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Old 09-07-2002, 12:52 AM
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Post Iroc Z overheating

Need help figuring this one out. The 1989 305 is completly stock, only 75K on motor. Brand new radiator, tried three thermostats. Fan working ok and comes on when it is supposed to. Water and exhaust been checked for head leaks, none found. Timing set to factory spec, 0 BTDC. My question is total advance timing was only 20 degrees, shouldn't this be around 30? What determines the total advance on this motor? A sensor, or distribitor weights, or what? Haven't checked the cat yet and I know if that is plugged could make it run hot also.
Appreciate any and all help.
Thanks
Rick

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Old 09-07-2002, 06:47 AM
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check your air dam in front of your car, if broken or missing, it wont direct air into your rad. is your car running lean, lean condition will cause an engine to run hot.also check your coolant flow in your rad, to see if your water pump is flowing coolant, if not remove water pump and remove the rear cover to see if the impeller finns are dammaged or rotted off. if your car is efi or feed back carb the timing is controled by the computer.some times doing a co2 test wont show up a cracked head.and yes check your conveter, usually a plugged converter wont let an engine rev or pull vary good.
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Old 09-07-2002, 08:35 AM
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I had the same problem with my wifes 86 Camaro. The cat was clamped on so I removed it, chipped all the ceramic guts out of it with long screwdriver,(Most all the little holes in the ceramic insert were plugged) reinstalled and the overheating problem was gone. As an added bonus it felt like it had another 50 horses after it was able to breath a little. Had to put a new cat on when smog check time came around and it still ran good.
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Old 09-07-2002, 12:26 PM
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Oh, man I love my vacuum guage!! You can check for a restricted exhaust before you tear into it. needle shows slow return to initial reading when rappin er up, smooth quick return means youre ok. Definately recommend a guage with the pump, you will use it a LOT!!
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Old 09-07-2002, 12:33 PM
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Someone posted a site that showed guage readings as they would look while testing a while back, cant remember where.
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Old 09-07-2002, 01:04 PM
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do you have dual fans or just single?


how far is it overheating?

check for leaves and **** in front of your condensor. When i got my car it had a freiggin forest down there
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Old 09-07-2002, 01:07 PM
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I almost forgot to tell you to pressure check the rad cap or replace it , there fairly cheep!.A bad cap will cause an engine to over heat!!!
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Old 09-07-2002, 01:54 PM
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I used a vacuum gauge and we even hooked up a pressure gauge to the exhaust and they did'nt indicate a restriction.I worked on this thing quit a few week ends looking for the answer. This was'nt my driver so the test drives I would take in it (after my wife complained to me 5 million times) were not long enough for the problem to show up and I just thought she wanted a new car. You counld'nt tell it was restricted unless you were driving at freeway speeds. Then the least little uphill would cause the temp to go up and the car was gutless when trying to pass.Finally I pulled the cat off and looked in there and the ceramic insert was 75% or more pluged. A new cat fixed it all. If yours is attached with clamps, just pull it off and look inside. You can tell right away if its blocked up. The ceramic insert has thousands of tiny holes in it. It does'nt take much to plug them. WE bought the car used, maybe someone run some leaded gas in it and caused this or its from normal heat and useage.Then again you may have a different type of converter.
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Old 09-07-2002, 04:39 PM
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Thanks Guys for all the input, this car is not a daily driver, sits in the garage most the time. Wife brought it brand new and will keep it forever, but she would like to drive it when she feels like it.
Yes, it only has one fan and it comes on when it is suppose to. It also has a new rad cap, 16lbs, is this too big? Air intakes are clean and free of debris. Last years smog check it passed with flying colors, not even close to half of the allowed limits so I figured the cat was okay.
The timing still troubles me, all my exprience has told me small block Chevys run around 30 degrees total timing and this one runs only 20.
The car still has plenty of power but will get hot real quick just driving around the block, 220-240 degrees.
I looked under it and yes the cat is clamped on so looks like I take it off and check it next.
Still scratching my head on this one, thanks again.
Rick
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