About two weeks ago I blew a water pump gasket and didn't notice. I was sitting at a red light and as it turned green I looked down and saw the needle buried on the wrong side of the temp guage. I had to drive maybe a mile before I could pull into a parking lot and shut down. Good news is the temp went down as soon as I started moving. More good news is that after I shut down I opened the hood and found the leak and was able to watch it leak for a couple minutes before it finally stopped. So I figured I caught it early and no damage had been done. I walked to a parts store, replaced the gasket limped home and that was that.

Now after the fix the car ran fine and didn't indicate any problems until yesterday. I stood on the gas getting onto a highway and it felt like the secondaries didn't open. It is a new carb and had only been on the car two weeks before the water pump gasket blew. I haven't changed anything on the carb other than swapping out a vac hose that was collapsing. Before the overheat it was pulling hard when I'd get into it and now it feels like it did before when I had a poorly adjusted throttle cable and secondaries that never opened. I'll try the paperclip trick later today but I doubt it's the secondaries because really nothings changed from the carb setup and it was running strong before the breakdown. I'm wondering if maybe it's realated the the overheat. Even though it didn't seem bad initially could it be I did some real damage? If so where do I start looking next? There's no apparent leaks, oil and coolant appear to be normal, no funny smells or smoke..... but it doesn't wake up when I get on it like it did prior to the overheat. Thanks in advance for the help, I'm learning one broken part at a time!

 

Cross your fingers you didn't burn up a head gasket. I had an issue very similar to that a few years ago. After fixing the leak, head gasket blew about two weeks later...Good luck and definately keep a cell phone with you just in case!

 

Well there's bad news and worse news. First I took a cruise and tried to get on it a few times to try the paperclip trick and that sucker didn't move at by the time I was back. How long should it take before the secondaries open, the roads here are wet and I didn't get to stay in it long once the rpms picked up as the back end was getting loose. I did put it in fourth and and mash on it for a good amount of time though. Do the secondaries open up later in the powerband or do they function when the throttle mashed and the primaries are at WOT?

Next I let her cool and too a peek at the coolant with the motor running once again. I have an aluminium radiator with no cap and an 'expansion' tank. There were bubbles in the coolant. Now is it normal to see bubbles in the expansion tank or is this an indication of a blown head gasket?

 

IMO , Bubbles in the coolant tank are not normal.
Sounds like a gasket leak. Probably need to pull the heads to check it out.

 

go to harbor freight tools get a coolant pressure tester for 30bucks and pump the water pressure up to 12-18psi with a pressure cap fitting that goes on the expansion tank if it holds the pressure for more than 15 minutes you are good if not you have a blown gasket do this before tearin into a head. If it leaks off then you will see the leak and find it if you cant see the leak it is internal and will be mixing into either the oil or dumping into the exhaust check for milky oil but if it is a freshly blown gasket you wont see the tell tale signs for a lil while the pressure test is your best bet to confirm a major problem

a blown intake manifold gasket will cause the secondaries not to open up correctly if they are vacuum secondaries an may have you not loosing coolant yet just baking it onto the cracked gasket when the engine heats up to operating temp

a blown head gasket will do the same but is much more of a pain in the *** hopefully when you overheated it you just got your valving in the carb stuck an is preventing the secondaries from opening an there is no blown gaskets if there is blown gaskets hopefully you have blown intake easy to replace and easy much less expensive. when overheating to the bury the temp needle you will often times overheat the mechanical fuel pump on the block an heated fuel can sludge up and cuase things to stick and plug clean the carb an pressure test the coolant

I had this exact same problem on a 70 montecarlo with a sb 383 it overheated b/c of the water pump and i ran it a few miles got way too hot i didn't loose a gasket but repalced them before i found that out and it still ran like **** three weeks in shop class and a total tear down later i cleaned my carb fixed the problem

 

also if you have a sealed readiator that fills by sucking coolant from the expansion tank you may have air in the system and needs to be blead or have more coolant air pumping through the system will cause air bubbles to feed back into the tank.
I am being as optimistic as possible not becuase i think a problem doesnt exist just think you should look at a few very simple posibilities before you tear into a major engine repair if it is not necessary. As a mechanic who got paid on commision if you take what you told us to any shop you will most likely be instantly told to put head gaskets on even if not necessary. The test i told you to do will cost you at least $2-3 hundred in labor alone figuring 100 an hour if taken to a shop good luck