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Post Info TOPIC: Rochester carb issues


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Rochester carb issues


I've got a '64 Parisienne Cutom Sport with a 283 2-speed, and I replaced the worn two barrel with a rebuilt Rochester four barrel on a cast iron intake.. The car runs terrible, bad idle, stalling, etc, and I can't seem to tune it in. I've replaced plugs, cap, rotor, and still no change. I've been told by numerous individuals to dump the Rochester and get a Holley or Edelbrock. A few friends have done this and the cars run great without any tuning. Which carb would be the better choice if I went this route.

Thx, Richard

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Guru

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I would go for the Holley as it is also a GM fitted option and presumeably maintainable! Tuning specs are in the GM manuals.

Pity I'm so far away as I have an original Dualjet in good condition that you can have!

My Rochester Monojet has been perfectly restored for R400 = $40 at the time!  Runs at 25 Mpg!

2009_0524Dual0002.JPG

-- Edited by Johann65 on Thursday 2nd of July 2009 11:52:02 AM

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Ah yes! I remember it well!!! (With Pictures)

  1. 1965 Malibu 4dr Sedan L6 (Original)
  2. 1975 Chevrolet Kommando 305 (Monaro Clone)
  3. 2000 Peugeot 406 2.0L
  4. 1996 VW Golf Chico


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Thx, that seems to be the common answer. Theres one for sale locally here that's the Rochester replacement.

Richard



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Have you checked for air leaks around the base. Have you adjusted the air idel mixture screws ? Do you have the correct base gasket ? I think there was something about the intakes with the hot slot on it you had to use the thin stainless insulater sheild .
 
I saw a white 64 conv. running down Day street the other day was that you ?




read this link to explain


http://forums.corvetteforum.com/c1-and-c2-corvettes/1978466-q-jet-carb-base-gasket-tech-info-the-hot-slot-manifold-problem.html

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No, not me. Mine is red in color. I've set the idle mixture screws but don't have the ss shield. Could be a leak there. Thx for the info, will check on that.

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I would keep working with the Rochester to get the bugs outs. Holley or Edelbrock(Carter) are no better or trouble free.

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Poncho Master!

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eeluddy wrote:

I would keep working with the Rochester to get the bugs outs. Holley or Edelbrock(Carter) are no better or trouble free.



I agree.  Who rebuilt the Rochester?  Any chance of getting them to have a look at it?  A vacuum leak anywhere can kill you so make sure everything is nice and tight.  Your problems sound like they could be float related, does the car seem like it could be starved for gas?

 



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Hillar

1970 LS4 (eventually an LS5) Laurentian 2dr hdtp
-and a bunch of other muscle cars...


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I'd fix the q-j. Does the intake have an internal balancing tube? Or do you have an exhaust tube? Could be a pluged port on the Intake b-t, causing carb icing/starving?

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Agree. Fix the Q-Jet if at all possible. But if not, go with the Edelbrock.

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what is that rochester off of?   It looks like a quadrajet from the late 70's - or 80's.  Was it rebuilt?   The offset air cleaner stud and fuel inlet are my clues that it's for a much later engine.

Carbs are tricky items, and to be honest it looks like you've taken something from a later model car, and you're expecting it to work on something it wasn't designed to work on.  There are numerous variables in the carbs, and any one of them can be the culprit.

- we had a guy in our local club that grabbed a quadrajet off a car in the scrap yard, then had someone rebuild it to the specs of a particular carb for his 455 SD.  They said "no problem".  It never worked right, and he now badmouths quadrajets.  I double checked this concept with John Sawruck at a POCI convention.  He said this fellow was sold a bill of goods, you have to start off with the right carb as there are numerous variables, and the carb body is built a particular way.  

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nothing wrong with a properly rebuilt and setup Q jet.

 



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I just had the same problem with my '64 283. Rebuilt the Rochester, but it still ran poorly. Changed the coil ($29 at AutoValue), now runs perfect.

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Poncho Master!

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I agree, Qjets are probably the most reliable carb ever. Just need to get a good rebuild on it by a good ol GM tuneup guy & you'll be fine. :If you change your mind though, I have a square bore Edelbrock(carter) with an electric choke almost new. They are probably the simplist carb out there and the 600cfm would be just right on your smalllblock.

-- Edited by Elroy on Friday 3rd of July 2009 10:52:57 PM

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Canadian Poncho Superstar!

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Fix the rochester. i have a rochester square bore 4GC on my 283. and all i can say is sweet carb.

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sTevE

55 GMC, 70 Pontiac 2+2 rag



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Thanks to everyone for your help and input. I will keep the Roch and get it rebullt properly. Seems to have a bad vacuum leak that has gotten real bad since last time. It is a late 60's model but I'm guessing the rebuild was more amateur than I expected. Got it cheap so I can't really complain.

Thx again.

Richard

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I know I'm months too late with my input but I bought a rebuilt 2 barrel and had the same problems - until an experienced guy found a hole behind the carb (right low down where it was difficult to see) that hadn't been plugged in the rebuild. It runs fine now, but - just like the old one - if I leave it more than a few days I have spray fuel on the air cleaner to start it.

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64PARCONUK wrote:

I know I'm months too late with my input but I bought a rebuilt 2 barrel and had the same problems - until an experienced guy found a hole behind the carb (right low down where it was difficult to see) that hadn't been plugged in the rebuild. It runs fine now, but - just like the old one - if I leave it more than a few days I have spray fuel on the air cleaner to start it.


That's a fuel pump problem. It's leaking back instead of maintaining minimum pressure, usually around 3-5 psi

 



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eeluddy wrote:

 

64PARCONUK wrote:

I know I'm months too late with my input but I bought a rebuilt 2 barrel and had the same problems - until an experienced guy found a hole behind the carb (right low down where it was difficult to see) that hadn't been plugged in the rebuild. It runs fine now, but - just like the old one - if I leave it more than a few days I have spray fuel on the air cleaner to start it.


That's a fuel pump problem. It's leaking back instead of maintaining minimum pressure, usually around 3-5 psi

 

 



I would second that. I've had the same problem, and a fuel pump should cure it.

 



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1966 Strato Chief 2 door, 427 4 speed, 44,000 original miles 



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A genuine GM replacement pump was fitted at the same time as the carb. The problem used to annoy me but I've got used to it now. I just feel lucky to have one of the handful of RHD 64s in the UK.

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what year intake? 1967 has exhuast risers into the carb that have to be plugged, or you get a vacuum leak . something to check..

later...rog

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Hmm, that is interesting.

The other possibility is that the carb bowl drains out when it is parked. However, that should also cause flooding if you shut it off and try to restart it an hour or two later, if the bowl has drained into the intake. Do you have any trouble with a restart after it has been parked for an hour or two?

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Thanks all for your distant diagnosis.   Carl, my first thought was that the float chamber was somehow draining but I (touch wood) never have any trouble starting hot or cold winter or summer - except if I leave her for more than about 3 days or so when I need to "prime" through the air cleaner.   I figure perhaps the chamber is draining somehow but so slowly it causes no other problem.    Strange thing is it's exactly the same symptom with rebuilt carb and new pump as it was with the 45 year old original parts.  



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Poncho Master!

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just the float being out a very tiny little bit for me was the problem i had with my two barrel on a 283. I had the same symptoms and even after the rebuild same thing. I took it apart 4 times and then realized the float was off a bit, fixed it and runs great. Same thing when i had a 4 barrel on my rochester, it was just in need of a rebuild and i had a guy calibrate it afterwards and never had a problem. I find the roch. easy to use and im a dumbass!!!LOL

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That's interesting.   I wondered if that was the problem after fitment back in the summer and adjusted the float on the rebuilt carb to hopefully fill the chamber a little more.   My amateur effort didn't make any difference    Is there a more exact way to adjust the float or is this something only an expert could do?

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In a rebuild kit you get a carboard caliper to use but any measuring tool should do. You measure from the float seam line with gasket in place. Looks like float line should be 3/4 in. from closed position (upside down with float clossing the neadle and seat) and float drop should be 1-3/4 in. (right side up).




img175.jpg

Chevy specs same as Canadian pontiac.

img176.jpg



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