Faulty accelerator pump, and/or faulty choke, and/or faulty fuel pump, and/or ancient gasoline. Check all. Fix the known problem(s) with the carb, see what happens with temperature. TEST THE SUNPRO TEMP GAUGE for accuracy.
Do this, take your balancer off and check to see if it spun. I have seen this on a few Nailheads and tons of Ford's and Chevy's. One of 2 things is happening since it won't start without help. Either timing is way off or you have a huge vacuum leak. Depending on who built it, they may just hammered the cam in there(most of the cams I have put in Nails fit really tight-to the point I have to polish the cam journals). Also, was motor properly broken in or just started?
...or properly honed. Valve seats making proper contact with the correct width/angle seats. I see those situations many times a year.
Is the gas new? When you look down the carb before starting,is it spraying gas on both sides when pumping accelerator? I guess we should get it running better before overthinking. This thing should literally purr,no shaking,vibration etc...at 800-1000 rpms,depending on your cam selection. There can be no vacuum leaks,carb base gasket,faulty power brake unit,open manifold leaks on carb or otherwise. These are generally a little cold blooded,but should smooth out nice after a few minutes of run time. I have to ask...RU sure firing order is correct? It would not hurt to post a pic of what you have,1000 eyes are better two. Something here is not making sense.
There was a gasket I think on the front part of the passenger side exhaust manifold that we did not put back on because I was told they were not suppose to have gaskets on them because they could cause cracks. Also the fan an fan clutch were painted and I'm thinking of replacing it with a new one. Another thing I think might need to be checked is the thing at the bottom of the factory passenger side exhaust manifold that has a plenum on it with a counter weight on the side of it. This thing is factory an turned freely before putting it back on but I'm wondering if it got stuck closed or is not opening enough. I'm thinking it is for helping warm up the car in the cold. Also the gaskets that were put on between the exhaust pipe and the manifolds were to tight an barely fit on so maybe there flap over to much restricting flow. I definitely could here some kind of exhaust leak on the passenger side while driving it a very very short distance before it starts overheating. Could the exhaust manifold leak be the whole problem or faulty fan clutch. I will try to post pics soon. Thanks everyone.
Does the intake manifold have an exposed exhaust crossover channel across the carb flange? If so, did you install a HIGH TEMPERATURE gasket on the manifold, then use a steel heat shield on top of the gasket? The carb base should be on the steel heat shield, there's no gasket between carb and shield.
I'm not sure what exactly what you are saying to look for a pic for reference would help.I did have a metal type exhaust manifold gasket between the front part meaning the part closer to the front of the car that was on it that did not get out back on. I was told these cars did not need exhaust manifold gaskets on stock manifolds.Mine did have I think at least one for sure cause we have it in the trunk with miscellaneous parts.
I was just thinking a pic from under the hood might help,but you are moving along with your perceptions. A bad fan clutch will definitely cause a problem. I welded my exhaust flapper open just for insurance and I think you are right that no gaskets were used on nailhead exhaust. I just want to make sure you are happy with its running and starting before the heat issue.
Yes I understand now I mis read earlier I do have both the high temp gasket an heat shield plus a spacer,i think1.5" thick between the carb and the top intake manifold on the motor. I got my fan shroud in today so we will find out tommorow if that helps.Thank you
Oh and I'm in the market for a good original radiator an fan shroud still, seeing how mine was shot an I went with this aluminum radiator an aftermarket shroud. Oh and does anyone used the FlowKooler brand water pump on they're nailhead? It has more impellars on it for better flow is what's advertised. Thank you
I have used the old design which fell apart. now am running there new design, it helps a little at idle mostly but it will don't solve your problem. need to look at the radiator flow, with the cap off start the car when the thermostat opens and rev the engine some and watch the flow going through the radiator tubes, should have strong flow at the higher rpms. also in drive put your hands over the carb to stop air flow, the engine should stop running, if the idle goes up you have a vacuum leak simple as that. I don't think so but if your timing chain cover is chewed up by the water pump it will not pump the water. simple right, check for vacuum leak and then flow of water in the radiator.
My 425 Nailhead runs cool as a cucumber. According to TT it is under-carbureted, but it has a large copper radiator and a 7-bladed viscous fan in a shroud. A properly set up Nailhead should not have a overheating issue and IMHO they are not noted for running hot. I'll go along with just about everybody here - get the basics correct - timing, fuel/air mixture (no vacuum leaks),be sure the timing mark on the vibration damper hasn't rotated. If all of this stuff is right, your Nailhead should be happy again.
Replacing a bad fan clutch this week and a fan shroud. I hope this solves the overheating issue. Still I've ran other motors with no fan shroud and have never had the temperature keep going up even while driving.
I would suggest 180 as 195 is winter type. Once i tried that route and it was to hot for my liking. My Riv with shroud and seven blade fan can sit for hours in summer traffic idling and now way she overheat. Peace,
That means the engine will never run cooler than 195*, and that thermostat will not be fully open until 215*.
Just out of curiosity have you used a laser thermometer to check the temps all over the radiator, hoses, water pump, gooseneck, heater hoses, etc?
I have not used a laser thermometer. But I did order a factory fan shroud an a six blade fan this week,i hope that cures the problem and of course the new fan clutch and 180 thermostat im putting in tommorow. If I do get a laser thermometer of course I would be looking for over substantial markings of heat but the degrees that are normal and not normal that I need to know? I just no it's still getting hot right now.
Before infrared thermometers we all did a lot of guessing. And that is all we can offer to you...lots of guessing without info from an infrared thermometer exam. On mine with a fully warmed engine running at 1200 rpm (fast idle cam) the hottest water temp spot is the thermostat housing and usually at the specs for the thermostat. The coolest spot is the water pump at the lower radiator hose and is usually about 20* cooler. The back of the right cylinder head at the temp sensor is only a little warmer (10*) since water has only circulated past the cylinders. More guessing: an extremely tight engine will generate more heat from friction. My cure is to dump the break-in oil after a few hundred miles and then run it hard.
A new engine isn't really tight and generating more heat...the rings aren't always fully "broken in" or the valve seats aren't making a full contact pattern yet. Combustion temps already generated are going to show the temp gauge to swing around more until heat transfers better. Interference angle VJ's contact on just a thin edge and the exhaust valve runs hotter. Wide exhaust valve seats are a major contributor to octane tolerance and the running temp of the exhaust valve has considerable influence to the overall equation of compression limits.
