SuRRRginG iDDDol
Thread Starter
Instructor
Joined: Oct 2008
Posts: 176
Likes: 1
SuRRRginG iDDDol
Hi everyone. I'm having problems with my rochester q jet. I have always noticed the surging idol on my 350. I recently rebuilt the carb trying to correct any error of previous owner tuning. Long story short carb is back on but engine still surges. I've completely seated the air idol screws and it preforms best here (smallest surge and doesen't stall). I know this is not how these screws should be set, but for lack of better solution I did. I've used a smoke machine to check for vac leaks found a few and fixed them. Engine runs better but still surges in neutral/park.
Where should I go from here?
Where should I go from here?
Melting Slicks
Joined: Jul 2008
Posts: 2,908
Likes: 3
Hi everyone. I'm having problems with my rochester q jet. I have always noticed the surging idol on my 350. I recently rebuilt the carb trying to correct any error of previous owner tuning. Long story short carb is back on but engine still surges. I've completely seated the air idol screws and it preforms best here (smallest surge and doesen't stall). I know this is not how these screws should be set, but for lack of better solution I did. I've used a smoke machine to check for vac leaks found a few and fixed them. Engine runs better but still surges in neutral/park.
Where should I go from here?
Where should I go from here?
Thread Starter
Instructor
Joined: Oct 2008
Posts: 176
Likes: 1
No, holds steady in drive.... Yeah I think I'm going to get a new one, the seconday rods on this one don't match. I've spoke with Lars, sounds like they're getting rare and expesive. Any recommendations I've have stock 350 block, edlebrock preformer intake, 64cc sportsman wc2 heads (2.020/1.6 valves), comp cam 1.52 roller rockers, headers, 2.5" exhast/high flow mufflers, hei coil. Not sure on camshaft... Runs like junk with intial timing set to factory spec, so it's retarted 4 degrees at idol, lobs a little...
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
Thread Starter
Instructor
Joined: Oct 2008
Posts: 176
Likes: 1
I played with it for a while. It was 4* retarted before I changed anything, when I tied the centrifical advance/ pulled vac advance and set it to 0*@1200 rpm, it was worse all around went back and forth best preformance with 4* retard. Since then found another vac leak fixed that going try timing again later
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
These engines like lots of advance. Generally the more advance you put in up to about 10°-12° the more the engine likes it and the idle rpm will increase. Then plug in your vacuum can and it will really rev. So something seems wrong with your basic setup, and certainly with the carb is it idles with the idle screws all the way down. Check Barry K's sticky for how to set up your timing.
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Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
It sounds to me like you have the engine idling on the main circuit. If you retard the ignition timing excessively you will have to open up on the idle speed adjustment. This can get so bad that you will be pulling fuel through the mains.
Check the damper timing ring for slippage. This could be giving you bad timing readings.
Also the idle pickup tubes may be plugged. This could be why the engine stumbles when you open the idle mixture screws.
If you decide to get another carburetor I'll take this one off your hands.
BigBlockk
Later.....
Check the damper timing ring for slippage. This could be giving you bad timing readings.
Also the idle pickup tubes may be plugged. This could be why the engine stumbles when you open the idle mixture screws.
If you decide to get another carburetor I'll take this one off your hands.
BigBlockk
Later.....
Melting Slicks
Joined: Aug 2004
Posts: 2,907
Likes: 229
From: Oakbank Manitoba
Two vacuum leak related items alot of guys miss are the HEI vacuum canister and the choke pull off on the front passenger side of the carb. Both have rubber diaphragms that eventually fail. The headlight vacuum circuit is connected at the back of the manifold. The actuators and vacuum reservoir eventually develop leaks too.Cap off this line to see if there is an improvement.