Here is a little background information. Friends of mine have taken responsibility of a family heirloom. a 1972 steel cities grey, convertible, 4speed, red interior, base 350 corvette...that has been sitting in a garage for 12+ years.

Other then covered with dust and some mold on the interior, it is great condition. Owner purchased it in 2004 or so, but only drove it 300 miles... and has been sitting ever since. It had a body off restoration before he purchased it, so i'm not even sure how much of a shake down it had before 2004.

So, we pushed it out of the garage, washed it off... and attempted to start it. After adding new points, condenser, and coil, the car starts (on the old gas in the tank). We take it for test spin, all is cool. It ran well at low rpms, but after exceeding 4k or so, it would start breaking up... which is understandable after coming back to life.

After shutting it off, it won't restart. Not sure if it was flooded, or there was no spark. In the mean time, fresh gas has been put in the tank, carb has been taken apart, cleaned and reinstalled.

So the pattern continues, even with fresh gas. Car will run when cool, breaks up at higher rpms, and will not start when hot.
The base timing set for 10, but we neglected to check mech advan. (was changing a leaking caliper today, safety items first)

I think it's an ignition problem, even though new parts were installed. What other possibilities could it be? Bad coil? Bad Condenser? is there a ballast resister that could be bad? I'm not ruling out the carb, but I"m not sure that will effect it when hot, other then perhaps fuel purculation? (hmmmm)

Sorry for the long post, any help is appreciated!

 

Sorry for the long post... my question is, is there a ballast resistor on a '72 that is subject to heat soak?

Thank you in advance.

 

Rebuild the carb. After sitting for 12 years, it's ready.

 

Welcome to my world. I've dealt with both issues recently.


I had a reproduction "original" coil that was no good above 3500 rpms. Car would sputter, even felt like it simply would not rev any higher.

Bought an original coil that tested out ok and it immediately ran better.

 

How long does it take for it not to start? Immediately?

Does it crank but not fire?

Do you smell gas 5-10 minutes after shut down?

If you smell gas you may be able to pop the hood and hear the gas boiling (if that's the issue)

 

I bet it needs to have its valves adjusted.

 

No ballast resistor on a 72. But there is a resistor wire that connects to the coil
Ed
Ed

 

ballast resistors usually aren't intermittent.....its a go/no go..... now coils and condensers can suffer from heat soak


does your 72 have an HEI unit? that's a really good upgrade if it doesn't.

 

you don't mention changing spark plugs or cap/rotor and plug wires...after 12 years those need to be changed also....

 

Plugs, cap, rotor and plugs wires have not been changed as of yet. Has new points, condenser and coil.

 

no valve noise, but not a bad idea.

 

Will not restart after a couple minutes... cranks, but no fire... YES Smell gas, almost like it's flooded.... cannont hear the gas boiling, however, it might be. I think you are on to the cause. Perhaps a larger carb gasket to insulate it from the heat?

 

i think there are several issues going on....one sorry to say, is never start a car on gas that is 12 years old it just moves all the old varnish and crap into the carburetor and causes more problems to deal with, i see you say you cleaned the carb make sure the needle and float are adjusted properly.

i think you need to look at this as a car that needs an entire tune up including adjusting the valves and replacing the fuel filter.... who know why the car was parked 12 years ago.....memorys get fuzzy about the actual details. any number of things will cause your problems...no power after 3or 4 k leads me to think it needs a valve adjustment. these cars will run even with really bad parts....they just will not perform very well.

i would tune it up with new plugs and wires , when it is running use a dial back timing light and map out your timing curve. may not be bad idea to do a compression check on all the cylinders and to verify where TDC and make sure the timing marks line up. hook up a vacuum guage and tell us the vacuum its pulling. i also would probably disconnect the fuel pump line to the carb and measure and time the fuel output when cranking....to make sure fuel pump is operating properly

look at it as a completely unknown engine that you need to verify everything with.

 

Bob, thank you for help it is greatly appreciated. I will follow up on how it's going. Here are a few pictures of what we are working with...

 

looks very nice good luck with it, bob

 

I don't want to hijack this thread but I'm having similar issues with a car that hasn't been sitting long and has fresh gas. Just in case its similar to what our friend is experiencing, I'll add some details and would love to hear your feedback.

In my similar case, the car starts up just fine when cold and runs fine. When hot, it will start right back up immediately. However, when warm (lets say 15-30 minutes), the engine cranks but won't turn over. Its almost like its flooded but with all the things I've tried, I don't think this is the case. I do smell a little gas and the smoke that comes out of the exhaust during the failed start smells rich. I'm not seeing any signs of boiling gas under the hood either. In fact, hot in my case might be as little as 200-230 or so.

Any thoughts that might benefit blk79nj and I?

Thanks!

 

what is the posiiton of the choke butterfly when its warm?

 

Yes, this sounds exactly the same however... i didn't check the smell from the exhaust. The choke in our instance was open.

 

Mine is open as well. The choke issue seems to be on the right track for my "version" of the issue though. I noticed while poking around that the replacement choke spring was manufactured with the hook on the wrong side, negatively impacting the temperature lever of the choke both in distance and direction. I put the original back on there (its been off for a while because I've had a few issues compounding) and it at least idled and restarted much better than before. I'm going to do some driving tests on the 4th and hopefully it will be a good day!

If it helps, a headlight vacuum issue resurfaced while diagnosing this and I was able to play with the switch to see the impact on starting/idling with the choke. The issues compounding made things a lot worse than they were alone. How strong is your vacuum?.

 

Didn't get a chance to check the vacuum.... perhaps this weekend.