secondary air valve shaft

[jbh7052]

has anyone ever had to put bushings on the air valve shaft?? I am haveing some wot issues. sometimes it doesn't pull or sound like the secondary's are opening. Sometimes it sounds like it opens but the engine pulls very weak and stumbles until I back out of wot. I have one turn on the spring but to push the flap open by hand it feels like it catches a little and then opens freely?. Carb #7045213. rebuilt with SR kit plus 76 jets, p-rods 43, sec rods DA, apt screw idle tubes(.036 or .037 cant remember) and power piston. Cliff had me tap the idle air bleeds to .059. This is a 355 with 8.5 compression. factory ram horn exhaust manifolds and duel 2.1/4 exhaust. Low performance aftermarket aluminum dual plane intake. Cam is .444 intake and 466 exhaust, intake opens 0 btdc and closes 34 deg atdc. exhaust opens 49 deg bbdc and closes -5 deg atdc. this motor is in a 82 jeep scrambler with 33 in tires and 4:10 gears with 350 turbo tranny. I have 15 deg of initial timing but have not measured the mechanical or how much vacuum the canister adds. sorry this is so long but wanted to give all the info I could so someone didn't have to ask for it! thank you very much guys! 

[jbh7052]

done a little testing and this is what I found. I don't think the air doors are catching, I believe it just takes a little pressure to get them started from a resting position. Now about the engine stumbling when in wot....It appears to be an rpm issue. if I pull the tranny into first manually where the rpm will continue to rise this things opens up and runs awesome! Pulls great without a hint of hesitation or stumble!! So I believe with some governor work I can have this worked out. The tranny is out of a Camaro and is now in a jeep with larger tires and probably lower gears. So I think if I get a governor spring and weight kit this can be solved. The tranny will shift through the gears before it hits 34 mph!! I don't really need WOT on a jeep with a 355 but I cant stand for things to not be right! I will post my success or failure as soon as I can get the kit! 

[jbh7052]

so I got the calibration kit for the tranny governor in Monday. I changed one of the factory 15 gram weights down to an 11 gram weight. First test is the tranny now shifts at 4100-4200 at wot verses the original 3200 rpm. This has effectively cured the bog. I believe it just needed a higher rmp when it shifted to continue to pull strong. I know this is still not an ideal shift rpm for street  rigs but for my jeep it is just fine! I may toy with it in the future just to be doing but for now it runs great! sorry this post went off in left field from the title but it just shows that I was way wrong on the secondary valves sticking!!

[Cliff Ruggles]

Regardless of shift points at WOT secondary performance should be smooth thru the entire load/speed range.  When things are set up correctly, you should be able to go to full throttle at any rpm, and shift at any rpm without any issues anyplace.....Cliff

[jbh7052]

thanks for the input Cliff....not sure what was causing the issue but raising the shift rpm must have put a Band-Aid on it cause it will ROLL now when mashed on! thanks for all your help! I do have one last question though if you get around to reading this. When the engine has been up to operating temperature and I coast for a ways and come to a stop. The rpm drop from my normal in park rpm of 650  down to 500rpm or just under. A quick tap of the throttle will help. it will not kill the engine but I have put this much time into the carb I might as well try to narrow this down and fix it too

[Cliff Ruggles]

Several things can cause this, worn at the throttle shaft is one, installing bronze bushings will correct that issue.  The distributors mechanical advance/springs will also cause this, varying ignition timing at low rpm's varies the rpms at idle speed......Cliff

[jbh7052]

thanks cliff. we can rule out throttle shaft since you guys put bushings in mine. I may try using some different springs. guess I could polish the weights and make sure they aren't binding or catching on something.

[Cliff Ruggles]

Those POS spring kits, light springs, or tired stock distributor springs cause more issues with idle quality that carb problems do.

The timing curve MUST NOT START until a few hundred rpms above the curb idle speed, or can and will add some timing at idle, and cause all sorts of idle speed and tuning issues.  I see this ALL the time as we build a LOT of factory distributors here.  ALL of those aftermarket parts, weights, cams, springs, etc go straight in the round file next to the work bench!....Cliff

[jbh7052]

10-4!! I am on it. ordering aftermarket today.