Temp keeps going up after shutdown
I finally had a chance to get my '67 L71 out for a long drive today. I had fixed the overheating problem with numerous things, and after a hour of 65 mph highway and abot 30 minutes of stop and go traffic it was cool as a cucumber. But when I parked her in the garage, after the drive with the temp reading about 170 or so (my thermostat I guess), I was working on the radio and left the key on and noticed the temp kept climbing for about 10 minutes to around 210 before it stopped. Is this normal? My '66 L79 doesn't do this, is this a BB thing? Thanks for any ideas.
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Big Tanks In the High Mountains of New Mexico -
Re: Temp keeps going up after shutdown
I'm sure others will chime in but can share with you my experiences with '66 427/390. The (new) engine is sitting in the frame but has seen quite a bit of run time before body drop. Each time engine has been run will reach operating temp (monitered by temporary gauge) and stay there till shut off. Shortly after, temp will rise up over 200 degrees and stay there for a short period of time then slowly come down. This action is typical for my engine but most likely any engine after shut off.....no water circulation. -
Re: Temp keeps going up after shutdown
Mike, perfectly normal operation, remember you were not circulating any fluid. You were seeing residual heat buildup. Bill.Comment
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Re: Temp keeps going up after shutdown
As others have said, you were simply observing normal heat soak back. If your key was actually left in the 'on' position while you were working on the radio, you might want to have a look at the ignition points for burning.Comment
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Re: Temp keeps going up after shutdown
Does it still have ported vacuum advance? If so...
Converting to full time has been discussed a zillion times.
DukeComment
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Re: Temp keeps going up after shutdown
Thanks for the replies. I was just curious since my '66 L79 doesn't exhibit that behaviour, it doesn't keep heating after shutoff. I have a Petronix system, so no points to burn. And yes Duke, you helped me a while back after I first got her and she overheated. I changed the vacuum advance to the NAPA part you recommended, put the VA on full-time from the center carb instead of ported, advanced the spark to 10 degrees BTDC, replaced the fan clutch, and had the radiator rodded. Lots of stuff, but thanks to your suggestions, no overheating.Big Tanks In the High Mountains of New MexicoComment
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Re: Temp keeps going up after shutdown
Michael,
Is the temperature sender mounted in the cast head on the L71? The L79 sender is installed in the aluminum manifold and the aluminum cools much faster than cast. That may be the reason you see the guage move on the big block and not on the small block.
You can bet both engines heat soak a little when shut off..
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Re: Temp keeps going up after shutdown
No, both have the temp senders mounted in similar places on the aluminum intakes near the thermostat housing, one left of it the other right. Not sure why the difference, could be the BB just heat soaks more.Big Tanks In the High Mountains of New MexicoComment
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Re: Temp keeps going up after shutdown
Then you've probably done about everything that can be done. The big block is a pretty big thermal capacitor - about 50 percent bigger than a small block. Since some parts of the engine are hotter than the coolant at shutdown, the coolant will heat up. This is typical with most cars, but not as noticeable since most cars don't have as much engine mass and modern aluminum will dissapate heat faster.
As long as the heat soak coolant temperature does not reach the 265F boiling temperature of a 50/50 antifreeze solution with a 15 psi pressure cap, then it's nothing to be concerned about.
DukeComment
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