oh yeah? You come up here and chip through all that JB Weld! In all honesty, I got a little crazy on my Doc Mod with the carbide bit and made the wall between the plenum and heat trough a little too thin for my liking - after I put the brass plugs in I packed it all with JB......I might run it with heat for a few runs, but it wouldnt last long before it ate through. We're talking knife thin.
The ignition system your now running needs full 12 volts to work correctly. The power your getting thought the resistor wire is not 12 volt.The pertronic III not going to work to its maxinum . Check out the following web site....Dan..... http://theamcforum.com/forum/new-pertronix-ignitor-iii-done_topic10306.html
Zinny is right about that,,,, If I am remembering right you gotta put a full 12 volts to the pertronix... that is what I have.....
I was told it could work either way (and worked well on the resistor for 3 years), but since we're throwing more fuel and air at it, it's probably time to rig it to full 12 volts... Made my first full runs this AM - Car launched hard and has some newfound top end, but couldnt come up with a solid ET because: Running out of fuel before the run is over - I kind of expected this...I'll need to cut down the float bowl insert, and likely change to a larger needle and seat like 6WildCat5 suggested. Secondaries slamming shut after the 1-2 shift (the only shift I've got) - at least thats what it feels like,RPMs drop for a sec and come back up and you can hear the secondaries open for a second time, and it doesnt feel like fuel starvation...Wasnt expecting this - I'll start with spring tension and see what I can do....this carb has that funky air valve limit arm and dashpot in the fuel well, dont know how or if that can be modified. The good news is despite all this, the car feels stronger throughout the range - and Doc will say I told you so when I complain about how complex this carb is to set up...
In all honesty, I will try the Holley -I have a 600 CFM spreadbore sitting on another car thats in pretty good shape. I just cant give up mid way thorugh figuring the QJet out..making lots of progress, moved the stumble higher up the throttle position and solved the secondary delivery issue - all I got left is to nail down primary mixture (I think) and fuel bowl capacity. And its only March! I'm way ahead of last year!
Spent some time on this yesterday and made some progress -Went up and saw Ken and we messed with the primary metering... I seemingly cured the WOT off idle issue by closing up the plug gap to .035 (?) but still had a sizable stumble while slowly rolling into the throttle that required "peddling" during the off idle cycle to keep the car going until the main metering system came into play. We deteremined the stumble was coming from a lean condition occuring before the accel pump came into play. Since the off idle fuel comes though the jets while the rods are fully seated, we decided to decrease the size of the rods. It came from Buick with .075 jets and .045 rods, and we switched out to a .044 rod. A quick test drive showed the condition was almost gone - it still stumbled, but you could drive through it and didnt have to feather the pedal. It also idled much smoother. I'm going to try a set of .043 rods next, and then start to look at the re-sizing the idle channel restrictions. Learning alot this week, and now recognize the same condition exists in my Pontiac. Still have to address the fuel flow rate as it seems to run out mid way though the run..I ordered a .145 needle and seat , but I understand I'll have to watch fuel pressure carefully. Also left is the issue of the secondary air valves slamming shut on the 1-2 shift.. I should be able to dial that out with spring tension. Everything worthwhile takes effort, I guess.
Rhett , Good to here your seeing light at the end of the tunnel . I can see where the change of pri metering would help because all of the fuel that ends up at the main nozzles flows through the main jets. I would still take a good look at the accelerator pump , when you move the throttle quickly you make a sudden lean condition and at that point it takes time for fuel to flow out the main nozzles. This is where the pump comes into play... When you snap the throttle the pump forces the fuel under pressure out the discharge port in the air horn... stumbling , hesitating , when you get with the program quickly all point to the "Pump". If it were me I would still do these mods, seat the checkball with a brass drift & replace it with a new ball ( inlarge discharge holes to .028 ) replace the accelerator pump with a new style HP short pump (more stroke) with garter spring & the blue rubber seal ,works better with the new style fuels . I used a pump from a vender that also had a stiffer spring under the pump & I have to say this was some of the best money spent to date ... it did away with my tip in stumble, carb # 7040240 q jet after this ghange i went back to 68 jets from the 71 jets used to cover up a tip in lean condition. Just a thought & you will improve pump perf for sure ! Mark (ick)
Thanks Mark - I forgot to mention I did pick up a new style pump, blue with garter. I have to measure the shaft length, but I did shorten my original at the garter (?) ridge, no more than 1/16th..still have good spray but didnt effect my condition. I dont have problems anymore when I stab the throttle, only when I roll in slowly. I am going to reseat the ball, etc..and we'll see if that has an effect on my off-idle issue.
Update - the .043 rods are too rich, I'm going to go back to the .044s and go .010 over on the channel restrictions - still have the stumble, but it's no worse than everything else I've driven for the last 30 years, just now i know it's not supposed to be there! Did replace the accel pump and glad I did, the one that was on there was very flimsy, and kinda oversized so it mus have been bunching up in the bore. This one is smaller circumferance but stroner, and has the garter spring....works well, but still didnt cure the stumble. Also loosened the air valve spring, no more on/off at the shift and OMG secondary response...people swivel their heads blocks away! Even with the stumble, this thing is ready for Lebanon...I hope to get some ET's measured tomorrow AM with the G-Tech.
Was able to get some runs in Sunday morning - The good news is I finally corrected most all the issues and was able to get the car to pull strong all the way through the 1/4 - no fuel capacity or secondary issues. The bad news: It was consistantly slower than the AFB, by about .3 across the boards. 60 foot and 330 are comprable, but by the 1/8 mile I'm down a 10th and 2mph.. I was surprised, thats where I thought the QJet would really take off - I still have some dialing in to do. I'm running long tip .0567 secondary rods and it smells lean under full throttle, but the plugs look good. I read alot of people are running .04XX rods on a street/strip car, so I'll work my way up and see if that gives me the top end I'm looking for.
Rhett,,, pard,,, richen the mixture right away... because a lean condition can hole a piston for you in one run..... get too rich and then back down... that is the safe way.... or you can just put your holley on......:laugh::laugh:
Another thought... What air cleaner are you using? I was using one that had a flat top for hood clearance, then switched to one that had a lower base and curved top... The flat topped one was not letting the air flow into the Q-jet correctly... Once I switched the air cleaner, I found an immediate improvement... Just a thought...
Doc! Sound advice... Good news is the plugs look good and no pinging. I'll run it up and back down again...I did grab a good selection of secondary rods from .0567 down to .0413 - one of them has to work.. And then as soon as I get it dialed in, I'll take it all apart agian and try the Holley! ---------- Post added at 02:54 PM ---------- Previous post was at 01:58 PM ---------- I'm using the standard GS/Riv GS pancake air cleaner with a K&N filter - but I've got the filter sitting on a ring of vacuum line, so there is about a 1/4 inch gap all the way around between the lid and housing. It's a very narrow housing, so I could see how it would be restrictive if all closed up. ---------- Post added at 02:54 PM ---------- Previous post was at 02:54 PM ----------
Two things, guys. First, if the air coming into the air cleaner is too cold, the resulting dense air will cause a lean out at any tip-in. With respect to the WOT issues, make sure that the secondary metering rod cam is moving the hanger. If it is not moving it sufficiently, the resulting fuel starvation will cause what you are experiencing. Food for thought...
Just found this thread tonight, and you guys seem to have it covered pretty well!, but I'll throw in my two cents worth.... I'm running 2 cars with the early Q-jets. The only problem I recall was a lean stumble on light acceleration. The cause was a float level that was too low. (who wudda thunk?) And Mark mentioned the different accelerator pump..... a stiffer spring will give more gas quicker, and a softer spring will give a slower shot of gas over a longer time duration. I'm thinking you may need the stiff spring to cover the lean spot.
