Posted By: Kern Dog
Leakdown testers and how to use...... - 02/07/11 08:56 AM
I have a problem with oil consumption and smoke in the 493 in my 70 Charger. The diagnosis has been a real puzzler, and I think that a leakdown test may be the last thing I can do before pulling the motor for a teardown and inspection.
1974 440 block, bored .030
Eagle 4.15 crank, Manley rods, Ross pistons
Edelbrock 88cc heads, unported
292/509 cam Eddy Perf RPM intake, BG 850 VS TTI 2" headers, 2.5 exhaust
2500 miles on rebuild.
The engine ran great for a few years, but over the last 3 it has developed the following problem: I can cruise around on the primaries just fine, but once I step into the secondaries, white smoke rolls out then clears away. When I slow down, the smoke returns.
I had a 292/509 cam in the motor when I first assembled it, then switched to a Comp 285 XE. The Comp ran great until it wiped a lobe. I slipped in another Comp on warranty and it ran great again for 2 years until it wiped THAT cam. Once again, only one lobe went bad. I took the oil pump apart to find debris in the rotors, so I replaced the pump. Over the years I have chased my tail trying to eliminate this smoke problem. I have ran the car with and without a PCV, checked the intake for squareness against the heads intake surface, replaced the valley pan twice, once with the paper gaskets and once without, replaced the valve stem seals, did numerous compression checks and this problem still remains. The last comp check was consistant with the others.... the highest was 192 and the lowest was 180. A 6% spread? Isnt that about the best you can hope for?
I have read the plugs...They get black all around the insulator after awhile. I had the heads off, all the exhaust valves were tan colored. ZERO vacuum leaks. Zero coolant loss. Plenty of power, but not as much as when it didnt smoke.
This is where the leakdown tester sounds appealing. I have never seen one up close, but from what I have read, they can tell alot about whats happening inside the motor. What is considered acceptable leakage and how is it determined? When I replaced the valvestem seals, I had to pressurize each hole while I had the springs off. You could hear a steady hiss. Given time, any cylinder will totally lose pressure, right? The rings are not a suction cup type of seal.
I know that with the 2 bad cams I need to pull the engine apart for a full teardown and cleaning. I am just baffled as to HOW an engine with such good compression numbers can smoke like this one does. Suggestions?
1974 440 block, bored .030
Eagle 4.15 crank, Manley rods, Ross pistons
Edelbrock 88cc heads, unported
292/509 cam Eddy Perf RPM intake, BG 850 VS TTI 2" headers, 2.5 exhaust
2500 miles on rebuild.
The engine ran great for a few years, but over the last 3 it has developed the following problem: I can cruise around on the primaries just fine, but once I step into the secondaries, white smoke rolls out then clears away. When I slow down, the smoke returns.
I had a 292/509 cam in the motor when I first assembled it, then switched to a Comp 285 XE. The Comp ran great until it wiped a lobe. I slipped in another Comp on warranty and it ran great again for 2 years until it wiped THAT cam. Once again, only one lobe went bad. I took the oil pump apart to find debris in the rotors, so I replaced the pump. Over the years I have chased my tail trying to eliminate this smoke problem. I have ran the car with and without a PCV, checked the intake for squareness against the heads intake surface, replaced the valley pan twice, once with the paper gaskets and once without, replaced the valve stem seals, did numerous compression checks and this problem still remains. The last comp check was consistant with the others.... the highest was 192 and the lowest was 180. A 6% spread? Isnt that about the best you can hope for?
I have read the plugs...They get black all around the insulator after awhile. I had the heads off, all the exhaust valves were tan colored. ZERO vacuum leaks. Zero coolant loss. Plenty of power, but not as much as when it didnt smoke.
This is where the leakdown tester sounds appealing. I have never seen one up close, but from what I have read, they can tell alot about whats happening inside the motor. What is considered acceptable leakage and how is it determined? When I replaced the valvestem seals, I had to pressurize each hole while I had the springs off. You could hear a steady hiss. Given time, any cylinder will totally lose pressure, right? The rings are not a suction cup type of seal.
I know that with the 2 bad cams I need to pull the engine apart for a full teardown and cleaning. I am just baffled as to HOW an engine with such good compression numbers can smoke like this one does. Suggestions?
is the rings, pistons and or bores are probably shot. If the motor was not tore down after you lost the first cam, most likely you have metal embedded in the skirts.