Good point
SS425HP said:
The strangest thing to me, is that these engines did not run hot when new. I know things have changed regarding cams, etc. A bigger cam should make them run cooler due to the overlap and more fuel going through. Roller rockers should run cooler. Roller lifters should run cooler. The only variable left is timing. Have we gone overboard on timing????? The cooling system is the same. We had 4 row radiators from the factory. They worked, along with the fan and clutch. Have the water pumps gone south due to age???????? Something has gone sour to cause all this overheating. What the heck is it? This thread has been all about securing a cure, but what is the cause???????????
I never owned a 409 car back in the day, so, I have no experience to say that '09's' ran cool or hot when they were new.
But, contrary to what you said, I was personnally told by a 409 guru that the 409 was always somewhat problematic -- being hotter running -- especially as compared to SBC's and later BBC's.
I thought for a bit that the layers of internal corrosion/rust might be the culprit, but, my 446 truck block spent over 30 years stored in a climate controlled environment, in an oiled bag! The internal casting surface looked brand new! So, at least for my 446 stroker, the internal corrosion issue was not a factor.
The use of unleaded fuels is definitely part of -- if not "the" -- problem. It seems that all of today's EFI engines run normally in the 210 range. But, when we get our carbureted 409's up to those temperatures, they don't run so well -- and boil-overs are not unheard of at all.
Lower octane fuels burn quicker than higher octane fuels. They are best described as "explosive" as compared to a slower and thus more easily controlled burn of high-octane fuels (106, 110, 112). The use of lead in such high octane fuels made the burn more predictable and controllable.
I've also encountered problems with electric fuel pumps, that seem to lose their ability to hold proper fuel pressure when they themselves have been running awhile and get hot. Any significant resulting pressure drop can result in a lean-burning situation, thus, a hot running operating temperature.
The use of a fuel-pump relay, where the switched power source is connected directly and close to the battery, and close to the pump should help to deal with the increasing amperage drain of a increasingly heated electric fuel pump. The pump itself, of course, should always be mounted AWAY from any direct heat sources, as well.
I'm not sure what you mean by "going overboard with timing". Running lower-octane unleaded fuels usually means needing to retard timing and slowing advance , which makes an engine run warmer, not cooler. One good characteristic of the "w's" seems to be that they can tolerate decent compression ratios, and fairly advanced timing, and lower octane fuels, without detonation (pinging).
Advancing timing helps an engine run cooler. Basic crank advance timing obviously can only go so far before the engine "kicks-back" -- the typical 12-13 degrees BTDC does not cause that. Higher octane racing fuels also help the engine run cooler because those fuels -- being slower burning -- can tolerate further basic advanced timing, and quicker mechanical/vacuum advance curves, but, running such fuels (110-112 octane) is both extremely expensive, and illegal on the street. And, I do not believe the "octane boosters" create a significant difference, and can also be expensive to use regularly, as well.
Bigger cams equate to more horse-power, which also means more heat. Higher compression (10.5:1 or above) also means more horsepower and direct heat generation as well. And, today's roller cams allow for horse-power gains that were unheard of back in the day.
What this all comes down to is this. The fuel availablity (93 octane unleaded) today is such that, even a perfectly tuned stock 409 will run warmer. There is no way of getting around this without a sophisticated amd properly programmed EFI system that, using a myriad of ambient sensors, would keep all heat generating factors constantly adjusted, to optimize efficiency of the burn.
What we have is a situation that mandates careful thinking in what we're planning in our engine builds, and the heat-generating consequences, of those decisions. Whatever we end up with, first needs to be properly tuned to minimize heat generation, and maximizing efficency.
With unleaded fuels, as compared to "good gas", any 409 combo of big-cams, high-compression, will be running warmer, and so the problem falls upon the cooling system's capacity for cooling the extra calories of heat.
What I'm saying is -- with 93 octane unleaded fuels -- no matter what 409 build we have, or how well it is tuned, we are always going to end up with either a slightly hotter running engine (let's say a stock configuration as compared to "the day"), or a significantly hotter running engine (big-cam, high compression).
Given the lack of availablity of any water-pumps that actually cool better (which the CRW pump DOES NOT do), we all need to realize that the ultimate solution will be in providing for a more efficient -- higher cooling capacity -- radiator, and air-flow system, that pulls or pushes cooling air-flow through them.
Let's look at another oddity of present day fanned cooling systems. I have a 600 h.p. 911 Porsche Turbo -- air-cooled only -- that has not ever had a cooling problem. Cooling air is drawn (sucked) from the engine lid grillwork and into a channeling of air-deflectors, that specifically guide the airflow to critical heat-generating areas (heads, particularly). The heated air is then immediately exhausted below the engine to the passing roadway.
In our water-cooled cooling systems, the heated airflow coming from the radiator is counter-productively blown directly back upon the engine! Wouldn't it preffered to have the heated air-flow made to channel downward (not blowing on the engine), and a seperate fan-forced-air system, to blow cool air directly on the engine?
Obviously this paradox was long ago overcome by simply having a larger cooling capacity radiator, with an efficient fan pulling or pushing system.... just a thought.
Submitted IMHO (in my humble opinion).
Denis
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Sorry
bang
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