C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
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Old Apr 19, 2021 | 08:26 PM
  #161  
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Originally Posted by michael lamoglia
So got old carb back in started her up pumped it few times and it started. Shut off. Did it again same thing. Advanced the dizzy a bit and it started up. Dies if I don’t give it gas. Any ideas. See my video.
https://youtu.be/7_FbMjZ1Q9U
Well did you time it yet? Im having issues getting my timing setup correctly and depending on where it is, it will cause that issue.

Last edited by augiedoggy; Apr 19, 2021 at 08:27 PM.
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Old Apr 19, 2021 | 09:16 PM
  #162  
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Do you have a timing light, or any other way of knowing what your timing actually is?

I'm not 100% sure, but that might be a ported vacuum port on the carb. You can test it with your finger. You want to move it to a manifold vacuum (you could even put it on the capped port on the manifold just to test).

You appear to have removed your choke heater. The choke will never open, unless I'm missing something.
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Old Apr 19, 2021 | 10:16 PM
  #163  
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YOU'RE having issues with timing? don't believe it lol.

anyway can't time if it shuts off. I cranked it to zero, dropped dizzy in at 1:05 meaning it's point right at one almost and about to head to 8. I read somewhere it's best to drop it in between 3 and 1. anyway, I also read you can't crank right at tdc 0. best to crank ADVANCED 4-8 degrees out (which are the numbers to the right of zero if i'm facing the driver's seat from the front of the car. Haven't done all that yet. could also be my hoses on my carb since I just plopped it in there.
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Old Apr 19, 2021 | 10:18 PM
  #164  
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Can't time if engine shuts off if I let go of gas. Which port did you think was ported? the one in the front or the small one in rear? If you want me to try the manifold port that's capped I'm assuming run a piece of hose to it. fun fun fun.
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Old Apr 19, 2021 | 10:22 PM
  #165  
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Also I'm pretty sure we can remove choke heater. Hence the plate it comes with unless I'm missing something?
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Old Apr 19, 2021 | 10:28 PM
  #166  
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Try the port marked "full vac" below (manifold vacuum). Vacuum advance at idle will make your engine happier, and may keep it running. You can also up the idle speed, though your fast idle cam should be set with the choke closed, so it should be trying to idle at 1100 RPM or so. Image found on the internet...





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Old Apr 19, 2021 | 10:31 PM
  #167  
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Originally Posted by michael lamoglia
Also I'm pretty sure we can remove choke heater. Hence the plate it comes with unless I'm missing something?
Only if you have an electric choke. I didn't see a wire in your video.

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Old Apr 19, 2021 | 10:51 PM
  #168  
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should at least not shut off at startup no? The holley going in next has the electric choke. Want to get this running and make sure it's all put back together ok.
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Old Apr 19, 2021 | 11:02 PM
  #169  
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you're right I remember now. All was removed because I was headed to an electric choke. I think I'm going to stop fooling around with this and plop in the new holley.
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Old Apr 19, 2021 | 11:17 PM
  #170  
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In your video you have two open vacuum ports one in front and one in the rear of the carb. . It probably isn’t going to idle with two vacuum leaks. Need to cap those off first.
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Old Apr 19, 2021 | 11:32 PM
  #171  
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Originally Posted by michael lamoglia
Can't time if engine shuts off if I let go of gas.
Will the engine run if you keep the accelerator pulled more than the position at idle? If so, screw in the idle adjustment screw enough to get it to stay running. Make sure every port on the carb is plugged or has a hose attached to something else.

Get a dial-back timing light if you don't have one -- or go Cadillac and get an Innova 5568 (https://www.summitracing.com/parts/ino-5568). Don't buy Harbor Freight or some other super-cheap light as you want reliable strobe circuitry. The Innova is nice because it can read RPMs, voltage, and dwell, as well as timing. If you don't have the Innova, you'll need a dwell meter too if you have a conventional points/condenser distributor (non-HEI) . You'll also need to have a vacuum gauge for making carb adjustments.

This bulleted list is intended to get your timing and carb set up to start and run relatively well – not necessarily to optimum, high performance.
  • Remove the vacuum hose from the distributor vacuum can and plug the end of the hose - no need to plug the canister as there's nothing there to seal off.
  • Slightly loosen the distributor hold-down so you can move it but with a little effort.
  • Hook up the timing light and dwell meter. (Dwell is the amount of space between the points contacts when they are at their most open.)
  • Start the engine and adjust the dwell to read 30°, +/- a degree. This only applies to points/condenser; HEI distributors do this electronically.
  • Rotate the light's dial or press the up/down buttons to set the light at 34°, then pull the accelerator up to 2500-3000 rpm.
  • Aim the strobe at the timing tab and rotate the distributor until the timing mark on the balancer lines up with the 0 zero mark on the tab. If you go too far in the wrong direction, the engine will run super rough and may die. Rotate it back approximately the same amount you moved it but this time rotate the other way to line up the mark.
  • Allow the engine to return to idle, shut down, reattach the vacuum hose to the canister, and cinch down the distributor bolt.

Now that your timing is set pretty close to optimum, you need to adjust the carb.
  • Screw in the mixture screws until they gently seat and then back them out 3 or 4 full turns.
  • Hook the vacuum gauge on a constant-vacuum hose coming from the carb or the main vacuum fitting on the manifold behind the carb mounting.
  • Start the engine and adjust the idle to spec (600 - 800 rpm is a good guess if you're not sure of spec).
  • Now adjust the mixture screws by screwing one inward in 1/4 turns until you see the vacuum needle go lower. Then unscrew it so the needle goes to its highest setting. Do the same with the other screw. Lastly unscrew each one 1/2 extra turn.
  • Check the idle speed and adjust again if necessary.
How's it running now? Get back to us and someone can lead you through troubleshooting further or fine-tuning.

Last edited by barkingrats; Apr 19, 2021 at 11:34 PM.
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Old Apr 20, 2021 | 07:29 AM
  #172  
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Originally Posted by michael lamoglia
YOU'RE having issues with timing? don't believe it lol.

anyway can't time if it shuts off. I cranked it to zero, dropped dizzy in at 1:05 meaning it's point right at one almost and about to head to 8. I read somewhere it's best to drop it in between 3 and 1. anyway, I also read you can't crank right at tdc 0. best to crank ADVANCED 4-8 degrees out (which are the numbers to the right of zero if i'm facing the driver's seat from the front of the car. Haven't done all that yet. could also be my hoses on my carb since I just plopped it in there.
Its not running correctly when timed with the proper method. I may have the cam degree'd a tooth off.
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Old Apr 20, 2021 | 11:38 PM
  #173  
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I changed out to a holley 4175 I scored cheap but the timing/idle info is pretty good
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Old Apr 20, 2021 | 11:40 PM
  #174  
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I'm having the same issues and remember my chain may have jumped a tooth when all this mess happened. Anyway now that I put in the holley I can eliminate that out of my way. If I have the same issue I'll continue to rotate a few degrees at a time and put in dizzy at new point. I suck at explaining what I'm going to do so I make videos all the time.
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Old Apr 20, 2021 | 11:48 PM
  #175  
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Seriously, get a timing light. Are you at least using a multimeter to determine degrees before TDC to start with? And have you moved the vac advance over to manifold vacuum? Please post photos (or video).

The Innova 5568 is great!
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Old Apr 20, 2021 | 11:53 PM
  #176  
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Of course I have a timing light. That's how I timed it the last time.

Remember I also changed the carb tonight to the new one and all is capped off. Will only connect the vac advance and cannister plus brake booster already connected. check out that video. I never thought to use the multimeter though. Any links for a quick study? thanks for all your help.

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Old Apr 21, 2021 | 12:21 AM
  #177  
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I don't know how you timed it before, I don't remember seeing any numbers posted (all-in RPM, final mechanical advance at all-in RPM, etc). Maybe I missed it!

Here's my go-to video for using a timing light. If you have the Innova light I linked to, you can do without the tape, but the tape is a great thing to have anyway. I'll see if I can find a good static TDC video for HEI, too.


EDIT: I can't find an initial timing video that does anything different than what you must already be doing, and basically requires a running engine. Hopefully with the idle screw, and some carb vacuum port covers, you can get the engine idling without intervention. There is a way to set initial timing with a multimeter on the coil, but it requires a points distributor.

This video shows setting the initial timing (only, which is incomplete, but will get you started), using a timing light very similar to the Innova 5568 (probably a rebrand of the same electronics). Anyway, it shows the function of the delay feature, with added timing markings.


Last edited by Bikespace; Apr 21, 2021 at 12:45 AM.
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Old Apr 21, 2021 | 12:50 AM
  #178  
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Also, a set of offset box-end wrenches might save you some time.


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Old Apr 21, 2021 | 12:55 AM
  #179  
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Originally Posted by michael lamoglia
Of course I have a timing light. That's how I timed it the last time.

Remember I also changed the carb tonight to the new one and all is capped off. Will only connect the vac advance and cannister plus brake booster already connected. check out that video.
Leave the vacuum advance disconnected from the distributor and plug the hose from the carb. (You could even disconnect the brake booster and other lines there on the manifold, plug those ports, and get the engine and carb settings correct without the potential negative influence of other components if they're out of whack. By eliminating the vac canister you are only timing the mechanical advance of the distributor as a first step and not having to deal with a second timing element from the vac canister. It won't harm the engine in any way and you are breaking down the variables one by one to get to a solid starting point.

Last edited by barkingrats; Apr 21, 2021 at 12:57 AM.
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Old Apr 21, 2021 | 07:20 AM
  #180  
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Originally Posted by michael lamoglia
I also read you can't crank right at tdc 0.
Yes, you can. It won't run very well, but it won't hurt anything and should still start with some throttle.
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