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printjunky
04-10-2011, 11:28 PM
I have a freshly rebuilt Rochester coming in the mail tomorrow - see if it helps any with my carbon-fouling problem - but it has a 58 jet in it. Terri Anne recommends a 50ish, I believe. Is a 58 too far off? If I need to replace it, where do I get one jet? Except for some references to Cali carb specialists, I don't get much insight googling it.

yorker
04-11-2011, 06:37 AM
http://www.jalopyjournal.com/forum/showthread.php?t=85426

http://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=698805

Also, when I last knew British Pacific sold Rochester jets. Last time I bought one I think I bought a 48 from them.
www.britishpacific.com

TeriAnn
04-11-2011, 09:43 AM
I have a freshly rebuilt Rochester coming in the mail tomorrow - see if it helps any with my carbon-fouling problem - but it has a 58 jet in it. Terri Anne recommends a 50ish, I believe. Is a 58 too far off? If I need to replace it, where do I get one jet? Except for some references to Cali carb specialists, I don't get much insight googling it.

I wrote that back in the days when petrol was 100% petrol and not 10% ethanol. These days you might start at around a 52 jet. I lived at sea level when I did my jetting. My suggested sizes should be close up to around 2500ish feet but it needs to be leaned out with increased altitude (less air to mix in with the fuel). This also assumes you have the smallest venturi Rochester. Larger venturis need a little more jet.

Always have the engine hooked up to an O2 sensor after you jet it to see how close you got with a new jet. Which ever venturi Rochester you have and whatever your altitude it will help you dial in the best jetting for your particular truck.

My carb also came with a 58 jet. It ran but flooded very easily, sometimes all it seemed to take was for me to just glance at the choke knob. Someone mentioned a 48 jet so I tried it. My engine ran so lean it would sputter at a higher RPM cruise. 50 or 52 worked for my truck living at sea level. Folks on the high plains seem to do well with 48 jets. It is a good idea to check the air to fuel ratio just to make sure you are not exhausting out expensive unburned fuel or likely to burn an exhaust valve.

The Rochester one barrel takes the same jet as the later Rochester two barrel so usually comes packed in pairs. Most carb shops should have a selection of Rochester jets for the Chevy sixes & 2 barrel V8s. Try searching for carb rebuilding shops.

By the way, my first name is Teriann, all one word. Middle name Jennifer not Anne.

east high
04-11-2011, 12:26 PM
I'm at sea level and I just swapped out my 50 for a 52 trying to tracking down the cause of my white plugs. I think a 58 might be too rich. I like TeriAnn's idea of using an o2 sensor for this sort of thing tho.

singingcamel
04-11-2011, 12:58 PM
I'm at sea level and I just swapped out my 50 for a 52 trying to tracking down the cause of my white plugs. I think a 58 might be too rich. I like TeriAnn's idea of using an o2 sensor for this sort of thing tho.
48 - 52 , you may need to sort it out...I m in Iowa as well..
www.singingcamel.com (http://www.singingcamel.com)

printjunky
04-11-2011, 03:26 PM
Marc, I'm looking forward to getting the Rover extended-road-trip ready and stopping by. I have relatives in the Twin Cities, and you're right on the way!

I'm at about 500 feet, right on the banks of the Mississippi. I called around a little today looking for someone that stocks jets, and so far have only been mildly mocked for looking for something "from the past." (!!) I do have a guy trying to find a #52 jet for me, though. (And yup, it's the same guy that mocked me, and whose workplace ADVERTISES (in the yellow pages) that they specialize in carburetors!)

According to the Rochester's PO, it came off of a 216. It doesn't appear to have a tag (hasn't arrived yet), so obviously I can't be 100% sure (I might check casting numbers to see if I can narrow the likelihood).

Also, short of welding in a bung and buying sensor/gauge (tempting since it is such a great diagnostic tool) how do I get an O2 check this far from the more emissions-conscious coastal regions? The few people I've talked to around here says that if they have to check the mixture they just dump the OBD data and use that for analysis. Needless to say the computer in my Rover isn't quite that advanced.

And Teriann, sorry about the name. It crossed my mind to go back to your site and check, but I looked and thought "that looks right ..." and just kept going. Saved myself .0975 seconds, there (lame). But I got it now!

printjunky
04-11-2011, 03:34 PM
Also, not an excuse (I still got it WAY wrong), but a possible explanation. I might have been thrown off by the CamelCaps in your signature, Terriann.

yorker
04-11-2011, 04:01 PM
http://forums.thecarlounge.com/showthread.php?1034920-A-DIY-exhaust-analyzer-from-a-oxygen-sensor

Sputnicker
04-12-2011, 12:51 AM
Since some of our cars (and some of us) predate oxygen sensors and exhaust gas analyzers, there are more traditional (and admittedly inferior) means of getting the mixture right, which might come in handy for those who might not have ready access to a sensor - like when you are out in the sticks or have just gained or lost a lot of altitude. It also works for those who are too cheap or lazy to go the sensor route.

Basically you drive the car and get it warm and off the choke; see how well it runs; see if it belches black smoke and then verify the mixture by removing and inspecting the spark plugs. It helps to start with a fresh set of plugs. And don't let the engine idle before cutting off the ignition - the idle circuit has its own mixture adjustment independent of the main jet. You want to see what color the deposits on the plugs were when it was at speed, under load and employing the main jet.

If it belches black smoke and/or the plugs are black and fuzzy, you are too rich. If it ran hot, was anemic, and/or there is no color (after a few miles), you are probably too lean. Goldilocks wants good performance, normal temperatures, no black smoke and plugs in the tan to light brown range.

There is a chance you can do some damage by running too lean, so err on the rich side starting out and work your way to leaner.

Using this archaic, but effective method will make you very proficient at removing and reinstalling very hot spark plugs quickly by the side of the road. It will also give you a better appreciation for electronic fuel injection.

printjunky
04-12-2011, 02:13 AM
HA! Nice post Sputnicker. That is certainly the best method for vintage vehicles. At the moment, one of the things I've been struggling with (and the reason I'm about to try the Rochester) is I am pulling and cleaning the soot off of my plugs about every 5 hours of runtime (including in the dark in mid-winter - so yes, I AM good at it!). And so I have plenty of experience with the "archaic" method. (Also, I know this could be a valvetrain issue, instead of a carb issue, but even with the rebuilt, lapped and quintuple-checked Zenith - float, jets, etc - I still have a little more suspicion about the carb. If I can track down the proper jet and figure out how the linkages mate up, I'll know this weekend.

printjunky
04-12-2011, 02:19 AM
Any advice on fitting the Rochester, once I find the jet? Terriann, your site says the linkage will need to be "fiddled with." Any more specific tips or tricks? You also recommend a K&N or similar for on-road. Do you know which model(s) fit on the horn?

TeriAnn
04-13-2011, 10:20 AM
Any advice on fitting the Rochester, once I find the jet? Terriann, your site says the linkage will need to be "fiddled with." Any more specific tips or tricks?

Sorry, I started my web site in 1998 but did the Rochester conversion around 1979 or 1980. So I never documented what I did. I went from a Solex to Rochester and as I remember all I did was just adjust a rod length or two (linkage for manual throttle). I know the zenith linkage takes a lot of fiddling. And of course you eliminate the zenith adapter that rotates the carb 90 degrees. It was so long ago I just can't remember the exact process.

Now if you want to set up Mustang EFI throttle linkage in a Series truck using a cable and 200tdi throttle pedal, I'm your girl.


You also recommend a K&N or similar for on-road. Do you know which model(s) fit on the horn?

Sorry again. British Pacific sells a K&N that fits the metal elbow for the stock air cleaner. I just used that as a no brainier solution. I never copied down the part number.

TedW
04-13-2011, 03:53 PM
Sorry again. British Pacific sells a K&N that fits the metal elbow for the stock air cleaner. I just used that as a no brainier solution. I never copied down the part number.

K&N #RU-2650

siiirhd88
04-13-2011, 08:30 PM
Most of the Rochester carbs have linkage that needs to push "up" to open the throttle, as does a Solex. The Zenith and Weber linkage needs to pull "down" to open the throttle. Since the pedal moves the under bonnet linkage rearward as the pedal is depressed, there are different bell crank assemblies that bolt onto the bulkhead support to change the direction of the carb linkage.

As TA stated, the 90 degree adapter that is fitted between the intake manifold and a Zenith or Weber carb needs to be removed. The Rochester might fit directly onto the intake manifold studs, but I have had to oblong the carb holes slightly to fit the studs. I also needed to use the phenolic spacer under the carb due to the height of the studs.

Some of the 90 degree adapters have a fitting for a vacuum hose for a PCV valve or plumbing. The Rochester carbs usually won't have a fitting or bung to fit one. You might have to add a fitting to the power brake booster connection on the intake, or use a T in the booster line for the PCV.

The Rochester on my 109 has a 58 jet, and the plugs tend to be a nice brown color, but I think my carb is a bit too large. 13 mpg is a good average.

If you are a creative bodger you might be able to swap around the linkage bits on the carb since pushing "up" could be pulling "down" ......

There are several different configurations and sizes of the carb to air cleaner hose adapters and rubber connector. My old Weber carb had a removeable ring that increased the diameter of the carb where the adapter hose connected, that was the exact size of the Rochester.

The Rochester is taller than a Zenith, Weber or Solex. I had to shorten the rubber adapter connector and trim the base of the air cleaner hose adapter to prevent the adapter from rubbing on the underside of the bonnet.

I think I have another Rochester that pulls "down" to open the throttle, and it might also have a smaller venturi. While it should fit and function on a 90 degree intake adapter, the bonnet won't close.... I could always add a really nifty hood scoop or more modern 'power bulge', or maybe plumb the carb directly to a snorkel.....:)

Bob

tvharwood
04-15-2011, 11:06 AM
This guy has them pretty cheap.

Ted

http://cgi.ebay.com/ebaymotors/Pair-60-9-Corvair-Rochester-H-and-HV-Carb-051-Jets-/290554187227?pt=Vintage_Car_Truck_Parts_Accessorie s&hash=item43a6610ddb