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kota on 20s
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6/01/2002
18:04:12

Subject: compression test results.. help!
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here is the results:

8=170........7=180
6=170........5=180
4=190........3=190
2=190........1=180

on the #6 cylender i tested it about 3 times. it ranged from 20# on the 1st crank to 90#'s... and the final # went from 155 to 165, then i put a small amout of oil into the cylender and i got 170.

the oil and water have not mixed, so could the head be a little warped, or cracked, or is it within the limits??
i think its odd that all are over 180#'s except 2 cylenders that are together.

what are your opinions?

Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more

moparjoe20
Dodge Dakota
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6/02/2002
01:09:16

RE: compression test results.. help!
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If oil caused the cranking pressure to jump up almost 20psi you have ring problems , do a leak down test on it to find out whats going on.



IntenseDak39
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6/02/2002
07:00:18

RE: compression test results.. help!
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i believe that those numbers are with in limits...

now when i did a compression check on my shelby i had:
1= 175
2= 170
3= 95
4= 130

i will look it up and see what i can find about the standard compression for your engine


intensedak39


CW
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6/02/2002
10:44:19

RE: compression test results.. help!
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Well within limits if not a little high. Every engine in the world will come up in compression with oil in the cylinders. I think you are allowed 15% varience and you are well within that. You are at sea level but at 3000 feet I see only about 140-150 from new engines. Dodge says anything over a 100 is good. :-/

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kota on 20s
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6/02/2002
12:05:11

RE: compression test results.. help!
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moparjoe, on cly #6, i got 155, then 165, then i put oil into the cylender and got 170. so with the oil i got another 5#'s

Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more

smart ass
Dodge Dakota
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6/03/2002
21:00:06

RE: compression test results.. help!
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Eric, dude,, you again are only testing the 6 banger, not an 8..



kota on 20s
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6/04/2002
00:43:40

RE: compression test results.. help!
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didnt you read my responce in the other thread?

Eric, 98 5.2 5speed, K&N gen II, 50mm TB, 2bbl M-1, 1.7RR's, JBA ciramic headers, carsound cat, dumped gibson, and a lot more

joel
Dodge Dakota
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6/04/2002
15:33:30

RE: compression test results.. help!
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Find the percentage of the variance from 165 to 190. Figuring in the pressure result using oil will mess up the results.

If 15% is ok and my math is right then your at 11.5% variance.

Joel



1Flamed92Dak
GenII
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6/04/2002
17:27:01

RE: compression test results.. help!
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He as long as your within 20% of each cylinder i think your fine and by your post you are within Tolerances less than 20lbs per Cylinder



Dr.Dakota
Dodge Dakota
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6/04/2002
19:51:34

RE: compression test results.. help!
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A brand new engine should have a maximum of a 10% Variance. If my math is right (and as a pHd in Biochemistry it better be) you have a 11% variance. That extra 1% could be from the compression gauge (is it a screw in or a rubber tipped type that you press on while someone else cranks) Anyways I wouldn't be upset over 11% variance, especially with psi that high. if you had a 15% variance on a screw in gauge and the highest was only, lets say, 120 psi then I would be looking for some worn rings, grooved cylinder walls, worn or burned valves. History of that engine would also play a part in deciding on its condition too.



Swany
Dodge Dakota
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8/03/2004
14:07:24

RE: compression test results.. help!
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Help!
Have a ford 2300 racecar engine breaks down above 4000 rpm . have change everthing electrical and electronic ,distribeutor , aux shaft , seated valves , all gaskets ,leak down test , valve springs , changed timing ,advanced cam , reset valves . Compression test is low on all cylinders 60 up 100 pounds after advancing cam . cam is now way out of specs for setup do to advancing it. problem started all of a sudden, engine did get hot at that time but only about 230 degrees. WHATS WRONG, TIERD OF CKRANTCHING MY HEAD. THANKS



uh actually
Dodge Dakota
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8/04/2004
16:35:30

RE: compression test results.. help!
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contrary to what some of you have implied, the correct way to test engine compression is AFTER
spraying a small amount of oil in each cylinder.

"If oil caused the cranking pressure to jump up almost 20psi you have ring problems , do a leak down test on it to find out whats going on."

What's going on is Moparjoe20 has no idea how to test properly.

One thing that no-one has yet to mention is that burned exhaust valves/seats can cause low readings in compresion tests.




Bob Lincoln
Dodge Dakota
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8/04/2004
18:51:32

RE: compression test results.. help!
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Uh, actually, actually...

You're wrong. Compression is tested before AND after adding oil to the cylinders. If compression increases significantly, ring wear is indicated; if no or little difference, valves/valve seal/guide wear is likely the issue.

Moparjoe does know how to test properly.



Wal
Dodge Dakota
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8/05/2004
02:15:04

RE: compression test results.. help!
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how about running a leakdown now ;-)



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