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Using high octane fuel in your 9: 1 compression engine is a wast of money. Also using a octane booster don't help either. High compression needs octane, so unless you had 11:1 pistons or higher put in your engine don't use it. It actually will make you car run worse.
My thought was maybe I got bad gas or water in the gas somehow. It had sat for a bit, so that is why I put premium and a octane booster in. But I don’t think that is the case.
*Update*
I was working on sanding the car today and started the car to show my brother-in-law how the car is running rough. Like it has been, it started fine and ran okay then as it warmed it really struggled. We discussed how it smells like it is running really rich. As we inspected the carb, we noticed that the choke flaps were almost completely shut. I manually opened it and it started to smooth out nicely. When I let go of it, it closed again and the car struggled. I know nothing about carbs which is why I got it rebuilt by lars. In the picture below, I pushed the lever (blue arrow) forward until it clicked and locked forward. This opened the choke and prevented it from closing. Anyone who knows about this have ideas? I don't understand why it would run fine and one day the choke would settle in a different spot. Not sure this is the entire problem but it sure seems like a big piece of it. The hot-air choke has been removed and I just took the vacuum line to the front. Do I need to bend the rod up to the choke flap? In the picture below that is where the carb is running rather smooth (note how open the choke is).
I would contact Lars before doing any bending. He rebuilt the carb and it should work perfect or with little adjustments which shouldn't include bending things. Call , text or e-mail Lars.
You are pointing to the choke pull off. Probably a new one installed during rebuild. Lars has an excellent paper regarding choke operation. Actually I think it is a sub section of a larger paper of his. I think Lars prefers to send you his latest paper rather than reference an old one. Contact him for his latest one.
I had a similar problem. The diaphragm in my new pull off failed and the choke would not open. NAPA has choke pull offs for maybe 20 bucks. There is an adjustment needed when you install it using that screw. You can test the pull off by putting a longer tube on it and sucking it or a myty-vac. You will see right away if it holds.
hat plate should be almost 90 degree perpendicular when the genuine is at operating temp.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
it sounds like your choke is operating backwards. As if it was installed so that it closes instead of opens as the motor heats up. Either the hot air spring is in backwards or its connected incorrectly.
The second option is its in correctly just set incorrectly. The big black cap adjusts the choke, just loosen the 3 screws and rotate the cap until the choke opens then tighten.
Last edited by Rescue Rogers; Mar 9, 2020 at 06:45 AM.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Rescue Rogers
it sounds like your choke is operating backwards. As if it was installed so that it closes instead of opens as the motor heats up. Either the hot air spring is in backwards or its connected incorrectly.
The second option is its in correctly just set incorrectly. The big black cap adjusts the choke, just loosen the 3 screws and rotate the cap until the choke opens then tighten.
I test all the chokes on every carb I build - that's not the problem. Look at his photo - he doesn't have the choke hooked up...
Originally Posted by tjmaniez
*Update*
I was working on sanding the car today and started the car to show my brother-in-law how the car is running rough. Like it has been, it started fine and ran okay then as it warmed it really struggled. We discussed how it smells like it is running really rich. As we inspected the carb, we noticed that the choke flaps were almost completely shut. I manually opened it and it started to smooth out nicely. When I let go of it, it closed again and the car struggled. I know nothing about carbs which is why I got it rebuilt by lars. In the picture below, I pushed the lever (blue arrow) forward until it clicked and locked forward. This opened the choke and prevented it from closing. Anyone who knows about this have ideas? I don't understand why it would run fine and one day the choke would settle in a different spot. Not sure this is the entire problem but it sure seems like a big piece of it. The hot-air choke has been removed and I just took the vacuum line to the front. Do I need to bend the rod up to the choke flap? In the picture below that is where the carb is running rather smooth (note how open the choke is).
You don't have your choke hooked up to the hot air supply. It can't operate the way you have it installed, so the choke will stay closed. Forever. Hook up the choke the right way and it will work - it was tested and verified, but it cannot operate if it's hooked up wrong, as you've done - you have locked your choke in the full-rich position.
Lars
Thanks Lars. I closed the exhaust cross-over when I installed the new intake manifold so the hot-choke won't fit. This set up worked great last summer but maybe it was because of the warmer temperatures? Sounds like maybe the only options I have is to adjust the choke to be open a little further but really the best alternative is to buy the electric choke conversion kit so it will actually work properly. Thanks again for all of your help with the rebuild and advice. I will email you separately to see about getting the choke adjustment papers.
Time to do some basic troubleshooting instead of shooting arrows this way and that:
- Throw a $12 vacuum gauge on the intake manifold and see what reading you get (needle steady?).
- Do a compression check (probably don't need to, but it's part of basic troublshooting). 4 'pumps' each cyl. Note how many pumps to get up to pressure ...and watch leakdown for a few seconds.
- Fuel pressure? Flow rate? Fuel quality (water?)
- Distributor inspection (weights, electronics (if any)), wires, etc
- Quadruple-check vacuum hoses, vacuum advance, thermal switches, Fuel canister switches (if applicable), etc.
- EGR working (if applicable)?
- Double-check carb power jet, warm up and pull off choke. Leaks around the base? Put hand over carb (to choke off engine), note recovery, etc.
- Plugged cat?
- Termac? EFE stuck?
- Water in the tank?
- Etc ...etc..
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by tjmaniez
Thanks Lars. I closed the exhaust cross-over when I installed the new intake manifold so the hot-choke won't fit. This set up worked great last summer but maybe it was because of the warmer temperatures? Sounds like maybe the only options I have is to adjust the choke to be open a little further but really the best alternative is to buy the electric choke conversion kit so it will actually work properly. Thanks again for all of your help with the rebuild and advice. I will email you separately to see about getting the choke adjustment papers.
There is absolutely no way that a hot air choke will function at all without the hot air tubes hooked up. It could not have ever "worked great" without the tubes installed - that's physically impossible. It may have opened partially just from engine compartment heat, but the secondary lockout lever would have remained engaged, disabling the secondaries. If you do not have the parts needed for hot air operation, you have to convert to electric, or you need to lock the choke in the full-open position.
If you send the carb back, I can do the electric choke conversion, setup, and test for about $50, plus cost of return postage.
Originally Posted by Mark G
Throw a vacuum gauge on the intake manifold and see what you get..
He has an inoperable choke (choke locked in the "closed" position). A vacuum gauge won't fix that. No further troubleshooting required. Fix the choke. Problem solved.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by lars
I test all the chokes on every carb I build - that's not the problem. Look at his photo - he doesn't have the choke hooked up...
Hey Lars I wasnt implyng you rebuilt it incorrectly, just that something the OP did when he re assembled it. I know we send you carbs but I dont think people send you the intake as well for you to set up everything in the choke and special gaskets so that they just bolt on the intake and go
From: At my Bar drinking and wrenching in Lafayette Colorado
Actually, I do set up the carbs and deliver them so they can just be bolted to the intake and go. But you have to actually hook them up - you can't leave things disconnected and expect them to work, as has been done here...
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by lars
Actually, I do set up the carbs and deliver them so they can just be bolted to the intake and go. But you have to actually hook them up - you can't leave things disconnected and expect them to work, as has been done here...
Probably a dumb question but to build my knowledge...when you push the lever (that my blue arrow is pointing to) all the way forward it clicks and locks into place thus having the choke wide open. What is the reasoning for this?
Probably a dumb question but to build my knowledge...when you push the lever (that my blue arrow is pointing to) all the way forward it clicks and locks into place thus having the choke wide open. What is the reasoning for this?
That's the weight for the fast idle cam. The choke spring takes over when cold and tries to lift it, if you crack the throttle with the engine off, cold, the weight will come up letting the choke close and the throttle blades will be held open on the fast idle. As the choke coil warms up, it will reduce spring tension, then if you tap the throttle slightly, it will drop down some to the next lower idle setting. When fully warmed up, it should drop all the way and let the idle down to the base setting controlled by the screw on the left side. The click you hear is the adjustment screw on the different steps of the fast idle cam.
