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Discussion Starter #1
I have an early SBC 350 it will overheat and top radiator hose is extremely hard. I did a crank compression test and have an average of 155.25. The spark plugs on cylinders #4 & #8 has a burnt crust on them, #8 more than #4, the remaining plugs are normal. These two cylinders have 150 psi in each. Initially the car didn't have a thermostat so I put one in. I'm now thinking the previous owner also had a problem. Oil & coolant is clean, the car starts and run great until you drive a few miles; do anyone have any ideas?
Thanks
Jaye
 

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Mike - 74 Nova Baltimore, MD
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First... what temp is the coolant getting to when overheating?... How did you confirm this temp?

Some causes of engine overheating may be clogged radiator and/or water passage ways within block/heads... insufficient airflow thru radiator... improperly sized radiator (too small) for engine cooling needs... bad water pump... improper ignition timing.... carb running too lean.
Could be any... or all of the above.
 

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1973 Custom hatchback
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Any chance you put the Tstat in backward? probably not but gotta ask. If your top radiator hose is hot and hard, then probably not the issue.
Are your belts intact and do they turn the water pump?
What symptoms of overheat are you getting? Is the cap on the radiator venting? does it have a overflow tank?
 

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Discussion Starter #4
The temperature gets up to 250 with a manual gauge, sometimes the overflow tank will spit out coolant, t-stat is installed correctly, I also thought about the radiator (original from 64)
 

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Mike - 74 Nova Baltimore, MD
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If your engine is overheating while cruising at speeds above 30mph, the radiator could be the cause... but it is still a good idea to check the other items I mentioned in post #2.
  • Do you know what your ignition timing at idle is?
  • How do the rest of your spark plug insulators look (tanish-brown, white, black w/deposits)?
  • How old is the water pump (internal pump vanes my be deteriorated)?
  • Is your fan/water pump belt tight and in good shape?
  • If you are using a clutch fan set-up, do you notice any fluid on the outside of the clutch?... with the engine hot, but not running... does the fan spin freely when turned by hand or is there some resistance felt? (A bad clutch fan would normally lead to overheating while idling and stop & go traffic).

If you decide you need a replacement radiator, Cold-Case Radiators is a site sponsor... and is running a special right now (see link below). From what I have read, this company produces a pretty decent aluminum radiator.

P.S. Can you post a photo of your current radiator & fan set-up?
 
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