Would my dual snorkel scoop be affecting my cooling at highway speed?

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Clelan

Clelan

Inferno Red Duster
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Location
Martensville Sask. Can.
74 Duster
360/A-500/3.23 gear
Stock Ignition
670 Holley Vac secondary carb
Cheap headers and dual 2.5" exhaust
Factory AC with 26" rad (recored to 3 core), factory shroud, 5 blade clutch fan from a mid 80s Dodge truck (1" off the rad)
External trans cooler
Timing set by vacuum gauge cause the balancer mark is way off. Vacuum advance currently disconnected.

Last Friday at the strip, it was started, stopped and idled between my 10 passes with no AC on for a few hours and the temp never topped 160*F. In traffic with the AC on, it does not go past 180*F. On the highway with the AC running 70ish MPH at 2000 rpm the temp goes just past 200*F and drops back to 180 once you are back in traffic.

Is this caused by my timing being out of whack or could my dual snorkel scoop be creating a positive pressure under the hood that limits airflow across the rad?

How does timing affect operating temperature? I searched and could not find the answer to that.
Cley
 
89on35s said:
74 Duster
360/A-500/3.23 gear
Stock Ignition
670 Holley Vac secondary carb
Cheap headers and dual 2.5" exhaust
Factory AC with 26" rad (recored to 3 core), factory shroud, 5 blade clutch fan from a mid 80s Dodge truck (1" off the rad)
External trans cooler
Timing set by vacuum gauge cause the balancer mark is way off. Vacuum advance currently disconnected.

Last Friday at the strip, it was started, stopped and idled between my 10 passes with no AC on for a few hours and the temp never topped 160*F. In traffic with the AC on, it does not go past 180*F. On the highway with the AC running 70ish MPH at 2000 rpm the temp goes just past 200*F and drops back to 180 once you are back in traffic.

Is this caused by my timing being out of whack or could my dual snorkel scoop be creating a positive pressure under the hood that limits airflow across the rad?

How does timing affect operating temperature? I searched and could not find the answer to that.
Cley
Click to expand...
If the scoop is hooked up like it's supposed to be (into the carb) then you shouldn't get much back pressure at all. If it's open under the hood then maybe yes. The more advanced you set the timing the hotter it will run. Also, for the highway, any places around the radiator where air can bypass the radiator fins will/can cause a problem. The trick is to seal all spaces around (top, bottom, sides) the front of the radiator so the air has no choice but to go through the radiator fins. Most Moaprs came with a rubber cowl to hood seal on top of the radiator just for that reason. Also, your condenser should be mounted as close as possible to the radiator to prevent cavitation.
Treblig
 
Is your scoop connected to a sealed air cleaner (like the 6 Pack hood)? I'm guessing it's not, or you wouldn't be asking. I really don't think the opening in the scoop is large enough to create enough positive pressure to offset the much larger radiator opening. Plus, the hood is a low pressure zone, unlike the grill. With a shrouded fan, high temperatures at low engine RPM and high speed might indicate an inefficient water pump. But since you know you have dodgy timing I would concentrate on that. Determine TDC with a piston stop and mark the balancer. Then set timing to spec and reconnect the vacuum advance, and see how that goes.

I'm thinking right now that when you set timing using vacuum, you are not optimized for highway conditions. Without the advance, it might be too retarded at that engine speed. Both too advanced and too retarded can cause high temps, for different reasons related to inefficient combustion. So without some idea of where your timing is, it's hard to diagnose.
 
Condenser is very close to the Rad. Scoop is open to the under hood area. I don't have the seal on the top of the rad support installed but I do have one in the shed. Maybe I'll try that. The Vacuum advance is disconnected so it shouldn't be too advanced at cruise. Big thing to me, is that if it cools at slow speeds then the cooling system is not the problem.
Thanks for the advice.
Cley
 
The fan blade should be 2/3 into the shroud, I don't think distance from radiator matters as much as the fan position/location??

treblig
 
Remember the more holes you plug (even factory spaces like around the AC lines) in your radiator support the more air you'll get through your radiator. Some of these old Mopars have been drilled and hacked by previous owners making the radiator support into Swiss cheese. Air pressure will always take the path of least resistance!!
 
Try running a 180 stat and see what happens. If you stat is always open maybe (just maybe...) the coolant is circulating so fast at Hwy speed that it doesnt spend enough time.in radiator to cool sufficiently.
 
mvh said:
Is your scoop connected to a sealed air cleaner (like the 6 Pack hood)? I'm guessing it's not, or you wouldn't be asking. I really don't think the opening in the scoop is large enough to create enough positive pressure to offset the much larger radiator opening. Plus, the hood is a low pressure zone, unlike the grill. With a shrouded fan, high temperatures at low engine RPM and high speed might indicate an inefficient water pump. But since you know you have dodgy timing I would concentrate on that. Determine TDC with a piston stop and mark the balancer. Then set timing to spec and reconnect the vacuum advance, and see how that goes.

I'm thinking right now that when you set timing using vacuum, you are not optimized for highway conditions. Without the advance, it might be too retarded at that engine speed. Both too advanced and too retarded can cause high temps, for different reasons related to inefficient combustion. So without some idea of where your timing is, it's hard to diagnose.
Click to expand...


I agree, you really need to know where your timing is, other wise how can you diagnose any problem. Your just guessing if you don't know the facts.
 
I agree with that. I do not know how timing affects heating. But I will check that. Thanks for the replies.

Cley
 
89on35s said:
74 Duster
360/A-500/3.23 gear
Stock Ignition
670 Holley Vac secondary carb
Cheap headers and dual 2.5" exhaust
Factory AC with 26" rad (recored to 3 core), factory shroud, 5 blade clutch fan from a mid 80s Dodge truck (1" off the rad)
External trans cooler
Timing set by vacuum gauge cause the balancer mark is way off. Vacuum advance currently disconnected.

Last Friday at the strip, it was started, stopped and idled between my 10 passes with no AC on for a few hours and the temp never topped 160*F. In traffic with the AC on, it does not go past 180*F. On the highway with the AC running 70ish MPH at 2000 rpm the temp goes just past 200*F and drops back to 180 once you are back in traffic.

Is this caused by my timing being out of whack or could my dual snorkel scoop be creating a positive pressure under the hood that limits airflow across the rad?

How does timing affect operating temperature? I searched and could not find the answer to that.
Cley
Click to expand...

The incoming air always affected the cars that I`ve been around, that weren`t sealed to the carb. So will not having a shroud and a rad to hood seal.
So will not having a shroud and rad to hood seal.
 
I will seal up the areas in the front and block off the carb. Also I will get this timing right then report back what I find. Likely I'll do the timing first then try it. Just cause I need to know.

Cley
 
was the radiator done by a quality shop? was it also boiled out? changing thermostat will not help. old radiator turned into a 3 core is not a great idea
 
It was done by a quality shop. It is a new core reusing the old tanks. Should be equivalent to a new rad. Whether I should have gone 3 core is debatable.

Cley
 
89on35s said:
I will seal up the areas in the front and block off the carb. Also I will get this timing right then report back what I find. Likely I'll do the timing first then try it. Just cause I need to know.

Cley
Click to expand...

Block off the hood first. See if that changed it first. Then fix the timing

Your never going to know about the scoop if you play with the timing first
 
Fix the dang timing systems;
If the balancer mark is off, figure out why; maybe it's shot!
Cruising at 2000 rpm, she wants probably over 50 degrees.But as close as you are likely to get is 20 in the Vcan and 20 to 25 in the mechanical, for a total of 40/45. My engine actually likes cruise timing in the high fifties.
It's real simple to make new timing marks.... any where that's convenient.
For under 30mph, I suggest to;
Get a 7-blade steel fan on a Thermostatic clutch, and a 180 minimum stat. I use a 195 and the system runs a minimum of 205*F.

Retarded cruise timing means the peak cylinder pressure occurs too late and it is not as high as it should be.It also means the fire in the chamber hasn't finished burning in the top part of the chamber and so instead of the heat going into expanding the gas and pushing the piston down, it goes into the cooling system thru the cylinder walls, and the charge finishes burning in the header pipes, destroying them(eventually), and destroying the headers scavenging ability, so the piston has to physically push the exhaust out. That's negative work. And a loss of fuel-efficiency.... big-time.
But it gets worse
To keep the engine from overheating the plugs and generating random misfires, you might richen it up, making a bad situation worse.
There very definitely is such a thing as running down the hiway at too low an rpm.
There is no way short of a computer to put enough cruise timing into her, and so fuel economy actually suffers.And therefore no way to not generate extra heat.

To determine the lowest rpm to cruise at; plumb a vacuum gauge to the intake, and slowly rev up the engine,in Neutral of course, until the vacuum peaks. The lowest rpm that it does so is the first rpm where the engine is no longer in reversion, and all the air going thru the carb is going in the same direction. Now you can run it a little faster,and a little hotter, and max out the timing, and finally,tune it lean.
 
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Great advice on the timing.

The original question was “does the scoop affect cruise water temp” guess we will never know.
 
89on35s said:
Thanks AJ, That's the answer I was looking for!

Cley
Click to expand...
If you want to experiment with cruise timing, get a dash-mounted, electronic dial-back, timing device and set it to it's mid-point before setting your base timing. Now you will be able to adjust the timing plus or minus 7.5 degrees, from the driver's seat, while flying down the hiway.
Find a section of flat level pavement at least 5 miles long. Enter the section at a stabilized cruise speed with a locked foot-feeder. Watch the speedo for the first mile. Then crank in plus 3 degrees; and do not move the gas pedal. If the car increases in speed, it liked it. If it slows it didn't.
_______________________________
I once had employment about 25 miles away, and every day I would go thru this section. And almost every day I would work the device. The first few adjustments were a no-brainer, she liked it. After a while, it got to a point where it seemed to plateau, more timing did not significantly increase the speed thru the section. I quit at 63*, @62mph=2150rpm. I arbitrarily cut it back to 58*, because the last 5* had not shown a significant speed change. Being a pioneer in this effort, I felt better safe than sorry.
> I had made a two-stage throttle return system, so I could accurately always hit the same throttle opening, and I didn't have to concentrate on keeping my foot steady..
> My 367engine was making 185psi,and the VP calculated to over 160, so the throttle opening to make 62 mph was very very small. It vacuum peaked at about 2100, or a little less.
> there is no way to build a power curve, for a 4-speed car, and still make 58* at 2150 for cruising; the biggest Vcan I could find was a 20* can, and I modded it to squeeze 2 more out of it, for a total of 22*. My engine was happy with the power curve I had built, using this same dial-back device to optimize it. So at 2150 the mechanical timing was 23*. So the best the non-dial-back system could do was 23+22=45. The DB had to kick in the rest or 13
> there's just one little thing; YOU have to remember to back it off when you come out of cruise mode.
I ran 32/34 power timing, and if I hadda forgot to dial out the cruise timing, it would have been 33+13=46, and Ima thinkin that 367 wouldda complained about that under WOT,loudly.
So be forewarned; if you experiment with this, the payback in fuel efficiency, with a high overlap/ short extraction period, cam, is not that much, and if you melt your motor down by forgetting about the DB, I will not buy you a replacement.
> With an ever so slightly smaller cam however,the mpg increase was, for me, phenomenal.
 
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My distributor was locked at 35 total advance. 456 gears and 5500 stall at 60 mph the temp was 180 steady. Hard to get it over 180 with the new B-cool rad. But I had and electric pump and fan so the water flow stayed consistent.

I also have a snorkle scoop it is sealed to the carb. Maximum holes in hood without sealing it to the carb was two holes 4 inches in diameter. air escaping out of the engine bay was always a problem. This is why old school racers lifted the back of the hood.

At one time I was having cooling problems so I made an air dam to put more air through the rad. I came to find out my coolant tubes were swelled from over pressuring the rad when testing for leaks and the air flow was restricted.

I bought a new rad. and left the air dam in place. At about 120 mph or above the front lifted under a hard pull in drive up a hill. Once the front lifted the whole car came up. Scariest day of my life. I thought the trans went it was the rear tire lost traction.

Here is a picture of the air dam I installed. Took it off and never used it again. I gave it to Dave for his Valiant. Also here is a video of a friends car 'Frank' who didn't have pressure relief holes in the interior. It blew the drivers door out at the hinge at around 200 mph turning him into the wall

Pressure builds higher than you think when you get up in speed.



spoiler pics 661.jpg
 
89on35s said:
Timing set by vacuum gauge cause the balancer mark is way off. Vacuum advance currently disconnected.

On the highway with the AC running 70ish MPH at 2000 rpm the temp goes just past 200*F and drops back to 180 once you are back in traffic
Click to expand...

Some general thoughts............

1....Should be easy to disable the scoop long enough to test, just pull the filter if necessary and plug it up with cardboard, rags, whatever...........

2.....Fer Lord sake, get your wheel degreed this is EASY. Use a piston stop. Surely you know this with that build

3.....After you get the timing straightened out I would for sure experiment with vacuum advance hooked up.

4.....I know some of these cars used a seal between hood and rad support, you might take a really good look at airflow through the rad
 
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