Compression results 1989 Johnson GT100 (J100STLCEM)

[tlocus73]

Hello,
I did a search and looked in my manual for the recommended (John/Evin) Compression for my engine but couldn't find any info.

Another thing (I really don't like my Clymer's manual) is I don't know where cylinder #1 is or the firing order, etc...

Also I read it may be a bit high if there's carbon build up and and may show in the numbers since I've been working on it (TACH & rect/regulator issue).

Compression done fully warmed up, WOT, all plugs removed and dry. Also repeated the results a few times.
Looking at the rear of the V4, directly at the plugs, top left gave me 120, top right gave me 124, bottom left gave me 120 and the bottom right gave me 130.

Wondering your thoughts on my results & any info on cylinder location is much appreciated.

Thomas

 

[V153]

Re: Compression results 1989 Johnson GT100 (J100STLCEM)

Those're purty good #s & well within tolerance. Is there a problem?

The top piston on the stb side is #1, bottom is #3. Port side is #2 (top) & #4. They're numbered from top to bottom in order of height.

 

[tlocus73]

Re: Compression results 1989 Johnson GT100 (J100STLCEM)

Thanks V153, no problem, just been several years since the last check.
And thanks for the info on cyl. #'s

t

 

[emdsapmgr]

Re: Compression results 1989 Johnson GT100 (J100STLCEM)

Numbers look strong. Not unusual for there to be a difference between the two heads, due the the way the block was originally made in the factory. 5# difference between heads is not unusual.