Compression testing after breakin, if its low can your engine blow up w/3000 miles?
 

I have this guy making me think that I am going to possibly blow up my engine because it could have low compression and I just dont know it and itll blow up with only 3000 miles , he says people have had it happen to them on here.

I just dont feel like compression testing it, I mean I drive it like its broken in hitting 7000rpm and 7500rpm every once in a while. (2000+ miles on rebuild)

Although Ive been told since I'm on used housings that full breakin can take up to 5000 miles on used housings.

The rebuild was done by kevin landers , I havent compression checked it just because its something I figured I shouldnt have to worry about since the engine is rebuilt.

Now after hearing all this stuff from my friend that he said I'm really aggravated , mainly because after investing all the money into my car I shouldnt have to worry about blowing up my engine when it only has 2500 or so miles on it.

edit - Another reason I havent compression tested is just because I dont really feel like spending the money to do it, I am pretty tight on money.

do yourself a favor and tell your friend to shut the hell up.... if you are worried just do a compression test but i hate people that spread rotary paranoia and just cuz it had low compression doesnt mean its going to blow up thats just stupid.. a running rotary is a running rotary. its like a lil pregnant

from what i hear, if landers built your engine, you should have nothing to worry about

Thats pretty much what I figured, thats why I didnt feel like going through the hassle of compression testing it, but my friend says its a good idea to compression test it just to know where its at.

I just feel like I shouldnt have to since its a rebuilt motor, I could see if it had lots of mile on it but being rebuilt compression shoudl be 100+ but checking myself would let me know for sure where its at , althought compression can increase as I put more milage on the engine if it is low now.

IME you will be pressed to make 100psi+ on used internals unless very good housings were available to him. This does not mean the motor is going to fail or close to it. It just means the seals wont seat as tightly against used housings or will need to wear in a little more to get fully seated as much as possible. Yes ignore your friend if you still are not satisfied contact your builder and ask him. Second you have no clue what your compression is to be concerned with you have never tested it so why your ignorant friend is spewing numbers out I have no idea. Maybe he had his cheerios stolen this morning.

It was done on used housings and I know they werent very good housings, they had the normal wear issues of housings with about 146,000 miles but they were usable.

Im confident in the builder than did the rebuild , Kevin Landers. I know he has built alot of engines and knows what hes doing.

edit - What do you mean by " You will be pressed to make 100+ psi on used internals" Are you saying that it would be hard to make higher than 100+ psi unless on very good housings ?

Im sorry i just didnt understand the lingo.

Compression testing can only tell you so much about how soon an engine will blow up. Let's review 2 seperate scenarios:

1) original 125k engine making 95psi compression, suffering from mild hot start flooding that is getting worse. Probably burning some extra oil and possibly even coolant. Engine is on a slow decline and will probably let go within 6-12 months. Usually due to blown apex seals, which break suddenly due to wear.

2) budget rebuilt engine making 95psi compression. Possibly having hot start flooding, possibly not (every car is different in this regard it seems). Not burning excess oil, or any coolant. Engine is going to continue to slowly build compression all the way until 4 or 5k miles, even though it's not necessary to baby it for that long. The main difference is that even though compression may still be marginal due to original housings, the apex seals are nearly new, not worn, and will not break or fail for a LONG time to come.

Clearly even though these 2 hypothetical engines are making similar compression, one is on the fast decline and could let go anytime, while another will either continue to increase, or at worst stay the same, for years to come. So compression results cant always tell the whole story.

Bottom line, you either have enough compression to start and run, in which case you should get in and drive, or you don't, in which case you need to worry about building the engine. RX-7 owners have some obsession with compression numbers. Mustang owners gather together and talk about what rearend gear they are running, rotary owners get together and talk about how much compression they are making. :dunno:

Thanks for the reply Kevin, I was pretty confident that I wont have to worry about any engine problems for years to come but I feel alot better now with you having responded.

My engine starts up and runs fine, so I think I have no problems to worry about, you did a good job on the build it pulls good, although in a way I wish i did keep my darned 5/6 ports in because my low end sucks, but 4000rpm and im pullin.

Oneday I plan on getting some numbers on the dyno to tell you how well your porting worked with all my mods.

Aron

Do a compression test.
You're just in denial.
Once you rule out that the engine is bad, THEN figure what the real problem is.
If anything, it's for peace of mind.


-Ted

Does it miss fire or run on one rotor?
Does it make any strange tapping/ticking noises, like someone is inside the motor taping with a hammer?
Have you overheated it?
Have you run it out of oil?

if yes then worry
if no then don't worry

Well I dont think I'm in denial...the engine doesnt have any problems at all starting up or anything, I mainly made this thread because I wanted to see if having low compression can actually cause you to blow your motor , since mine is on used housings and compression will take longer to get to its full potential.

My engine has no problems, but youre right it would be for peace of mind but I dont expect any superb mind blowing numbers.

I just think the engine will last for a while since its rebuilt, so I dont think a compression check is necessary unless I just want to know the numbers, compression test is more necessary for someone who thinks there engine is on the verge of blowing up, whereas mine was just rebuilt so that is ruled out.

None of the above, though I have overheated it in the past but it wasnt any excessive overheating and the car has had no problems since, it was actually due to a bad clutch fan.

Now the car runs and drives great, never overheated since fixing the bad clutch fan. Basically stays between 175-180 degrees on my watertemp gauge, which gets the reading from where the sensor is mounted in the waterpump.

The numbers should be up there with that kinda mileage on the rebuild.
Kevin doesn't build junk.
I'd expect 100+ psi on all faces easily, even if the original mileage on the housings were that high.
Unless you're running really hard seals like RA's?
Last I heard, Kevin likes Atkins seals, which should break in pretty quickly.


-Ted

Most s4 used housing engines wind up making 100-110psi from what Ive seen. They rarely come back after breakin for me to check, though.

kevin is my hero.. sigh sooo dreamy..... chuckle like i said kick your jerk friend in the shin

kevin is the man!
im saving as we speak for him to rebuild my S4 motor so i can make 450WHP.
i trust him.