Confused, need someone's help

[Chezedik]

Just got finished rebuilding my engine again. Decided to do a quick compression test while I was only on one mount (in case I had to pull the motor later). With fresh rings (chrome top, cast iron second), filed, and the walls honed, stock cams and no intake mani it pulled 90psi dry. When I added a tablespoon of oil it pulled 240psi! This is only cyl 1, but I don't need to go any further if this is what I can expect. The starter sounds like it is turning slow, so I will charge the battery again. But it sounds almost identical when the battery is fully charged (I've done this a time or two). So I suppose that could explain the initial low compression number, and hydro-lock could explain the second high one. Or am I missing something? Can someone please tell me what this means?

[Florida240sx]

Bad pressure gauge????240psi is high never seen any reading liek that before. New engine not broke in yet so probably have air leaking past rings until it gets broke in for 500miles. Also #2 suppose to compression check on a warm engine.

[Chezedik]

Can't check the compression on a warm engine, since I haven't got it ready to start. But this is the second time I have done this, and I was just wondering if I should depend on this to get better, or just give up and buy a spare engine?

[Globalsilence]

Your rings have not seated yet so the 90 is probably accurate. Once the motor gets about 200 + miles check the compression again, the rings will probably have seated by then.

[Chezedik]

That is what I wanted to hear, but are you sure?

[Florida240sx]

Yea just Like I said. Engine isn't broke in yet so your rings are seated properly. Kinda seems low figured it would be higher.Why comp pistons are you using?Figured it would at least be around 110.But your compression will be x better once you allow the engine to break in. Don't forget to change your oil the first 50miles. You'll find many many metal shavings in it. Also if oil pan is still off might be wise to put a magnet in the bottom of it.

[Chezedik]

Stock pistons.

[Globalsilence]

Run a compression test after about 200 miles, the rings should have seated and you should get in the 180 - 190 range. With a compression test you want to look at the difference between the numbers, not necessarily the numbers. Just as long as the numbers are similar and not within like 14 psi you are good.

[fiznat]

+1 for the break the motor in and then find out theory. Rings need to seat against the cyl walls, which takes quite a bit of time suprisingly. Give it a tank of gas worth of driving and you should be good to go.

[Chezedik]

I know, but for now, we are all in concensus that it will be good enough to start (barring any other problems)?

[WDRacing]

Did the same thing on my RB over in Japan. Was nervous myself. Ran the piss out of it for two days, 170 accross the board.

Break the motor in like you're going to drive it evreyday. In other words don't baby it during break in. Atleast thats the school of thought I use. Some will say tip toe through he tulips during break in, but I think they might be a tad light in the loafers.

[HardcorePS13]

The high number was caused by pouring too much oil in the cylinder. You are picking up the hydraulic pressure in the gauge.

As far as the 90 PSI, that's normal. Drive on the car for a day and re-check it. You might have alot of disparity between the cylinders but the rings will seat.

[Chezedik]

But I should rape it? That is also what I wanted to hear! I have a clutch to destroy afterall! It was going to break my heart to have to drive it like an old woman for the first 10K. I think I will do that, besides I will probably pop it when I turbo (eventually), motors are just as consumable as anything else.

[WDRacing]

Atleast you've got the right frame of mind.

[DammitBobby]

Seems strange the engine break in theory. When I bought my new car last year they never told me to drive it a certain way to seat the rings. Hell with my new motor I did some testing to make sure nothing was leaking, or over heating. Slapped the turbo on it make sure it is warmed up and drove it for 20 minutes. Then started boosting.

[Chezedik]

Yeah, I think you're right. Even if it is the commonly held belief, it doesn't really apply to guys like us. It isn't that big of a deal to overhaul a motor if we pop it. Oh yeah, and WD, I was very serious. I have a gently used Centerforce clutch and flywheel to put in when I burn through my 240z clutch. I am hoping to have all of my turbo gear together by then. But I just got laid off, so it may be a while.

[Florida240sx]

From what I have agthered on the break-in theory is this: Drive car normal until it gets to operating temp. Give it nice steady throttle but not too hard.Make sure everything is working alright. Tach it out a few times but nto too much where engine gets hot.Also don't do it too logn due to all the metal shavings.Do oil change and repeat process abotu 3 times.By then most metal should be out. Also ring are close to being sealed if not already.If they are drive it like rally because you are ready to go.If not give it a few spirited runs but don't drag race form stop to go to stop. Allow motor to stay at normal operating temp. But make sure the rings get broke in.

[Edub1]

I've always heard it's best to take it easy for the first 5K miles and varry your speed. That is, try not to stay at one cruising speed.