I just checked for a stuck power piston by sticking a thin screw driver down the round vent hole located in the center front of the card. It feels as if ther is an 1/8 or 3/16 downward movement in the power piston. So the next step would be starting the car and and repeating this check but I should not get any movement if the vacuum is holding the power piston down. Correct??
Correct, and with the screwdriver in place, you should see the screwdriver jump up when you suddenly wing the throttle. What kind of ignition are you running?
I had to see if there was sufficient vacuum to hold the power piston down. So I started the car and the movement I felt before started was gone. So I say the power piston is free and the vacuum holds it down. So taking a big leap with out any knowledge I need to swap out either the rods or jets or both to lean out the F/A ratio? How are the rods and jets coded for size? 77/46 now so what is less fuel?
OK, I just started the car so I will go do it again and this time see if I can see the screw driver move when operating the throttle.
Weak ignition and/or cold plugs can contribute to this as well. What ignition are you running, what spark plugs?
Well, there is no movement when moving the throttle. To me that means there is enough vacuum at idle to pull the power piston down. Is that good or bad???
MSD pro billet. The fouled plugs are Autolite 665, I replaced those with a AC/Delco Rapid Fire 19307139. The plugs cross reference with each other.
You really have to wing the throttle to drop the vacuum enough for the piston to move up. That isn't a problem. When the throttle openings are wider, vacuum drops and the piston pops up pulling the wider portion of the rods OUT of the jets. This richens the mixture. The fact that the piston is being held down at idle is normal, and is not the cause of your fouled plugs. I would not automatically assume you need a jetting change. The cause may be a weak ignition or wrong plugs.
My timing is set at 6 degrees but I have a 30 degree mark so at 3000 rpm total timing is 36. I was watching for the screw driver to move down not up. So I will do it again. I told you I don't know **** about carbs! But I will learn. I don't think I have enough cam to make it lose vacuum even at WOT
Are you running points, GM HEI, Mallory, MSD? What kind of ignition? What spark plugs are you using? Part number?
Well, I couldn't tell if the screw driver rose any or not way to much engine movement for these old eyes to tell anything. I will make a reference mark on the screw driver and try it again. I need to take the wife to lunch so I will be slow to respond. A happy wife is a happy life!
OK, I understand my car does lose enough vacuum for the piston to rise or it wouldn't accelerate, a senior moment
Quadrajet Power did my QJ on my 462 with TA Stage 1 ported aluminum heads with 10.5 CR and 468 HP. My Jets/rods were 74/42 with a DA secondary rod and mixture was about right. Check that the power piston is seating at idle vacuum and that float level is right. You should be able to either get a QJ book or change jets/rods using Utube videos. Easier to do if you remove the carb and do it on the bench.
agreed plugs look like running too rich, and blue smoke when starting usually means valve seals are leaking. Don't know the record on SMI for rebuilds, but if the carb is a remanufactured Q-Jet core, it's likely junk...those units are only built to pass emissions tests & nothing more. Trying to rebuild those cores is a lost cause. If the well plugs weren't sealed, the bowl could be leaking which would also create a rich condition.
New question, am I running the right heat range plug? Mark, I have no idea why the threads are oiled other than lubrication for installation.
I see you are using the msd pro billet distributor. Your initial timing is 6* before tdc. So your throttle plate may be excessively opened at idle. I would change the distributor bushing to the black one. Put 2 medium springs in. You have 3 sets supplied. I think they are blue? Set initial timing at 20 degrees before tdc at 900 rpm. Your total should be around 35. You will be able to turn your idle screw down and adjust your mixture screws better. Check idle and vacuum on the carb and get back to us.
SMI is Sean Murphy Induction. try the distributor adjustments first. Let us know how that works out. First.
