Rochester Quadrajet

[Russ33]

Hi Folks,
Love the forum. I have run into a snag. I have a 1972 Chevy pickup 4x4 3/4 ton. The drive train is all original. My Rochester Quadrajet carb needs a new power piston assembly. I can't find one anywhere. Anyone have any idea's? I would like to keep the original carb on it.
Thanks,
Russ

[brown7373]

www.cliffshighperformance.com sells the best kits for all Quadrajet carbs, and he will have whatever parts you need. Kits are all with rubber parts impervious to ethanol and better gaskets to insulate from heat.

[geezer#99]

Try here instead.
http://quadrajetparts.com/rochester-...62e0cf2f119b98

[Russ33]

Thanks guys. I had already checked those sites. They have everything but the power piston assembly. I think I may just have to buy a parts one from ebay. I read somewhere that the size is different on 1973 and later models So I will have to find a early one.
Thanks again,
Russ

[midnight rambler]

Get ahold of rick walker in el cajon calif. He might have what your looking for

[brown7373]

Did you call and talk to Cliff?

[Russ33]

I have not called I will do that tomorrow. Thank you all for your help. I'll post how it turns out.
Russ

[Wrenchbender Ret]

I have some canabilized Q-jets. If you post a photo & dementions I can match it up. Ther are some variations in them.

[brown7373]

What is wrong with your existing power piston that requires replacing it?

[cherokeejohn]

I recommend replacing it,I replaced mine, I have a 72 1/2 ton that sat for 21 years. When I got started working on it, the first thing I did was replace the original Q-jet. I also (at that time) wanted to keep it close to original as possible. I got a total rebuilt carb from Gaurenteed Carburator in Florida.The came up when I Google searched "rebuilt Quadrajet Carburators. I think it was around $289.00. You have to send them your core (they provide a shipping return label) I am satisfied with it, It is as clean as a brand new one in and out, have had no problems at all out of it, And it was a bolt on and go (pre-adjusted) I shopped around for a couple weeks and in the end their price was around average, maybe $20 cheaper than competitors. Mine is a Remote Choke model , but they went off the VIN# and it turned out to be the original carb. If I had to do it again tho, I would have went with a Edelbrock 1406 for the reason that I uprated to a HEI Distributor that required a Ported Vacume- (Increases with the RPMs). the Quadrajet only has a Manifold Vacume-(full time). So I just have it capped off now and run with no vacume advace, until I can afford a Edelbrock. Good Luck, and I hope this helped

[geezer#99]

Originally Posted by cherokeejohn

I would have went with a Edelbrock 1406 for the reason that I uprated to a HEI Distributor that required a Ported Vacume- (Increases with the RPMs). the Quadrajet only has a Manifold Vacume-(full time). So I just have it capped off now and run with no vacume advace, until I can afford a Edelbrock. Good Luck, and I hope this helped

I find that weird that your 72 carb doesn't have a ported source.
The one on my old 70 did.
You got a pic of your carb John?

[brown7373]

72 had ported vacuum advance, but it did run through and was over-ridden by the Transmission Controlled Spark which only allowed vacuum advance in high gear unless the engine was overheating. Most people disable the TCS years ago and simply hook the vacuum advance directly to the port on the front drivers side of the carb, above the throttle plates, which makes it ported vacuum. See page 6T-12 of the 1972 Service Manual.

Also, vacuum advance, whether ported or manifold is almost identical once off idle. The argument over which is better has been raging for years. But to not run vacuum advance of one kind or another on a street driven vehicle sacrifices drivability and mpg. vacuum advance lets your engine run as far advanced as it can (based on how you have it set up) at light engine load which helps cooling and increases mpg.

[Russ33]

As always there is a wealth of information here. The truck sat for a long time with the hood off and the original power assembly piston is rusted and can't be used,same with the needles but those can be easily found. I need to post some pictures of the truck.
Thanks again,Russ

[frank69]

Post a pic and if wrenchbender does not have one let me know; if I have one it's yours Frank

[ChevLoRay]

Back in 2000, I bought an Edelbrock Q-Jet to replace the Edelbrock AFB-style carb that was on my small block. Since that time, Edelbrock has quit offering them. But, my engine ran much better, and leaner, than it did with the one that was on it...which replace the original Q-Jet.

Within the past couple of months, one of the Power Block programs had a lead-in that made me believe they were going to go thru a Q-Jet. However, they simply removed the Q-Jet and replaced it with the Edelbrock AFB-style.

Nothing about what they lead me to think I was going to see.

[WIDESIDE72]

Correct me if i am wrong but iirc the average carb kit includes new rubber diaphragm for the power piston. Are you needing the actual pin that the diaphragm attaches to? If it is rusted through, i would think the whole carb would be in pretty bad shape. (?)

[brown7373]

There is no rubber on a power piston. It is made of brass and holds the primary rods. The Accelerator Pump has a rubber cup, and it is critically important that it be made of a rubber compound that is impervious to alcohol. Many parts store carb kits will fail in short order, so buy a kit from a known good shop like Cliff. He is not the only place, but personal experience says his parts WORK! I had parts store pump cup fail in less than one day. It swelled, stuck in the bore and pulled right off the shaft of the accelerator pump.

[WIDESIDE72]

I got the accelerator pump and power piston mixed up. Still confused as to how it could get damaged.

[68Gold/white]

Originally Posted by brown7373

Did you call and talk to Cliff?

You need to send Cliff an email. He is approx one year behind in his carb building, but can accomodate folks quickly w/ parts. He has NO time to be blabbing on the phone all day. You need to give him your carb #, also...

[Russ33]

I did send Cliff an email. Just have to wait and see what he says.