ja78911sc

The question is:

Why are the leak #'s on 1-4 basically the same as the two cylinders with higher compression?

You would assume the lower compression cylinders would have a higher leak # ?

Indycam

The gauge is fine . It's not about the number it's about the % vs the number . A cylinder that is fine is fine no matter what the other cylinders read .
1) Lets say you test a motor and it has 200psi in all cylinders but one that reads 175 psi . By the 10% rule that motor "needs" a repair because of the 175 psi cylinder .
2)The next motor that is checked reads 175 psi on all cylinders and is said to be fine and needing no repair .
3)The 3rd motor reads 157 psi on all but one that reads 175 psi , this motor is said to be needing repair because the one cylinder is more than 10% away from the others .
1) 175 psi = to low compared to the others = repair
2) 175 psi = fine = no repair
3) 175 psi = to high compared to the others = repair


This is a question about the psi in the cylinder and what you think it says re rebuilding .
If one day a cylinder is fine to run at one psi reading , and then the next day at the very same psi reading it isn't fine to run ...

They make from the factory cylinders that switch on and off . There are motors that are meant to have dead cylinders .

FeralComprehension

Oh, jeeze. Perform an Italian Tune Up and then retest.

Seriously- get it hot and then thrash it for an hour- curviest roads you can find, up and down thru the gears, WOT/redline as much as possible.

1. It'll be good for your soul

2. It'll blow out any accumulated gunk*

(*technical term)

naidoo2610

3 days before I had the tests done I drove the car 100 miles to an autocross event, had 5 good runs and then drove 100 miles back.

FeralComprehension

Well, that may or may not have made a difference. How long is an autocross lap, time-wise. 2 minutes? Vmax?

If you said you'd been to DE....

100 miles highway? Soft duty.

Whatever- your numbers are not anything I'd be concerned about given the age/mileage of the car. I imagine it runs entertaininly strong, and your oil consumption seems very reasonable.

Again, I'd run it unless you were looking for an excuse to get the work done, in which case your numbers are terrible and you need to have it serviced immediately

naidoo2610

I would love to get the engine rebuilt but the $$$ start adding up very quickly. I think I will enjoy her for few more years. Most of the oil leaks should be resolved at the next valve adjustment.

Thanks again to everyone for their input.

berni29

Hi

One last thing, it may be worth running a can of BG44K through the fuel system. It may clean up the combustion chambers and even out the compression.

Berni

Gus

To me, what is important is the difference from the original compression ratio-
Were all rated at 180 psi or was there a different ratio for the 4 at 160 originally.
If all were at 180 psi as stock - and 4 have lost 20 psi, but the leak down test doesn't show any significant leakage difference from those at 175-180 psi, then were is the issue. Could the 4 @ 160 have been less originally - maybe 170
I would say that if you have the original compression numbers ( which none of us have) that this is what you want to pull your evaluation from - as it will tell you what you have lost - without it it is a shot in the dark to come to any major decision as leak down is not that bad. ( if all were done correctly)

FeralComprehension

Undesirable? Sure. Unacceptable on a hard-run street car with 150k and no significant oil usage? Get over it.

LouZ

If you use the criteria of a previous poster where 100 PSI was the so-called number, then 90 PSI was 10% low and 110 PSI was 10% high. Now looking at the OP's #'s we can apply the same factors where 175 PSI is the mid-range, therefore, 160 is only 9%, and 180 isn't even 3%!

Therefore, you are dead-nuts on for variations. DON'T WORRY ABOUT IT!

Even if you took the extremes 180/160 = a whopping 12.5% (judging by the increments of 5 PSI the error in reading the gauge would account for 2.5%)

naidoo2610

Thanks for letting me know about the BG44K, never heard of the stuff before but I just did a little research and lots of entusiasts sweat by the stuff.

Unfortunately I could not find it so I went with Techron which also seems to get good reviews.