need help with 84 caprice

Hi I got an 84 caprice that was given to me by my uncle. The car starts but sounds horrible. When I drive it I have to mash on the pedal to get it to stop missing. Once I get her going she rides fine but from a dead stop she putters a lot. Also I have to stand on the brake and its still not stopping fast enough. It has the stock 305 with the electronic choke rochester quadrajet. Any advice would be greatly appreciated. Trying to go the cheapest route possible. Thanx

Do you know if someone had tried to adjust the valves?

If someone messed that up and made the adjusting nuts too tight that will cause it to not idle well and to make poor vacuum for the power brakes.

There is a LOT of bad information out there about adjusting valves. MANY resources say "spin the pushrod till you feel resistance then add preload" but in reality by the time you feel resistance at the pushrod the preload is already too tight.

No I don't know if they did. How would I go about adjusting em. Also noticing black smoke from exhaust and strong smell of gas. I can tell the car has been poorly maintained

No I don't know if they did. How would I go about adjusting em. Also noticing black smoke from exhaust and strong smell of gas. I can tell the car has been poorly maintained

your problem is the cannister control valve. this is in front of the carb over the intake manifold. it has about 5 vacuum lines going to it. remove the big vacuum lines and if you smell or see gas then the internal diaphram has a hole in it. then this sucks gas from the tank vent line directly into the intake manifold port under the carb. after you fix this make sure you change the oil and replace those plugs.


the intake manifold has EGR passageways. these may also need cleaning. directly under the carb is where this opening gets plugged up with black carbon which does effect engine performance.

removal of the carb from the intake you can get to this . it is between the 2 primary holes in the intake. if plugged you will not see any hole.

the engine does not have adjustable valves. you may have dirty lifters. use 4 oz of marvel mystery oil to the engine oil and make sure the oil is hot when changing. use good oil filters like wix/pure one purolator/mobil 1 etc..

DO NOT USE FRAM FILTERS.

I will not argue the possibility of the canister control valve.

I will however ask on what planet you come from does a 305 not have adjustable valvetrain???

I based my guess at misadjusted valvetrain on my direct experience with my old 1984 305 Caprice. Back when I was new at mechanicals I made the mistake of thinking an exhaust leak was a loud lifter and adjusted them using the "spin the pushrod" method and had the bad idle, no vacuum symptoms he described because on my first attempt I set the preload much too tight.

The blacks smoke and smell of gas comments he added afterwards do not fit what I saw with misadjusted valves though.

my work with this engine is if the valves are not working correctly this is due to damaged engine components or bad lifters. the valves are not adjusted to correct these issues, if they are adjusted this means parts are worn/defective.

I have seen these go over 200,ooomi with no valve adjustment issues. to try and adjust a valve because of a worn engine component will not work.

once these are set according to the proceedure engine off , when the engine is rebuilt , thats the end of it.

could be also bad valve springs.

I would confirm that all vacuum lines are attached and not rotted or cracked thus causing a vacuum leak. If the vacuum line have never been replaced, it is time to do so.

Then confirm that the choke is operating properly and that the choke pull-off is opening the choke some after the car is started when it is cold. As the car is warming up, keep an eye on the choke plate to see if it opens fully after the car is at operating temp.

Also, when was the last complete tune-up?

my work with this engine is if the valves are not working correctly this is due to damaged engine components or bad lifters. the valves are not adjusted to correct these issues, if they are adjusted this means parts are worn/defective.

I have seen these go over 200,ooomi with no valve adjustment issues. to try and adjust a valve because of a worn engine component will not work.

once these are set according to the proceedure engine off , when the engine is rebuilt , thats the end of it.

could be also bad valve springs.

I never said the valves needed to be adjusted, I asked if they maybe had been, maybe try and read that slowly so it registers.
It is common for people to try adjusting valves when the real issue with a noise is an exhaust leak or such.

Can you please clarify whether 305s on your planet have adjustable valvetrain? First you said they didn't then you said that adjusting because of a worn component wouldn't work.

I never said the valves needed to be adjusted, I asked if they maybe had been, maybe try and read that slowly so it registers.
It is common for people to try adjusting valves when the real issue with a noise is an exhaust leak or such.

Can you please clarify whether 305s on your planet have adjustable valvetrain? First you said they didn't then you said that adjusting because of a worn component wouldn't work.


the valves are NOT adjustable.

you could however change the proceedure to try and compensate for valve issues. this would be done with the engine running to try and work out a valve issue. this is as I mentioned not recommended and also not the proper way to set up the valve train with an engine overhaul.

this usually ends up with the cam being damaged .

I doubt this engine has any valve problems. most likely it is the cannister control valve. and with the high idle a bad electric choke coil. this would cause high idle and with this type setup a very common failure .I had to replace one with only 50,ooomi on it.

A guys check my lil video I put up on youtube. "chevy caprice 305 v8...HELP!!!" Is the title

While the CCP is a possibility, I'd bet a lunch that there is a bigger problem at the carb. I have been into one or two Q-Jets and I have only seen a handful that did NOT have a leakage problem at the main well plugs. Whatever you do, DO NOT discard the carburetor in favor of an aftermarket replacement. Since you will likely have to perform some cleanup and adjustment of your almost 30-year-old Q-Jet you might as well do it right. The repair is relatively easy:

http://www.wwdsltd.com/files/Q-JetWellPlugID.jpg

Clean the area and apply a little fuel-resistant epoxy, and drive it another 25 years:

http://www.wwdsltd.com/files/Q-JetWellPlugSealed.jpg

When the bottom is sealed properly, flip it over, reassemble, and finish the adjustments.

If you have a second thought about discarding the card, please PM me and I'll pay for the shipping. They're worth more in bad condition than any four new Edelbrock replacement carbs.

Thanx. I was really considering a new carb but didn't want to spend 300+ for 1. And I check the control canister valve and I smelt gas and look like maybe a lil oil. Decided to just take it to a shop and get the major tune up and then go from there

the valves are NOT adjustable.

you could however change the proceedure to try and compensate for valve issues. this would be done with the engine running to try and work out a valve issue. this is as I mentioned not recommended and also not the proper way to set up the valve train with an engine overhaul.

this usually ends up with the cam being damaged .

I doubt this engine has any valve problems. most likely it is the cannister control valve. and with the high idle a bad electric choke coil. this would cause high idle and with this type setup a very common failure .I had to replace one with only 50,ooomi on it.

All SB Chevy engines (Gen 1 and Gen 2) have adjustable valves. The 305 is a Gen 1 engine. I don't know where you got the info that it wasn't.

The current engine is non adjustable. The 305 is not a current engine.

My personal thought, based purely on intuition, is that this vehicle has a faulty/maladjusted carb and a worn cam, possibly a stretched timing chain and possibly a failing sprocket (if it's aluminum with nylon teeth - not sure if they were still using these by 1984).