Need Buying Advice (Compression #'s)

[leftysmoke]

I'm looking at a Whippled '03, super clean and it's a fair price. I told myself I wouldn't go for a TS car, but I'm seriously considering it. The buyer had a compression test done and the results were as follows (1-8):

150, 150, 151, 155, 150, 148, 151 & 161

Is this a healthy car or do these seem low? The car has a slight "miss"/putter, when idling. I know this can sometimes be attributed to the injectors.

I'm looking at a few other cars, so I'm not sure yet. Thanks in advance for any advice.

 

[hotcobra03]

dont know if this helps but ive just checked mine because of a miss...

mine were 1-5 read 180psi..cyl 6-8 read 195psi...stock engine at 297,000

i found my miss is being caused by a bad coil...i found a guy with 8 new ford coils that let me try them for testing

 

[leftysmoke]

dont know if this helps but ive just checked mine because of a miss...

mine were 1-5 read 180psi..cyl 6-8 read 195psi...stock engine at 297,000

i found my miss is being caused by a bad coil...i found a guy with 8 new ford coils that let me try them for testing

On average, I've seen most healthy cars in the 170-180 range, so your readings look outstanding. That's why I wondered if these #'s seem low to anyone else. I know there shouldn't be a significant difference from cylinder to cylinder, but 150 avg just seems low to me. Thanks for the post.

 

[hotcobra03]

On average, I've seen most healthy cars in the 170-180 range, so your readings look outstanding. That's why I wondered if these #'s seem low to anyone else. I know there shouldn't be a significant difference from cylinder to cylinder, but 150 avg just seems low to me. Thanks for the post.

if you werent the 1 who did that test,,,maybe it wasnt done proper..

mine was engine warm,throttlebody in wot,fuel shut off,no oil added to cyl

ive tested mine cold and got lower numbers

 

[TRBO VNM]

if you werent the 1 who did that test,,,maybe it wasnt done proper..

mine was engine warm,throttlebody in wot,fuel shut off,no oil added to cyl

Correct.

I have seen them in the 150 range though. Typically they are in the 170-180 range, but I have seen plenty in the 150-160 range.

 

[leftysmoke]

if you werent the 1 who did that test,,,maybe it wasnt done proper..

mine was engine warm,throttlebody in wot,fuel shut off,no oil added to cyl

ive tested mine cold and got lower numbers

It was done by a supposedly reputable shop. I'm not sure if the motor was warm or not. I'll have to ask.

Correct.

I have seen them in the 150 range though. Typically they are in the 170-180 range, but I have seen plenty in the 150-160 range.

So would you conclude that an average of 150-155 is pretty good then?

 

[Quick Strike]

Compression testers tend to read different from one to the next. The best indication of cylinder health is how close they are using the same tester (unless they are all extremely low). Any cylinder more then 15% below the others is a cylinder with troubles.

 

[leftysmoke]

Compression testers tend to read different from one to the next. The best indication of cylinder health is how close they are using the same tester (unless they are all extremely low). Any cylinder more then 15% below the others is a cylinder with troubles.

Thanks for the info. According to what you posted, this car would appear to be healthy.

 

[Quick Strike]

Does it have aftermarket or other Ford cams? Longer duration camshafts (later closing intakes) reduce dynamic and cranking compression. That would also shed light on the stumble at idle. I had about 155 psi (+ or - 5) with my tester on all of my cylinders when stock, and still have 155 psi on my tester with 9.8:1 compression and bigger cams.

 

[leftysmoke]

Does it have aftermarket or other Ford cams? Longer duration camshafts (later closing intakes) reduce dynamic and cranking compression. That would also shed light on the stumble at idle. I had about 155 psi (+ or - 5) with my tester on all of my cylinders when stock, and still have 155 psi on my tester with 9.8:1 compression and bigger cams.

Nope. No cam or anything like that lol. I wouldn't be asking about the idle if it had a cam... :lol1: