installed GRIFFIN and STILL running hot!

[Guest tom sixbey]

ok here's the low-down. I was talking to an old Zracer, and this is the problem - especially for the inliners, and those with scarabs. The radiator support is largely to blame. When you mount a different radiator, you ABSOLUTELY must seal the radiator to the opening of the radiator support, and plug off all the holes in the radiator support. With a scarab or an inline, the air has no place to go once it passes through the radiator because it stacks up in front of the motor. when this happens, the incoming air finds it easier to go around the radiator than it does to go through it - so essentially at speed, the is an insufficient flow of air through the radiator.

Another problem area is the hood. That sharp lip along the edge of the hood creates a huge boundary layer in front of the radiator - this type of airflow is virtually useless for cooling purposes, and will make for a hot car regardless of how nice a radiator it has.

 

Here's my plan:

 

i intend to build an airbox that completely seals the front grille opening to the hole in the radiator support. by doing this, i hope to "funnel" all or most of the intake air into the radiator cores. I also intend to build an air extraction system to help remove this hot air from under the hood. I've been thinking on this for a little while, but i havent found an area of low enough pressure on the hood to place extraction ducts. I'm guessing that Terry Oxandale's hood would be one possible solution - also making sure that the hood opening was completely sealed to the radiator cores. This would essentially take the entire intake ram, force it into the radiator, and direct it out over the top of the car. My only concern is that the air extraction duct might not be in an area of low enough pressire, and in turn complicate the problem by again creating a stagnant air zone around the radiator.. - Any thoughts/experiences on this subject, Terry? - after all you are the duke air extraction hoods! hehehe

[Trevor]

Air-in-the-system problem reminds me of my boss's Pantera (Ford 351C engine in the back, radiator, with the filler neck, in the front). He had cooling problems in Scottsdale, Arizona - (go figure) They had to raise the front end up on ramps, put a sheet of cardboard over the radiator and a brick on the gas pedal and let it run up to operating temperature. It hopefully quickly circulates the air out to the filler neck. Getting the air out cured its problems.

 

For my Z project, my radiator doesn't have a filler cap. I bought a filler neck/thermostat housing similar to Dedenbear, from Summit. I think it was $29.

[blueovalz]

Based on tufts of yarn to visualize air flow over the hood, I found that any sign of turbulance (and hence, I conclude reversal of air and high pressure) pretty much ends about 12" forward of the rear of the hood, and even with this, I found little turbulance up to the cowl cover. The area just beneath the windshield was chaotic in terms of air movement, in fact, almost a dead zone. With the modified hood, I found than full straight yarns all the way to the cowl cover were the observation in the area aft of the radiator out-vent.

[Pop N Wood]

Might not be related to any of your problems. But the early Z's had airflow problems through the radiator. Datsuns's fix was to install a sheet metal shield between the frame rails that extends from the back of the radiator to somewhere near the steering rack unit. This was to cut down on the turbulence underneath the car. This is a stock Nissan part.

 

Also the JTR manual goes on and on about installing a fan shroud. Seems likes a good idea.

 

I don't know if anyone has mentioned this but flushing the engine block can't hurt. If you bought the car used there is no telling how many cans of stop leak might be gunking up the works. Know this one from personnal experience.

[Guest tom sixbey]

hey jim - its funny you mention that, cause it was the first thing i did when i got to the cooling system. As it turned out - years of gunk and rust were the only things sealing the radiator. After flushing the system i sprang three different leaks in the original radiator!!! talk about a buzzkill. It seems like whenever you try to do something good for the car, it just jumps up and bites you in the ass! hehehe

[Dan Juday]

Guys, I feel very confident that the problem can be solved with a proper shroud. I am an air conditioning technician and I know about heat transfer. I work with it everyday. If the radiator is of sufficient size, and it sounds like it is, and your fan can move enough air, and that sounds good too, then the problem is where is the air moving. The guy that recommended sealing off the rad support was right. But a good shroud will help more. You must pull cool air through the rad. Wherever it goes from there is meaningless. I have personally witnessed the drastic change in temperature of a liquid when a shroud is removed or damaged. Others, no doubt, will argue with me on this but just try it. Shrouds can be made cheaply with simple sheetmetal. You don't need to be an engineer. Look at a couple on any car that has one and just make one that fits and looks like it. JTR is dead right on this one.

[Guest tom sixbey]

i'll take your word for it and build a shroud. right no i'm running a 16" flexalite trimline that has it own little shroud around the fan blades (it sits directly against the radiator).. - is that enough, or do i need to mount that to a shroud that covers the entire radiator?

 

would a big shroud limit air flow at high speeds?

[Guest Anonymous]

I'd say if you can get 70-80% coverage of the hot side of the core, you'd probably be ok. I can't believe its still overheating after what you've done. How much air does that fan pump out? Also I didn't go back and read the whole post, but do you have any form of vents on the hood, or the back of the hood elevated open slightly (this actually works ok, leave it up a 1/2" or so, with a stock hoodlatch this would take some mods). Just some thoughts, good luck.

 

Regards,

 

Lone

[Dan Juday]

Tom, if I remember you don't have a lot of room up front between the rad and the motor. If you can pull it back from the rad some that will help. I'd make the shroud to cover the whole core.

 

Good point about limiting airflow at high speed. A way to counteract that without sacrificing the airflow your fan makes is to add barometric dampers to the shroud. Fancy word for backdraft flaps. Try it with out them first. You can always cut them in later. They would simply be flaps that cover holes in the shroud and are hinged at the top and open rearward. When the air being forced through the rad exceeds the pull from the fan they open letting more airflow through the rad.

 

Give it a try, Tom. I've seen those types of fans and I always think, "They are wasting most of the power of that fan".

 

Air conditioners are made as cheap as possible. They use the smallest, cheapest fan motor they can get away with and compensate for it with a good shroud because shrouds are cheap. They also make a tremendous difference. All A/C's, good and bad, use fan shrouds.

[R0N]

I was running slightly hot but use a product from Redline called water... something. It works very well.

[Guest Anonymous]

I know I've been on a campaign of jetting here lately, but look for vacuum leaks or lean jetting. My brothers 390 in his T-bird was constantly running hot with the air on in trafic, its all new.

The other day his brake booster went out and caused a massive air leak. Long story short, we plugged it till he can get to repair in, the motor straighted out and idled fine and a side benefit, no more overheating.

 

So, just a tip, overheating issues are not always cooling system related and can be both timing and or carb jetting issues. Just thought I'd pass it on since we just dealt with it, also after I jetted mine fatter in the primary, it runs 5 degree's cooler and no longer gets warmer on the freeway (which is where the primary is running full time, thats why it was getting hot on the freeway but not around town.)

 

Regards,

 

Lone

[danj]

The additive that Ron is referring to is called "Water Wetter" by Redline. I have used this product and it did lower my operating temp by about 5-10 deg. It's cheap and available at many auto parts stores, I got mine at Pep Boys, so it's worth a try.

 

Dan H.