1968 390 overheating
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1968 390 overheating
-points gap adjusted .020
-adjusted timing 10 deg BTDC with vacuum line disconnected and plugged.
-changed coil and negative wire to the distributor.
-cleaned up some electrical connections
Now it runs rough and is overheating very fast at idle, ran at 160 degrees before.
-adjusted timing 10 deg BTDC with vacuum line disconnected and plugged.
-changed coil and negative wire to the distributor.
-cleaned up some electrical connections
Now it runs rough and is overheating very fast at idle, ran at 160 degrees before.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
How do you know it was running at 160° before? I just ask this from the standpoint of whether this is or was a dash gauge indication, or something decidedly more accurate. Stock Thermostat is probably 185° - 190° btw. That's what you want to see imo. Is it actually overheating ie. spitting coolant.
Retarded ignition timing will cause engine to run hot, though not necessarily rough, unless severe. Just for grins, how much manifold vacuum does it pull? Normally a stock engine will pull 18" to 20" steady at idle if ignition timing and everything is OK.
What was the initial timing indicated on the damper before you adjusted it to 10°? Sounds a little bit like your damper is lunched if I had to guess.
Retarded ignition timing will cause engine to run hot, though not necessarily rough, unless severe. Just for grins, how much manifold vacuum does it pull? Normally a stock engine will pull 18" to 20" steady at idle if ignition timing and everything is OK.
What was the initial timing indicated on the damper before you adjusted it to 10°? Sounds a little bit like your damper is lunched if I had to guess.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
How hot is "too hot"? Normal operating temperature is somewhere around 200° - 212°, 250° would be "too hot". The dash temperature gauge on these trucks weren't known to be particularly accurate in any way. That's part of the problem with remote troubleshooting.
Senior User
Joined: Aug 2017
Posts: 199
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From: Berkeley, CA
Retarded timing will cause an engine to overheat fast. Since it seems you messed with the distributor just before this issues I'd double check to make sure you are actually at 10* BTDC with the #1 cyl on the compression stroke.
Confirm TDC on #1.
Then check balancer shows 0 (balancer could have slipped).
Then confirm you have the distributor rotor ready to fire on #1 (if you're at 0 on the balancer and you set the dist to 10BTDC the rotor may be slightly past #1)
Lastly, if you removed all the plug wires maybe you have them all 1 wire off on the cap. Which could severely retard your timing.
Also make sure you reconnected that vacuum line.
Confirm TDC on #1.
Then check balancer shows 0 (balancer could have slipped).
Then confirm you have the distributor rotor ready to fire on #1 (if you're at 0 on the balancer and you set the dist to 10BTDC the rotor may be slightly past #1)
Lastly, if you removed all the plug wires maybe you have them all 1 wire off on the cap. Which could severely retard your timing.
Also make sure you reconnected that vacuum line.
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