Hi, this problem has plagued me since i've owned the car. when i drive my car and its fully warmed up and i come to a red light the idle on the car starts to falter a bit to the point where i think its going to stall. sometimes i put the car in neutral and with my foot on the brake I rev it just to keep the engine going. i think this is mostly just paranoia in my mind, that the car is just going to die on me. i have a 350 with a rebuilt qjet, performer intake, hooker headers, flowmaster mufflers, ummm hei distributor. i don;t think this is related to any of the mods i've made, car has always kind of behaved this way and has actually stalled once or twice. when i put a way too big camshaft in with a lumpy idle the problem seemed more pronounced. now i went back to a milder "daily driver" camshaft with low duration and its still not running smooth when sitting at a red light. as soon as i step on the gas the car is fine, no stutter or hesitation.

btw i am having other issue with my exhaust that i posted but that started after i put the rebuilt qjet on, this stuttering problem at a red light precedes that latest modification.

 

sorry, i have a 71 cutlass, 350 with #7a heads. they were reconditioned, mild porting polishing. i think this problem precedes this modification as well when i had #8 heads on the car.

 

Whats the manifold vacuum reading at idle, warm? Whats the curb idle RPMs set at? Whats the base timing set at(vac can plugged off)? Whats the vacuum assisted timing number(vac can hooked up)?

 

The last time we discussed your problem, the car was running rich, you had a vacuum reading of 14.5, and your a/f mixture screw did nothing. Has this been rectified?
This thread:
https://classicoldsmobile.com/forums...e-exhaust.html

 

i re-evaluated the a/f mixture screws, just had the car warmed up and cranked one side of the carb's a/f screw all the way to the right and it definitely affectd the running of the car. turned it back to the left to pretty much what it was and the engine smoothed out. turning the a/f screw did not affect the excessive exhaust issue i talked about in that other post. still puffing out a lot of white vapor while in park.

 

curb idle - if you mean while its in park its around 750 rpm.

base timing is at 16 degrees


how do you take manifold vacuum, i usually take the vacuum reading off the carb. maybe i'm doing it wrong. vacuum reading i get is a steady 14.5


i appreciate all the help.

 

You should take vac readings off the intake not at the carb. You should have a nipple somewhere, say the one for the trans modulator?

Base timing is a little high but I dont think thats your problem. Curb idle is ok. 14.5 vac signal is somewhat low but could be normal for the cam? Do you have the cam card showing the cam specs? Is the 14.5 steady or does it jump more than +/- 2-3 degrees?

If you have a vacuum gauge use it to adjust your A/F mixture and to adjust the timing with the vacuum advance plugged in. Try to obtain the highest vacuum reading possible by adjusting both of these settings. Little tweaks to each...take note of what the final settings are for future ref.

Did you run a new keyed 12 vdc, 12 gauge, stranded wire to the HEI dist? Or are you using the wire that the points distributor was using?

Pull and read all 8 plugs. White=lean, Black=rich, Brown=normal. All 8 should be fairly uniform in color.

Are you using any coolant?

Ill assume you have a TH350 or TH400 trans? Check your trans fluid level....is it unexpectedly low? Check the trans modulator line for evidence of it sucking in trans fluid. Pull the line down at the modulator you shouldn't see any fluid coming out of the modulator at all. If so there's your smoking problem and possibly the stalling at a stop problem too. Does the trans shift ok? Does it have the stock torque converter? A large cam with a stock converter can cause stalling issues. Whats the car idle at in gear? Any lower than 500 it will stall. And you need a looser converter.

 

yeah, the cam is important to know...
also, what is the carb id number?
It could be the carb needing to get more idle bypass air and/or needing more fuel in idle.

 

here's the Cam info.
Advertised Duration (Int/Exh): 256/262
Duration @ .050 (Int/Exh): 213/219
Gross Valve Lift (Int/Exh): .485/.499
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1000-5300


no not losing any coolant least i don't think so. th350 trans with stock converter. not familiar with this trans modulator, will take a look at my manual today and try and find it.

i'll also take it out for a run then check my plugs.


not sure about your distributor wire question. please clarify. when i got the car the dist. was not running points.

 

I'm assuming this is your cam. You need to advance your timing a few more degrees 18-20, and raise your idle so that you run about 700 rpm in gear. Your vacuum will be a bit lower with this cam.

http://www.lunatipower.com/Product.aspx?id=2347&gid=287

 

yeah okay thanks. yes that's the info from lunati. just checked idle while in gear and it was hovering around 580 rpm.

 

pulled the rubber hose off the end of the modulator and nothing came out. trans fluid seemed fine, checked it after warming up the car and while running in park as directed and it was fine halfway between add and full which is what the manual says it should be.