I have an complete original 73 Camaro. It is a complete numbers matching off body restoration. I removed the engine & trans and did a complete overhaul on the original numbers engine & trans. After boring it , I decided that the Qua jet original carb was not efficient. I installed a single barrel Holly Carb which works perfectly. When the car is very hot, engine and also if it really hot outside physically. I am noticing that the car / carb is choking. The car has no acceleration, bucks and chokes. Then its OK for a min. In the cold weather, there are no issues. Someone told me that the carb needs a riser and that this would solve the issue. Has anyone ever heard of this heat chocking issue before. I love the car and it is simply amazing.

 

Should have stayed with the Q-jet for starters unless you are going high performance above what it's capable of handling.
Single barrel Holley? That makes no sense on a v-8 engine,must be a 4 barrel carb at least.
Before we can diagnose we'd have to know exactly what carb and intake you have.
If your car is real deal Z28 it should have a Holley as a stock carb with an aluminum high rise intake not a Q-jet.
Not enough info here.

 

When you say choking I don't think that is what you mean. Is it a hesitation? lack of power? black smoke? Who picked the size and model of the carb? Has the carb been adjusted? Holley carbs are designed to go on anything. For that reason everything is adjustable. A skilled old school tuner can take up to an hour to get a carb right at his shop with all the right tools, parts and dyno. I have seen amateur's try to tune cabs for months and never get it right.

Holley carbs can have 3 different choke system. None, manual and electronic. If you are really sure this is a chock issue would would need to know model and choke configuration. Even the choke setting is something that will change from one engine to another.

 

Please note that I made the engine more powerful. The original Q Jet carb could not dump enough fuel. The Holly is a single pump and is working perfectly. Its fails either when I take a very long drive or if it is extremely hot outside. Everything on the car is original except the carb. I mounted it the original 1973 manifold. Also, yes the word chocking is exactly what you are describing. Hesitation and sometimes white or black smoke...I appreciate the feedback. Looking for a solution.

 

Please note that I made the engine more powerful. The original Q Jet carb could not dump enough fuel. The Holly is a single pump and is working perfectly. Its fails either when I take a very long drive or if it is extremely hot outside. Everything on the car is original except the carb. I mounted it the original 1973 manifold. Also, yes the word chocking is exactly what you are describing. Hesitation and sometimes white or black smoke...I appreciate the feedback. Looking for a solution.

 

I does not have a Holly from original. I looked up the vin and it is and should be a Q Jet with a heavy cast iron manifold.

 

This makes no sense. How can a stock all original engine be more powerful? The only thing the choke needs to do when the car is hot is to be open. You can just look at it when its hot, Is it open? if it is it is not the issue. If it is not temporarily wire it open. Does the problem go way? If so post a picture of you crab and the model and I will tell you what parts your need.

The choke on the car only works when the car is cold. Many race cars do not even use chokes. I seriously doubt your issue has anything to do with the choke. When cokes fail most of the time the car runs like crap cold be fine hot. The carb may be leaning out when hot, the engine could be getting too hot, you plugs may be causing your cylinder heat/pressures to get too high. That is 3 possibilities out of 300. In a way it sound like maybe your coil is failing. There is no way anyone can really help you because this is a very technical problem and we have no solid technical information. You need to seek out someone that has years tweaking these cars and let them figure it out. I have spent hours on the phone talking to friends about a car problems when they finally brought the car in it took me less then 10 minutes to fix.

 

Okay well you posted "single barrel" so single pumper is a whole different thing,both carbs are four barrels,it sounds to me like you may be having a vapor lock issue.
As Gorn stated how can you have made the engine more powerful if the only change is the Holley carb?
If the engine is completely stock the Q-jet carb should have provided enough fuel,the Holley could be more responsive but won't add any power.
As for the choke as Gorn mentioned it should only be closed when the car is on a cold start but I think you may have confused him (and me) by saying choking when you weren't talking about the choke on the carb but the way it is running,
Vapor lock would explain the situation,if the gas cap or gas tank is not properly vented it will create a vacuum in the tank cutting off fuel supply and hot days it's more likely to be an issue. Another possibility is a bad gas line that is collapsing

 

Please allow me to clarify. When the car is physically HOT from the sun or it has been running for a while, the car will hesitate and stall and blow a puff of white smoke. No power at all. Allow it to sit for a min and she starts right back up. As far as more powerful, I had the engine bored out and now it has 383 horse power to the rear wheels. She runs like a champ. The Holly single barrel / pump part number # 0-80555C 4175 univ 650CFM dichromate. Again, I do apologize if I was unclear. I am being told that changing the carb will not solve the issue, however to install a riser gasket to absorb the heat. Again , sorry for any confusion.

 

So what you have is a basic Holley 4 barrel car with a single a line, single pump (accelerator pump) and vacuum secondary's . You have a electronic choke with a vacuum pull off. Just to be clear the size of the carb will not cause smoke or missing by itself. You will just have less power at higher RPMs.

You can not just bore a motor to get to 383 wheel HP. which would be about 450 to the cranks. To hit 450 HP at the crank takes a LOT more then just boring. Could it be the the motor is bored and stroked to 383 Cu inches? In that case your carb is a little small but that would not cause your issue.

Here are some question.
1.) Has the motor ever run right since it was built?
2.) Did it run better or the same with the Quadrajet?
3 .) If the engine ran good at some point what happened right before the issue started?
4.) Did the car sit for more then a year at any point?

The issue could be Vapor locking as Y2Keglide said but I am use to vapor locking shutting the car down and the take 30 plus minutes to restart. Because of the way the cooling system works a car will get hotter after it shuts off. It is normal for a car to reach is max temp 20 minutes after it is shut off if it was run hard. When I hearosi that a car cools down real fast and starts working again quickly I think electronics. A wire building resistance dropping power to a distributer, A coil braking down, Carbon tracking in the distributor cap or rotor, even a condenser assuming your car still has points. Mechanics have a thing called a oscilloscope that can pin point an electric issue like this. The scope can also show if the carb is working right. and even if you have a vacuum leak.