I think it mite be time for a rebuild...... car is 2 years old or so bought it off a friend work great for a while....i will go to punch it and it chokes like stumbles then takes off ive played it the accel pump cams , squiters, ive jeted it up and down and nothing....no matter what jets i put in it it runch really rich.
Carb is a 850 holley 4150.... how much for a rebuild and who does the best work

 

have u messed with the set screws in the metering block?have u set timing correctly and adjusted idle accordingly?do you have a blown power valve?

 

timing is total of 20 degress the idle is adjusted correctly,.... ive played with the set screws and no matter what it still does it
how do i tell if i have a blown power valve

 

Dude, your timing is way off!

Even the most mild small blks need at least 30-34 degrees total.

The only way at least that I know, to check a pwr vlv, is to remove the bowl and metering blk and take the pwr vlv out and look very closely for a small tear, also, if the vlv is the wrong size for you motor it will be a problem as well. They have a tool, but few own one.

The stumble, and the rich condition may be 2 separate issues.

 

Dude timing will not make it do this....i will put more timing in it down the road. i did some research and the blown power valve will make it run very rich at idle. the stumble is relate becuase i jet the carb down thinking it was way to rich....when i go to hit it its geting tomuch air and not eought fuel....atleast i hope...i will tear it down tomorow around noon and get back to you guys

 

I wana keep the timing down on pump gas becuase im runing 11to1 i dont wana be on the edge......

 

Jetting has nothing to do with throttle response, jets only come into play once past the intermediate circuit is passed, then the jets are feeding the motor.

Are you adding any octane booster? You are correct 11 to 1 is close on pump gas, but you should be able to add at least 4-6 degrees timing.

Now depending on the size of the vlv, it could be causing the rich condition and not be blown, you need to se where your vacuum is at idle, then you want to cut the pwr vlv size in half or less. Say if you are at 14", then you'll want a 6.5 vlv, or 12" will want a 5.5, and so on.if the size is too close to idle vac., then it can open when you don't want it to.

Good Luck!!

 

20 DEGREES TIMING !!!!!Holt **** thatg thing must be a friggin POOCH!!!Put like at least 36 in it,11 to 1 on some good 93 will be fine...,I got 383 sbc's i built running 11.75-1 on pump gas driving to the track 38 degrees timing no problems...
I would suggest replacing your power valve, putting at least 36 degrees timing in it(I would do 38) and then let us know how it runs..

 

Thank-You LS1!!

 

power valves are not blown..... i even had a 64 jets in the front and a 68in the back and it still was black smoke at idle.....the only #s ont he power valve was 62 and 85 on the hex like part...i put the vavvum gage befor i took it apart and it makes 8" of vaccumm

 

whould a bad needle and seat cuaise it to run rich at idle

 

i agree with these guys, that thing needs around 38 degrees of timing before you even start tuning the carb.regardless of how much you think it should have.big blocks can generally take more advance even with decent compression b/c the flame has further to travel across the combustion chamber.start with like 12 degrees initial and 26 deg adv by 3 grand

how did you test the power valve? if it is an 8.5 PV and the motor pulls 8" of vac@idle it is open at idle and will run hella rich, it doesnt matter what jets are in it either.ctsv05 is right, pick a power valve around half or less of the idle vaccum and it should be real close

tuning is about giving the motor what it wants,not what you think it should have

 

Put your motor at 38 degrees timing total max by 3000 RPM if not sooner around 2500 within that range you should be good..Now once you do that start tuning your carb, it sure sounds like you got a bad power valve or too small of one...Needle and seat would not cause it to run rich unless its dumping fuel, and usually when it dumps it will raise the idle, well you should notice that if it is...

 

the lowest vaccum u made was 5-6" at like 700 rpms so a 2.5 power valve whould do the trick?

 

we use 4.5's in all the motors we build...

 

ok i will order then up now. thanks For all the help guys i will put some more timing in it then try tuning it......should do it friday after work

 

put the 2.5 power valves in put new needle and seats in...it idels fine but now once u hit it it blows black smoke and stil has the dead spot.....i have a 76 jets in the frotn and 82s in the rear....what else whould cause it to do this

 

i also got 36 degrees of timing at 3k rpms

 

put 38 degrees timing in it for the love of god trust me on this...unless your engine builder used some foreign parts unknown to man the motor should love 38*...Also put 4.5 power valves in it not 2.5 and put the jetting on the carb back to the stock out of the box specs...and next turn the fuel screws that are in the side of the metering block..turn each screw in till the motor stumbles then turn it out 1/2-3/4 of a turn..Do it to all four screws,all of them should look like they stick out an equal amount,then go have fun and it should be good to go...