350 chevy backfire??
Question: I just bought a chevy truck, 76 with a 350, here in Reno theres a hwy 421, going to tahoe steep uphill as i entered the hill, the truck dropped down into second and after it went back into 3rd i had a backfire through the carb. its still there. i replaced the cap and roter, next on my list is new wires and plugs, now im getting all kinds of feedback of people who think they know whats wrong, I've read all the questions on here, and there all close to what i have going on, but not dead on. sounds fine at idle. soon as you rev it up, its backfire'n solid as long as your above 1500 RPM, gets worse as it goes up, it didnt have this before, but now it has a tick- tick- tick, noise..not loud, but there. oil pressure is there,,,and its full ,40-60 psi. It would be great to hear from a chevy guy that would be able to tell me what to do, if i still have this problem after i change the plugs and wires. thanks guys,,have a great day. PS Id hate to think its a cam, do they go flat that fast?
Answers: I've run into this problem several times. Most likely a dished lifter on an exhaust valve. Not all the exhaust makes it out of the cylinder, so when the intake valve opens, it goes out that way.
Sounds like a bent valve, broken springs can cause the valves to come into contact with the piston and bend the valve. Pull the valve cover off on the side the ticking is coming from. Start wiggling rocker arms and checking for broken springs. Look carefully as some engines have dual springs on each valve. You will have to tap the starter a little to rotate the engine and check the rockers again. Do this a few times to be sure you're checking the valves in a closed position. This check will also tell you if one of the cam lobes is worn off. If it is the valves or the cam then it's probably time to rebuild or replace.
Adjust the timing if that don't work it's time to rebuild the top end
It could be your advance for your timing. Check the timing and make sure you have no vacuum leaks going to the distributor.
They had a problem with rockers and push rod in those years
Find out the side that is making the noise, check rocker for ware and rocker stud to see it stretched or pulled out of the head, replace push rod if it shows any ware at all
You can do most of this work your self,except the rocker stud if it needs to be replaced. if is OK , you can change lifter,rocker, push rod and gasket for under $50.00
Answers: I've run into this problem several times. Most likely a dished lifter on an exhaust valve. Not all the exhaust makes it out of the cylinder, so when the intake valve opens, it goes out that way.
Sounds like a bent valve, broken springs can cause the valves to come into contact with the piston and bend the valve. Pull the valve cover off on the side the ticking is coming from. Start wiggling rocker arms and checking for broken springs. Look carefully as some engines have dual springs on each valve. You will have to tap the starter a little to rotate the engine and check the rockers again. Do this a few times to be sure you're checking the valves in a closed position. This check will also tell you if one of the cam lobes is worn off. If it is the valves or the cam then it's probably time to rebuild or replace.
Adjust the timing if that don't work it's time to rebuild the top end
It could be your advance for your timing. Check the timing and make sure you have no vacuum leaks going to the distributor.
They had a problem with rockers and push rod in those years
Find out the side that is making the noise, check rocker for ware and rocker stud to see it stretched or pulled out of the head, replace push rod if it shows any ware at all
You can do most of this work your self,except the rocker stud if it needs to be replaced. if is OK , you can change lifter,rocker, push rod and gasket for under $50.00
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