Blacktop Compression Test Results

[Matt]

Hi All,

Just picked up a fwd clip ae111 20v blacktop, and did a comp test on it.

DRY Results Were

170 175 175 170

For 11:1 comp this is a pretty low result.

Wet Results (Added cap full of oil to spark plug gap)

215 220 225 215

I would have thought a wet test would have only given a 15-20 increase in PSI, not 50.

I read the blacktop manual and it indicates that 193psi is the recommended compression, but 156psi is the minimum. I've got a month warranty on the clip, but i'm worried that i'll be putting it in to discover it burning oil.

Is this something to be worried about? I'm pretty confident I'll have it running next weekend as I'm 90% done on the wiring loom mods.

Thanks

[blake.]

probably rings. wouldn't be woried bout it till you start it tho.

[Sam-Q]

I have a thought, maybe this engine has been sitting around for a while and there was not much oil in the bores anymore causing a low result.

[Matt]

I ran it up for around 10 minutes (mostly idle) prior to doing the comp test on Saturday morning to get some temp into it.

The last thing I want to be doing is putting it in for a week or so and having to pull it back out again.

[slider4life]

well i done a comp test on my 20v black top a few weeks ago i had 200 in all cylinders cold and hot about 210 to 215 hope that helps

[LittleRedSpirit]

I ran it up for around 10 minutes (mostly idle) prior to doing the comp test on Saturday morning to get some temp into it.

The last thing I want to be doing is putting it in for a week or so and having to pull it back out again.


I guess if you wanted that much peace of mind you shouldnt have bought an import used motor, or you should have had it rebuilt. Its a lottery of sorts. May as well give it a spin before you get too worried.

[Jonny Rochester]

From your results, I guess you have a fairly good engine and there is no reason to make a waranty claim. Even if it did burn a bit of oil, which it will. The AE111 is 10 years or more old now. My AE101 20v burns a bit of oil, but otherwize it's fine. Fitting a new headgasket, rings, bearings, valvestem seals is going to be less work than it was to put the motor in.

[H8CHIR6KU]

personally i find that alot of compression testers give random readings. ive had some read different to others ont he same motor, by up to 30psi

the most important thing is how close the readings are in relation to each other. your readings even when dry are only like 3% different.

also its amazing how easy it is to have sticky rings. you might find the rings are stuck cause the motor has sat around for so long

[Matt]

Thinking the rings might be a bit stuck too... I've got them soaking in diesel atm and once day light hits i'll be blowing it out with the compressor and dropping the engine in.

But thanks everyone for your input. I'll let you know how it goes.

[Lexsmaz]

Hope the Diesel does not loosen up too much carbon, when pistons & rings are worn you can get a carbon build up in certain areas & can help to seal things up a bit, the diesel could start to erode some of the carbon build up & you could have a bit of a smokey motor now ( fingers crossed not in your case ) .. Also the cap full of oil, what was the cap off, i pressume you mean a capfull of oil from the top of an oil container ? if so that is too much, hence your quite a bit higher readings when wet tested .. i use roughly 4 or 5 squirts from an oil can & crank for 5 or so seconds & then test ..

[marvis]

I thought if you did a wet test and it was more then like 5-10 PSI difference your rings were fucked..



That is a BIG difference.

[H8CHIR6KU]

I thought if you did a wet test and it was more then like 5-10 PSI difference your rings were fucked..



That is a BIG difference.

nah 5-10 is nothing. its more when your taking 40-50 then you know rings are fucked. but like above posts, sticky rings and too much oil in the cylinder will give same results as fucked rings.

at the end of the day you will know when its running if the rings are fucked. if it runs sweet then you got nothing to worry about

[Matt]

Thanks everyone for your help...

Its in and running, drove it to / from work yesterday without any real issues other than a slight puff on gear changes or noticable oil usage... I'll be nice to it for a week or so to give the rings a chance to re-settle, and then see what happens when it gets opened up.