Idles hot...

chargerdon · June 24, 2020, 10:25:50 AM

My 74 Challenger has a 360 LA with stroker kit to 408. Engine was built to be about 9.8 to 1 static compression ratio, and has a Lunati 703 Cam. It also has a stock water pump and 190 degree thermostat and a Champion aluminum 2 row 26" radiator rated for up to 500 HP and 6 Blade 16" direct water pump fan. Standard 15 psi radiator cap. I also have a Vintage Air air conditioning, so there is the Air Conditioning Condenser bolted to the front of the radiator. (it works great !)

In hot weather (anything over 80 degrees) it will run great around town, or on the highway at 70+ mph...no issues. The temperature gauge will stay just into the first part of the stock gauge. I have shot the radiator hose neck when at this temp and it shows around 195 and the top of the radiator and exiting (bottom) at around 160.

However, any prolonged idling and the gauge will rise to about 3/4 of the way which i believe to be around 200-210 range...hot but still not overheating. ... Not overheating, however, at that raised temp it will idle plenty rough and drops its idle rate from the 800 to 600 RPM. Same for real low speed driving (like in a parade) i do a lot of "parade driving" with my car club and would like to remedy this issue. Right now i dare not turn on the air conditioner for fear of overheating or stalling.

It didn't have a fan shroud and i couldn't find a new one for it...for some reason all of the new shrouds sold on Ebay for 26" E Bodies lists them for 70-73 not 74's. ????? So i made one for it and it didn't make much difference.

Suggestions while keeping the cost down. My thoughts are:

1) Try a different shroud... even tho i cant find one for "74 Challenger"...

2) replace the stock water pump with a high flow pump?? Suggestions?

2) Replace the 2 row aluminum Champion radiator with a 3 row ?

3) Remove the 6 blade pump fan and replace with a set of electric fans? Suggestions as to brands ?

72 Challenger · June 24, 2020, 10:39:59 AM

you have the opposite problem I am having in my post!

nothing to add but best of luck!

73440 · June 24, 2020, 05:22:11 PM

The shroud depth covering the fan makes a difference .
Don't remember the correct coverage, thinking 1/2 but not sure on that.

Is the fuel and fuel line getting too hot while idling ?
DEI wrap on the fuel lines.

https://www.flex-a-lite.com/blog/the-perfect-fan-shroud-position/

dodj · June 25, 2020, 05:39:52 AM

I don't think there would be a difference between the 73 and 74 fan shrouds, but blade depth is important for best efficiency. As 73440 said, half of the blade into the shroud.
I'm not a fan of electric fans.
If you have a clutch fan it is possibly faulty and not moving the air it should at higher temps.
When I went to an aluminium high flow water pump and housing, my cooling improved noticeably. How deep the impeller sits in the housing is important. Use the thinnest gasket you can.
Are you running really lean?
That's all I can think of.

YellowThumper · June 25, 2020, 07:25:32 AM

Shroud issue for a 74 is probably due to the overflow tank introduced that year.
Agree fan placement is critical. 1/2 in and out is what I have been told. Too far in and it creates turbulence. Too far out loses ability to draw thru radiator properly.
Check your initial timing as well. Too retarded (factory specs) can cause hot issues.
Fan clutch as noted could be an issue if bad. Turn fan by hand when all is warm. There should be resistance. Carefully with proper protection...
Seal off all intrusion areas that allow air to bypass radiator.
Even the hood to core support is necessary.

Now to open the over discussed and never concluded debate on electric fans...
I like you do a lot of stop and go and stop and stop driving.
Had same issues (la360) with extended low mph.
Went dual electric fans and never looked back.
Overheating became a thing of the past.

If you have addressed all items noted previously. As a test you could try and install a pusher fan in the front that is only switched on when necessary.

PLY474 · June 25, 2020, 08:24:02 AM

Try changing the vacuum advance from ported (above the throttle plate) to manifold (below the throttle plate). This will advance the timing at idle and result in cooler idle operation. I run my 318 (with a 19" stock radiator) with manifold vacuum and it runs almost too cool. I'm actually considering changing my thermostat from 180 to 195.

Interweb search ported vs manifold vacuum to learn more. I did a quick search and came up with this link where the author says, "For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum." https://www.camaros.net/threads/timing-vacuum-advance-101.150344/

chargerdon · June 25, 2020, 11:00:48 AM

Quote from: PLY474 on June 25, 2020, 08:24:02 AM
Try changing the vacuum advance from ported (above the throttle plate) to manifold (below the throttle plate). This will advance the timing at idle and result in cooler idle operation. I run my 318 (with a 19" stock radiator) with manifold vacuum and it runs almost too cool. I'm actually considering changing my thermostat from 180 to 195.

Interweb search ported vs manifold vacuum to learn more. I did a quick search and came up with this link where the author says, "For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum." https://www.camaros.net/threads/timing-vacuum-advance-101.150344/

Yes, i run mine with vacuum advance on the full manifold vacuum side. I did this long ago, so that i can run with a much higher advance at idle, and still not have problems turning the engine over when hot. My initial advance is around 16 degrees, plus another 8 for the vacuum ( i turned it down from the factory 10), then a limiter in distributor so that mechanical is max 14. This gives me 16 while starting, 24 while idling and tops out at 38.

dodj · June 25, 2020, 02:42:37 PM

Quote from: YellowThumper on June 25, 2020, 07:25:32 AM

Now to open the over discussed and never concluded debate on electric fans...

Yes, the debate never ends..lol

It's like 'what oil is best' debate.

JonH · June 25, 2020, 03:06:17 PM

Keep the thought process simple. If you only have issues at idle, it is easy to conclude you do not have enough airflow through the radiator when the car is not moving or moving slowly. AC condenser only exacerbates the problem. Your choices are simple to me, either ad an electric fan for low speed operation or go to a 3 core radiator. It will only be worse if you run your AC. If you run your heater at full blast, (acting as a second smaller radiator) does it help at idle? This would reinforce the idea of low air movement/radiator capacity. Personally I would replace the radiator and be done with it....

Chryco Psycho · June 25, 2020, 08:06:53 PM

Heating at idle generally is lack of air or coolant flow or timing .
A clutch fan with 5-7 blades & shroud that are working correctly are the #1 issue , as above the clutch has to become tight with heat if not it is faulty . I have found this is the most effective system when working correctly .
Timing was my next suggestion you need advance to reduce heat but you semm to have that under control .
I have rarely seen a high flow water pump change temp much so that would be the last thing I might try .

YellowThumper · June 26, 2020, 07:10:48 AM

Quote from: dodj on June 25, 2020, 02:42:37 PM
Quote from: YellowThumper on June 25, 2020, 07:25:32 AM

Now to open the over discussed and never concluded debate on electric fans...

Yes, the debate never ends..lol

It's like 'what oil is best' debate.

Lest we not overlook the debate about ported or manifold vacuum advance.
That has been the best "heated" discussion I have had at other times.

Back on point.
Air flow gets my nod.

chargerdon · June 27, 2020, 08:42:17 AM

Quote from: JonH on June 25, 2020, 03:06:17 PM
Keep the thought process simple. If you only have issues at idle, it is easy to conclude you do not have enough airflow through the radiator when the car is not moving or moving slowly. AC condenser only exacerbates the problem. Your choices are simple to me, either ad an electric fan for low speed operation or go to a 3 core radiator. It will only be worse if you run your AC. If you run your heater at full blast, (acting as a second smaller radiator) does it help at idle? This would reinforce the idea of low air movement/radiator capacity. Personally I would replace the radiator and be done with it....

I don't have enough room to "add" an electric fan to the belt driven fan. So my choices seem to be either replace the belt driven fan with a pair of pull electric fans and the solenoids or replace the two row radiator with a 3 row radiator.

I don't know that 3 row would be any better than two row? I know that when i bought the 2 row 26" champion i talked with the vendor who sold both, and he said that his 2 row and 3 row were both rated the same for cooling. That the 3 row had smaller tubes to fit in the same space as the 2 row... So, i'm confused as to how that would solve the problem. If i knew for sure, then i would go that route as i don't really want to mess with the electric fans...

Id probably have to replace the Alternator (stock 45 amp), with at least a 60 amp do handle the power flow (already have a 10 gauge wire from alternator to the starter relay and voltage rather than amp gauge.

I do believe tho that the twin electric fans would definitely solve the problem... Not so sure about 3 row radiator.

So... what is the group consensus?

70 Challenger Lover · June 27, 2020, 09:14:41 AM

When I owned my 70 SuperBee, it came stock with a 22" 2 row radiator. It was adequate for the stock engine build but once I rebuilt the engine and ramped up the power significantly, I found that even a thicker 22" radiator couldn't remove enough of the heat. I tried electric fans and everything else but eventually the cure came from a thick Griffin radiator that had two long thin rows and a much higher cooling capacity. I also had to run a solid 7 bladed fan. A lot of fan noise but it worked.

I agree that more initial ignition timing helps but with your higher performance engine, it's hard to get away with that compared to us doing it on low compression 318 motors.

Chryco Psycho · June 27, 2020, 08:38:31 PM

Here is my $.02
Electric fans will not cool as well , I have Never seen them outperform a clutch fan , also each fan can draw 15-18 amps so I would be looking for 100 amp alt , bypassing the ammeter & adding a bypass between the alt & start relay.
As afr as the rad goes you already know the answer 2 & 3 row have the same cooling rating .
SO you can waste your $$ & try to prove me wrong .

chargerdon · June 29, 2020, 12:14:34 PM

Quote from: Chryco Psycho on June 27, 2020, 08:38:31 PM
Here is my $.02
Electric fans will not cool as well , I have Never seen them outperform a clutch fan , also each fan can draw 15-18 amps so I would be looking for 100 amp alt , bypassing the ammeter & adding a bypass between the alt & start relay.
As afr as the rad goes you already know the answer 2 & 3 row have the same cooling rating .
SO you can waste your $$ & try to prove me wrong .

Hmmmmm what to do ...what to do...

First, i double checked my timing... found...don't know why...but the static timing had somehow dropped to about 11 BTDC... So, i bumped it up another 5 degrees to around 16... Now along with the vacuum (it is dialed down to about 8-9 degrees) advance it idles at around 25-27 BTDC. Took it for a ride and no ill affects...so keeping it there. It was 88 degrees here in NC so when i got back from my test drive the temp gauge was sitting at about 20% of the middle bar..right where it usually is... I shot the goose neck (hose to top of radiator fitting on intake manifold) with my infrared and got 194...

Then i let it sit there idling in the hot weather for about 6-8 mins... the temp gauge rose to about the middle of the gauge, and shooting the goose neck was then getting around 205-207 degrees. However the idle stayed rock solid, so i guess the extra 5 degrees of advance is helping that... Then temp seemed to stay right around there..

Also, i checked carefully the positioning of the 6 blade 16 inch diameter flex fan and it is completely inside my home made shroud. The article in the link posted here says that that the fan blades should only be about half way in the shroud...that completely inside will cause turbulence and not pull thru the radiator at full capacity. So, i THINK im going to bite the bullet and purchase a factory style plastic shroud...see ebay item 254534171977 part number 26" OER 2998326 . I am concerned that all of the available shrouds seem to all state 70-73 Mopar B and E body, but since i do NOT have a stock mopar radiator with overflow tank i have to believe that this shroud should fit on my Champion 26" radiator????? I also have in my garage a 5 blade flex fan that is 20" wide (it wont fit in my homemade shroud..). This shroud states opening of 20.5 inches so it should fit in this shroud and provide more air flow than the 6 blade 16" i currently have on.. Will try it also..

Anybody have any other suggestions for shrouds before i spend the money on this one...again ebay item 254534171977 OR 26" OER 2998326... .