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Leak down/compression test results built motor

.obes.

By .obes.,
in Engines & Forced Induction

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.obes. Newbie

.obes.

Posted
Posted (edited)

Hey Team.

 

First time posting after many years out of the gtr scene and now looking to get back into it. Been hunting for a while for a 32 and looked at a few, but finally Found one that I’m pretty interested in and have just had a compression and leak down test completed on the motor. Hoping to get some advise or feedback. So thanks to all in advance!

 

Motor in the cars a reasonably freshly built. 2.8 stroker. 

 

compression came back at a consistent 130 across all cylinders.

leakdown results as follows.

 

Cylinder 1 - 18%

cylinder 2 - 22%

cylinder 3 - 13%

cylinder 4 - 13%

cylinder 5 - 18%

cylinder 6 - 22%

 

motors done around 2k km from being built, over last couple of years so not driven often. Spoke with mechanic who did testing and he said these numbers where ok, but they seem a bit high/all over the place to me.

 

Any help, greatly appreciated.

 

can provide more details on motor build or other info if needed?

 

cheers.

O.

 

Edited by .obes.
KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Leakdown more than 5% is sub par.

I would have expected more like 160 on the compressions.

To my way of thinking these numbers are not good for a built engine with only 2k on it.

Meathead Collaborator

Meathead

Posted
Posted

Was engine cold  when leak down done. 

Mine has big overlap so dynamic compression test only good for comparing other cylinders.

After around 3000km since overhaul leak down is between 1 and 2% on mine.

I would keep looking if I was you.

 

.obes. Newbie

.obes.

Posted
  • Author
Posted (edited)

Thanks for replies guys. Cam is a cam tec 413b. 270 duration. 242.50. 112lsa 10.8mm lift.

was told by mechanic who checked the motor that compression good and in line with where it should be due to motor build and cams/top end. But felt leak down wasn't right? He did say as the vehicle spent alot of time sitting round since being built valves may not being seated/sealing right? Something along those lines.

Haven't seen the car in person as it's interstate but am going to inspect next week.

Car currently on e85 running 470hp at wheels on 23psi with hks gtss turbos.

Engine was built by a reputable shop. Compression check was done warm and cold but I'm unsure of leak down.
 

Is there a process of elimination to determine if leak down results are through top end?

 

Appreciate the replies.

Edited by .obes.
GTSBoy Grand Master

GTSBoy

Posted
Posted

There's really 2 options.  The valves are leaking, or the rings are.  On a built engine it is far more likely that the rings didn't get a good bed in than it is that the valves are leaky on all cylinders.  Unless the guy who did the head needs a kick in the nuts.

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted
12 hours ago, .obes. said:

 

Is there a process of elimination to determine if leak down results are through top end?

 

 

Experienced operator should be able to tell by listening (with stethoscope if available)

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

These are the numbers for my RB25DET with 143,000km (at least) before I broke some ring lands and went RB30/25 (NB at this point it was running ok...but it didn't last!)

 

2012.04.06 EHD341 Leak Down 001.bmp

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