timf

The stock 4-blade right up next to the radiator doesn't work out here. A 5-blade fan and shroud will pull air through the radiator so much better. A rag placed on the front of the radiator will be pinned up against the radiator at idle. I believe your problem getting more air through the radiator at idle would be solved with this set-up. The bolt pattern and dimensions on GM products around this time were all the same if memory serves me correct. Its been a few years, so bring yours along to match-up. Hope this helps. TimF

Las Vegas, Nv is the overheating capital of the world--I've felt your pain. It sounds to me like your problem involves getting more heat transfer to the air passing through the radiator. The air passing through the radiator is greater at moving speed, hence a cooler engine. Sitting in traffic the only air going through the radiator is that pulled by the fan, hence, overheat. Here are some of my solutions: Do you use a fan shroud, and if so does the fan sit @half-way into this shroud? Do you have a rigid five blade fan with a hydraulic clutch? You can find the clutch fan assemblies in salvadge yards. General Motors water pump pulleys and clutch fans generally interchange--take your pully with you to match-up the bolt patterns. You can buy a new clutch fan and swap the five blade to it. Get a heavy duty truck unit with little slippage compared to passenger car units with more slippage(fuel economy and quiet operation.) Bear in mind these heavy duty units consume a little more engine power and are noisey. Then there are electric fans. Get a large single, or a twin-fan unit that covers the whole radiator. You'll need a good alternator because these will suck electrical power. A puller fan works better than a pusher fan. Some people out here use a pusher fan in conjunction with a belt- driven-clutch-fan-shroud set-up. One other thing, the store-bought Flex Fans don't work very well out here. Their individual blades flex to much and are too small to pull the air through the radiator. Hope this helps. TimF

Thanks, I'll check this out. TimF

Thanks, I'll double check the ignition primary wiring. TimF

Thanks for the info. I'll try to locate a rochester rebuild kit. I only raised the primary side 1/8 inch and left the secondary side at stock settings. Do you think I should have raised both primary and secondary floats? This is good food-for-thought. Thanks TimF

Thanks, I'll double check those items. I've had the carb off and disassembled numerous times and so far managed to locate a new base gasket for the reinstallation. The gist of what you saying is that there may be a vacuum leak I have not considered. I wonder if the top lid of the carb itself could be warped enough, or the overused top-lid gasket could be giving a false signal to the power circuit. That's food for thought I will look into. Thanks for giving me a new angle of attack. TimF

The factory spec for the float setting is 1 3/8 inch. The float drop is 1 13/16 inch. I suspected the float level as well, and raised it to 1 1/4 inch. This helped but did not solve the problem. I'm afraid I'm simply masking the real problem. Its those twin floats on those long arms that really make the early Rochesters a challenge.

UBB7-ML-227711-ML- Moved thread from Buy/Sell to the Tech Questions forum. (Peter J. Heizmann)

My '57 Pontiac Starchief with a 347 cu in engine unexpectedly stalls while rolling through either a right or left turn, and occassionaly, while coming to a stop. If I start the turn from a stop, it does OK. I've gone through the entire fuel system chasing this problem, and I'm looking for advice in its repair. I rebuilt the Rochester 4GC to factory specs and installed a new fuel pump. The new fuel pump puts out @4psi and its volume exceeds one quart in one minute. The fuel line from the tank to the pump is undamaged and clear. It supports a minimum of 10 inches vacuum. I removed, cleaned, and inspected the fuel tank and its sending/pick-up unit. The power valve and its corresponding vacuum actuating rod seems seems to funtion properly. Idle speed, choke, and mixture adjustments have no effect on this problem. However, the frequency and severity seemed to be reduced after I raised the primary float setting from 1 3/8 inches to 1 1/4 inches--the float drop was kept at 1 13/16 inch. I upgraded the ignition with an MSD 6A amplifier, and inspected the distributor's vacuum and centrifugal advance. The engine starts-up and comes off the choke step good. It idles smooth and pulls a minimum 15 inches vacuum. On the road, it has adequate power with no missing, and has normal operating temperature. The problem appears after driving awhile and becomes more frequent the longer you drive it. Please let me know if anyone has an idea of what demon I need to slay next to solve this problem. Thanks TimF

My '57 pontiac 347 starchief unexpectedly stalls while rolling through either left or right turns. If I start off from a stop it seems OK. I've gone through the entire fuel system. I rebuilt the Rochester 4GC, adjusting float levels and drops to factory specs. The fuel pump's pressure and output are good. The fuel line going from the tank to the pump is undamaged and clear. It supports a minimum of 10 inches vacuum with the engine running. I removed, cleaned, and inspected the fuel tank, along with its sending unit. The power valve seems to be working ok. I've played with the idle mixture screws along with curb idle settings. Raising the primary float level from the factory spec of 1 3/8" to 1 1/4" reduced, but did not eliminate this occurrance. The engine starts-up good and comes off the choke step good. I idles smooth and pulls a steady minimum of 15" vacuum. It has good power with no missing. It seems to occur more regularily after the engine has been running awhile. If anyone has any ideas, please drop me a line. Thanks TimF