Gain extra benefits by becoming a Supporting Member Click here find out how!
Silver
Gold ***Platinum***
deek01BigDogSS (6)jk56chevy (11)WarrenL (2)Jens (10)
edad2000Custom_Deluxe_20VetteGyrl (2)JohnB (2)
speedygman (7)rickityfiftyMafo971Clifford Lao502drfleetline
Jud Leowish Non-synchronizedWGS53MobyVandurahereford
gary635g (6)
johnhem (10)
Greyimpala (5)
emil
axmaker (3)
socalarch (3)
usmile4 (8)
Classic Performance Products Classic Parts
Ciadella Interiors American Auto Wire Art Morrison.com
Exile® Battery Keeper™ 6/12 volt charger w/ LED battery monitor
Low priced Genuine GM Auto PartsEcklers AutoMotive
Hellwig Products IncPerformance Rod & Custom
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy

Recent Hot Topics
Current Quote
"Another reason of why this site and the people that participate in it are great. I have been in need of a good running engine for the fleetline and thanks to Patgizz I now have one. He was kind enough to give a nice 250 I6 motor. Thanks again Pat!!!"
~ Member
Recent Topics
Join the Community today







Username Post: Carburator Adjustment Issue/ Rochester 2 Barrel        (Topic#59652)
rox56 
Member
Posts: 8

Reg: 01-25-04
03-07-04 05:19 PM - Post#405453    

Here is what happened: I ran down the interstate a a pace to keep from getting run over and when I stopped for the exit turn and hit the accelarator the engine died. Got it started OK and parked for a while. Later I ran back up the interstate headed for home and was in the turn lane for the entrance to home and the engine died when I hit the accelerator. Started/hit the accelerator/quit several times, and finally pushed my sweet 56 into the drive. Got it started and with a very gentle press on the accelerator was able to get it into my garage.
What I think and Did: It seemed like the carb was loading up and killing the engine. I had to take the oil bath air filter off of the carb sometime ago because the bridge on top of the carb that holds the allthreads screw for the breather had cracked and broke. I put a small NAPA air filter on the carb and it got me through a 1200 mile trip to my winter home. When I took the little air filter off the carb and went for a test run, the carb worked fine, and did not stall the engine. When I put the air filter back on the carb, the problem returned. I leaned out the carb jet adjusting screws by one turn and it seemed to help. The engine will now stall when I hit the accelerator real hard, but does OK if I go easy on the start up.
My Conclusion: I think the carb is air starved because the little air filter is beginning to foul. The problem is most severe when the engine is hot, or sitting at idle at a stoplight. I want to keep the stock 2 barrel on this 265 engine.

Any Suggestions!!!!!

Rox 56

 
This Forum is Sponsored by

bobsclassicchevy.com
Coley 
My Birthday Week
Posts: 3973

Age: 72
Loc: Milledgeville, IL. 61051
Reg: 11-23-00
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-07-04 07:20 PM - Post#405454    
    In response to rox56

Hi, it sounds to me more like your accelerator pump is shot. With the engine warm and you hit the gas and it kills sounds like no pump action. With the engine off look down the carb and see if you get 2 small shots of gas when you open the throttle. They should be strong shots not just a couple dribbles....adjusting the idle screws won't much affect part throttle operation.....
Any man that thinks he is too old to learn new things, probably always was....


 
Anonymous 

Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-08-04 02:07 AM - Post#405455    
    In response to rox56

Ditto on Coley's post.

Time for a rebuild.

 
rox56 
Member
Posts: 8

Reg: 01-25-04
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-08-04 01:35 PM - Post#405456    
    In response to Coley

Thanks for the reply Coley and Bowtieollie. I took the air filter off and looked to see if there were two strong squirts of fuel when I hit the accelerator, and it sure looks like the pump is working pretty well because it delivered a couple of healthy shots of fuel. This carb was rebuilt a couple of years and about 1500 miles ago. I ran a test run again with the air filter off the carb and the engine did not stall when I hit the accelerator. I am going to get a bigger/better air filter and try it on a couple of short runs to see if that helps the problem. I would like to get it figured out before we go on a 400 mile trip in a couple of weeks.

Thanks again for the suggestions.

Rox 56

 
Ronnie44 
Senior Member
Posts: 9041
Ronnie44
Loc: Tampa Bay, Florida
Reg: 12-23-03
Re: Carburator Adjustment Issue/ Rochester 2 Barr
03-08-04 02:15 PM - Post#405457    
    In response to rox56

Try hooking up a vacuum guage to the engine. Check your vacuum with and without the air cleaner. It shouldn't change, unless there is an excessive restriction. You may have an intake leak at the base of the carb, or at the intake manifold itself, in which case the vacuum reading will either fluctuate, or be low. Intake leaks can vary depending on the heat of the engine. They usually get worse as the engine warms up. You should have a nice steady vacuum reading of around 18. While you are doing this, you can adjust your idle mixture for maximum vacuum. Hope you find your problem.
In memory of George K Fullam(Goodwrench) Died 31 Mar 2005

To view my '57 Bel Air, and my previous '55 & '56 hardtops and '56 Corvette: Click Here


 
Robert_May 
Old as Dirt Member
Posts: 6939

Loc: San Marcos, CA USA
Reg: 01-03-02
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-08-04 04:52 PM - Post#405458    
    In response to rox56

That you had to lean out the idle jets indicates that the filter is getting clogged.
What is probably happening is that when you get on it, the additional vacuum at the top of the carb is sucking fuel into the main circuits and dropping it into the engine, making it run very rich.
Robert May Fat? Eat less and you will get thinner!


 
brad_bb 
Valued Contributor
Posts: 4255
brad_bb
Loc: Joliet, IL.
Reg: 07-13-01
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-08-04 05:37 PM - Post#405459    
    In response to rox56

Since your accelerator pump is working fine, I would suspect two things. Vaccuum leak is the first suspect. It could be coming from any of the gaskets or a crack. The second suspect is a sticking needle/dirt getting lodged where it shouldn't. A rebuild is in order and it is very easy on this carb. I would also replace the broken upper air horn(upper carb body). After you're confident with the rebuild, It's time to understand proper adjustment of the Rochester 2gc. Start with a base setting for the idle mixture screws (a think it's 2.5 turns out if memory serves). Then check the timing- 4 degrees BTDC. Then connect a vacuum gage- I remove the plug from the back of the carb base and install a vacuum fitting. Also connect a tachometer -I use a Sun dwell/tachometer. You can buy these sun tune up tools used on ebay. Now adjust the idle speed screw, located on the linkage on the side to about 500 RPM. There are three different RPM settings listed depending on whether you have a PG, manual trans or depending on which listing you are looking at. I've seen 425, 475 and 500. I found that on my PG car a setting at 500 was preferred. Once you have your idle RPM on the tach, start adjusting your idle mixture screws one at a time until you get maximum RPM and maximum vacuum. There is one point were you will maximize both RPM and vacuum. Note: Your vacuum will be somewhere between 11 and 15 mmHG(millimeters of Mercury). After acheiving that with both screws, check to see what your tach RPM is. If it is no longer on your original setting, start over by resetting your idle speed screw on the linkage. Then go though the same adjustment procedure on the idle mixture screws. It should only take two rounds of this to get it finalized(maybe three). Now your carb is properly adjusted.
A couple other things I would do before the carb procedure -fully check out your distributor. Especially check for bushing wear which can cause erratic timing issues. Also verify (on a distributor machine) that the centrifugal and vacuum advance are working and in spec.
Do all this and your Rochester 2BBL should be as reliable as can be.
If someone else can design it, I sure as heck can figure out how to fix it!


 
rox56 
Member
Posts: 8

Reg: 01-25-04
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-09-04 03:21 AM - Post#405460    
    In response to brad_bb

Thanks Ronnie, Robert, and Brad for the additional insight on my ailing carb. I especially appreciate the detailed procedure for adjustment. I will be checking for the leaks and possible distributor problem. I may have to find a local carb shop to help with the tune up tools. Since I am a Snowbird, I never seem to be able to drag enough tools along to fix every problem. I sure do love cruising in the sunshine of southwest Florida.

Rox 56

 
57_sedan_delivery 
Old as Dirt Member
Posts: 6720

Loc: Hog Valley, Fla.
Reg: 02-19-01
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-09-04 03:31 AM - Post#405461    
    In response to rox56

Are you in Fla. now and if so where? A thought that came to mind is I once had the vacuum port somehow go bad on a 2-bbl carb as I was driving it, wouldn'gt pull away from a light hardly at all. Took a long time to find that one at night in an old garage that was ready to close.
Mike W.

Founding father Desert Classic Chevys in Phoenix, Az.

1957 sedan delivery 454 TH400
1956 windowed sedan delivery US Dept of Ag car
1956 Chevy 3100 US Navy pickup
1959 rare GMC 100 fleet option 100 pickup


 
brad_bb 
Valued Contributor
Posts: 4255
brad_bb
Loc: Joliet, IL.
Reg: 07-13-01
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-09-04 05:37 AM - Post#405462    
    In response to rox56

The tune up tools are easily purchased on Ebay. Just do a search in ebay motors>tools and search for "SUN" or go to sears as they carry them. Sears always carried them and now seem to have the same ones only with a different name. I prefer the original sun equipment from the 80's that i can purchase on ebay -Chrome timing light, remote starter, dwell/tachometer, and vacuum gage. There is a full kit that Sun used to sell with all of these items in a red case with tune up instruction manual that you sometimes see go on ebay for about $120-$150. Definitely worth the money. I strongly recommend that you buy or borrow these tools and do the procedure yourself(including carb rebuild). You will learn a lot and be very confident in the reliablity of your vehicle, plus you will be very good at diagnosing problems in the future with other vehicles.
If someone else can design it, I sure as heck can figure out how to fix it!


 
carbking 
Senior Member
Posts: 1210
carbking
Loc: Missouri
Reg: 06-14-03
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-09-04 01:26 PM - Post#405463    
    In response to rox56

While I would certainly agree that the carburetor should be adjusted for optimal running; your own tests indicate looking at the air cleaner rather than rebuilding the carb.

Start the car, and allow the engine to obtain normal operating temperature. Stop the engine, remove the air cleaner, hook up a tachometer and vacuum gauge. Now restart the engine. Adjust the idle (air cleaner off). Note the idle vacuum, and idle RPM. Now reinstall the aircleaner. If the air cleaner is large enough, there should be no change in either idle vacuum or idle RPM. If either change, replace the aircleaner.

Some of the small aftermarket aircleaners don't flow enough CFM to run a good running 4 cylinder, let along a 265.

Jon.
Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
rox56 
Member
Posts: 8

Reg: 01-25-04
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-15-04 06:15 AM - Post#405464    
    In response to 57_sedan_delivery

Mike,

We are in the North Port/Port Charlotte area. Looks like you are near Ocala. We will be in the Villages on Sat, March 20 for the monthly car show/cruise-in. Ivory over Matador red 56 Belair 2dorr if you are in the neighborhood.

Rox 56

 
57_sedan_delivery 
Old as Dirt Member
Posts: 6720

Loc: Hog Valley, Fla.
Reg: 02-19-01
Re: Carburator Adjustment Issue/ Rochester 2 Barrel
03-18-04 09:52 AM - Post#405465    
    In response to rox56

Don't know if I will make it as the wife just got out of the hospital, have to play it by ear and see. Actually I'm up by Rodman Res. between Ocala and Palatka.
Mike W.

Founding father Desert Classic Chevys in Phoenix, Az.

1957 sedan delivery 454 TH400
1956 windowed sedan delivery US Dept of Ag car
1956 Chevy 3100 US Navy pickup
1959 rare GMC 100 fleet option 100 pickup


 
This Forum is Sponsored by

bobsclassicchevy.com
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

6604 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.227 seconds.   Total Queries: 15   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 07:27 PM
Top