73 corvette question performance issue...?

Fuel filter,plug wires,maybe there is crud in the float bowls or the power valve is bad? Maybe the timing is late.Maybe the EGR valve is not working,if it has one, I have had a 78 Vette for 17 years and disabled all the smog equipment and it runs fine. Feel free to contact me at zz383corvette@yahoo.com

What kind of carb do you have on it, look down the bores to make sure your accelerator pump is squirting, and make sure there are no vacuum leaks Make sure the carb isn't too big, 600-650 is plenty for a small block

Does it have vacuum advance, if so make sure it is working, and as far as the timing, crack the distributor hold down bolt just loose enough so you can move the dizzy. Keep advancing the distributor a bit at a time, driving it in between, until the car pings, then back it off a bit until it stops pinging. Also if it has a hard time starting when it is real hot, you may have to back it off a hair more, but old Chevys don't like timing lights!

Also make sure the gas tank is venting, and I would check the EGR valve to make sure it isn't stuck open, and if you don't have smog checks where you live, block the vacuum off to it for good!

I am aircraft tech and master auto tech and do tons of dirt cheap basket case vehicles to teach troubleshooting and as a hobby to teach my three sons skills. Have seen this problem before on a truck was dirt in the fuel tank. Also I work at workds largest maintenance base and get to swap stories with thousands of others with similar hobbies and skill sets. The other time I have heard this happening on vettes is the years so equipped (think like '75-'77 or so but not sure) with the rear carb bores activation switch actuated by the gas pedal I believe located near top of pedal or the linkage that switch just is not designed well and fails. You should always drop the fuel tank on a vehile this age and check the pick up sock and the connections for float and be sure the seal is not shrunk and the vent lines are not cracked. After verifying and eliminating all above. Then give me feed back and I can write a troubleshooting tree or flow chart it it still evading you after looking into that year specific stuff more and seeing if I can find someone here to drill on the way chevy set that one up.I cut my teeth on a '74 nova with 350cid and my neighbor had a daily driver from that era I picked up stuff on but pretty sure it was later a bit and not sting ray but this is generalized issue based on symptom and will not be a year specific quirk I am very sure. It would benteriffic to hook up a fuel pressure guage and watch it during issue. If its good look at the vacuum if so equipped or mechanical links but since replacing carb is unknown as to exact condition an dthere are few left that do a very through job on those ere carbs but since problem persists I will rule out the carb itself at this point. Converting to fuel injection at this point and era in time with reas gas going way of dinos it will make fuel management problems easier to fix. I know that carb was probably around $800 so likely your not wanting further large expenses just letting you know what the trends are in this era of vechicle. I specialize in japaneese but keep some chevys around and still take outside of my comfort zone but like these olders cars due to the ease of figuring things out as the computers they dont have dont cover thngs up. I learned on this stuff and did my first electronic ignition conversion back in 1986. Good luck but persistench usually wins.

Your idle will have to be set higher because of the lope caused by the lumpy cam in your engine. Be sure when checking timing you have the vacuum advance vacuum line off the distributor and plugged. Else you will get a false reading on the timing. Your timing could possible be advanced further than factory spec's depending on what they did when they re-build the engine. Did they give you a timing range to tune to, or a total advance value for your timing? Getting the timing to what they designed the engine for, vs factory timing spec may also play a little into the lope you have at idle.

Sounds like its pulling timing for some reason. Fuel filter? Had a similar problem with a Daytona but it got fixed with Sea-Foam. Or you could be hitting the Rev Limiter if it happens right after shifting from 1st and 2nd. I sorry to say but it could be lots of things. For ex, torque management.