I had a 1978 AMC 340 engine completely rebuilt.
After I installed it in my J10 truck, I ran the engine at about 2000 RPM to break in the cam. Timing was at this time top dead center.
Didn't really drive the truck much because I had been working on getting the timing right, and trying to get the motor to respond to the throttle without hesitating. I set the timing to 8~10 degrees ahead the engine would start good and didn't hesitate when it was cold. I could not and still can't hook up the vacuum advance. With the vacuum advance connected, the engine will idle, but if you give it gas it shuts off. Reading up on it, I probability have been installing it on the wrong vacuum port. I've been leaving it disconnected.
I only would drive the truck short distances and kept the speed under 50 MPH.
The rocker arms have always rattled when the engine is running. If you rev the engine and release the throttle the rockers will rattle and then quiet up, but still lightly tapping.
One day I decided to drive the truck about 10 miles on the highway, averaging a speed of about 55 to at times 60 MPH. My axles are 4.10's. Several of the push rods began to make very loud rapping noises. I slowed the truck down to 50 MPH or less and drove the truck home.
It was suggested the push rods were too short. I removed the valve covers and inspected the rocker arms and push rods.
some of the push rods were bent slightly, the rocker arm guides on a few of the cylinders were quite worn.
At the time it was also through that the timing at the higher RPM may have exceeded the cam timing causing pressure on the valve train not allowing the valves to open causing the push rods to bend. I also measured the straight push rods and found them to be at different lengths.
I reset the timing to 3 degrees ahead. I replaced the rocker arm guides and installed new push rods. The same length as originally installed when the motor was rebuilt.
I drove the truck to the shop where the engine was rebuilt and asked for suggestions on what to do with the rocker arm noise. It was suggested to install longer push rods. I called the cam manufacture Ericson Cams and explained my concern. They suggested to increase the push rod length by .100".
I decided to go with .050" longer. The replacement push rods are 7.850" long.
As I installed the push rods, I noticed the valves being pushed down as I tightened the bolts.
The engine cranked as usual and started up. The lifters still rattle as before.
When I drive down the road the engine sounds like a sewing machine. The rocker arms quiet down while I'm sitting at a red light. And rattle away when I drive off.
It was suggested the oil pressure gauge, since its electric, may be off and not giving me the correct pressure reading. I installed a manual gauge to verify the pressure reading. 73lbs cold high idle, when warmed up, I have 20lbs at an idle, and rev up the engine and get 50 to 60 lbs of pressure. When the warm engine is idling you can see the pressure pulse as the engine fires on each cylinder.
Today I removed the valve covers and rotated the engine so I could measure each push rod length. To do this I rotated the engine so each cylinder I was checking had both valves closed, The piston may not be at the top, but it should be on compression stroke. I used an adjustable push rod to remove the play.
Here are my results:
#1 E 7.720"
I 7.693"
#3 I 7.686"
E 7.715"
#5 E 7.717"
I 7.692"
#7 I 7.700"
E 7.700"
#2 E 7.718"
I 7.697"
#4 I 7.695"
E 7.704"
#6 E 7.728"
I 7.695"
#8 I 7.702
E 7.746
After seeing the first few measurements I reinstalled the 7.800" push rods. the 7.850" push rods are two long.
The cam I had installed is called a RV cam. the grind number is E710012. The cam cam with lifters and valve springs.
I'm thinking I may not have the correct lifters. I have read where some people have received lifters for a Chrysler engine rather that an AMC engine. The cam is the same , but the lifters are not??
Could I have the wrong lifters?
I went to Advance auto parts and asked to see if they had replacement lifters for an AMC 304 engine. They did, but the lifter they showed me has a thin grove high up on the lifter. Near the top. The spring in the lifter was also easy to push on with your finger. The lifters in my 304 are hard to push down.(Maybe because of the oil inside.) I thought the AMC lifters have a wide grove around the middle.
Any ideas of what is wrong with this engine?
Less than 150 miles on the engine at this time.
After I installed it in my J10 truck, I ran the engine at about 2000 RPM to break in the cam. Timing was at this time top dead center.
Didn't really drive the truck much because I had been working on getting the timing right, and trying to get the motor to respond to the throttle without hesitating. I set the timing to 8~10 degrees ahead the engine would start good and didn't hesitate when it was cold. I could not and still can't hook up the vacuum advance. With the vacuum advance connected, the engine will idle, but if you give it gas it shuts off. Reading up on it, I probability have been installing it on the wrong vacuum port. I've been leaving it disconnected.
I only would drive the truck short distances and kept the speed under 50 MPH.
The rocker arms have always rattled when the engine is running. If you rev the engine and release the throttle the rockers will rattle and then quiet up, but still lightly tapping.
One day I decided to drive the truck about 10 miles on the highway, averaging a speed of about 55 to at times 60 MPH. My axles are 4.10's. Several of the push rods began to make very loud rapping noises. I slowed the truck down to 50 MPH or less and drove the truck home.
It was suggested the push rods were too short. I removed the valve covers and inspected the rocker arms and push rods.
some of the push rods were bent slightly, the rocker arm guides on a few of the cylinders were quite worn.
At the time it was also through that the timing at the higher RPM may have exceeded the cam timing causing pressure on the valve train not allowing the valves to open causing the push rods to bend. I also measured the straight push rods and found them to be at different lengths.
I reset the timing to 3 degrees ahead. I replaced the rocker arm guides and installed new push rods. The same length as originally installed when the motor was rebuilt.
I drove the truck to the shop where the engine was rebuilt and asked for suggestions on what to do with the rocker arm noise. It was suggested to install longer push rods. I called the cam manufacture Ericson Cams and explained my concern. They suggested to increase the push rod length by .100".
I decided to go with .050" longer. The replacement push rods are 7.850" long.
As I installed the push rods, I noticed the valves being pushed down as I tightened the bolts.
The engine cranked as usual and started up. The lifters still rattle as before.
When I drive down the road the engine sounds like a sewing machine. The rocker arms quiet down while I'm sitting at a red light. And rattle away when I drive off.
It was suggested the oil pressure gauge, since its electric, may be off and not giving me the correct pressure reading. I installed a manual gauge to verify the pressure reading. 73lbs cold high idle, when warmed up, I have 20lbs at an idle, and rev up the engine and get 50 to 60 lbs of pressure. When the warm engine is idling you can see the pressure pulse as the engine fires on each cylinder.
Today I removed the valve covers and rotated the engine so I could measure each push rod length. To do this I rotated the engine so each cylinder I was checking had both valves closed, The piston may not be at the top, but it should be on compression stroke. I used an adjustable push rod to remove the play.
Here are my results:
#1 E 7.720"
I 7.693"
#3 I 7.686"
E 7.715"
#5 E 7.717"
I 7.692"
#7 I 7.700"
E 7.700"
#2 E 7.718"
I 7.697"
#4 I 7.695"
E 7.704"
#6 E 7.728"
I 7.695"
#8 I 7.702
E 7.746
After seeing the first few measurements I reinstalled the 7.800" push rods. the 7.850" push rods are two long.
The cam I had installed is called a RV cam. the grind number is E710012. The cam cam with lifters and valve springs.
I'm thinking I may not have the correct lifters. I have read where some people have received lifters for a Chrysler engine rather that an AMC engine. The cam is the same , but the lifters are not??
Could I have the wrong lifters?
I went to Advance auto parts and asked to see if they had replacement lifters for an AMC 304 engine. They did, but the lifter they showed me has a thin grove high up on the lifter. Near the top. The spring in the lifter was also easy to push on with your finger. The lifters in my 304 are hard to push down.(Maybe because of the oil inside.) I thought the AMC lifters have a wide grove around the middle.
Any ideas of what is wrong with this engine?
Less than 150 miles on the engine at this time.
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