hello guys,
I had a strange problem yesterday and have no idea where to start?
I put a new radiator in my 76 vette, L-82 350 sb. the last owner had put stop leak in the thing and it was plugged up. anyway, I put in a Dewitt aluminum radiator and kept the mechanical fan! (i had ask about electric fans in the forum before) the car ran fine before this change. since I have had the car less then 6 months, I have changed plugs and wires, cap and roter, had carb rebuild, remove the A.I.R smog pump. checked timing and just general maintenance.
the car has been running fine, but yesterday we drove it about 40 miles on the highway, it ran great on the interstate with no problems but once we got off at our exit and hit the first stop light the car died, it started back up (was hard to start) and i would have to stay on the gas to keep it running. almost like it was flooding out or not getting enough fuel. It done this though 3 stop light before I pulled into a as station. I topped the car off with fuel even though the gas gauge still said a half a tank. I do believe the gas gauge is correct as it only took 6 gal to fill it up. also when we restarted the car the gauge went to full.
the car ran fine after we stopped so we went on the our july 4th party.
we then headed home, again the car ran fine and we made the 40 mile trek on the high way home, once we got off the interstate the second time the car ran fine idled fine, ect...I have not had it act up again but was wondering what the heck was going on. as we make this trip a lot (wife's family) and do not want to get stranded or hurt the motor ect...

anyone else have this problem? any ideas what i need to be looking at?

by the way, the temp in the car (accorind to the gauge) never got over 195, oil pressure was good ect...

 

Could be the fuel was percolating because the fuel line from the pump is too close to the block or exhaust manifold.

 

Was it cooler out when you returned?

 

Who rebuilt the carburetor?
Is the carburetor a Quadrajet?
Any idea what they set the float level to?

 

It was not really any cooler out when we came home, I have a metal fuel line from the fuel pump not sure I could get it any fuhrer away from the block maybe it needs a heat shield?
i had the carb professionally rebuilt I have no idea what the floats are set at it is a q-jet carb, just seem strange the car had been running fine up until this, Took it out just a bit ago and it ran fine

 

Just out of curiosity, how old was the fuel that was in the car when it started "acting up"?

 

Bad gas? Water in the fuel? There is enough alcohol in today’s fuel that topping up the tank may have absorbed the water. (Alcohol will mix with the water and allow it to pass through the engine.)

 

It might be flooding out. Next time it happens take the air cleaner lid off and see if there is gas spraying everywhere when you crank it. Have an extinguisher handy.

 

That's was I was leading up to...

 

You changed plugs, wires, cap & rotor.
What about the "Modge"?
Modules hate heat and will give you issues until it cools down.

 

I can guess a couple of things, stuck floats or jets, clogged fuel line or filter. Its most likely a coincedence as it more likely may be crap in the tank or water. You need to start keeping track of the weather, the fuel level and engine temps. I used to ahve a mustang that had crap in the tank and it wa ony really bad at lower levels

 

we have been driving the car so the gas was not very old, modules? i do not know what that is? sorry if that is a dumb question

 

I think hes referring to the Modules in a HEI distributor under the rotor

 

They will born to fail starting in 1976. Most quit at 60,000 miles. As they get hot, the heat breaks the electrical contacts of the circuits inside the unit. When it cools, the contacts are joined again.

Its an easy fix and reasonably priced. Go to Summit Racing and click Ignitions / Distributors. If you buy a new one, make sure it either comes with Heat Sink Compound or buy that separately. Keep the old modge in the compartment behind the passenger seat, just in case.

 

Also, the float in carb can either get a pinhole leak (if brass) or become gas-logged (if resin). Either way, float gets heavy and sinks rather than float; that causes the carb to flood.

 

Note, that it is heat sink compound.(or grease) Some people think that since the module is an electronic device, that it needs dielectric grease. That is not the case. Heat sink compound is a heat conductor made to conduct heat from something that generates heat, e.g. the HEI module, to something that can absorb the heat and send it somewhere else, e.g. the big block of aluminum the module sits on. Dielectric grease is an electrical insulator and is often a good heat insulator. Thus putting dielectric grease under your module could prevent heat transfer the aluminum block and thus be worse than putting nothing there at all.

 

Could also be the Ignition coil is starting to fail.
They will break down when they get warm and function fine when they cool down.
They are cheap and easy to replace.

 

If the vacuum advance on the distributor is fed from 'ported' vacuum source on the carburetor (as specified in the GM books), that...along with ethanol in the fuel...will give you percolation issues after a long run and then back down to idle condition. For best operation, vacuum advance should be supplied from a 'manifold' vacuum source. That will advance the ignition spark at idle conditions--like the GM engineers designed the engine to do. 'Ported' vacuum is an emissions "thing"; but it runs the engine hot. Now that we have ethanol in our fuel, the problems 'ported' vacuum creates for ignition timing are magnified.

 

Interesting, for sure...............