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Rough night. Stayed up til 5 AM (still awake) working on it. Got the throttle replaced, but it was a nightmare putting the linkage for the gas pedal back in. But that would all be fine if it weren't for what happened when I tried to start the car.
The engine screamed. SCREAMED. When I hit the accelerator. Smelled a little smoke after. I am scared to death I somehow messed something vital up while tinkering with the throttle, but idk how. Maybe I damaged some wiring while under the dash. Or maybe my new setup is causing the scream (again, its not a squeal. A SCREAM.) Take a look at my new setup and see if you can spot any potential causes of the noise.
I am a little relieved because I googled engine screaming, and it sounds like it could just be alternator belt. But why on earth was that affected while I worked on my carb?
Other details: I HAD been hearing a sortve high pitched buzz when I drove earlier in the week. Maybe that was the belt in the early stages of going bad?
I also took out the AC plastic from behind my dash. My AC isnt equipped, so it was just in the way. Again, idk how that would cause the noise but just giving all the information.
Also, not positive, but it sounded like it was coming from just beyond the firewall! Can't be sure. Definitely from the driver side. But if it's up near the firewall it cant be the alternator. Man I'm worried!!
Does it scream at idle? A mechanic's stethoscope will help you find the source. You can make one with a piece of vacuum tubing in a pinch. Hopefully it's just a squealing accessory bearing.
Also, here's a drop-base air filter housing, 2" K&N filter, and valve cover setup that might work for you. PM me if you are interested. I'd like to see it used.
Also, not positive, but it sounded like it was coming from just beyond the firewall! Can't be sure. Definitely from the driver side. But if it's up near the firewall it cant be the alternator. Man I'm worried!!
The carb gasket is hanging into the open space under the butterflies and vibrating from the air rushing past.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
What rpm is your motor running at?
In attempts to fix the carb throttle problem before, did you adjust the low speed stops?
I would also make sure your linkage is moving freely and theres a liitle slop in the cable at idle.
If you want to eliminate the possibility of it being the belts, just remove them and start it again briefly . Like bike space said, you can identify it after you eliminate other possibilities.
What ever it is, its from you changing something.
I doubt its a gasket or vacuum leak. When you say scream, i think loud and high rpm, so give us some more info please.
It should be easy to fix, on the plus side, it started so you got something right.
Last edited by Rescue Rogers; Apr 26, 2019 at 09:58 AM.
The carb gasket is hanging into the open space under the butterflies and vibrating from the air rushing past.
You nailed it. See, I must have mistunderstood Rescue's instructions. I used the open spacer, with an open gasket above it and the 4 barrel below. I changed the 4 barrel to an open gasket and noise vanished completely. THANK YOU!!!
Car started up, no noise! Took it out. The throttle definitely opens more, but not close to WOT.
(Also, just to be safe - when I manually open the throttle with the motor off, after it's been running. There's a tiny bit of vapor/smoke coming out of the butterfly valves. I googled it, and I read it's normal. Is it? Just wanna double check.)
Here is the pedal and the linkage. Pic 1 is me holding it up. Pic 2 is where it settles on the floor. This has to be the reason why I can't get WOT, right?
Could this guy below be the culprit? When I try to tighten that bolt (while the pedal is lifted off the ground like in pic 1) it doesn't really stop the rotating shaft above it from moving. Isn't that its function?
Or could this guy be the issue? I found nothing about this part in the original assembly manual. And it was an absolute S.O.B. to put back on. Could NOT get it screwed into the firewall AND aligned with the holes for the black pivot bracket I circled above.
What does this thing do? It has a little electrical thing on it. Is it some kind of sensor? It is stationary, and when I press the gas, the pedal arm leans back and hits it.
What does this thing do? It has a little electrical thing on it. Is it some kind of sensor? It is stationary, and when I press the gas, the pedal arm leans back and hits it.
Throttle Control Transmission Kickdown SWITCH (GM pn 01242101) for TH400 auto transmission
I'd take out the switch and see if that fixes your throttle problem. I'd think you'd want the kickdown feature, though. I'd imagine that GM included a slotted, adjustable hole to allow the switch to activate without blocking the pedal, or a splined adjustment at the pivot point, or a tab that you can bend, or some other way that lets you adjust the set point of switch engagement, assuming that this is where your throttle is hanging up. Perhaps the AIM or shop manual says something.
It looks like there is a bolt that goes into a captured (welded?) nut at the top of those photos. Time to crawl under the dash! I find it's a lot easier with the seat out, then I either kneel on a pad with the car elevated on jackstands or a Kwik-Lift, or I can lay upside down with my head under the dash, back on the carpet, and legs sticking up (it's a lot easier with a bubble window C3). Make sure you have all the tools you need, or a helper to hand them to you.
Last edited by Bikespace; Apr 26, 2019 at 05:39 PM.
I'd take out the switch and see if that fixes your throttle problem. I'd think you'd want the kickdown feature, though. I'd imagine that GM included a slotted, adjustable hole to allow the switch to activate without blocking the pedal, or a splined adjustment at the pivot point, or a tab that you can bend, or some other way that lets you adjust the set point of switch engagement, assuming that this is where your throttle is hanging up. Perhaps the AIM or shop manual says something.
It looks like there is a bolt that goes into a captured (welded?) nut at the top of those photos. Time to crawl under the dash! I find it's a lot easier with the seat out, then I either kneel on a pad with the car elevated on jackstands or a Kwik-Lift, or I can lay upside down with my head under the dash, back on the carpet, and legs sticking up (it's a lot easier with a bubble window C3). Make sure you have all the tools you need, or a helper to hand them to you.
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OP ... seems you're in dire need of a Corvette Shop Manual and a study-break with same !
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by BlankSlate
You nailed it. See, I must have mistunderstood Rescue's instructions. I used the open spacer, with an open gasket above it and the 4 barrel below. I changed the 4 barrel to an open gasket and noise vanished completely. THANK YOU!!!
No kidding, I wouldnt have thought a gasket could make that much noise!!!!
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by BlankSlate
Here is the pedal and the linkage.
Could this guy below be the culprit? When I try to tighten that bolt (while the pedal is lifted off the ground like in pic 1) it doesn't really stop the rotating shaft above it from moving. Isn't that its function?
Are you saying that when you tighten this bolt, the upper arm isnt solid with the pedal? They should move as one unit, thats what your throttle cable should be connected to. If it isnt one unit your not going to get the full travel of your cable
I was looking for that thread to help the OP..........glad you brought it up. I remember tack welding the two pieces together at the bolt to stop the slipping movement. Also if you bend the thin piece where the accelerator cable comes through the hole toward the inside (toward the car seat), you increase the radius you can get for full throttle. I bent mine about a 1/2", pulling the cable back the 1/2" more that I needed.
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
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