How to feel for poor compression....

Best to check it properly with the right equipment.. Especially if its a intended purchase.. you would need to listen for any uneven cranking pulses with the ignition coils and fuel supply disconnected. Best do it properly because you cant hear 20-50 psi down. It would need to be pretty bad to hear it..

 

Just do a compression test?? Or wait till engine out belt service and power the starter for a test to see what health shes in. Leak down aswell since the engine is on the operating table,may aswell.

 

You cant. Example; Compression checks are part of every aircraft inspection and the results determine the health and life on the motor, but unless there is a major issue like a hole in the piston, valve stuck open, or rings missing, the performance of engine with 80/80psi is not negligible different than an 80/70 or even 80/65psi.
Same thing applies to a car motor, possible even to a lesser extent since the rpm is higher. The reason is at 2700rpm in a lycoming, or 7500rpm in a 355 motor, the piston is moving so fast that there is literally no time for compression to leak out.

So unless there is "blow-by" shooting out the breather or not enough compression to start, the only way your going to tell is a compression test

 

If a Camry pulls away from you on the highway as you are billowing mushroom clouds of oil smoke that would be a bad sign

Otherwise as mentioned, compression and leakdown tests should give you a good indication of the health of the engine.

I suppose you could run it on a chassis dyno as well. If it's down a lot of power something is off.

 

We had bean burrettos for dinner last night, lots of compression and that F1 sound for sure

 

You could say that.

And my learned friend misspelled it. It should be Burritos

 

I'm the F1 sound my wife sounds like an old Detroit Diesel LOL

Spelling is not my strong point in Spanish

 

Other ways to feel for poor compression:
Let it sit a year or two
Never drive over 3000rpm
Use a Harbor Freight compression guage
Advertise your car for sale

 

You mean any aircraft with a piston engine. Haha

As for a 355 only way to have a seat of the pants feel would be to drive a dog and then a known good car and have a ton of time in the good car. Its hard to tell just driving the car.

Since my 95 is all apart for guides failed the compression test and the guides were toast 15,000 mile engine.

I also built a simple tester for testing the liners and rings and liners.
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I would think a roll on test with another car and it would be obvious

 

How so? How can you possibly determine it is a loss of compression that causes one car to be slower than another. I almost never see proper running 355s, once in a while it is because of compression.


There is one way and one way only to know about compression.

All the other horse**** here is horse****.

 

as others have stated: compression & leak down test

(corrected)

 

Um, if you want to see if you have low compression, do a compression test. If compression is low,then do leak down to find out why.

 

"Feeling for it" is kind of like a prostate exam, except you have to stick your gloved, lubed finger way up the tailpipe.
Alden

(Seriously, just do a compression test with good equipment)

 

oops ....corrected

 

Brian,

I've heard this statement from you and others about not seeing proper running 355s very often. What do you attribute this to ? I.e., what is typically out of wack ? My car seems to run well, but I've never driven another example to compare it to.

Thanks

 

So much bad work being done by those that don't know what they are doing. Had the same conversation the other day about F40's. Same thing.

 

Totally agree I have not seen many 355's that are running correctly. Took me 2 years to get mine close. I still need attention in a few areas. They are tweeeker then a crackhead

Sure takes some loving care and lots of time, and I dont mean changing tires or adding carbon fibre thingys

 

How would you tell when a car is not running right, or when it is? If there are no CELs, it starts, idles OK, drives OK, revs smoothly, doesn't misfire, accelerates well under throttle, passes emissions, and doesn't leave a cloud of smoke or puddles of fluids in its wake how would you know? You guys make it sound like a correctly running 355 is less common than a unicorn.

 

Just an arrogant observation on my part

Much like the way a wine dude appreciates a fine wine
A audiophile seeks the best sound.

My taste buds don't care for wine and my hearing sucks but I sure appreciate a fine running motor.
I am never satisfied how good a motor can run, it can always run better so my expectation is higher then average in that arrogant way.

 

As a life long audiophile I eventually came to the realization that the many thousands of dollars I spent looking for perfect sound was little more than a useless obsession. Constantly listening for faults and seeking solutions, rather than relaxing and enjoying the music I love. After 50 years I switch from an audiophile to a music-phile and have learned to ignore the faults and just enjoy listening, be it Beethoven, Bach, the Dead or the Airplane. Same with my cars. I'm sure they could run better in some insignificant way if I changed the plugs every 100 miles, pulled the heads and cleaned the carbon every 1000, ... But as long as I can take the car out for a 100 mile drive through New England back roads and make it home with out a problem and a smile on my face, I'm good.

 

LOL I am right behind you for sure

I let go of most all my obsessions as did my wife. I used to love audio myself BTW thats another subject. Carriage House studio in your neck of the woods. We enjoy the quality moments.
With all my spare time I keep 1 of 8 cars in that condition and it is my least enjoyable car as I am always looking for something thats not there.
My favorite to drive is a 04 toyota matrix dented all around w 150k+ on it
I can leave that car anyhere with no worries. I do get the occasional business card put on it saying "we buy junk"

Now let me go smoke a big fatty and wax my lugnuts LOL