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  #1 (permalink)  
Old 02-02-2009, 03:40 PM
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Default Engine compartment cooling

Hi Everyone,

For the last year I have had a problem with my engine running hot. A few questions first. This is a Midstates cobra with a 428 SCJ motor with slight mods. What is the max temp when I should start to worry? What temp thermostat should I run? (currently 160 deg) I have had differing responses to this. I have been able to address a lot of heat problems by going to an aluminum radiator. Had a custom shroud made to fit it and am running an electric puller fan. Have mounted two original looking pusher on the front with a remote switch. I have no problem while moving at a speed in excess of 35 mph. The problem seems to be a build up of heat in the engine compartment. Approaches I have been looking at to resolve this problem 1. Add a Flex-a-lite fan to the water pump (Looks tacky in the engine bay) 2. Try to find a 4" squirrel cage blower and mount one above each header an force hot air out side lovers. 3. design a ducting system of some sorts. 4. put lovers in the back of the front fender wells to force air onto the headers. My problem is while cuizin in stop and to traffic in 80+ degree days.
Does anyone know the normal hot running temp of a 428?

Thanks for any suggestions and assistance.

Mark
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  #2 (permalink)  
Old 02-02-2009, 06:16 PM
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normal temp, in summer should vary from 180-200. i would be worried if it gets over 210 sitting in traffic. the temp rating of the thermostat is when it opens, not what temp the motor will run at. a 180 deg thermstat should work fine. the problem with the air flow is usually the distance the air needs to move to get to the radiator. it takes quite alot of cfm to draw from the grill opening. i have a 3300 cfm puller and it seems to be ok with a 7 core aluminum rad, and shrouding. however i currently have a 160 deg thermostat in mine with 3 small holes drilled in it. i am going to change back to a 180 with no holes drilled. on the highway it runs too cool. 140-160. in town with 90 deg weather i'm at 195-200, which i can live with.

fred

note: octane boost ie: lead additive will help the in town cooling. maybe by as much as 10 deg.
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  #3 (permalink)  
Old 02-02-2009, 06:22 PM
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One thing that you need to watch for is too low rating of thermostat. If the rating is too low it will not let the water stay in the radiator long enough to keep the water cool.
I had a 77 vette with a 160 t-stat. Car always ran in the 200-220 range. Changed to a 180 t-stat and it ran aroun 190 all of the time.
JMHO

Terry
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Old 02-02-2009, 06:35 PM
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Mark do you have any sort of fans at all, and if you do it is very important that the pitch of the blades are going the right direction, and also turning the right way, you might double check that.
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Old 02-02-2009, 08:53 PM
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I have a 514 in my SPF. I can sit in 100 deg weather and it stays under 200 deg. I put a high flow 180 deg thermostat in. The SPF's have two puller fans that are completely sealed in the front and rear, so everything the fans pull in, goes through the radiator and into the engine compartment.

What do you have the timing set at??

Scott
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Old 02-03-2009, 03:31 AM
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You really can't make that correlation between under hood temps and it causing your engine to run hot. That is, unless your engine compartment is so tight that your puller fan doesn't have enough power to push the air out from the engine compartment. I doubt if that's the case. A "near overheating" engine will cause the engine compartment to run unusually hot, not the reverse.

There's plenty of possibilities for a too hot coolant during idle problem:

Water pump/crank pulley ratio off, under driving the water pump. Aftermarket pulley manufacturers (March included) like to under drive the accessories with their kits, including the water pump. 1 to 1 is an ideal ratio.

Under voltage condition to fan caused by an inadequate wiring/alternator system. A lot of wiring harnesses do not have an adequately sized fan circuit for today's hi amp monsters out there. I run #8 stranded for my fan circuit and run the Bosch 60 amp screw lug relays. My main feed wire to the alternator and battery is 0. For what it's worth with my Painless wiring harness I had a whopping 10.6 volts at idle making it to my fan and the alternator output voltage dropping to 11.6 volts, with the lights off. Problem solved, with a one-wire 180 amp alternator and new hi-amp wiring. Now have 14.2 volts at the alternator and fan with the motor idling and every electric/electronic device installed on the car running. The fan now spins noticably faster.

If you don't already have a shrouded inlet (in front of the radiator) then there's a potential problem. At a stop the "hot air" pressurized engine compartment has a tendency to recirculate the air to the front of the radiator.

Run a Mr. Gasket/Robertshaw performance thermostat. It has a larger open "free area" which, all thing being equal, flows more coolant than a standard thermostat.

Its an easy check on the electrics and pulley ratios.

Good luck on the fix...
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Old 02-03-2009, 05:09 AM
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I had the same problems with excessive heat at intersections,,waiting for long signal lights when the outside temps. are above 100 degrees here in the desert. After doing everything possible, verifying temp. gauge accuracy, 180 thermostat, burping the system , strong puller fan with shroud, recovery bottle and proper coolant..everything worked much better.
I max. out at about 210 in those situations, so I experimented with the installation of a couple of "boat bilge fans" to exhaust the engine compartment heat while sitting at intersections.
I mounted them on each side of the engine, just under the fenders w' 4" flex tubing to direct the hot air out the side vents. I only use them periodically to get the heat out and they seem to pull the temp. down about 5 degrees. The biggest problem was that the fans are plastic so I had to insulate them on the inside and outside.
They sort of look like crap, but do seem to help and give me another option to control the environment.
Bill
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Old 02-03-2009, 05:40 AM
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Default Overheating

I agree with everything UNDY said. Especially the portion concerning the front shroud to seal and force air through the radiator. I had similar heating problems until I made and installed an aluminum shroud that fit between all the body panels inside the front opening, up to and all around the radiator. I did leave a slight "crack" opening above and across the top of the radiator that is about 1/2 inch wide. Plus, I installed a 3300 cfm fan and shroud to the rear of the radiator. The fan is a Zirgo that is widely available. I also run the twin polished fans in front of the radiator. With a 180 HIGH FLOW thermostat and 3 small holes drilled into the flange, the motor runs @ 180-190 on the highway and 190 in stop and go traffic, all in 90 plus temperatures.

I made the front shroud from templetes cut from poster board material so it could retain some of the curved shapes. Cut the templete pieces to fit the shapes required. After fitting all the paper pieces into place to look like a factory installation, I removed them and cut the sheet aluminum to fit the templetes. Each piece of the shroud is installed individually and attached to either alum. or SS brackets to the radiator mounting flange with #8 SS button head screws to allow removal if needed later. Other attachments to inner body panels are with same, or you can use alum poprivits that can be drilled out for removal.

It is very easy to make. Look at several similar installations on other cobras to get your ideas. Bob
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  #9 (permalink)  
Old 02-04-2009, 11:38 AM
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Thanks Guys,

Things that I have already done prior to this Request.
1. I had made and installed aluminum panels around the radiator completely sealing off the engine compartment air can only enter through the radiator.

2. I am using a 1850 cfm puller with 's' blades.

3. I have 2 small pusher fans with 8" blades on the front that can be manually turned on if needed.

4. I have the stock cast iron water pump.

5. The pulleys are stock only had them chromed. Water pump pulley measures 5 3/4" in diameter and the crank pulley is 6 3/4" diameter. I realize this is not what all of you have been talking about but since it is stock shouldn't it be good?

6. I had an aluminum radiator made to fit the opening available with 1 1/4' tubes.

I will get a high flow 180 deg thermostat and install it. The wiring i used was a Painless system and used the wires that they marked for the fan and I am using a one wire 100 amp alternator. I will check the amps as suggested. Do you think that an aluminum Edelbrock water pump would be more efficient then the stock? I am using a 50:50 ratio in coolant and waterwetter.
Why did you drill holes in the thermostat?
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Old 02-04-2009, 12:55 PM
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Default Cooling...

I would also go with the Edlebrock water pump, or a similar high flow unit. As I mentioned earlier, I use a 3300 cfm rear puller fan that has made a big difference in air flow. Combined with the front shroud, the larger flow fan with a rear shroud that overlays the entire rear radiator surface made the biggest improvement for mine. When the car is idling or just parked turned off, and you rurn on the big puller fan and stand beside the engine compartment with the hood down you can feel the "breeze" on your feet that the fan creates. But it is pretty quiet. Instead of the normal high pitched sound from so many other fans, it makes a much lower pitch and is not objectionable at all.

The figures you gave for the stock pullies seem a little smaller than I remember them being.
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Old 03-04-2009, 07:07 PM
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Mark, Based on what you have described your lay out to consist of, 1850 cfm is not enough to cool you at idle with no road speed. The two main factors to consider are coolant flow rate and air flow. With no or near zero road speed conditions. 2,500 cfm is the smallest you want to go for V8s (up to 350 hp) with 2700-3300 cfm better suited to protect larger HP motors. Look at SPAL fans, high quality reasonably priced, and they have data to back their fan specs. Use the largest puller fan or fans that cover as much of the core area as possible. COOLANT FLOW: You can't have too much gpm's of coolant flow rate at idle, period. What governs this is radiator tube/core design and water pump flow rating. Once you are moving enough air through the core at higher road speeds, if your radiator and water pump flow rates are OK, the fans will not be needed. The fans should be thermostatically controlled to turn on/off at temps near 180-185. Dont forget to check the voltage drop at the fans to make sure your are providing the max voltage to the fans, otherwise they wont flow the air they are rated at. Even 3,300 cfm fans means nothing if fans are only getting 10 V.

If you are running 160-180F at higher road speeds your coolant flow rate may be adequate with the cast iron OEM pump but you may benefit with a water pump that has higher gpm flow rate at low speeds. Your pulley ratio is OK based on sizes you mentioned for street duty. Stewart coolant pumps have a good reputation and flow charts are available for their pumps. Be careful of folks selling hi flow pumps with no flow chart data to back their claims, same goes for aftermarket elec fans.

All, I learned alot from these articles, clear and NO BS, pretty accurate. Very helpful.

http://www.streetrodstuff.com/Articl...g_Suggestions/

http://www.streetrodstuff.com/Articl...g_Suggestions/


Bill
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Last edited by kitcarbp; 03-06-2009 at 01:40 PM..
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  #12 (permalink)  
Old 03-05-2009, 01:53 PM
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Thanks KITCARBP and SIDEROILER.

I have just purchased and received today a Edelbrock high flow aluminum water pump and a Mr Gasket high flow 180 T-stat. I will be installing them this weekend. Thanks for the recommendation of the Spal fans. I was looking at their web site and it stat under the 3300 cfm fan not recommended for street use. Do you think that that a 3000 cfm will be adequate? Do you have any other recommendations on fan manufactures? It hit in the 50's today and I am hoping that I will be on the road soon to test these changes.

Thanks again. The people on this site have been wonderful.
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Old 03-05-2009, 02:34 PM
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They nailed it. Change out the thermostat to a 180 and upgrade the puller fan to a 3000 cfm or more.

Unless radiator is too small, that will cure the problem.
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