How do modern cars regulate temperature so well?
If your temp creeps up in this situation with the fans running full time, your system needs work.
Your engine is the first part of the equation
And in that, you gotta think about what is going on in the combustion chamber at idle. I'll guess you have this cam.
HUG SMC1326AL
This appears to be a small at .050 cam,
claiming 213/226/109+5 But Hughes doesn't tell you that the advertised is probably close to 264/276/109.
Now, what you gotta see is that, in at 104 , the compression degrees are just 124, with an Ica of 56*.
The power duration is just 108*. and
The overlap is quite generous at 52*.
Lets stack 'em up
264/124/108/276/52overlap; and the factory 318
240/133/121/248/22
So what is that showing us?
Well, check out your compression degrees of 124 versus the stock 133, So your cranking compression is expected to be 128psi (720ft elevation) compared to 137psi for the nominal factory 8/1 engine. What this translates to is a Dcr of 6.8 for you compared to 7.1 for the stocker. Not too big a deal by itself.
But check out your power degrees of 108 versus the factory 121. This shows us two things; 1) you get lousy fuel mileage, because the pressure in the combustion chamber is released very early at just 108* ATDC, compared to the factory at 121, or 13* later; and so that pressure could have been used to turn the driveshaft. Instead it is running out your headers, heating them up. But on there way out, they cook the water in the heads, surrounding the ports.
And now, the overlap. This is the time in the cycle, during which BOTH intake and exhaust valves are open. The piston is at TDC or within a few degrees. The headers if working right,are tugging on the chamber to pull the last of the exhaust out. But, since both valves are open, that tug goes right across the chamber to the intake plenum and gets that started towards the chamber too! In your case your Whiplash has 52* of time for this to take place , which is a lot of time. It is 42% of your compression duration and 48% of your power duration, so that's a lot. So what's going on here at idle?
The header is gonna pull some of that intake charge straight out into the exhaust system. Where, it could catch fire when it gets to the merge, because of the still burning residues from other cylinders.
So, taken all together; at idle; This is a terribly inefficient running mode, with a lot of the energy being wasted as .............. heat , external to the combustion chamber. If you couple that with retarded ignition timing, which causes the mixture to still be burning with the piston on it's way down in the cylinder, and so heating up the water jackets; You got a lot of heats to deal with; namely; Water jackets, exhaust ports, headers, and even the exhaust pipes.
Please, tell me your carb is sucking air NOT from under the hood. That would be like feeding a runaway nuclear reactor.
Remember, we are still idling in traffic.
Where is all this heat going?
The only way out, is under the car; and stopped, your fans are gonna have to push it out, cuz hot air rises, and continuously heated air rises continuously. So your heads are being triple-cooked; once from the water,once from the hot exhaust,and once from the underhood hot-air. And your induction system gets a double dose, and your engine oil is not liking it either.
So, before you condemn your cooling system, consider what it is trying to deal with.
You might think that retarded timing does not apply to you. But I can tell you that for sure your idle-timing is retarded. Go warm up your engine. Check the timing. Now loosen the D and crank in a bunch more timing, until the rpm no longer rises; now read the timing again. This is the idle-timing your engine wants, at whatever rpm it climbed to. Don't be surprised to see high 30s* and more. Ok now retard it back to whatever she earlier had. I'll guess you were at or near 50%.
So what's the solution?
Well you know where I'm going, but before I say it, prove me wrong.
How?
Warm your engine up; crank the rpm to 1600, then advance the timing, to peak the rpm. Continue until she hits about 1800 rpm; then turn the fans on full time, leaving the hood open. Finally, twiddle the mixture screws for best lean rpm.
Grab a beer and your IR gun, and watch the temperature. This set-up, eliminates most of the sources of waste heat, and allows what is being created, to escape, and gives your carb half a chance at finding cooler than 350* air.
Wait 3 minutes and record the hottest spot around your stat housing. Mark the spot. Wait 4 more minutes and check again. Continue this way until you get two consecutive same/similar readings, or if the temp exceeds 220.
At the end of the test, idle the engine down, retard the timing back to the start. and give her a break.
What's it mean?
What we have done, is take the worst case situation, and made the best of it. This is the potential your current system has. If it cannot maintain a sub 220 temp, you are gonna have to make some changes.
Obviously you cannot drive with your hood open. This was an effort to give your carb cool air, and to give your fans an alternate place to send the air. You could repeat the test with the hood down, but I don't see a way to IR shoot the stat-house for an apples to apples test. Perhaps if you have a fast-acting water gauge and had recorded the temps previously, comparing them to the IR gun. If that shows the same temps, then you can try the test again with retarded timing, or retarded timing and open hood ,etc; until you find the worst contributor ...... and then you will have an idea of what to do.
In a later post I'll tell you what I exactly know to have cured my over-heat problems to the point that my system runs within a couple of degrees no matter what the circumstances.
The hardest test for a cooling system is Idling,stopped in traffic, on a hot tarmac, with the hood closed. If your system cannot keep your engine cool enough to satisfy your opinion of what "normal" should be, then it needs tweaking, to satisfy your opinion. Or you gotta change your opinion.
If your temp creeps up in this situation with the fans running full time, your system needs work.
Your engine is the first part of the equation
And in that, you gotta think about what is going on in the combustion chamber at idle. I'll guess you have this cam.
HUG SMC1326AL
This appears to be a small at .050 cam,
claiming 213/226/109+5 But Hughes doesn't tell you that the advertised is probably close to 264/276/109.
Now, what you gotta see is that, in at 104 , the compression degrees are just 124, with an Ica of 56*.
The power duration is just 108*. and
The overlap is quite generous at 52*.
Lets stack 'em up
264/124/108/276/52overlap; and the factory 318
240/133/121/248/22
So what is that showing us?
Well, check out your compression degrees of 124 versus the stock 133, So your cranking compression is expected to be 128psi (720ft elevation) compared to 137psi for the nominal factory 8/1 engine. What this translates to is a Dcr of 6.8 for you compared to 7.1 for the stocker. Not too big a deal by itself.
But check out your power degrees of 108 versus the factory 121. This shows us two things; 1) you get lousy fuel mileage, because the pressure in the combustion chamber is released very early at just 108* ATDC, compared to the factory at 121, or 13* later; and so that pressure could have been used to turn the driveshaft. Instead it is running out your headers, heating them up. But on there way out, they cook the water in the heads, surrounding the ports.
And now, the overlap. This is the time in the cycle, during which BOTH intake and exhaust valves are open. The piston is at TDC or within a few degrees. The headers if working right,are tugging on the chamber to pull the last of the exhaust out. But, since both valves are open, that tug goes right across the chamber to the intake plenum and gets that started towards the chamber too! In your case your Whiplash has 52* of time for this to take place , which is a lot of time. It is 42% of your compression duration and 48% of your power duration, so that's a lot. So what's going on here at idle?
The header is gonna pull some of that intake charge straight out into the exhaust system. Where, it could catch fire when it gets to the merge, because of the still burning residues from other cylinders.
So, taken all together; at idle; This is a terribly inefficient running mode, with a lot of the energy being wasted as .............. heat , external to the combustion chamber. If you couple that with retarded ignition timing, which causes the mixture to still be burning with the piston on it's way down in the cylinder, and so heating up the water jackets; You got a lot of heats to deal with; namely; Water jackets, exhaust ports, headers, and even the exhaust pipes.
Please, tell me your carb is sucking air NOT from under the hood. That would be like feeding a runaway nuclear reactor.
Remember, we are still idling in traffic.
Where is all this heat going?
The only way out, is under the car; and stopped, your fans are gonna have to push it out, cuz hot air rises, and continuously heated air rises continuously. So your heads are being triple-cooked; once from the water,once from the hot exhaust,and once from the underhood hot-air. And your induction system gets a double dose, and your engine oil is not liking it either.
So, before you condemn your cooling system, consider what it is trying to deal with.
You might think that retarded timing does not apply to you. But I can tell you that for sure your idle-timing is retarded. Go warm up your engine. Check the timing. Now loosen the D and crank in a bunch more timing, until the rpm no longer rises; now read the timing again. This is the idle-timing your engine wants, at whatever rpm it climbed to. Don't be surprised to see high 30s* and more. Ok now retard it back to whatever she earlier had. I'll guess you were at or near 50%.
So what's the solution?
Well you know where I'm going, but before I say it, prove me wrong.
How?
Warm your engine up; crank the rpm to 1600, then advance the timing, to peak the rpm. Continue until she hits about 1800 rpm; then turn the fans on full time, leaving the hood open. Finally, twiddle the mixture screws for best lean rpm.
Grab a beer and your IR gun, and watch the temperature. This set-up, eliminates most of the sources of waste heat, and allows what is being created, to escape, and gives your carb half a chance at finding cooler than 350* air.
Wait 3 minutes and record the hottest spot around your stat housing. Mark the spot. Wait 4 more minutes and check again. Continue this way until you get two consecutive same/similar readings, or if the temp exceeds 220.
At the end of the test, idle the engine down, retard the timing back to the start. and give her a break.
What's it mean?
What we have done, is take the worst case situation, and made the best of it. This is the potential your current system has. If it cannot maintain a sub 220 temp, you are gonna have to make some changes.
Obviously you cannot drive with your hood open. This was an effort to give your carb cool air, and to give your fans an alternate place to send the air. You could repeat the test with the hood down, but I don't see a way to IR shoot the stat-house for an apples to apples test. Perhaps if you have a fast-acting water gauge and had recorded the temps previously, comparing them to the IR gun. If that shows the same temps, then you can try the test again with retarded timing, or retarded timing and open hood ,etc; until you find the worst contributor ...... and then you will have an idea of what to do.
In a later post I'll tell you what I exactly know to have cured my over-heat problems to the point that my system runs within a couple of degrees no matter what the circumstances.
