Compression Test Results

Dean85GT

New Member

Nov 27, 2004

502

1

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Thorold, Ontario, Canada

Aug 24, 2005

#1

• Aug 24, 2005

• #1

Today I decided to give my stang a nice compression test. I had done one when I first got the car but I never did it properly cause I was more caught up in just driving it. Since the day I bought it the car has ran very strong but I planned on building up a fresh motor for it this winter. Long story short, I did a compression test (wide open throttle, engine warm) and got the following results.

1 ----- 145
2 ----- 135
3 ----- 145
4 ----- 145
5 ----- 140
6 ----- 148
7 ----- 147
8 ----- 140

I think those are pretty damn good numbers, especially since the engine has 216000 km on it without a rebuild! Keep in mind that this is an 85 which came with less compression from the factory. As for piston 2, I think if I was to test it again it would be right with the other numbers cause it was the last piston I did and I was kinda rushing it...

Anyways....New Intake, carb, and hopefully heads here I COME!!!!!!!!!!

 

D

Daggar

New Member

Jul 19, 2004

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Aug 24, 2005

#2

• Aug 24, 2005

• #2

Well... shop manual calls for a max of a 25% difference between cylinders. Your best and worst is well within 10%. I'd say you're in excellent shape!

 

Mavrick

Founding Member

Aug 29, 2002

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Collingwood, ON

Aug 24, 2005

#3

• Aug 24, 2005

• #3

I got basically the same results on my 89 motor. All cylinders were within 15lbs of eachother, lowest being 135 and highest being 150.

I forgot to have the throttle body open though, not sure whate difference that makes.

 

D

Daggar

New Member

Jul 19, 2004

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Aug 24, 2005

#4

• Aug 24, 2005

• #4

Mavrick said:

I got basically the same results on my 89 motor. All cylinders were within 15lbs of eachother, lowest being 135 and highest being 150.

I forgot to have the throttle body open though, not sure whate difference that makes.

Click to expand...

Not much so long as you tested all the cylinders under the same conditions.

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

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Aug 24, 2005

#5

• Aug 24, 2005

• #5

And as everyone knows, doing a wet test thereafter can help one to get a feel for how rings are doing (even if numbers are good, as yours are).

Leakdown is further revealing yet.

 

Dean85GT

New Member

Nov 27, 2004

502

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Thorold, Ontario, Canada

Aug 24, 2005

#6

• Aug 24, 2005

• #6

I think the motor is ready for all boltons but if I was to go with forced induction I would obviously get a rebuild. Do you guys think my car will be ok to handle a 75 shot? I was actually looking at a Sneaky Pete system in particular.

 

VibrantRedGT

"STANGNET'S PENGUIN SMACKER"

15 Year Member

Nov 29, 1999

14,679

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Boca Raton, Florida

Aug 24, 2005

#7

• Aug 24, 2005

• #7

Those are damn good numbers. I'd say your good to go with future plans. As mentioned the throttle body wide open is recommended as well as a strong charging system to get accurate numbers. I normally do it with a battery charger on during the test with 10 minute intervals. It's also recommended to have the motor warm (not hot).

 

Dean85GT

New Member

Nov 27, 2004

502

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Thorold, Ontario, Canada

Aug 24, 2005

#8

• Aug 24, 2005

• #8

VibrantRedGT said:

Those are damn good numbers. I'd say your good to go with future plans. As mentioned the throttle body wide open is recommended as well as a strong charging system to get accurate numbers. I normally do it with a battery charger on during the test with 10 minute intervals. It's also recommended to have the motor warm (not hot).

Click to expand...

Ya I had the motor warm and all...I'm pretty pumped now too that the motor is in this good of shape. My friends have a dyno day booked this saturday. Maybe I'll throw my car on for ****s and giggles and to get a baseline. What do you guys think it would put down with just flowmasters and upgraded ignition? My guess is probably around 170. The dyno is a mustang dyno and my car is a 5 speed.

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

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Aug 24, 2005

#9

• Aug 24, 2005

• #9

Having a warm motor is a must with forged slugs IMHO. It is still pretty important with hypereutectic slugs, but with their tighter fitment and lack of expansion (silicon content, etc), it is not as huge a deal.

 

vristang

15 Year Member

Mar 31, 2005

4,933

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124

Seattle

Aug 24, 2005

#10

• Aug 24, 2005

• #10

HISSIN50 said:

Having a warm motor is a must with forged slugs IMHO. It is still pretty important with hypereutectic slugs, but with their tighter fitment and lack of expansion (silicone content, etc), it is not as huge a deal.

Click to expand...

Forged Al pistons have to be hot. I am learning this first hand right now. hyper pistons will not be as touchy.

I would also suggest the leakdown and wet compression test as mentioned above, but it sounds like you are good to go.

Happy Modding,
jason