KQQLCAT Posted November 5, 2010 Share Posted November 5, 2010 I have a 1962 Olds Rochestor 4GC that is giving me problems. A little history. I am converting my 61 Olds 88 394 from a two barrel to 4 barrel. It ran fine with the 2 barrel but I had to do a valve job and since I had all the parts to convert it and had it all apart I figured I would change it out. I had a local carb rebuilder (The Carburetor Shop) restore/rebuild this carb. It looks great but It has 2 problems. It has a major bog when I touch the accelerator and if I get into the secondaries and go to idle it has a real rough idle untill I pump the accelerator a couple times then it idles smooth again. I plan on taking this back to the rebuilder but I want some ideas to tell him to look at.Thanks for any advice you can give,Pat Link to comment Share on other sites More sharing options...
Guest Jim_Edwards Posted November 5, 2010 Share Posted November 5, 2010 The first thought that popped into the head was "if you have to tell him why it's doing what it is doing then you need to find another carburetor shop." But having rebuilt a few carburetors myself that didn't turn out as expected, I can think of seven things from your description that could be happening. Five in the first case and two in the second case.1. Bogging down could be distributor vacuum advance issues, incorrect float setting, or bad accelerator pump diaphragm (new ones right out of the box have been known to be bad), incorrect accelerator pump adjustment, or vacuum leak beneath the carburetor.2. The second problem sounds like secondary linkage is binding once secondaries have opened or the throttle plates on the secondaries are otherwise not closing to their proper "rest" position and binding against the venturi bores.Hope this helpsJim Link to comment Share on other sites More sharing options...
starfireelvis Posted November 6, 2010 Share Posted November 6, 2010 Amateur armchair quarterbacking here, but I can tell you from experience that the carb in my '62 Starfire has had to have the accellerator pump replaced/redone several times in all the years I've owned it (keeping in mind I've driven the car over 53,000 miles in the decade and a half it's been mine); I am told it is in large part due to the horrible effects of ethanol gasoline on many of the components.Someone competent should be able to resolve this issue without too much problem; I am now using a marine-grade fuel stabilizer to help fend off the effects of such. Link to comment Share on other sites More sharing options...
rocketraider Posted November 6, 2010 Share Posted November 6, 2010 And that is how Mike and I met, when his black Starfire was having a bad case of 4GC-itis at the Springfield IL OCA National meet. Link to comment Share on other sites More sharing options...
carbking Posted November 8, 2010 Share Posted November 8, 2010 First I would like to point out there are more than one "The Carburetor Shop".Second, a bog on acceleration from a stop is often caused by having the idle screws out too far.If you wish, give me a call at 573-392-7378 (9-4 Mon-Wed central time) to discuss your issues.Jon. Link to comment Share on other sites More sharing options...
KQQLCAT Posted November 9, 2010 Author Share Posted November 9, 2010 This Carburetor Shop is in St. Paul MN. I will try to readjust idle screws. How many turns out after engine starts to kill? Link to comment Share on other sites More sharing options...
carbking Posted November 10, 2010 Share Posted November 10, 2010 Try turning them in until lightly seated. Now back them out each 1 1/4 turns. Start the engine, and run at a fast idle until engine is at full operating temperature. Now adjust the idle with the curb idle positioner screw.If you have to burn ethanol fuel, you might need to go out another 1/4 turn. Any further than 1 1/2 turns required, and you will probably need to modify the idle jets in the carburetor.Jon. Link to comment Share on other sites More sharing options...
Guest Jim_Edwards Posted November 10, 2010 Share Posted November 10, 2010 Try turning them in until lightly seated. Now back them out each 1 1/4 turns. Start the engine, and run at a fast idle until engine is at full operating temperature. Now adjust the idle with the curb idle positioner screw.If you have to burn ethanol fuel, you might need to go out another 1/4 turn. Any further than 1 1/2 turns required, and you will probably need to modify the idle jets in the carburetor.Jon.Uh, oh! You left out the part of blocking the vacuum line to the distributor advance before making those adjustments. Link to comment Share on other sites More sharing options...
Guest 64 starfire Posted February 4, 2011 Share Posted February 4, 2011 sounds like accelerator pump is bad. i also had problems with the secondary spring adjustment Link to comment Share on other sites More sharing options...
dlh61olds Posted February 5, 2011 Share Posted February 5, 2011 You might also check the jet sizes.Stock 1961 Starfire 394 used # 56 mains and # 80 secondarys.You might have to tweek the mains for your elevationbut the stock setup seems to be fine except for running rich at Colorado Springs altitude. (6350 at my home).I am running #57 mains and get 16 MPG here. However at Dallas Texas altitude it would barely pull itself onto the showfield.Good luck, Dave Link to comment Share on other sites More sharing options...
Starfire61 Posted February 5, 2011 Share Posted February 5, 2011 Not to hijack the thread, but where can you get jets for a 4GC? Can you recommend any sources?Thanks-Chuck Link to comment Share on other sites More sharing options...
D Yaros Posted February 5, 2011 Share Posted February 5, 2011 Not to hijack the thread, but where can you get jets for a 4GC? Can you recommend any sources?Thanks-ChuckDaytona Parts Co. http://www.daytonaparts.com Link to comment Share on other sites More sharing options...
dlh61olds Posted February 5, 2011 Share Posted February 5, 2011 Here ia a source on e bayJETS NEW ROCHESTER 2GC CARBS ALL SIZES SMALL BASE - eBay (item 270697788595 end time Feb-25-11 05:24:20 PST)They fit both the 2GC and the 4 GC Good price too.Dave Link to comment Share on other sites More sharing options...
Guest Julian Posted February 14, 2011 Share Posted February 14, 2011 ( it has a real rough idle untill I pump the accelerator a couple times then it idles smooth again.)..........These 4 GCs are a bear arn't they Link to comment Share on other sites More sharing options...
Guest Julian Posted May 18, 2011 Share Posted May 18, 2011 did you ever get your little 4gc straighened out??? Link to comment Share on other sites More sharing options...
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