wvumtnbkr Posted October 24, 2018 Report Share Posted October 24, 2018 Okay, I am going to try to add a pic of the front of my car right....... Here.... So, as many of you know, I have been having some heat related problems on my car. This all started when I did the swap from the rotary to the GM3400 V6. At the same time, I got rid of my splitter and installed an airdam. (I hate remaking splitters....). So, is there something wrong with the way I made my airdam? Is it the issue with my brake and radiator cooling (seeing temps of 240+ with this radiator: https://www.eastwood.com/maxx-power-tri-flow-22-in-aluminum-radiator.html?reltype=2&parent_id=52397) Seems like the radiator should be big enough (replaces the stock single pass rad of the same size). The back of the radiator is sealed off with angle aluminum and roll plastic to form an air path that goes from the radiator out through the hole in the hood. Hopefully this is obvious from the pics. The brake ducting holes are 3" holes to 3" hose as close to the center of the car that I can get without blocking radiator flow. What can I do to improve this? Or, should I be looking elsewhere? Thanks in advance! Quote Link to comment Share on other sites More sharing options...
cagedruss Posted October 24, 2018 Report Share Posted October 24, 2018 Have you taken temps from the top and bottom of the radiator and the thermostat housing and compared them? Need to determine if the water is traveling to slow, to fast or just right though the radiator. Are you running factory pulleys? What rpms are you running? Are you over spinning the water pump which causes cavitation? There are many reasons this could happen. What is your total timing you are using in the engine? To advanced or retarded can cause heat issues. Are you running a thermostat? Is it working properly? Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 24, 2018 Author Report Share Posted October 24, 2018 Wow, good questions... Factory pulleys. Factory tune. Factory type thermostat which appears to be working. If I can manage to keep rpms low and go faster, the temps will decrease by 10 or so degrees. I attributed this to needing increased airflow. We are using factory red line of 6k rpm. Quote Link to comment Share on other sites More sharing options...
cagedruss Posted October 24, 2018 Report Share Posted October 24, 2018 I think it is more water related than air related. Your pulleys and radiator are designed for the street. How often do you run around full throttle at 5,000 to 6,000 rpms for hours at a time? Impellor is really spinning in the water pump. My SBC was doing the same thing. Had a great radiator and a custom air box to direct all the air through the radiator. Once I slowed down the water pump temps dropped significantly. Water wasn't getting through the block quick enough to cool off the temps. It can do the same if the water moves through the block to quickly. Are you running a heater core or is it blocked off? If blocked off that could also cause a little heat issue. GM designed the system to circulate water through the back of the block to the front keeping the rear of the block cooler. If you think it's air then you need to make sure the front of the radiator is sealed so all the air gets through the radiator and can't bypass the front. Also check the radiator. I've never used the brand you have and know nothing about it. Was it designed for hot rod use or performance? What size tubes, tanks and fins? Small tubes can fill with rust and slow the movement of water. Had that problem with my Ron Davis rad. After 2 seasons of running water only to meet the rules the corrosion of the cast iron block restricted the flow. Water was rusty everytime I drained the system. Quote Link to comment Share on other sites More sharing options...
Zauskycop Posted October 24, 2018 Report Share Posted October 24, 2018 With the flow of the air over the top of that hole, it is a high pressure area, equal with the pressure, or higher than the pressure, passing thru the radiator and out. Perhaps a small lip or something on the front of the hole would lessen the pressure over that hole and provide a low pressure area to suck the air thru? Just a thought... 3 Quote Link to comment Share on other sites More sharing options...
JDChristianson Posted October 24, 2018 Report Share Posted October 24, 2018 Do you have ducting in front of the radiator to make sure that the air going in goes through the radiator and not around it? The points that @cagedruss is making about the water pump potentially spinning to fast are valid for sure. An electric water pump can cure that or possibly a bigger pulley to slow it down. Quote Link to comment Share on other sites More sharing options...
TiredBirds Posted October 24, 2018 Report Share Posted October 24, 2018 It looks like your inlet is flat. Perhaps if you added a small "lip under it and folder the sheet metal in (directing more air in) it would help. Ours takes air from the front and directs it into the openening. Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Ray Franck Posted October 24, 2018 Technical Advisory Committee Report Share Posted October 24, 2018 Duct work from the bumper to the radiator is free ,from the radiator back will be material points. 1 Quote Link to comment Share on other sites More sharing options...
Ian Posted October 24, 2018 Report Share Posted October 24, 2018 Are you choking coolant flow with the 3 pass radiator. That seems live a very small amount of tubes to flow all the engines coolant through. I'd be worried you're significantly slowing coolant flow. The slower the coolant flow, the less heat it picks up. In practice, you can't really flow coolant too fast. The larger the temp delta between water and engine, the faster it will absorb heat. Fast moving cool water does a much more efficient job of drawing out heat compared to slow moving warm water. 1 Quote Link to comment Share on other sites More sharing options...
mender Posted October 24, 2018 Report Share Posted October 24, 2018 (edited) On the Fiero with the 3500 (essentially the same engine), stock thermostat, pulleys, single pass radiator and typical 5500 rpm shift point. If you have a close look at my profile picture, you'll see basically the same rad inlet and outlet as your car. I ducted from the bumper inlet to the rad with a flat bottom and sides but shaped top then curved the ducting up and out the hood. That's it. I think the key to the efficient cooling on my car is ducting the air to the rad. On the racecar stuff we don't worry much about where the air goes after leaving the rad because the engine bay is very open. Water temps on a 85-90 F day and 2 mile track are about 190 F, oil temps with a factory water to oil cooler were about 40 F above that. The stock rad handled both the water and oil cooling chores. On a shorter track (1.67 miles, 14 turns) temp went up about another 10 F, partially due to the 6300 rpm we were using to avoid shifting on the short straights. I had considered adding a lip at the front of the hood outlet to help pull the air out but the car always ran cool so didn't bother. Edited October 24, 2018 by mender Quote Link to comment Share on other sites More sharing options...
LAMR2 Posted October 24, 2018 Report Share Posted October 24, 2018 Water moving too quickly through the block or radiator is an absolute myth. More massflow through the radiator will always cool more quickly. I'll echo the ducting question above. The air is going to take the path of least resistance, and can take some surprisingly sharp turns when there's a large enough pressure differential. You have to give it no option and force the flow to go where you want it, not just encourage it. As for the brake ducts, I don't know if your inlet location is doing you any favors with the design of your air dam. The center of the car is going to have the highest pressure, but your front end is so flat that it's not going to vary much for a ways outboard. A lot of air is going to be sucked into the rad opening, and if the pressure differential through that flowpath is less than through your brake ducts, it could easily starve those ducts since they're so close. The inlet size is also pretty small. You generally want a significantly larger inlet for a duct than the size of the duct itself. I'd highly recommend using something like this: https://www.pegasusautoracing.com/productselection.asp?Product=3624 Quote Link to comment Share on other sites More sharing options...
Fitsbain Posted October 24, 2018 Report Share Posted October 24, 2018 I'd say cavitation on the water pump (stock pulley), And do you have an oil cooler? They make an incredible difference. Quote Link to comment Share on other sites More sharing options...
mhr650 Posted October 24, 2018 Report Share Posted October 24, 2018 10 minutes ago, LAMR2 said: Water moving too quickly through the block or radiator is an absolute myth. More massflow through the radiator will always cool more quickly. But a cavitating water pump won’t pump very efficiently at all, on the rotary a small pulley makes a big difference. You didn’t mention if you have any fans in the system, I have always ran without a fan on the theory that it is just in the way at racing speed, but I have regretted it during red flag and slow full course yellow periods. Another thing that I noticed is that you don’t have a kick up lip on the front of your exit hole in the hood, which is good to insure that you get a proper low pressure area in the extraction area. Quote Link to comment Share on other sites More sharing options...
ben 594 Posted October 24, 2018 Report Share Posted October 24, 2018 56 minutes ago, Ray Franck said: Duct work from the bumper to the radiator is free ,from the radiator back will be material points. Ray, What line is this in the 2019 or 2018 BCCR? I am looking I don't see this and a control 'f' search misses it too. Thank you for the help. 1 Quote Link to comment Share on other sites More sharing options...
LAMR2 Posted October 24, 2018 Report Share Posted October 24, 2018 11 minutes ago, mhr650 said: But a cavitating water pump won’t pump very efficiently at all, on the rotary a small pulley makes a big difference. Right, but he's running a GM V6 with a stock pulley. Others running the same setup don't have cavitation, so I'd be surprised if he does. 1 Quote Link to comment Share on other sites More sharing options...
Fitsbain Posted October 24, 2018 Report Share Posted October 24, 2018 1 minute ago, LAMR2 said: Right, but he's running a GM V6 with a stock pulley. Others running the same setup don't have cavitation, so I'd be surprised if he does. ya go me there Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 24, 2018 Author Report Share Posted October 24, 2018 I have the rad fully sealed and the only exit for the air coming in the front of the air dam is through the radiator and then out through the hood. It is sealed pretty well! I can definitely add a gurney flap to the front of the opening on the hood. I could try a different pulley for the water pump. As far as the radiator is concerned, the capacity of the radiator is same as stock. It is just forced to make 3 passes through (like a "Z"). I will look at temps from top to bottom on the radiator (what am I looking for? What sort of gradient would be indicitive of "good" rad cooling?) I do have an oil cooler. Oil temps have recently been around 240 to 250. Water coming out of the block and radiator looks like you could drink it. I can see down into the radiator and it is still looking brand new. Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 24, 2018 Author Report Share Posted October 24, 2018 From a few articles I have read, the "funnel" (size) at the opening of the brake duct hoses doesnt really matter. Does anybody have any sources that disprove that? Also, I wouldnt think the opening in the airdam for the radiator would "suck" at all. Does the opening for the radiator actually create a pressure difference that would "steal" air from the brake ducts? Isnt there enough air hitting the front of the car for both the radiator AND the brakes? I do not run a fan. I figure they just block air flow at race speeds. Quote Link to comment Share on other sites More sharing options...
Ian Posted October 24, 2018 Report Share Posted October 24, 2018 I really think that goofy triple pass radiator deserved a second look. You're forcing all the coolant through just a dozen or so tubes, instead of 30-40. This could potentially be a BIG bottle neck in the system. And as others have said, you need to block the trailing edge of the hood vent from a foreword perspective. Its not letting air out, its fighting the air trying to get in. Subarus have the same issue with their silly hood scoops, take a look at the WRC cars vs the road cars. Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 24, 2018 Author Report Share Posted October 24, 2018 (edited) Actually, the rad is a pretty common design for racing. The air is going past every tube, not just a dozen. The area of the tubes is greater than the area of the radiator hose. I am not understanding the second comment. Why would I need to block the trailing edge of the hood. Why would air try to get in that hole? Isnt it like blowing across the top of a straw? Isnt the flow over the hood going to pull air out? Edit: I just found this on Speedway motors website. Maybe the Rad is a problem? I do not have a high volume pump.... Edited October 24, 2018 by wvumtnbkr Quote Link to comment Share on other sites More sharing options...
LAMR2 Posted October 24, 2018 Report Share Posted October 24, 2018 39 minutes ago, wvumtnbkr said: From a few articles I have read, the "funnel" (size) at the opening of the brake duct hoses doesnt really matter. Does anybody have any sources that disprove that? Also, I wouldnt think the opening in the airdam for the radiator would "suck" at all. Does the opening for the radiator actually create a pressure difference that would "steal" air from the brake ducts? Isnt there enough air hitting the front of the car for both the radiator AND the brakes? I do not run a fan. I figure they just block air flow at race speeds. If there's a significant difference in backpressure, yes, it could pass over the brake ducts and head to the rad duct due to their proximity. If you have the rad duct sealed up really well then that makes it less likely, since the air going through the rad duct is all going through the radiator. Quote Link to comment Share on other sites More sharing options...
LAMR2 Posted October 24, 2018 Report Share Posted October 24, 2018 11 minutes ago, wvumtnbkr said: I am not understanding the second comment. Why would I need to block the trailing edge of the hood. Why would air try to get in that hole? Isnt it like blowing across the top of a straw? Isnt the flow over the hood going to pull air out? A Gurney flap at the front of the hood opening forces the air flowing over the hood upwards, lowering the pressure over the opening and making it easier for the air coming through the radiator to exit your vent. Very few cars with hood-vented radiators don't do it. Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 24, 2018 Author Report Share Posted October 24, 2018 56 minutes ago, SonsOfIrony said: I really think that goofy triple pass radiator deserved a second look. You're forcing all the coolant through just a dozen or so tubes, instead of 30-40. This could potentially be a BIG bottle neck in the system. And as others have said, you need to block the trailing edge of the hood vent from a foreword perspective. Its not letting air out, its fighting the air trying to get in. Subarus have the same issue with their silly hood scoops, take a look at the WRC cars vs the road cars. I reread this a few times. Are you saying I need a turkey flap at the front of the good opening (towards the front bumper). I think that is what I am understanding. Pretty sure I agree with that! Haha. Beat me by a minute or so. 1 Quote Link to comment Share on other sites More sharing options...
JDChristianson Posted October 24, 2018 Report Share Posted October 24, 2018 Turkey flap @red0 must have 5 or 6 gifs for that 1 Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 24, 2018 Author Report Share Posted October 24, 2018 Stupid auto correct... gurney.... Also, I assume I have to go either single pass or triple pass since I need the inlet and outlet on opposite sides.... Quote Link to comment Share on other sites More sharing options...
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