another 360/408 over heating

Im working on a 360 stroked to a 408 and bored .030. It has a Comp cam that is 575 on both intake and exhaust, compression is at 10.5 - 1.
Has steel J-heads with oversized valves.
Running an edelbrock victor intake with a 750 holley double pump. TTI headers.
Has a mechanical auto gauge, sending prong is in the intake just behind the thermostat housing
New Champion 3 core radiator, 2 electric fans pulling 2300 CFM each. Fans come on at about 160*
Coolant is at +5* and I have 1.5 bottles of water wetter installed after the first drive listed below.
Here are pics

The pulleys seem to be the same size or very close. Looks to be about 6.25".
The water pump is a napa high flow with 8 veins.
Timing is at 14* base and 32* at 3K
The holes that appear on the shroud I just did and have not driven on the road since this was done.

Im overheating, Ive had this on the road for about 12 miles. it was 2 different nights and both drives were 3 miles and a stop of about 15 minutes then the 3 mile drive home. Temp both nights was around 60* in the evening. First drive was with a 180* thermostat. When i got to the stop at the 3 mile mark it was running at 195* on the gauge. After about 15 minutes I started up and drove the 3 miles home. By the time I arrived and put in the garage the temp went to 225* where I turned it off.
Next night I installed a 160* thermostat and drove the same trip. Temp went to 195* and again by the time I got home I was at 225*.
Next night I installed a 195* but didnt drive it. I just left it run in front of garage. It took about 25 minutes or so but it went to 225*.
I have not left the temp go abouve the 225* as thats were I have turned it off before it can go higher.
So tonight I remove the thermostat and took some numbers as the car sat and ran mostly at idle which is about 1100 RPMs.
The Intake sensor, upper hose and head temp are from an infra red tester.
Here shows the head area I am measuring, and the temp unit in the intake.

I started the car at 9:27
Gauge Temp Intake Sensor Upper Hose Head
9:30 125*
9:33 150*
9:36 165* 145* 141* 158*
9:39 170* 155* 150* 165*
9:42 190* 165* 165* 180*
9:45 195* 175* 170* 195*
9:48 205* 185* 178* 210*
9:51 215* 195* 190* 210*
9:54 220*

Turned the car off at this point. The radiator at this point is only at 110* on top of the tank at the inlet, the fins at upper hose in the radiator are at 190*, the lower tank at the lower passenger side is at 115* while the lower fins near the lower hose passenger side are at 165*.
Heres the part that bothers me. I ran a test with a block tester that uses the blue fluid and pulls the coolant vapors and will turn green/yellow if carbon monoxide gases are present in the coolant and mine tests positive. I Had the heads magnafluxed before the build as well as the block. No issues. I struggle to believe a head gasket issue but I guess anything is possible.
During the 2 drives or even the last 2 times just idling I have not lost any fluid while driving, the car has not spit any coolant out, and the radiator runs cooler when on the road even tho the gauge goes to 225* the radiator has always been around the 150-160* temp. Also there is no build up of pressure in the system as the hose can be compressed.
Ive also done the old school test where I removed the water pump belt, taken the thermostat housing off and filled intake to top. Start the car and I get no bubbles at all.

My next test will be a stewart high flow 180* thermostat. also a new gauge although I think this gauge is reading close compared to infra tester
What are your thoughts? Did I leave out any info that would help figure this out?
Thanks Rod

I don't have the exact answer for you. But I do know two things. 1 You can stop buying and replacing thermostats. They are proving they are working. When they say 195* that means they fully open at that tempature. Not that they will keep your motor at that temp. In each case they prove they are opening and doing their job. 2. I would not have cut those holes. You want everything sealed up on the fan side. You only want it pulling air from the side of the radiator. Any pull from the fan side is wasted. #3 for ***** and giggles. I would not use the napa high flow pump. You can pull the fluid so fast that heat doesn't transfer. You are kind of showing that with the lower temps in the radiator. Lastly, the most thermally efficient at conducting heat and moving it is water, snake oil be damned. I know I know I hear the arguments.

Run a pressure test on the radiator system.

Impressive amount of test data, hats off to you.

One of the duties of the thermostat is to slow the flow of fluid so it has time to remove heat from the engine.

I am not a fan of shrouds, especially ones that are flat and close to the rad.

If you have a 16 lb rad cap and no leaks you should build pressure.

Your test that showed exhaust gas in the fluid should be examined with a pressure test.

I wonder if you replaced your fluid with normal 50/50 mix what your results would be.

I'm also not sure that 220 is too high for a properly functioning pressurized system. iirc 16lbs raises boiling point to 250 deg.


Another thought... air full ratio? Are you running lean?

Dana67Dart
I should have mentioned it in the original post but my first drive was with a 50/50 coolant which had the coolant at around -20*. Before i did the 2nd drive I cut the coolant to about a +5* and thats when I added the water wetter.
Are your thoughts on shrouds because you restrict free flowing air while driving the car down the road? Thats the reason I cut the holes in the shroud but I havent gotten to drive it since I did that. As mentioned in the first response from Blind Squirrel that holes can cause issues I plan on putting some rubber flaps on the holes so when idling the holes will be closed forcing air to be drawn from the front.
As for the gas in the coolant my compression tester just arrived today and I also plan on doing a cylinder leakage test. Even tho I hate to believe the test of gas in the coolant the reality is that it tests positive and chances are that could very well be some if not all of my issues. I would just like to cover any and all other bases before tearing the heads off. I do have a set of aluminum performer heads ready to go on should I find the heads are the issue.
Rod

I remember buying a brand new 340 radiator and all that crap when I got my 340 going 20 something years ago and and it would overheat eventually...

What is the initial timing and full Advance timing? Let's say the timing is perfect just to give you a little info here , Does it overheat driving down the freeway for that entire time ..? ...or is it only overheating when you sit at an idle?
If it's only overheating when you sit at an idle you don't have enough fan n that fan shrouds a piece of **** ..so you'd need to put A real fan/s on it. If it overheats while driving down the highway...you have two things going on ... either wrong timing and detonation...or clogged/too small radiator, too lean/ too rich..blown head gasket worst case.

I had the same problems as you. Started with a single electric fan on my 340. Overheated.. went to dual electric and it still overheated.. went to a fan clutch and factory shroud, fixed it..
Put almost the same 408 as you have and figured it was a 340 issue and went back to dual electric fans, overheated.. went back to fan clutch and shroud and barely crack 200 on the hottest days.

My vote is 1 of two things. Not enough air flow or not enough radiator. Remember, new doesn't mean good.

That said, you say the temp coming out of the radiator is 165*, is that right? If that's really the case, then I think you've narrowed it down to lack of air flow. If those crappy lookin little fans pull 2300 CFM each, I would be absolutely stunned. What "I" would do here is, remove the fans and that shroud "thing". Get a Mopar viscous fan package and a more factory style shroud. "I just bet" your problem goes away.

What does it do out on the highway? You didn't get specific there. Does it cool down at all at speeds over 45 MPH? Even if it does not, you have a lot of shroud blocking the core......even with the holes. The core is only either 22 or 26" wide. A hot small block needs every stinkin inch of that exposed to air flow and you have a lot of it blocked off.

Get a playing card and when the car is idling with fans on, see if it gets stuck to the radiator, if not you do not have enough pull of air through the radiator, Buy the biggest flex fan you can fit probably a 22inch put those electric fans on the other side of the radiator. now you will have the problem of running too cool. I have seen people run 440s with and 2 row slant six radiator, the secret was the huge flex fan constantly pulling air through the small radiator. Looking at the pictures those fans are too far away no pull of air.

OP. When you make a shroud or buy one... you want flappers over the holes so that the fan pulls through the radiator and not around. Flaps close with vacuum from fan but they then open air speed is greater and still allow the airflow at cruise.

Volvo wagons have very nice light weight cross flow style shrouds that house the fan, great example . If you're even gonna bother with a shroud, it should have trap doors.imo

Would like to thank everyone for your thoughts. Here's what I can tell you to answer your questions or tell you additional things I may not have put in other posts. First this is in a 66 Dart. Originally was a 273. All pulleys are from the original motor. My water pump snout to radiator clearance is only 2.5 inches at most. So a fan clutch will not fit unless there's one I haven't looked at yet?? The shortest one I found was 2 5/8". I can put the original 4 blade fan on and give that a try. I pulled it out a few nights ago and was thinking of trying it. Is there a steel 6 or 7 blade that would fit with my tight clearance? I would have no shroud to fit it so I would need to fab one up.
As for the holes that I put in the shroud, again I just did that and the reason was to see if that helps cool it while driving as the temp does climb while driving (up to 220*+) and I want to see if air flow from driving would at least cool while moving. As for how much air the electric fans pull I would tell you it's a surprising amount. Problem is they are only 9" fans because I had to stagger them around the water pump due to lack of space. I originally had bought a large single electric fan with shroud but it would not fit between the radiator and water pump snout.
As for the playing card I did not try that but I will. I did put a shop towel (the paper type) to the outside of the radiator and the fans pulled that tight against it.
Lastly, as I said in the original post my timing is at 14* initial and 34* at 3k. Plugs look good so I'm not thinking a lean condition at this point.
I'm away for the weekend so I probably won't get back on this until early next week but if you think of anything else please post. I'm open to trying anything that would help!
Thanks, Rod

Best combo would probably be a Champion 2 core radiator with the 1 inch rows and the Hayden 2765 fan clutch with a factory 7 blade fan and shroud. That would fit within your clearances and kick butt!

I messed with various combos of electric until I switched to the above setup which made it run nice and cool.

rod7515 said:

compression tester just arrived today

Click to expand...

I was thinking more about a cooling system pressure test since you say it never pressurizes.

my work with airflow suggests that anything flat directly behind the radiator causes a high pressure zone that blocks air flow.

As others have noted the flappers are there to close in stop and go / ideling and force air to pull through the rad but allow for free flow of air at most other conditions.


Simple thing to do is measure the diameter of every opening in the shroud and do the math to find area for each opening A=3.14 x (D/2) x (D/2) (Area = Pi x R squared) (R=D/2)

As illustration...

assume 6 holes 3" dia and 2 holes 12" dia

6 x 3" holes total = 42.4 sqin
2 x 12" holes total = 226 sqin
total area = 268.4 sqin

22" rad = 21x17 core area ( where air can flow) = 357sqin

That results in about 25% blockage of air flow at speed, idling is a different ball of wax
(This is just illustration only, your numbers will be different)

I realize I am old and "out of touch" with modern, but IF we could cool these cars with OEM parts decades ago then why is it people seem to think they need elecrtric fans now on these old cars???
I understand bore a motor out 60 thous, change cams, timing etc and that does make a difference, but...................

barbee6043 said:

I realize I am old and "out of touch" with modern, but IF we could cool these cars with OEM parts decades ago then why is it people seem to think they need elecrtric fans now on these old cars???
I understand bore a motor out 60 thous, change cams, timing etc and that does make a difference, but...................

Click to expand...

For me personally it's getting rid of the twirling blade of death. Now that I've had electric fans for a while I've gotten used to not having that big metal blade flying around when I'm playing around with my motor. and it's certainly not that electric fans can't do the job it's just things have to be configured properly..

Dana67dart, I probably mislead you a little. When I say no build up of pressure I'm talking blow out pressure where fluid is pushing out all over the place. I don't even get anything expanding into the over flow.
This morning when I went out and I pulled the cap after it sat all night. There was a very slight suck sound from vacuum from the coolant. I'm sure that was from the hot expansion while running then cooling overnight. And again I'm talking very slight sound but enough to hear.
Here's a question/thought.
This engine has a roller cam so I didn't have to do the higher rpm break in as you would do with a flat tappet cam where everything gets superhot. Could there still be that much friction in the engine from all new parts and if I took it for a 50 mile drive maybe the heat would go away. Should I let the temps go higher and see what happens?
Just a thought.
Thanks Rod

My temp gauge always rises after shut down. Heat soak.

For my 2c I'd look at pulley diameters...crank should be larger than wp to overdrive it.

theres a whole lot of posts about it from last year...

Might be a silly question, but have you bled your cooling system at all? Especially with two refills, you might wanna put the front
end up on stands/an incline and let it run with the cap off
It could even be an air bubble in the heater core

Those fans are probably pulling more air around the gaps between the shroud and radiator and the bypass holes than they are through the radiator. As otherwise noted, the fans aren't up to task, either. I would realistically think that you are looking at something like this, Zirgo Ultra High Performance Electric Fans ZIRZFU16S , and then making a shroud that seals completely to the radiator and fits the fan tightly. One common recommendation I have seen from members here that have a whole lot more experience than me in going with electric cooling fans is to use an electronic fan controller like the Dakota Digital units. These units control the fan speed to maintain a preset temperature. As you have suspected, one potential trouble area is with the J heads. Some of the J head chambers are really detonation prone, and there doesn't seem to be any specific obvious cause other than factory casting tolerance stack up causing improperly shaped and sized chambers leading to detonation.

rod7515 said:

Dana67Dart
I should have mentioned it in the original post but my first drive was with a 50/50 coolant which had the coolant at around -20*. Before i did the 2nd drive I cut the coolant to about a +5* and thats when I added the water wetter.
Are your thoughts on shrouds because you restrict free flowing air while driving the car down the road? Thats the reason I cut the holes in the shroud but I havent gotten to drive it since I did that. As mentioned in the first response from Blind Squirrel that holes can cause issues I plan on putting some rubber flaps on the holes so when idling the holes will be closed forcing air to be drawn from the front.
As for the gas in the coolant my compression tester just arrived today and I also plan on doing a cylinder leakage test. Even tho I hate to believe the test of gas in the coolant the reality is that it tests positive and chances are that could very well be some if not all of my issues. I would just like to cover any and all other bases before tearing the heads off. I do have a set of aluminum performer heads ready to go on should I find the heads are the issue.
Rod

Click to expand...

Couple ?'s
What head gaskets are you using?

With the radiator cap off and the t-stat open(hot)/removed is there coolant flow?

If so, does it take longer to overheat sitting at idle than driving?

Does the high flow 8 vane WP have closed, semi open or an open impeller

rod7515 said:

Would like to thank everyone for your thoughts. Here's what I can tell you to answer your questions or tell you additional things I may not have put in other posts. First this is in a 66 Dart. Originally was a 273. All pulleys are from the original motor. My water pump snout to radiator clearance is only 2.5 inches at most. So a fan clutch will not fit unless there's one I haven't looked at yet?? The shortest one I found was 2 5/8". I can put the original 4 blade fan on and give that a try. I pulled it out a few nights ago and was thinking of trying it. Is there a steel 6 or 7 blade that would fit with my tight clearance? I would have no shroud to fit it so I would need to fab one up.
As for the holes that I put in the shroud, again I just did that and the reason was to see if that helps cool it while driving as the temp does climb while driving (up to 220*+) and I want to see if air flow from driving would at least cool while moving. As for how much air the electric fans pull I would tell you it's a surprising amount. Problem is they are only 9" fans because I had to stagger them around the water pump due to lack of space. I originally had bought a large single electric fan with shroud but it would not fit between the radiator and water pump snout.
As for the playing card I did not try that but I will. I did put a shop towel (the paper type) to the outside of the radiator and the fans pulled that tight against it.
Lastly, as I said in the original post my timing is at 14* initial and 34* at 3k. Plugs look good so I'm not thinking a lean condition at this point.
I'm away for the weekend so I probably won't get back on this until early next week but if you think of anything else please post. I'm open to trying anything that would help!
Thanks, Rod

Click to expand...

Toss the original fan put one of these You can buy them at oriellys , you don't need a fan clutch plus they are too tight in an early a body. There like 30 bucks. Make sure it's as close as it can be to the radiator there are different shape spacers

I never had any luck with electric fans for a street application.
I run a Griffin 2 row one inch core radiator with factory 7 blade fan, factory shroud and stock water pump.
My crank pulley is much larger than the water pump pulley, overdriven for factory A/C car.
30 over 340, roller cam with 727 trans runs 180 w/o A/C, 195 with A/C on.
In the past when I ran electric fans I had to divorce the Transmission cooling from the radiator, taking the trans heat load out of the radiator.
Griffin radiators rock!
Good luck

rod7515 said:

I don't even get anything expanding into the over flow.

There was a very slight suck sound from vacuum from the coolant.

Also there is no build up of pressure in the system as the hose can be compressed.

Thanks Rod

Click to expand...

Replace the radiator cap.

Slantsix64 said:

Toss the original fan put one of these You can buy them at oriellys , you don't need a fan clutch plus they are too tight in an early a body. There like 30 bucks. Make sure it's as close as it can be to the radiator there are different shape spacers

View attachment 1715326326

Click to expand...

Personally, I wouldn’t recommend using a flex fan to anyone, these fans have repeatedly been responsible for vehicle damage and worse still, serious personal injury.
They are a ticking time bomb - DO NOT USE!

Cal Tonsley said:

Personally, I wouldn’t recommend using a flex fan to anyone, these fans have repeatedly been responsible for vehicle damage and worse still, serious personal injury.
They are a ticking time bomb - DO NOT USE!

Click to expand...

Been using them for 10 years on 4 different cars, no problems ever. A metal fan will do some serious damage to your hand a flex fan won't do as much. The only problem I have with them is the engine runs 5 degrees cooler than the thermostat.

Slantsix64 said:

Been using them for 10 years on 4 different cars, no problems ever. A metal fan will do some serious damage to your hand a flex fan won't do as much. The only problem I have with them is the engine runs 5 degrees cooler than the thermostat.

Click to expand...

I’m glad that you’ve been lucky, it’s just that I’ve seen and know of countless cases where these devices have let fly after being repeatedly flexed. Here’s a post right here on FABO that illustrates my point.
*MUST READ*--Flex Fan Danger--Be very careful working on old cars