Quadrajet carb question

The 9 cap is available at your local GM dealer. Ask for AC Delco type RC32 part and a 10 cap is available at most autoparts store under a Stant part number , if they don’t have it, have them order it for you. The lower pressure rated caps are not carried by the store much but they are available. Wright One item that makes the radiator leak is using the wrong Pressure Cap. Should be 9 pounds no greater than 10 pounds. Therefore I use a 7 pound cap for many years. Also your coach is running much

How to rebuild a Rochester Quadrajet 4MV carburetor

I think what people forget is that some people want different things from a cam. I am willing to trade 50HP total for the ability to slip off the clutch slowly at rpm and take off and not stall. I know cliff is a fan of some other grinds that he has seen make “more power” and the has seen the stock manifold make “more power” than the performer even though Jim hand showed it made a tiny bit of difference for him.

The thing is, “more power” to you guys is like 10hp! As a pontiac HOBBYIST on a site about street performance, i can’t be bothered to chase down every last 5 hp at the cost of decent right of idle performance, and vacuum, and fuel economy.

Rochester Carbs Quadrajet parts page many hard to find parts Jets chokes pulloffs rods fuel fittings.

Distributor advance It doesn’t matter what kind of ignition you have, if the advance curve is not set properly it won’t make any power. The ignition is advanced so you reach peak cylinder pressure right after TDC top dead center. If the spark comes too soon the burning fuel will try to push the piston back down the cylinder before it reaches TDC, resulting in a loss of power and possible engine damage. If the spark is too late you will not reach full power and get poor gas mileage.

There are two major factors that effect how much advance is required, engine speed and load. You increase advance with rpm and decrease advance with engine load. You don’t need a distributor test stand to curve a distributor. All you need are some basic hand tools, a timing light, and a tach. The first thing you should do is find a shop manual for your particular car. Read about the advance mechanism and make yourself familiar with the different components. Before doing too much you should check the condition of your advance mechanism.

If your vacuum diaphragm is bad replace it.

Top 20 Carb Questions Answered

Theory Overlap is the portion of the engines rotation for which the exhaust valve is still open right at the end of the exhaust stroke, and the intake valve is also open to give a head start to the incoming charge. The exhaust gas is whistling out of the exhaust port at the same time the intake charge is starting to trickle past the intake valve. If you have more than about degrees of overlap, you’re looking at something more like a race cam than a street cam.

Lobe centre angle, on the other hand, is the number of degrees between the point where the intake valve is at maximum lift and the point where the exhaust valve is at maximum lift. This angle is commonly in the degree to degree range you mentioned, which is why I think you’re really interested in LCA, not overlap.

Authentically reproduced vacuum advance lines run from your distributor to your engine vacuum source to provide timing advance to your ignition are pre-bent to factory specifications and are available individually or in complete kits, which include the correct retaining clips and rubber hose portions for installation.

There are more vacuum ports on the Quadrajet then on the Edelbrock and I’m wondering if anyone knows where I should hook everything up. I put the brake booster on the back in the same place it was on the Quadrajet. There is another small vacuum port at a 45 degree angle that I hooked up the vacuum advance on the distributor to. The pcv valve went to the lower one on the front. Lastly I have one that is hooked up to my th trans that I put somewhere, can’t remember off the top of my head.

I guess I’m wondering if I installed the vacuum advance and tranny line in the correct locations. Sorry for no pictures and a bad description. I looked in my book and couldn’t find anything that looked like my quadrajet. Thanks in advance Click to expand Vac advance is the bottom port on the drivers side front of the carburetor, PCV is the large port on the rear.

Do you have emissions equipment on the truck, or is it stripped bare?

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Car Year, Make, Model: Tuning carb with a vacuum gauge Hook up your vacuum guage to the intake manifold port of the carb sucks at idle. Set you rpm about where you want it to be. Adjust your idle mixture screws to give you the highest manifold vacuum reading which should be the highest idle rpm reading with the throttle butterflies closed.

May 10,  · The problem arises when I hook up the vacuum advance. The advance canister is adjustable, but unless I adjust it to the point that it does not advance at all, it causes a misfire. When vacuum is applied manually with a hand pump, the advance plate moves and it holds vacuum so the diaphragm doesn’t appear to be leaking.

Mike Ervin To start this off, I just wanted to tell a little bit about the stock Q-jet that came on my truck C When the engine is cold, more fuel is needed for transition from idle to part-throttle. When the engine is warm, less fuel is required. Dual capacity pump solenoid plug on top right front of carb is activated by coolant temperature sensor sensor in thermostat housing. At degrees pump solenoid energizes, dual capacity pump valve opens and pump capacity reduces by about one-half. I had performed some of the mods in this article on my stock carb.

After it started leaking around the air horn where it had been over-tightened at the carb mounting bolts, I decided to replace it with an Edelbrock Q-jet. The stock Q-jet is an emissions carb as most Q-jets in the early to mid 80’s are. These carbs aren’t computer controlled as many people think. The only thing electrical about them is the dual capacity pump. The carb has to be plugged to the sensor in the thermostat housing in order to work right.


A minimum of 1. External rub rails will not be permitted. Threaded rods will not be permitted.

Vacuum secondaries typically only apply to Holley-style is a diaphragm with a spring inside that sits off to the side ofthe carburetor but is still part of the carburetor and.

Please keep an eye on the following areas during dis-assembly and rebuild. You can try the smaller shot and if that works well, use it. There are several different accelerator pump rod lengths used depending on the carb, if it’s the wrong length this can cause the pump to work poorly. If the springs are reversed and the return spring that should be under the pump assembly is used as the override spring on the shaft, and the override spring is used under the assembly, that can cause it to work poorly.

Sometimes the fuel filter spring gets mixed up with the accelerator pump springs as well. There’s a ball that acts as a check valve under a screw in the float bowl, driver side.

Vacuum Advance readings

How to Adjust Vacuum Advance Timing by Michelle Schaefer The correct adjustment of a vacuum advance unit is critical to ensure that an automobile engine runs at its peak performance. The vacuum advance mechanism allows the distributor to vary the spark timing to compensate for the load and speed requirements of the engine. During light loads on the engine, the cylinders burn leaner and require the spark to be initiated earlier in order to obtain optimum power.

Everything went well until I went to tried to hook up the vacuum advance. The port was threaded to metric and a barbed fitting was threaded in, there was no way the original fittings would fit, who in knew what metric was.

At my Bar drinking and wrenching in Lafayette Colorado Posts: Which quadrajet port for vacuum advance??????????????????? A ported vacuum source produces no vacuum signal at idle, but produces normal vacuum signal once the throttle blades are opened up just a tad. The ported vacuum source on the early Q-Jets is the port on the forward, driver’s side of the carb just above the idle mixture screw. All other ports on the Q-Jet are direct manifold vacuum. You had mentioned the “front left” port I assume you mean the port on the front passenger side left side looking at the front of the carb

Vacuum Lines Connection