Anyone have experience with this? (new power head)

[Houniac]

Newly rebuilt power head. Compression readings are before the engine has been broken in and the rings seated. Engine is 93 Johnson 200 O Runner. Obviously not good numbers. The questions are, can they improve with break in or are they too far off now, indicating a major problem; or is a compression test before break in unreliable enough to not know? I'm going to run it this weekend & will post results after break in but was seeking someone who has experience with this stuff.<br />1,3&5 are 125#,100# & 95#<br />2,4&6 are 120#, 85#,& 90#<br />Thanks in advance<br />Houniac

 

[Walker]

Re: Anyone have experience with this? (new power head)

40 psi difference between #1 and #4<br />That ain't right. Was the powerhead rebored with new pistons and rings?

 

[Houniac]

Re: Anyone have experience with this? (new power head)

Yes. I know the numbers are bad. Is it possible they can improve once the rings have set?

 

[Walker]

Re: Anyone have experience with this? (new power head)

I really doubt it. Something wasn't done right in the rebuild.

 

[reeldutch]

Re: Anyone have experience with this? (new power head)

it doesnt look good,<br />can you tell us more about why it was rebuild in the first place.<br />how it is rebored and honed, type of pistons<br />etc etc.<br />it can improve but yee its a whole lot.<br />maybe something went wrong installing the pistons.<br />i would run it with 25:1 for 2 hrs in the water idle.<br />than do a other compresion test.<br />if you see some improvement do another 2 hrs and check again.<br /><br />the 4 hrs should seat them a little so if it will improve you will be seeing some.<br /><br />good luck.<br /><br />i'm not a mechanic so may be you should ask around further but if that will not work your back to the drawingboard.

 

[rodbolt]

Re: Anyone have experience with this? (new power head)

something is way wrong. the numbers should be someplace between about 80-90 psi on that motor. were it mine I would do a leak down test before running it. look for broken rings or possibly pistons installed on the wrong bank. that number spread is way to high and no amount of running will correct it. in fact by running it you may make a salvagable job into a junker. is it possible that someone has placed a lot of fogging oil or other liquids in the bores? anyway ya go you have to get the mumbers evened out. try to post all the details about the so called rebuild. some people seem to think a used piston and 1 set of new rings is a rebuild.