TECH 101 Compression testing 6.9/7.3 Engine

[OLDBULL8]

From the Haynes Diesel Tech book. Just excerpts from manual.

Ford engines need to be warmed up before compression testing.
Crank engine over at least 200 RPM. Crank over 6 strokes of cyl. being tested.
First stroke compression indicates wear of rings, if low and then increases considerable on successive strokes.
Low compression on first stroke and doesn't build up, indicates leaking valves or headgasket blown, cracked head or deposits on underside of valves. My addition: Cavitation.
Engine overhaul specs compression ratio.
84 and earlier 21.5 :1
84 and later 17.5 :1
Compression 260 to 460--- 20% between cylinders is acceptable

 

[icanfixall]

Where did the 84 and later of 17.5 to 1 compression ratio come from. I really can't buy into that low of a ratio. Sum ting wong.....

 

[riotwarrior]

From the Haynes Diesel Tech book. Just excerpts from manual.

Ford engines need to be warmed up before compression testing.
Crank engine over at least 200 RPM. Crank over 6 strokes of cyl. being tested.
First stroke compression indicates wear of rings, if low and then increases considerable on successive strokes.
Low compression on first stroke and doesn't build up, indicates leaking valves or headgasket blown, cracked head or deposits on underside of valves. My addition: Cavitation.
Engine overhaul specs compression ratio.
84 and earlier 21.5 :1
84 and later 17.5 :1
Compression 260 to 460--- 20% between cylinders is acceptable

Looks to me 440/450 is not too damn bad at all then eh? Hmmm....interesting!

 

['94IDITurbo7.3]

Nice work once again Al!one thing....did you have a battery charger connected to one of your batteries? I have always been told in school to do so...just to do like you said, keep everything equal across the board.

 

[riotwarrior]

Nice work once again Al!one thing....did you have a battery charger connected to one of your batteries? I have always been told in school to do so...just to do like you said, keep everything equal across the board.

Thanks,

Nope no charger I've got two batteries throwing 900-1000 CC out and with no GP's in thus no compression and some time to recover after each spin, I'm golden. These batteries spin that pretty darn good IMHO. Never once did it slow down.

I suppose I could have had my charger on but wasn't out back at shop where power is so didn't bother.

Again thanks for the compliment.