straight 6
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Freshman User
Joined: Sep 2016
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straight 6
My 75 F100 has a tired engine with major oil loss and poor compression readings. I was able to find a newer straight 6 engine for free from a family friend. He claims it was "overhauled" 15,000 miles ago. thats really neither here nor there as the engine was given to me for free. My main objective is to to test for good compression and if it has good compression swap the engines out next spring. I currently have to engine on a stand and would like the forums opinion on determining this engines compression and worthiness of the swap.
Elder User
Joined: Jan 2003
Posts: 759
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From: North Dakota
Tough to check compression on an engine stand - no way to spin it over quickly...
Your best bet would be to do a leak down test on it... auto parts store should have the tool.
Personally, I would pull the oil pan and plasti-gauge the bearings and also look at their overall condition.
Your best bet would be to do a leak down test on it... auto parts store should have the tool.
Personally, I would pull the oil pan and plasti-gauge the bearings and also look at their overall condition.
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Freshman User
Joined: Sep 2016
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I picked up a leak down tester from harbor freight and not having very good luck with it. since I have the valve cover off I can easily loosen all of the springs and check to make sure all the valves are sealing. I know a cold motor will always have some air leakage past the rings. hopefully I can make that judgement by ear.
thanks for the tip on pulling the oil pan. what do you mean by "plasti gauge"?
thanks for the tip on pulling the oil pan. what do you mean by "plasti gauge"?
Elder User
Joined: Jan 2003
Posts: 759
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From: North Dakota
http://www.plastigaugeusa.com/how.html
Basically, you pull a cap, put a piece of plastigage in, and torque to spec. Remove and measure how much it squished out and you have your bearing clearance.
As for the leak down test, put a couple squirts of oil in each cylinder and roll it over a couple of times for a "wet" test that would be closer to testing a warm engine. At least that's how I have done it... leak down test is best for checking how the valves seal, I forget what % is normal... I think about 10% is considered near new.
https://mobiloil.com/en/article/car-...-leakdown-test
Basically, you pull a cap, put a piece of plastigage in, and torque to spec. Remove and measure how much it squished out and you have your bearing clearance.
As for the leak down test, put a couple squirts of oil in each cylinder and roll it over a couple of times for a "wet" test that would be closer to testing a warm engine. At least that's how I have done it... leak down test is best for checking how the valves seal, I forget what % is normal... I think about 10% is considered near new.
https://mobiloil.com/en/article/car-...-leakdown-test
Logistics Pro
Joined: Aug 2003
Posts: 4,701
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My opinion is that these are so stupidly simple and overbuilt that it will probably be fine, especially for the price you paid. Just run it. Even if it isn't perfect, it will probably run forever.
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Cargo Master
Joined: Jul 2005
Posts: 2,309
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From: Kansas
if you really want to check it before you install it, you can run a compression check just by hooking up a battery to the starter...just make sure your flywheel clears your engine stand. if you want to go further, it wouldn't be that hard to wire up the ignition and and start it on the stand...
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