Comp Test - Rb26dett - Only 70,000 Kms

[performance-wise]

After some advise as Im in the market for a R33 GTR atm and I got some comp test results back from one seller and they seem a bit low.

Apparently the engine has only done 70,000km.

Results: 1=125, 2=125, 3=120, 4= 130, 5=125,6=120

Im not sure if this was done cold or hot. Would it make that much of a difference?

Apparently the reason for it being so low is because the car has a HKS head gasket. Does this sound right?

Will a leak down test determine correctly if the comp is too low?

Any advise is appreciated

[wrxhoon]

After some advise as Im in the market for a R33 GTR atm and I got some comp test results back from one seller and they seem a bit low.

Apparently the engine has only done 70,000km.

Results: 1=125, 2=125, 3=120, 4= 130, 5=125,6=120

Im not sure if this was done cold or hot. Would it make that much of a difference?

Apparently the reason for it being so low is because the car has a HKS head gasket. Does this sound right?

Will a leak down test determine correctly if the comp is too low?

Any advise is appreciated

A thicker h/gasket will decrease compression because the compression chamber is bigger.

Compression numbers will depend on a few things , like how it was done , warm engine, cold engine, WOT and finaly the gauge itself .

From the numbers you posted it doesn't look good because of the variance ( 3+6 =120 4= 130) I know the varaince is within Nissan specs but to great for my liking . Why use a thicker h/gasket to lower comp so much???

A leakdown test will confirm the condition of the engine, under 5% leakdown = excellent engine , above 25% = rebuild or dodgy past rebuild .

[GTR1993]

when i bought my gtr the comp test was 125 across all cylinders. had larger cams and forged pistons with metal head gasket, so i assumed the compression had been dropped a little.

[performance-wise]

thanks guys thats very helpfull.

Is a leak down test less accurate than a comp test?

[wrxhoon]

thanks guys thats very helpfull.

Is a leak down test less accurate than a comp test?

Different test, it will give you a % of cylinder leakage and you can even hear where its coming from the top end or bottom end . They are both accurate if done properly, with leakdown test it makes no difference what the comp ratio is , so even if she has a thick gasket , a good angine should have very little leakdown .

[performance-wise]

awesome, thanks for clearing that up

[monga]

mate I bought a gtr with compression of 150 147 151 145 150 151 and less than 5 % leak down

then the bastard spun a big end after 6 months or so