Holley 600 vaccum secondary carb, fouls plugs like crazy and the mixture screws dont work set them all the way in and all the way out and it runs about the same.. fuel pressures 6 psi and it wont idle under 900 rpm and i know the transition slots are probably exposed. fouls spark plugs with in 5 minites of running and it has a plug instead of a power valve. floods under the throttle butterflies because i can't see any gas on the top, dry as a bone. floats are set right and has two brand new fuel filter on it

So after you took the PV plug out and put that back to stock for the carb, and completely rebuilt it, and then followed the "Holley Tuning" sticky at the top of this forum, how did it turn out?

yeah, it's rebuilt, took it apart 5 times now. to the point were i just want it to run, i will get the right size jets and power vavle later when i get it running. i've spent so much money on plugs and if i can't get it runnning soon i might get a new carb. i really wanted this carb to work out.

If you know the transition slots are exposed (too much), then the throttle stop screw is cracking the butterflies way open. Therefore high idle and overwhelmed idle screws.

Why no PV? Assume you have huge jets to compensate = way rich and fouling at cruise/high vacuum.

Sounds like u need the right ones sooner rather than later.

Not a jet problem (at least at idle)...99% sure it is a timing issue. You have the throttle blades opened way too far just to maintain a 900RPM idle (timing is not advanced enough). What is your base timing and timing advance with vacuum hooked up? If you say "I am not sure", then you have a lot of timing work to do to fix your carb problem.

Good point Pancherj.

tuning 101:
set timing 1st! then dial in carb 2nd.
all the carb work in the world wont fix inadequate timing.

A hotter initial spark will also keep your plugs alive. Also its pretty hard to actually "foul" a plug to the point its junk. clean them up, set the gap properly and throw them back in.
It should also be on you list of to-dos to make sure the advance curve fits the application. If you are running a MSD or similar, they come with kits to adjust the timing advance window by controlling the overall advance and the speed/rpm at which the weights move.
For example my engine made peak power with 37* total timing but with my engine combination, I needed to be somewhere in the 18-20* initial timing range. I installed MSD smallest window bushing (18*) that sets me at 19* initial and allows my peak timing of 37* then based of MSD's charts you want to dial in your curve My car being pretty light and steep gears behind a stick wanted a more aggressive curve, so I swapped my springs to allow a full timing advance much sooner than a stock engine would need. the results: better combustion more power no fouled plugs!



As for carb tuning, set idle 1st, working on getting the mid-wot tune dialed in, then set cruise/idle circuit. Get a wide band, it will cut your trial and error time in half.

You can buy really good books on holley tuning (which i really reccomend as it helps you really understand the total function of the carb and all of its systems and how they effect the over all performance) and if all else fails go to holleys site, or youtube and watch the step by step videos until you have a strong understanding of the process.


You mentioned you have taken the carb apart 5x? Why? unless you know you did something wrong, thats not gonna cure your tuning problem. most likely it'll cause vac leaks from the gaskets not sealing after repeated assemble disassemble scenerios

i only took the power valve out to see if that was the problem has the jets from the factory in it, .65's?. and i mean that i want to get a vaccum reading first before i buy a power valve rather then have my 6.5 that i think is no good in there. i have no idea what the vaccum is going to be on this motor. and my qusetion is that even if it was running on the transition slots at idle won't it foul the plugs even if i was crusing? i'm going to lock the distributer tonight to 36 degrees and got brand new plugs and i will open the secondaries up till i square the transition slot up, same with the front. see if that does the trick. dont want to foul my 4th set of plugs. trying my stock plugs in it, ac delco's r45ts's had some e3's in there and some cr43ts's in there. never changed a bit. fouled them right up to the point were they crack the inside and wasn't firing at the tip anymore, it was firing inside. never seen that happen before.

and why i went through it 5 times was im and very OCD about gaskets not being right and i wanted to make sure everything was right, like when i switched over to the holley i thought it might be the timing marks on the cam not lined up, tore that all apart and it wasn't that.

should i ran vaccum advance with a locked dizzy?

if its truely locked, vac advance wont be functional

i mean welding the mechanical in one spot, wouldn't the pick up coil still be able to move around? use the ported vaccum won't i get some high advance for crusing purposes?