap too.. thanks guys

01-12-2011, 06:40 PM
i had a brain fart and ajusted the accelorator pump so when i pushed the pumparm all the way up i then ajusted the screw for the feeler gauge... well i should of pulled the other arm up and put it so the pump arm was barly touching.... new things learned for me today..... but hell you cant learn if you dont tear it all apart and hit your head many times trying to stick it all back togeather right!

01-16-2011, 09:39 PM
truck is still doing funky stuff... it seems to run great, a little trouble staying running on startup.. but when you rev it up it has trouble going back down... stays reved up a little and then goes down... its deff not the cable and everything seem to move freely..

01-17-2011, 08:54 AM
Check ur mechanical advance might be sticking or broken spring

01-17-2011, 06:19 PM
i found a vac leak coming from the sleaves on the linkages... is it normal the the fuel drains out of the filter back into the pump once i shut it off for a bit?
and does anybody know what they call the little sleaves in the linkage or is it just a pain in the ass...

m j
01-19-2011, 06:36 PM
throttle shaft bushings?

pics would help

sounds like carb needs lotsa help, post lotsa close pics of it from both sides

the linkage should push both primary and secondary throttle blades closed when you let off the gas, the link rod on the driver side is what pushes the secondarys off, it might need to be bent a bit to fully seat the secondaries

sounds like a used carb that others have tinkered with