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I've been chasing my issue with a 360 rough idle for quite a while. I held the dollar bill next to my passenger side exhaust and it was getting sucked in = burned exhaust valve. I did a compression check and cylinder #1 read 70psi, cylinder #4 read 95psi and rest were 120-125psi. No oil is being burned. All I know is the the previous owner had the timing all f'd up until I bought the truck 2.5 years ago and got it tuned right. I did the the dollar bill test a year ago and did not see any issues. Otherwise the truck runs fine and does not miss at any speed.
1: Is this issue prone to develop into a major issue until I tear into it (few months) and can it lead to a disaster meanwhile. I need to drive it up 200 miles this weekend.
2: I do not trust any of the local mechanics in Brooklyn (from what I've seen most are just knuckleheads that just create further damage). I would rather pull the heads myself, ship them off for a valve job/rebuild and install them myself. Is there a specific procedure to rebuilt head installation specific to valve rocker/pushrods? Can I put everything in the same order?
I drove 2 years and 8000 miles with a cracked exhaust valve in #3 cyl. on my last 360. lol It did slowly get progressively worse. As in the tick got louder and the compression on that cylinder got lower. I wouldn't recommend going that long but I knew I was going to go full rebuild when it came time anyway. If you take it easy, no high revs and such, I think you'll be ok.
When you install the fresh heads everything goes back in the same order but you'll need to check pushrod length and valve clearance. I'd recommend an adjustable pushrod so you can easily determine what length you'll need when checking clearances. That'll make sure you only buy pushrods once. This is the way the Ford manual recommends checking with non-adjustable rockers. Lifter preload and valve clearance
You'll need Ford tool T58P-6565-A to bleed down the lifters. Or you can just get a set of adjustable rockers and set to "0" lash and back off 1/2 a turn. It might be a good idea to check the suspected burnt valve to make sure it's still in proper clearance until you can fix it. You don't want it out of spec and "pounding". That could lead to the valve breaking.
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Jeremy
1976 F250 4x4 Ranger XLT. 445FE, NP435/205, D44/60 4.10
AKA the never ending project.
How does the dollar bill trick work? Do you hold the dollar at the tailpipe?
I'm guessing that with dual exhaust, you have 4 cylinders pushing exhaust out, so if one exhaust valve is burned you will get a vacuum every 4 pulses but not a constant vacuum? Is this correct?
How does the dollar bill trick work? Do you hold the dollar at the tailpipe?
I'm guessing that with dual exhaust, you have 4 cylinders pushing exhaust out, so if one exhaust valve is burned you will get a vacuum every 4 pulses but not a constant vacuum? Is this correct?
Atom
Pretty much, it's an old mechanic's trick. With everything firing right, the dollar bill is blown out like it was being pushed by a fan. If one cylinder is misfiring, that creates a reversion wave in the exhaust and the bill will want to get sucked towards the tailpipe whenever that cylinder fires...or in this case misfires.
Good to know. I'm a mechanic and didn't even know that one. Many thanks!
Welcome to FTE, stick around and you'll learn a lot of the old tricks that mechanics have used over the years.
There are a lot of good people here more than willing to answer any questions you might have.
Pretty much, it's an old mechanic's trick. With everything firing right, the dollar bill is blown out like it was being pushed by a fan. If one cylinder is misfiring, that creates a reversion wave in the exhaust and the bill will want to get sucked towards the tailpipe whenever that cylinder fires...or in this case misfires.
This check has never failed me. I just used it on a coworker's 3yr old ride. I couldnt tell him exactly which cylinder, until I read his codes. Two cylinders were mis-firing intermittently. Botom line, it was a blown head gasket between both cylinders.
That's a good one to use, but try a compression test for more certain results.
Absolutly, I would also add a pressure leak down test. A compression test will isolate the problem to certain cylinder, a leak down test will isolate the loss of compression to the exhaust\intake valve or the rings in a cylinder.
Now you can do a cranking compression(relative compression) test WITHOUT removing any spark plugs using an oscilloscope and a clamp on current probe. You hook the clamp on probe around the heavy gauge red or black wire going to the starter or block. These two wires carry all the current the starter uses to spin the gas engine. That's ch1 on the scope. Ch2 goes around an ign or inj wire for #1 cy to sync off of #1 cy so you know which cy is misfiring based on the firing order which you already have memorized, right? Crank the engine and look at the waveform shape which should look like a bunch of camel back humps lined up in a row. If a hump is not as high as the others the compression is lower(not as much current needed to spin that cy). That's when you get out the leak down tester for the one cylinder that was low(relative to the others). Alternately you could put a pressure transducer in that bad cy and crank the engine over and watch the waveform again. Based on a good waveform(iATN)you can tell which stroke of the 4 stroke cycle is malfunctioning. It's like magic.
Now you can do a cranking compression(relative compression) test WITHOUT removing any spark plugs using an oscilloscope and a clamp on current probe. You hook the clamp on probe around the heavy gauge red or black wire going to the starter or block. These two wires carry all the current the starter uses to spin the gas engine. That's ch1 on the scope. Ch2 goes around an ign or inj wire for #1 cy to sync off of #1 cy so you know which cy is misfiring based on the firing order which you already have memorized, right? Crank the engine and look at the waveform shape which should look like a bunch of camel back humps lined up in a row. If a hump is not as high as the others the compression is lower(not as much current needed to spin that cy). That's when you get out the leak down tester for the one cylinder that was low(relative to the others). Alternately you could put a pressure transducer in that bad cy and crank the engine over and watch the waveform again. Based on a good waveform(iATN)you can tell which stroke of the 4 stroke cycle is malfunctioning. It's like magic.
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