1985 Mustang Carbie. Bogging under light acceleration

[NAZ]

Hi. Ive put a new holly carbie in my 85 mustang, but it still bogs under light acceleration and pours out greyish smoke under heavy acceleration. Any thoughts?

Otherwise can someone recommend a good local mechanic in Perth who knows carbies? Thanks.

John

[Clubman7]

What size carb did you fit?
Guess it's a stock 5.0 litre?

[GLENN 70]

Yes what size is it ? ,what is the list number on the choke housing ? . It might be running lean . The front accelerater pump may need adjusting .

[boofhead]

Check you idle screw positions as this feeds the transition slots. I have seen a few lately where the idle screws are in way to far. Also, check float level is correct. Worry about the jets after you get this sorted.

[NAZ]

Hi. Thanks for replies. Its got an aftermarket Holley 4160 600cfm carb. Ive adjusted the idle screws to get max vacuum. hmmm...Im not sure how to check float level or adjust accelerator pump. Will google. Any recommendations for a reasonable perth carb engine mechanic? Thanks.

[GLENN 70]

The screws should be the same amount out . From all the way in how far are they turned out ?  1 1/2 to 2 turns  out they should be .  Check your timing is ok and not retarded also . Yes Google about tuning of the carb . About 14 tho on pump is ok .  Float level is checked by taking out side plug ,but google it also .

[NAZ]

Thanks. I did quarter turns on both sides until I got max vacuum. Timing is spot on. ive tried different accelerator pump nozzles and even swapped out jets with originals. I cant believe a brand new carb can be so much hassle. Ive had it to a few shops in perth and they cant seem to sort it out. My last hope is to consider swapping to a FItech system, but no guarantees there either. Im starting to wonder if it is the carb....

[NAZ]

Also, when I first fire it up it spits out soot from the exhaust every time. Clears up once its warmed up.

[GLENN 70]

Ok you need to check the float levels . Have you replaced the power valve ? How many turns out are the screws ? 

[NAZ]

Hi. Thanks. I was just reading up on power valves. Ill double check my vacuum inches of mercury and see if it makes sense to resize. I dont recall how many turns. I only went until vacuum was best. Will look into how to check float levels....thanks much.

[GLENN 70]

Holley carbs are easy and basic to work on . The power valve maybe leaking and should be a 6.5 . 1 st just adjust the mixture screws out to 1.5 turns and see how  it runs .  It might need a new power valve I don't know . Adjusting the float level is quite hard on a 600 and you have to take the bowls off to do this . Google everything it will be easier than me trying to explain it on here .  Still ask questions tho  .

[unilec5544]

Just take it here, very good with Mustangs.

http://www.franksclassicgarage.com.au/

[sms777]

It's a brand new 600 Holley for fark sake....it should not need farkink around with jets and power valves on a stock 5.0 litre. Jessus... . It is quiet obvious your problem is somewhere else. I would start looking at your ignition system starting with your distributor, leads, spark plugs, coil.......Send it to Sydney....I will fix it for you.

[GLENN 70]

Me stupid ,didn't read that part about a new Holley  hey Chris is your new name mike ? 

[sms777]

Nah....I am not that bad yet, am I? Where is Mike anyway? I am starting to miss his annoying posts.....

[NAZ]

Thanks. Ive been there with the ignition system too. Replaced everything.  Wiring harness, coil, all new distributor, cap, rotor, wires, plugs, everything....same problem. Also replaced all the sensors.  Its still bogging and backfiring at the carb under light acceleration, and blows soot out the exhaust until it warm up. I just swapped the power valve and jets with the OEM carb I still have. Same problem. I also had an adjustable cam timing gear which was on the advanced 1.5 deg, so I put it back at 0. Car started easier but still boggs, etc. I may try a 6.5 power valve just for fun...I also checked compression. All cylinders same and good. Sux!!!! Ill try the perth recommended mechanic. Thanks for the help.

[Clubman7]

Harmonic balancer slipped?

[sms777]

One more question NAZ. Automatic choke or manual? If it's auto it could be stayin closed for too long and can be backed off quiet easily. It could give you the simptoms you are talking about.

[GLENN 70]

Advance the timing up by hear . Test drive and keep advancing it and see if it solves the problem but don't let it ping .  If it fixes the problem then put a timing light on it and see where it's at . Check the timing markings on the balancer . It sounds like it s retarded and not a carby problem .

[NAZ]

Ill have another go wih the timing. i think it was at 10deg. I dont think the harmonic balancer has slipped. Not sure how to check that..im def a novice. Auto choke. It still has same symptoms even after its warmed up. Light acceleration at any speed it boggs. Ive tried different accelerator nozzle sizes too...before you ask. No luck there either. Thanks for ideas. Ill try playing with timing to see what happens.

[evan]

Long shot but what if the modulator is leaking (assuming it's an auto) & engine is sucking tranny fluid? Wouldn't that pump out greyish smoke? Very easy to eliminate by clamping/blocking vacuum line to transmission. Just a thought.

Evan.

[NAZ]

Thanks. Its a manual tranny. 5speed.

[evan]

Thanks. Its a manual tranny. 5speed.

Scratch that suggestion then 

Evan.

[GLENN 70]

Is the carby new ? . The carby should be put back to std .  Std jets and a 6.5 power valve ,std squirters  and mixture screws at a starting point 1.5 turns out . Make sure the front acc pump is working for starters and adjusted correctly .  Back firing is either,  lean mixture ,no fuel from acc pump or the timing is retarded . If the carby was new you should have left it alone and played with the timing . As I said do it by hear and road testing and not by a timing light at this stage .as for the grey smoke it must be running lean ,why  fuel pump ,fuel line or blocked filter . The soot might be the choke on too long or the float level too high .