BB engine overheating? Falling a part?
Thread Starter
Instructor
Joined: Oct 2005
Posts: 165
Likes: 0
From: White Plains MD
BB engine overheating? Falling a part?
I need a reality check here. I have a BB with the GM TBI unit and th 400. I think it's overheating. First, I have a 180 thermostat with fresh 50% coolant. The temperature gauge during a drive goes up to 240 and a little past that with the a/c on. Good oil pressure -if it makes any difference.
The engine compartment is getting extremely hot. I can see some scorching of the sending unit wires, plug wires, etc. If I put my hand about 12" from the exhaust pipe, I can only leave it there for a few seconds or risk getting first degree burns.
On start up I can hear a type of "clacking" type sound only when I'm moving and start to accelerate. It goes away after a few miles. Any ideas? - liftters -piston
-exhaust leak 
The engine is currently not in my vette it's running my truck ...but maybe not for long??
Thanks guys.
The engine compartment is getting extremely hot. I can see some scorching of the sending unit wires, plug wires, etc. If I put my hand about 12" from the exhaust pipe, I can only leave it there for a few seconds or risk getting first degree burns.
On start up I can hear a type of "clacking" type sound only when I'm moving and start to accelerate. It goes away after a few miles. Any ideas? - liftters -piston
-exhaust leak The engine is currently not in my vette it's running my truck ...but maybe not for long??
Thanks guys.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Yep, that's overheating. 
Are you seeing any significantly increased oil consumption yet? If so, you've "collapsed" the rings.
There are a number of things to check that can cause or contribute to the heat, but the fact that your exhaust gasses are extremely hot together with high-temps and scorching going on under the hood lead me to think the timing is too retarded and/or the A/F mix is way too lean.
Overly retarded timing can result in the exhaust valve opening up while the A/F mix is still burning, which means it completes it's burn in the exhaust manifold. Lean mix can also lead to very high exhaust gas temps, and can "burn" a valve, which may possibly result in it sticking.
...or that clacking noise could be a lifter, but it could be something else. Just how pronounced is that clack and can you tell if it's at engine rpm or half of that?
Are you seeing any significantly increased oil consumption yet? If so, you've "collapsed" the rings. There are a number of things to check that can cause or contribute to the heat, but the fact that your exhaust gasses are extremely hot together with high-temps and scorching going on under the hood lead me to think the timing is too retarded and/or the A/F mix is way too lean.
Overly retarded timing can result in the exhaust valve opening up while the A/F mix is still burning, which means it completes it's burn in the exhaust manifold. Lean mix can also lead to very high exhaust gas temps, and can "burn" a valve, which may possibly result in it sticking.
...or that clacking noise could be a lifter, but it could be something else. Just how pronounced is that clack and can you tell if it's at engine rpm or half of that?
Thread Starter
Instructor
Joined: Oct 2005
Posts: 165
Likes: 0
From: White Plains MD
Thanks, I'll try to see if it's at half rpm. I does clack faster as I accelerate....you might be right though. It's not a constant noise it does skip a beat or so. I'll check in the morning.
You are scaring me with the collapse rings. I add about half quart every 1500 miles (35mph tops), unless I drive it on the highway (65mph tops) then I need to add about two quarts every 300 miles or so. It doesn't smoke so I'm baffled.
I'm so lost here...
You are scaring me with the collapse rings. I add about half quart every 1500 miles (35mph tops), unless I drive it on the highway (65mph tops) then I need to add about two quarts every 300 miles or so. It doesn't smoke so I'm baffled.
I'm so lost here...
Yep, that's overheating. Are you seeing any significantly increased oil consumption yet? If so, you've "collapsed" the rings.
There are a number of things to check that can cause or contribute to the heat, but the fact that your exhaust gasses are extremely hot together with high-temps and scorching going on under the hood lead me to think the timing is too retarded and/or the A/F mix is way too lean.
Overly retarded timing can result in the exhaust valve opening up while the A/F mix is still burning, which means it completes it's burn in the exhaust manifold. Lean mix can also lead to very high exhaust gas temps, and can "burn" a valve, which may possibly result in it sticking.
...or that clacking noise could be a lifter, but it could be something else. Just how pronounced is that clack and can you tell if it's at engine rpm or half of that?
Are you seeing any significantly increased oil consumption yet? If so, you've "collapsed" the rings. There are a number of things to check that can cause or contribute to the heat, but the fact that your exhaust gasses are extremely hot together with high-temps and scorching going on under the hood lead me to think the timing is too retarded and/or the A/F mix is way too lean.
Overly retarded timing can result in the exhaust valve opening up while the A/F mix is still burning, which means it completes it's burn in the exhaust manifold. Lean mix can also lead to very high exhaust gas temps, and can "burn" a valve, which may possibly result in it sticking.
...or that clacking noise could be a lifter, but it could be something else. Just how pronounced is that clack and can you tell if it's at engine rpm or half of that?
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
If you have other options, I'd leave it parked until I could do some diagnosis. A compression test will quickly tell if you've hurt the rings. If so, I'm afraid you're looking at a teardown, and the sooner the better. Either way, you need to identify the culprit. So, verify your timing is correct, not just at idle, but throughout its curve, followed by checking out the carb to make sure it is in proper tune.
If neither one of these is out of whack, then suspect the cooling system. It could end up something as simple as a stuck thermostat, but that may be a stretch here. Beyond that, you might not be getting oil delivery to every component.
You may be able to figure out what's clacking with a mechanic's stethiscope.
Sorry I don't have better advice. I sincerely hope someone else looking at this from a different direction puts their finger on someting simple I've somehow overlooked.
If neither one of these is out of whack, then suspect the cooling system. It could end up something as simple as a stuck thermostat, but that may be a stretch here. Beyond that, you might not be getting oil delivery to every component.
You may be able to figure out what's clacking with a mechanic's stethiscope.
Sorry I don't have better advice. I sincerely hope someone else looking at this from a different direction puts their finger on someting simple I've somehow overlooked.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
with the above. I would start checking timing and a/f ratio if possible. Then make sure that all your radiator seals and front spoiler are present and accounted for. The C3 is a bottom breather and needs all the help it can on sealing the radiator to the core support so all the air goes through the radiator.
Thread Starter
Instructor
Joined: Oct 2005
Posts: 165
Likes: 0
From: White Plains MD
I checked the timing today. 4 deg ATC ...yup.
I have change the timing to the original spec of 4 BTC. I certanly screwed this one up.
I ran the engine, the big clack sound went away. But now I hear a toc sound only when cold or rapid acceleration. I'll do a compression check tomorrow and see what happens.
The story continues... what type of damage do you think I caused?.
I have change the timing to the original spec of 4 BTC. I certanly screwed this one up.
I ran the engine, the big clack sound went away. But now I hear a toc sound only when cold or rapid acceleration. I'll do a compression check tomorrow and see what happens.
The story continues... what type of damage do you think I caused?.
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Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Timing that far behind can definitely cause some heat, so maybe that's the source of the problem. You might want to consider advancing that timing up to 12-14 initial, regardless of what the smog spec is. Look over Barry K's timing sticky for more info. In addition to bringing the heat down some more, there's potential to unlock some performance if everything's OK.
But, first you need to check that compression out. So, take it one thing at a time, and we'll hope that "toc" isn't something in the bottom end.
Good luck, and post up...
But, first you need to check that compression out. So, take it one thing at a time, and we'll hope that "toc" isn't something in the bottom end.
Good luck, and post up...
Last edited by TheSkunkWorks; Sep 2, 2007 at 12:43 AM.