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JAH11's 1968 GTO

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This is my 1st forum , hope I'm doing it right . I have a 67 GTO , with a new engine , that overheats like the old one . My electric rally gauge is incorrect , and I'm using an infrared thermometer currently . At an idle of less than 1000 rpm temp is about 170 degrees on front of intake , and about 185 or less on radiator tank . At 2000 rpm , I get to 200 degrees at intake , and close to 215 at rad. I've mounted a 3000 cfm pulling , cooling fan within my original fan shroud . The car has Vintage Air , and trans cooler , but will still  slightly pull a bag to the grill . It really doesn't do any more for the temp than the clutch fan . I have an aluminum rad that is supposed to flow more than the old one . The engine is a 455 with 670 heads , and 30cc dished pistons that are supposed to make it less than 9.5:1 .   

I'm planning to drive to the GTOAA convention in WA from PA on July 9 , but only if car is drivable . Please give any answers that may help . Thanks , Brad

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The first thing that I would do is to pull the thermostat and re-assemble everything.  Fill the rad back up and then run it.  If that solves your problem then it was a bad thermostat. You put in a new radiator.  Are all of the air bubbles out of the system?


Good luck with it and i hope we can help.

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Sounds like you're a victim of the parts cannon. Too many new parts all at the same time can make it tough to figure out where the problem lies. You say it'll only barely pull a bag into the grill .... Might I suggest an air flow check. Any good A/C shop should have a meter like this http://www.ebay.com/itm/AIR-FLOW-METER-ANEMOMETER-Measures-AIR-FLOW-CFM-/350462949072 If you're letting too much air get in around the sides of the fan, that would definitely cause problems. Shroud and fan have to be pretty close. Maybe a cheap electric pusher fan mounted in front?

I'd love to have something like this flow gauge mounted in the radiator line sureflow_tt_01.jpg to show exactly when the thermostat opens and how well the water pump is doing.


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Thanks for the responses , I just finished putting in a mechanical gauge , a 195 degree thermostat , and a 16 lb. cap ( all at engine builders request ) . Car is at 205 at idle and driving , and up to 215 with a/c on driving . Some are telling me that is normal .

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In your OP you say NEW engine. How long has it been running?

A new complete build is always going to run hotter until everything sets in/up.

That being said the numbers you last posted are not off the chart. 

215 with AC on is a good number.

You shouldn't start worrying until you see the high side of 240.

You'll know when your having problems as shes going to puke and let you know shes to hot.

When we get the '67 out on a 95+ day she will jump to 215/220 very quickly and will run all day with no issues.

We did add a catch can just to be sure we were not loosing Fl and did have to go back in to correctly clearance the WP divider plate.

Keep driving/enjoying her, but keep an eye on it.



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Yeah, I'd be happy with those numbers. Water alone boils at 212F, but a 50/50 mix of prestone boils at 265F. Add 16lbs of pressure and that boiling point goes even higher. Toss a little Water Wetter in there to reduce surface tension and she'll shed heat even easier.


It's tough to beat good old mechanical gauges. Drives me nuts not having them in the wagon.

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