Carburetor Replacement

[ChrisM]

Hello all,
I have a 1973 delta 88 with the stock 350 and 2 barrel rochester carb. I am having acceleration problems. I had my mechanic check out the accelerator pump, etc, but my mechanic has said that there is something internally wrong with the "lower" portion of the carb so he is suggesting a replacement. He wants to put in a aftermarket(holley, edelbrock, etc) with a new manifold, etc. I don't really have the money for that right now, so does anyone know if this carb from Autozone will bolt right up to my existing manifold. http://www.autozone.com/R,3145039/ve...ductDetail.htm

I know that you all will probably want to know what numbers are stamped on my intake and carb so that you can answer the question, but I really don't know where to look. If you need this info, please let me know where to look for it.

I'm sure I'm leaving something out, so please ask any questions you have...

Thank you all,
Chris

[dan2286]

I would be getting a different mechanic.

What exactly is happening with the car? What kind of acceleration problems? It might come down to not even being your carb.

[Olds64]

I would also get a different mechanic. He just wants to replace parts to diagnose problems. That is the skill level of a high school kid that works at Auto Zone.

If you really like your mechanic and want to give him your business then ask him if he can rebuild your carburetor. A rebuild kit costs about $15 and a good technician can rebuild a carburetor in about 2 hours.

You probably don't need a new carburetor and you almost definitely don't need an aftermarket intake manifold, especially if you haven't done any other performance mods to your engine.

[ChrisM]

Dan2286,
My acceleration problems are that if I just step on the gas pretty hard, then the car loses all power and if I floor it, the car could actually stall. It is more noticeable when starting from a stop, but I think it is there a little at higher speeds.
I looked into the carb to see if the accelerator pump was really working and it was squirting gas. My concern though is that it was really just squirting a stream of gas in to both barrels of the carb. I was kind of expecting a mist or something a little more spray like. Am I wrong? Is the accelerator pump maybe sending too much gas and flooding the carb with an unignitable amount of gas when I step on the pedal. This is going way back to high school classes, but isn't a mist of gas particles more easily ignited than a puddle?

Olds64,
I appreciate your comment. In fact, I am thinking of just digging into the carb myself. I really don't know much about them, but I am tired of not understanding why problems aren't fixed when I get my car back from a mechanic. It's lond overdue, but I think I need to do this all myself. I am getting in over my head?

Luckily, I found a rochester manual on the Old Car Manual website, so I will have some literature in front of me to guide me in my journey.

Chris

[Oldsguy]

I know you have heard that it is difficult to troubleshoot problems on the internet but I would ask you to check the vacuum advance. Yes, the accelerator pump squirts two little streams of fuel that really don't look like a mist at all, that is normal. Back to the advance, if you have a timing light you should see an initial increase in timing at the first instance of acceleration. The timing mark should move counter-clockwise a couple of inches from somewhere around two o-clock position to somewhere around noon or 11 o-clock position. This is with a "blip" on the throttle, then it should settle back down. While you are at it, a check of initial timing, and dwell (if applicable) would not hurt. Not sure if this is going to solve your troubles but I hope so.

[Olds64]

If you are good with a wrench and can followin instructions you should be able to rebuild a Quadrajet yourself. I suggest using a workspace where you can stand or sit with plenty of light that is well ventilated. Make sure you have an entire Saturday when you start rebuilding the carburetor. It could take you up to 5 or 6 hours to rebuild it since it is your first time. When you rebuild a carburetor all you have to do is folllow the exploded diagram that is in the rebuild kit. The book you found will definitely help.

[teacherofphysics]

Hello all, I have the EXACT problem with my '68 Delmont 88's acceleration described by Chris M. Whenever I push the accelerator, hoping for the 455 to really move the car forward, the engine "bogs" down. I rebuilt the carb (Roch QJet) this past summer hoping it would help, and perhaps solve the problem. When I did bolt on the rebuilt carb, I did get some improvement, but the 455 still hesitates on acceleration. A friend of mine, who's good with a wrench, suggested I focus on the vacuum advance - just as suggested by "Oldsguy". My question is, if the timing light shows no counter-clockwise movement (a couple of inches from somewhere around two o-clock position to somewhere around noon or 11 o-clock position), what do I do? I have not measured the timing yet - the question is just hypothetical. And, sorry for my ignorance, what should I be looking for with the dwell meter? I have a dwell meter, but have no idea how to hook it and what it's measuring and how I know if the measurement is good or bad??

Any comments to this would be appreciated...


And, back to the carb rebuild, when I unbolted the Qjet from the manifold, one of the screws that faced from the bottom up and into the base of the carb must have loosened over the years. So... as I lifted the carb off the manifold, this screw fell right into the intake ports of the manifold. Luckily, (a) I heard if fall, and (b), it landed in a spot that I could reach with a needle nose pliers. Be careful when removing the carb!!

[J-(Chicago)]

Check the float height.

[Olds64]

You might also need to adjust your secondary air valves. If these are too tight you won't get good acceleration the engine will just fall on its face or act constipated when accelerating.

[Oldsguy]

Teacher, if you have not indication of timing advance you should follow the vacuum line from the vacuum advance cannister on the carburetor back to the manifold. Inspect it well and replace it if you find damage. If you have a vacuum meter you could attach it to the hose in the stead of the cannister and see if you get a change in the reading from idle which should be around 15 inches. Dwell is a measurement in degrees of the distributor rotation that the points are closed. This affects the spark which affects the combustion. Too long or too short and the combustion will not be optimal. Oldsmobiles vary from about 28 to 34 degrees depending upon the engine. This is not measured for HEI distributors, only points style distributors.