Compression test results????????????
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Compression test results????????????
Hey guys I’m in need of some advice, My 88 F-150 2x4 with a 300 strait six shakes pretty bad at idle but when you rev it up, it doesn’t shake. I checked the motor mounts and I just got done with a compression test and here are my results, from the front of the truck going back 1. 100 2. 120 3. 15. I know that’s not even close to normal 4. 110 5. 100 6. 110. I figured that my problem might have been the spark plugs but I changed them and that didn’t help and after todays results i know thats not my problem. Sense #3 has pretty much no compression I think that’s my problem. Dose any one know of what I can do to try and fix this or is it going to be rebuild time? Thanks in advance Ryan
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From: Conyers
Compression test results????????????
All your cylinders are LOW. My 300 cranks out 165-175 in all the cylinders depending on the day (air pressure, ect) It looks like there is an overhaul in your future. It could be a bad thing 
or a good thing 
hint hint...while your in there (headwork, bump in compression, now would be that time to install a nice fat cam)
or a good thing hint hint...while your in there (headwork, bump in compression, now would be that time to install a nice fat cam)
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Compression test results????????????
I just thought i would check if i did the compression test right, I took one spark plug out at a time and ran the starter long enough to get a reading for each cyclender. Well if i do need to overhaul my engine where would be the best place to get all the parts that i need as well as not cost an arm and a leg, this is just one of my landscapeing trucks. Also do you know of any books and or videos that walk you step by step through the rebuilding of this engine? I have never rebuilt an engine, but its with in my abilty if i can get a book to help walk me through some of the sticky areas. any ideas on total cost, where as compaired to geting a remanufactured one? thanks for the fast replies ryan
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From: Topsfield, MA
Compression test results????????????
https://www.ford-trucks.com/dcforum/DCForumID18/1445.html
Check that out for more info on what to do.
Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster American Thunder Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds
.
Check out my Gallery for a look-see.
Then theres:
99' Mustang GT 4.6L
88' F-250 Heavyduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Weighs around 7,000lbs w. 65mph top speed, who wants to race me!
Check that out for more info on what to do.
Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster American Thunder Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds
.Check out my Gallery for a look-see.
Then theres:
99' Mustang GT 4.6L
88' F-250 Heavyduty 4x4 351/c6
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 with a
3 spd column shifter. Weighs around 7,000lbs w. 65mph top speed, who wants to race me!
Elder User
Joined: Feb 2002
Posts: 504
Likes: 2
From: Saddle Brook United State
Compression test results????????????
Hi, you usually take out all the plugs and have some one spin the starter and insert the tester and let the engine turn over untill you get the highest reading you can get for that cylinder. You are not letting the compression build up the way you are doing it.
ALSO after you have done the check with all the plugs out and recorded the readings squirt oil in all the cylinders and turn the engine over some to distribute the oil around the cylinder and retake the test. If the readings are much higher you have bad rings if the readings are the same or just a little higher you have valve problems and it will require head work.
BUT remember this if you do a valve job with the engine having bad rings chances are that the ring problem will get worse due to the higher compression resulting from the valve job. If you need parts try this, I have used them and they are guick and reasonable. www.rockauto.com
Bob / stractor
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Joined: Dec 2001
Posts: 340
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Compression test results????????????
I feel your pain. My compression averages about 130 lbs per cylinder and I can feel the loss of power. I was thinking about a short block, to save time and not have to worry about every part of a rebuild. One of my concerns is other things like fuel injectors, water pump, all sensors.... seems like it would be nice to replace everything, but that adds up to quite an expense. If I ever get the guts up to do it, I'm hoping to keep the cost below $1500.
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