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Discussion Starter #1
My car is overheating on hot days. Like 90* days. Every day lately. If I don't do something it's going to ruin my new crate engine. I already changed to a 180 high flow thermostat and got a new water pump, which helped, but for some reason my temps start to creep up as long as I'm climbing a hill, or If I decide to gun it. It's gotten as high as 230 coming up the hill to my house. 2nd gear doesn't help either. I seem to have some type of load related issue. I've played with the timing, but to no avail. Currently it's at 14*btdc. I've flushed the radiator, everything came out clear. I have a 6 blade summit 17" flex fan that fits very well in the stock shroud; it was always sufficient for the 307 but my Gmpp 350 still manages to overheat. Do I, or should I, need an aluminum radiator? Or is there anything I can do to reduce the temps? Does that water wetter stuff actually work? My car has 2.56 rear gears and tall tires, so I suppose that is probably contributing to my problem.
 

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Honestly, the first thing I would do is dump the flex fan in favor of the stock fan and clutch assy. As your RPMs increase, the flex fan flattens and moves less air. The theory is that you're going faster and thus, the airflow through the rad is increasing, so the fan shouldn't have to pull as much. The reality is they never seem to work as well as the stock clutch fan.

If you still having problems, I would consider having the radiator recored for more capacity.
 

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Personally, I've never seen a flex fan that was worth a damn. A 7 blade clutch fan from a heavy duty application (truck, taxi, police car...) works far better in my experience.
 

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Discussion Starter #7
Just checked the plugs. Pretty sure I'm running lean because they all tend to be a little whitish on the ground strap. Although now I have other problems, my engine refuses to idle without surging. It revs just fine--and there's no smoke or oil in water/water in oil so I doubt it's a blown head gasket, although given how badly it overheated today that's not out of the realm of possibility. I noticed that if I cover the carburetor with my hand it smoothes out and revs up, so it seems like my mixture suddenly went awry do to either carb problems or a vacuum leak. Can't seem to find the vacuum leak though...
 

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Seems lean to me, what kind of carburetor is it? I run a Holley street avenger and had to jet it up 2 sizes as I had a similar problem. Temp would creep up under a load..
 

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Discussion Starter #10
It's an edelbrock 1405, it is lean according to my plugs, which is weird because my brother has exactly the same carb on his 350 and his runs perfect. He does have a little smaller cam than the one in my crate engine though. How exactly do I go about tackling this problem? I've never tuned a carb before.
 

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There should be a thread in the drivetrain and performance section. Type carb adjust into the search forum box... you could also try and find the instuctions online for your Edelbrock carburetor..
Basically If your timing is set start with both mixture screws about a turn and a half out from seated position. Provided your idle speed screw is not set to high (screwed into far) this setting should be close enough to start fine tuning the mixture.
The rest I feel you should research "read"... only then will you have a better understanding of what your actually adjusting. In = lean, out = rich
A vacuum gauge will help your quest. But try that base mixture screw setting and let us know how it works....all the info you need to do it is on this site!:yes: As far as jetting your carburetor you will probably need a jet kit to start with.
 

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I have seen retarded timming cause some over heating issues as well.

I would check and see what yout timming is at 1500-3000 with the vac. unhooked (if you have a vac advance).
 

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Does that water wetter stuff actually work? My car has 2.56 rear gears and tall tires, so I suppose that is probably contributing to my problem.
If you are running a tall tire with 2.56 gears, you are probably lugging the car, especially if you are going slow and up hill.

I have used a water wetter called "40 below" and it really works.

I was at the NSRA Nats in Louisville in my 400 c.i. sb powered 39 Buick coupe. Temp was hitting 220-230.

I poured a can of it in the radiator. The results were immediate and the temp dropped to 180.

Of course, this is not a permanent fix for your problem, but it is a nice product to keep in your trunk, in case of emergencies.
 

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Just a tid bit of info. that happened to me. My 70' 442 with a stock 455 was overheating as well. Did all the stuff you have done then I took the rad. to a shop for cleaning twice, but still would overheat on hot days. Next thing I did was replace it with a new one,,, problem fixed.........
 

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Discussion Starter #15
My initial timing is now at 12* btdc. I'm thinking I'll probably get an aluminum radiator in addition to retuning the carb. My radiator is probably the original and I noticed the fins are getting pretty crusty. Plus I just noticed that the trans cooler cracked where the line attaches. Can anyone recommend a good radiator? I've looked at Be-Cool and the Summit direct fit ones but they are ****$. I don't really want the internal trans cooler anyway.
 

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I advised this in another thread. Get yourself a shroud, 16 inch clutch fan, 180 deg therm (which you have) and an aluminum radiator. Then you will be done with it. That's my setup and it NEVER goes above 180 in ANY HIGH HEAT DAY.
 

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All good tips however I use a cheap azz flex fan on my ZZ383 and no cooling issues what so ever. Although I'll be removing it over a clutch type and staggered blade fan, the flex is really loud and annoying.

The only other thing I'll add is don't discount vacuum advance if you aren't using it, you would be amazed at how cool it keeps your motor at cruise speeds. Keeps the motor at peak efficiency, and inefficient running motor runs hot. Yes, hard to set up and get it right but well worth the effort. Your total mechanical advance is also of great importance to keeping the motor cool.

Get the timing down first, then the jetting, Eddy's are super easy to change rods and jets. I'm almost betting you'd be fine with just that. You can go down several sizes of rods before you need to change the main jets.
 
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