Low end knock?

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mike2u
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Re: Low end knock?

Post by mike2u » Fri May 05, 2017 6:42 pm

The engine will only run completely leaned out at all times. And that was the reading at roughly 800 rpm. Heavy fluctuation between 18-16 pounds.


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Re: Low end knock?

Post by emptyhead2 » Sun May 07, 2017 1:09 pm

I'm sorry if I'm hijacking your post but I'm basically having the same issue with my HalfTrack. Running rough and I pulled plugs 4 5 and 6 all at once with no change.did compression test running and not running with reduced compression while running. Vacuum guage jumping all over the place. Good spark change intake/exhaust gaskets went through three head gaskets and still no answers. Engine was rebuilt by professional. So I'm kind of in the same boat. Hopefully you get an answer and I can be pointed in the right direction. Good luck

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Re: Low end knock?

Post by artificer » Sun May 07, 2017 2:22 pm

emptyhead2 wrote:....Running rough and I pulled plugs 4 5 and 6 all at once with no change. Did compression test running and not running with reduced compression while running.
The compression test MUST be done properly & we need to see the results
Vacuum gauge jumping all over the place.
Pretty hard to interpret with that description, do better.
Good spark
One can have good spark & cross firing.
Check for pyrotechnics in the dark & inside the distributor cap for carbon tracking.

change intake/exhaust gaskets went through three head gaskets
Why? When it appears there was nothing wrong with them.
Who would pay their mechanic to do anything like that for no result?
Compression test:
With a fully charged battery
1. Warm up engine
2. Remove all spark plugs & check for colour etc.
3. Remove king lead unless engine starter will turn over with ignition off [lead between coil & distributor cap].
4. With the transmission in neural & throttle held/wired wide open
5. Hold the compression gauge rubber taper tightly in the spark plug hole & get a helper to operate the starter to get 4 or 5 revolutions of the engine to obtain the maximum gauge reading. Do this in each spark plug hole in turn.
6. Record the readings
7. Wet test....exactly the same procedure again with a few good squirts of oil in each cylinder just before pushing in the gauge & hitting the starter.
Record your readings.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Low end knock?

Post by motto » Mon May 08, 2017 6:21 am

Once again, check for a broken (inlet) valve spring. It is a real possibility. I have encountered this on White half track, Dodge Weapons Carrier and Studebaker US-6. (Hercules JXD). The effect is much as described. A bouncing valve disrupts the breathing of adjacent cylinders.

David
Last edited by motto on Mon May 08, 2017 1:14 pm, edited 1 time in total.

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Re: Low end knock?

Post by artificer » Mon May 08, 2017 12:05 pm

Vacuum gauge reading:
"with the engine running at idle, fluctuating heavily from 16-18" inches of mercury

If this reading fluctuates more quickly relative to increase in RPM David's suggestion is a good/real possibility & may be related to poor idle. See if this idle can be corrected.

Also leaky valve, ignition timing & incorrect/unequal spark plug gaps can provide similar gauge readings.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

mike2u
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Re: Low end knock?

Post by mike2u » Wed May 10, 2017 10:39 am

With my scout car being nearly 80 years old, I decided to just pull the head and have a look. Will report back with findings.

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Re: Low end knock?

Post by artificer » Wed May 10, 2017 10:56 am

Suggest a comprehensive compression test first. Once the head is off one can't test anything.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Low end knock?

Post by mike2u » Wed May 10, 2017 11:54 am

Will review your steps and test compression.

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Re: Low end knock?

Post by mike2u » Thu May 11, 2017 4:44 pm

I just complete a compression test and the results were as follows.
Cylinder #1 113
Cylinder #2. 123
Cylinder #3. 120
Cylinder #4. 117
Cylinder #5. 115
Cylinder #6. 112

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Re: Low end knock?

Post by artificer » Thu May 11, 2017 4:58 pm

Wet?
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Low end knock?

Post by mike2u » Thu May 11, 2017 4:59 pm

I should have mentioned, this was a dry test

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Re: Low end knock?

Post by artificer » Thu May 11, 2017 5:12 pm

What was the wet?
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Low end knock?

Post by mike2u » Thu May 11, 2017 6:01 pm

I will have to run the wet test tomorrow. It should be worth mentioning that plugs 1-4 were covered in a heavy black soot, the 2 dead cylinder, 5 and 6 were relatively clean.

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Re: Low end knock?

Post by mike2u » Fri May 12, 2017 4:42 pm

'k, so I redid all my testing following Artificer's directions to a T. The results are as followings. Working from the front of the engine to the rear.

#1 dry 120................. Wet 124
#2 dry 128..................Wet 141
#3 dry 129................. Wet 140
#4 dry 125................. Wet 136
#5 dry 121..................Wet 136
#6 dry 120..................Wet 125

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Re: Low end knock?

Post by artificer » Fri May 12, 2017 10:22 pm

mike2u wrote:It should be worth mentioning that plugs 1-4 were covered in a heavy black soot, the 2 dead cylinder, 5 and 6 were relatively clean.
Are all the spark plugs the same brand & heat range [identifying number code].
As for the compression test seems the engine is a little tired. Wet test rise 2,3,4,5 is indicative of maybe worn or stuck rings.
As this engine has a compression ratio of 6:1 approx. the dry readings are up a little on what one might expect.
This could indicate carbon build up due primarily to lack of use & what is called a decoke may be in order. You might like to check this out & not pull the head BUT ensure to add very very slowly.
https://www.youtube.com/watch?v=KFtp_jmLF3k
There is another method using auto trans fluid on Hemmings.
These engines love a good hard long run & we all know about the practicalities of doing that!
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.


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