i have a 1971 buick skylark with a 350 quadrajet and hei distributor i was wondering if any of you guys have any insight as to why in drive i idle at 600 rpm and when i put it into park it idles at 1500 rpm. i tried screwing the idle speed screw but rpm doesn't change much. but today it didn't happen idles normal again in park. also i checked for vacuum leaks already. im stumped
Check the choke linkage. There is a fast idle cam that rotates with the choke, but it can become gummed up and stuck. The fast idle cam is on the passenger side of the carburetor along with the fast idle screw. Other causes can be misaligned throttle blades that won't close all the way. You have the curb idle screw backed all the way out?
A bad pcv can be a bad vacuum leak if it’s not sealing . Will cause a high idle. Is it doing it at operating temperature or at other times?
i sprayed starter fluid around the intake manifold and carb base no rpm or noise change. also i cant get the car past 160 degrees the guy before me put a big aluminum radiator and im not shure if he put the thermostat back in also, should there be a fan clutch? ll check the choke linkage.
You should see if there is a thermostat in it. I'd say there probably is, and it is probably a 160* stat. Put a 180* stat in it and it will run closer to that. Drain the radiator partially and pull the upper hose off the stat housing and look to see if there is a thermostat there. If not, put a 180 in. If there is, put a 180 in.
If you have AC I would think there would have a clutch cooling fan in 71, my 72 does. No AC I am not sure.
i checked for vacuum leaks with smoke. the only place i saw smoke coming out was through the front of the carb through the primary throttle blades or air door. Is that normal? Maybe thats why when i bought it the guy only had one return spring? Also it doesn't have a pcv just a breather.
Why is there no PCV? You need to remedy that. There is no reason to run without a PCV system. Leaks at the throttle shaft are common on the Q-jet. You can get the throttle shafts bushed to tighten the clearance up. https://cliffshighperformance.com/Q...uadrajet-parts/category/quadrajet-bushing-kit
First thing is to install a PCV valve. The breathers are nice but its not POSITIVLEY venting the crankcase, the only way the crankcase is getting "vented" is with the downward stroke of the pistons creating pressure, but some pistons are going up at the same time creating a vacuum, so its kinda moot, that's why the need for POSITIVE crankcase ventilation, a constant vacuum sucking nasty fumes and letting the engine burn it. On your idle issue, try more initial timing, if you don't have enough initial, it WILL idle in park, (no load) but under load ( in drive) It wants to stall, so you open the throttle with the idle screw to get it to idle in gear, now you put it in park, (no load) and the idle shoots way high because of the increase throttle opening required to idle the engine in gear (load) Where is your initial timing at??
Quick and dirty check for a vacuum leak- lower the idle in park to 600-700 rpm, slowly start to cover the air horn with you hand. Start smothering the carb of air. If you have a vacuum leak, the rpm will go up. If you don't, the rpm will drop and the engine will get choked out
