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post #1 of 18 (permalink) Old 07-23-2013, 07:31 PM Thread Starter
 
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Another overheating question

Hello everyone.

I have a 67 GTO with original 400, .30 over, mild to hot cam, 650 Edlebrock (though I need a 750 Holley), aluminum non AC radiator with a shroud, overflow, and an electric assist fan on a manual fan.

So, It's gotten a lot better but since adding the shroud, aluminum radiator, overflow and assist fan. But last week I went to a car show that started around 2:00 pm. We staged at a parking lot and then everyone paraded to the street they had closed off. While I was driving slow and waiting for my turn to park in 85 degree weather with the electric pusher fan on, I got up to about 235 and still rising.

I've adjusted the pump plate and have good flow.

My question is, can I add a larger radiator? I would prefer to modify my radiator support instead of buying the AC version. I don't have AC now but plan to add an after market package some time.

Has anyone cut there radiator wider to fit a wider radiator?

I hate dealing with heat issues.

Thanks
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post #2 of 18 (permalink) Old 07-23-2013, 09:42 PM
 
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Hotterna$2pistol...

First, make sure you're running a healthy vacuum, 17"-21" is ideal, depending on elevation, cam, etc... then MAKE SURE that your vacuum advance at the distributor is engaged full on at one or two inches lower than your actual vacuum reading. (Use a hand held vacuum pump- rent one at the parts store if need be-and watch the advance plate move to the full on (stop) position, and at what vacuum, and adjust accordingly, if your can is equipped). Set your distributor as per Lars', Bears, Geeteeoh!guys', and others on the forums' suggestions. Make sure your advance curve falls into the suggested range. Then use your vacuum gauge to set your carburetor. I had ongoing hot running issues, until I finally paid heed to these guys' instructions.[B]USE MANIFOLD VACUUM FOR YOUR VACUUM ADVANCE!!!!![B] Tap into one of the plugs on the manifold if you don't have manifold vacuum at the carburetor. Small carb. can cause problems also, although my 455 has a 625 cfm Carter on it, and am happy for now with it. No more running at 235+! Good luck. The old salts on this forum will guide you and ease your pain. But you must follow their procedures. You CAN get to the bottom of this! Good luck! P.S. Get yourself (or rent) good test equipment: Tachometer, vacuum gauges, dial back timing light (or timing tape&light), etc... Save yourself a load of grief right off the bat!!!

Last edited by gjones; 07-24-2013 at 12:41 PM.
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post #3 of 18 (permalink) Old 07-23-2013, 09:48 PM
 
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In my experience, a pusher fan in front of a mechanical fan was worse than the mechanical fan on its own.

I'd start with the basics:
Firstly and most importantly, have you confirmed the gauge readings with a known good gauge or infrared thermometer?
Is the air-fuel ratio correct? (too lean=too hot)
What is your base timing?
Are you running vacuum advance? If so, how much at idle?
What type of fan are you using?
Is the fan the correct diameter and pitch?
Is the fan properly positioned in the shroud?
If using a fan clutch, is it working correctly?
Was the engine built with zero deck height or are the pistons well below the deck at TDC?

1968 Pontiac GTO
1983 Pontiac Bonneville (G) wagon
2008 Pontiac G8 base
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post #4 of 18 (permalink) Old 07-23-2013, 09:59 PM
 
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Sounds as if you have battling this for a while. The basics should be looked over first. I'd start the car cold with the radiator cap off and watch for coolant flow as the thermostat opens. I'd check the radiator cap for the ability to hold pressure.

You might drain a bit of coolant when the engine is cold and inspect the tubes that run across the radiator. If you can see a lot of barnacle like deposits on the ends of the tubes, the radiator is plugged.

Fan belt tight? Fan clutch working? You might consider and heavier duty fan clutch with an external temperature controller. No obstructions such as driving lights or a separate trans cooler?

As you mentioned, there is a plate between the water pump and timing cover that might be corroded and not allowing the water pump to do it's job. There are two press in tubes with seals that contact the back of that separator plate that might be damaged and not sealing well against the plate.

Airflow management around the radiator is important. The fan shroud should fit well around the radiator and the fan itself should be inside the shroud. a spacer may need to be added to get the correct depth.

There are soft rubber baffles that seal up areas around the radiator and core support. If they are missing or hard, they may not be preventing air from leaking around the radiator.

All that OK. Have you tried a "water wetter" type product? Sometimes they can help a marginal situation. A 50-50 mix of water and coolant is important. Too much coolant concentrate can cool poorly.

Finally, the radiator may indeed be too small. If you are going to change the radiator, install a new larger aftermarket unit such as the "Be Cool" brand. Aluminum cools better than and old brass/copper unit.

Before purchasing that new radiator, be sure the tune up is good. Retarded timing or a lean condition can make the engine run hot. Have you overhauled the engine recently? An improperly installed cam can add to your problem.

There is your "homework" to do. Check it all out and let us know what you find.

By the way, that add on fan may be too small. To keep my drag car cool in the Texas heat, I'm running a 4,000 CFM twin electric fan set up. Sometimes I need to run the engine in the staging lanes to keep the temp up!

Last edited by mikea455; 07-23-2013 at 10:08 PM. Reason: more text
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post #5 of 18 (permalink) Old 07-24-2013, 12:27 AM Thread Starter
 
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First of all, thanks for all the responses.

gjones: I have an MSD ignition that is not attached to the vacuum. I should have added that into my original post.

The engine is newly rebuilt, about 4000 miles now. After I installed everything I took it to a very reputable shop that mostly works on classics for a new engine tuning. They dialed everything in for me. It made a big difference in performance. That was during fall when it is cool around here. They pointed out a problem with the carb. When I got this car, the first thing I did was buy the 650 edlebrock. I was able to fire the engine but it ran like crap. Also I had not changed the tank yet and I clogged up the idle circuit. (first classic car for me. rookie mistake) The mechanic was able to get one open but not the other. The car runs fine but it's clogged. I don't know if that is part of the problem or not.

JMT455:I only use the pusher fan if I am stopped in traffic etc. It makes slows the heat rising, depending on the outside temp. I have to check the timing again, I think it was 36 and 18 or there abouts. I have a 6 blade fan 18" fan without a clutch. The fan has about 1/2-3/4 inch around the shroud and is half in and half out of the opening. The deck height I will have to check with the machine shop.

MikeA455: The radiator is new so now barnacles. I have ran it with the cap off and as soon as the Tstat opens I can see a rush of water movement. I have adjusted the plate and both tubes are installed. I have good airflow across radiator. I was told to put a dollar bill against the outside of radiator while at idle and see if it suck onto it. It does. The baffles you are talking about I don't have. So I will look into that. I am using Water wetter and I am using 70 anti and 30 water per the instructions. I will try a 50 50 if you think that will help.

So I think I will try the to do the following
baffles around the radiator
look into a new carb
change to 50/50 anti water

thanks again.

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post #6 of 18 (permalink) Old 07-24-2013, 12:05 PM
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I agree with the above posts. Installing huge radiators and extra fans is a band aid to cover up the real problem. If all components are up to snuff, a stock cooling system will work just fine. Check the tune, verify the temps, etc. Lean carb=hot. retarded timing= hot. Poor airflow through the radiator core = hot.
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post #7 of 18 (permalink) Old 07-24-2013, 01:31 PM
 
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Advance to go. Collect $200.

Not having a vacuum advance for a street driven car is a major no-no! (Or at least that's what I've been told). It's o.k. not to have it when the car is driven mostly at the track and isn't sitting at a stoplight in heavy traffic in 96 degree outside temperatures. That alone could be the culprit. At idle with a vacuum can, you're running a full 17 degrees advance, say, at the distributor plate. Then add your initial timing in the mix, say 14 degrees, bringing in the total advance at idle, in gear with your foot on the brake at that stoplight, running the engine at 31 degrees advance. Take the vacuum advance out of the mix, and now you're idling at that same stoplight at only initial retarded timing of say (let's be generous) 18 degrees btdc. A far cry from that 31 degrees with the vacuum can. As was stated earlier, retarded timing=hot running. Voila! There you have it. Unless that MSD ignition compensates for that, I think the above statements are correct. GUYS???
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post #8 of 18 (permalink) Old 07-24-2013, 04:03 PM
 
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" (though I need a 750 Holley),"

If this is a street car, you "need" a good Qjet All good topics mentioned above. I will just add that my 9.4:1 iron head 455 will idle all day long at 190 on the hottest MN summer day (high 90's and 70+ dewpoint. I know, not Texas, but hey, it is hot for us!).

Does not seem to matter where my Dist Advance is connected. My cooling setup is a FlowCooler pump that came with a parts motor, and a stock-size aluminum rad in my 66. The rad uses one wide core, as opposed to a traditional "4-core". I have two 12" puller fans that are mounted on an aluminum shourd as shown in the pic. I do not like the sound of the electric fans, but they seem to work so well, I hate to change it. Plus, I like the nice clean look as shown in the other pic.

Only time my temp got above 200 and creeped up to 225 was during cam break-in. I think half the reason was I realized I forgot to plug the fans in, and did not get them running until it was already at 210...

To Geetee's point, nothing radical to keep my engine cool either, so focus on the basics.
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post #9 of 18 (permalink) Old 07-27-2013, 08:57 PM Thread Starter
 
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Ok. I just put the new Holley Street Avenger 770 on. It is nice to have working idle mixture screws. I still have a few adjustments to dial it in but so far I am very happy with it. I do notice that I have power higher up in the RPM range. Off the line It is a little less peppy but It spins the tires more.

But for the important thing. I let it sit parked and running. The temp hit 180 and stopped. Today is not a hot day, in the 70's, but on a day like this with the old carb the temp would go from 180 to 190 then back to 180 over and over again. So I am hopeful that this will cure my heat problem.

Thanks for all the ideas. I'll let you guys know how it goes.
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post #10 of 18 (permalink) Old 07-28-2013, 09:47 PM Thread Starter
 
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Ok. So the temp is still good. Still not a warm day though.

I have a tuning question now. I followed the directions for tuning. I used a vacuum gauge found the highest vacuum at idle which was about 18. Remembering I have a little bit of a wild cam so I expected to have low vacuum. Once I set the idle screws to give me the highest vacuum my idle speed was 1700-1800 rpm with the idle speed screw backed out all the way. I called Holley and the tech told me richening it up a little will bring down the idle speed. I adjusted it and the rpm dropped to about 1100. Drove for little while found that strong gas smell and a little white smoke coming from the exhaust. So I leaned it out but the rpm is back up to about 1300-1400.

When I changed the carb i added a fuel pressure gauge. It read about 4 psi. Holley said 5-7 was needed for this carb. I bought a performance Holley fuel pump and now I am at 8. Is that a problem?

Is carb tuning get close then trial and error?

Thanks
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