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Discussion Starter · #1 · (Edited)
I have car with a 468 Chevy and a 671 Blower. This car has been nothing but trouble. When I first got it and took it for a ride, it overheated. I brought it to someone that builds race motors. The radiator cap was bad, so we changed it from a 15 lb to a 7 lb, changed the thermostat and added two more breathers in the valve covers to release pressure from the blower. There was gear oil in the distributor caused by a leaky blower gasket. Ok, that was all done, the blower was rebuilt and I brought the car home. The car makes a horrible tapping noise in reverse and now it is starting to do it when going forward. There was white smoke which I think is condensation (since the car mostly goes in and out of the trailer and doesn't get to temp.) I took the valve covers off and there was some stuff that looked like mayo...I cleaned it up and took the car for a ride to get it hot, shut it off and restarted after an hour and no more smoke.
Took the car out today for a ride, shut it down and the radiator hose blew off at the bottom of the hose. Checked the oil breathers and there is white goop again. Can this be a blown head gasket? Also the oil pressure is at about 70.
 

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I don't know why you would want a 7# cap on a blower motor that tends to run warm, let alone a BB. You've got more than enough breather, but do you have a PCV system? I suspect the milky oil is from not allowing the motor to warm up enough to evaporate condensation in the pan, it's mixing with the oil. As far as the tapping sound, could it be an exhaust leak? Without a better description, hard to tell. Where is it coming from?

If you suspect a blown head gasket, you should see bubbles passing through the radiator when the cap is off, thermostat open.
 

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If you have aluminum valve covers and the car is not run enuff to generate oil temp. You will constantly get the whitish condensation/water on the inside of valve covers.

Condensation from weather humidity is a fact of life. But if oil starts to look like chocolate shake. Start looking for a serious problem. Do a compression check. Also if you are having heating problems. Go to a higher rated cap, not a lower.

Better check out the noise.. Not good.. 70 psi is a bit high. But, the builder probably used a hi-vol pump.
 

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Discussion Starter · #4 ·
The guys that worked on the motor suggested a 7# cap, really don't understand why. I do think the white stuff is condensation because the oil is perfectly clean. We do not have PCV system, there are 2 Devinci racing carbs on the car and you cannot connect a PCV to them.
There was an exhaust leak but the has been fixed. The loud sound sounds like a bearing kind of sound but more like metal banging against metal.
There are no bubbles with the cap off and running and a pressure test was good.
This car is driving us crazy:confused:
 

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I've had mains go bad that were more metallic sounding than a rod bearing gone bad on a couple of early GTO's, but you have good oil pressure. Is the knock sound consistent? Does it increase with rpm's? Is it only present free revving, does it go away when a load is on the motor? Have you tried pulling plug wires to isolate a cylinder that might be influenced by combustion?
 

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Discussion Starter · #6 ·
We don't know where the sound is coming from, first it only did it when you stepped on the gas in reverse, now it will do it in drive when you step on the gas, but if you give more gas, it will go away and it comes and goes. Sometimes I want someone to listen to it and it won't make a sound.
 

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Have you looked at your torque converter bolts or for a crack in your flexplate? Not likely a metal to metal sound, but your fan shroud, possibly a broken motor mount allowing the motor to raise up?
This is where I would be looking also for your noise, specifically loose converter bolts or cracked flexplate. The cracked flexplate can be hard to see, so look close, especially up around the bolts that hold it to the crank.
 

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Have you looked at your torque converter bolts or for a crack in your flexplate? Not likely a metal to metal sound, but your fan shroud, possibly a broken motor mount allowing the motor to raise up?
x2 :thumbup: on this one, loose converter bolts sound like a rod hammering, ive heard this before on my buddies 250 straight 6, he had converter bolts loose, once tighten noise went away asuming you dont have a cracked flex plate.. blown BBC is going to have termendous amount of torque, so very good chance your noise is in the flex plate, converter area
 

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Discussion Starter · #10 ·
Thanks everyone, I will check this. I had a problem with a starter that broke a tooth off of the flywheel so I will check all of this. I will keep everyone posted.
 
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