compression testing old motors

[mykwikcoupe]

So Im about 90% on my b20a fabrications and last night/this morning about 4am I decided it was time to see if the internals needed to be redone for the little turbo or if they would spec out ok. I bust out my compression tester (spark plug type not leakdown) and start pulling plugs. All the plugs look ok use wise with mild oranging.

As I spin the motor with the socket Im not getting any numbers above 30 psi with no spark plugs installed on the other cylinders. On a second pass, I pour some 14w-40 in the head and start again. same resolve about double but super low.

My engine has sat on an engine stand for about 5 years now and Im not sure about what its life was like before it came to me. Ive had the vlave cover off and the oilpan dropped and everything looked great nothing noticable that I could tell.

Ive rebuilt domestic motors but never had to trouble shoot an engine that sits as long as mine. Should I plan on getting it installed and crank it a few times without the coil hooked up and wait till everything gets good and lubricated? Thanks Mike

[2ndGenGuy]

Did you have someone hold the throttle wide open?

EDIT: Never mind, it was on an engine stand... Unless the intake manifold was attached, and the throttle body was closed... Maybe?

[mykwikcoupe]

Did you have someone hold the throttle wide open?

EDIT: Never mind, it was on an engine stand... Unless the intake manifold was attached, and the throttle body was closed... Maybe?

throttlebody cloed yes but that shouldnt matter as the theory is compressing the air in the cylinder whether it got there through the intake or exhaust doesnt matter

[2ndGenGuy]

throttlebody cloed yes but that shouldnt matter as the theory is compressing the air in the cylinder whether it got there through the intake or exhaust doesnt matter

Well, I was instructed to make sure the throttle was open when testing mine. And I found out why very quickly. I about cried when I got 50psi on my freshly rebuilt motor. Then I got in and cranked it with the foot to the floor. 180 across the board. Can't hurt to give it a try...

[Hauntd ca3]

you'll never get a good comp reading turning it over by hand.
wangle a way to bolt up the starter so it can turn at normal cranking speed
and you have to hold the throttle wide open to.
a leak down is a better idea inf you can get your hands on a tester

[AccordEpicenter]

you'll never get a good comp reading turning it over by hand.
wangle a way to bolt up the starter so it can turn at normal cranking speed
and you have to hold the throttle wide open to.
a leak down is a better idea inf you can get your hands on a tester

yes yes and yes, yes.

That wont ever work, youll have to crank it over to build compression. Leak down is the best way to go hands down especially in this situation

[thegreatdane]

I would recommend taking a look at your bearings also, there's nothing as depressing as finding your bearings coming out with the old oil with a toasted crank to go with it.

I just tore down my spare JDM B20A engine with 122.000km on it yesterday, and the bearings in that was just about ready to get replaced if the engine was supposed to be doing anything above stock performance later on.
The state of each individual engine will vary of course depending on the oil quality been used on the engine and the oil change intervals throughout its life.
But rather spend money on new bearings than having to throw your crank in the garbage later on.

And if your going to do compression testing on a stand, you should put new oil in the engine if it's been sitting for that long. That old oil wont provide much protection to your bearings and journals and lobes.