Just did a compression test on my blktop - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Realnez · 02-27-2007, 10:01 PM

Ok so I just got my blktop shipped in and obviously the first thing Im gonna do is a compression test.

So I take off the cover and plug wires and I notice on cly #1 there is a bit of surface rust inside where the spark plug is (maybe from sitting i dunno). Anyways I take out the first spark plug and its covered in oil and I look inside and notice its all covered in oil too. Same goes for each cylinder, all coated in oil. I do the compression test and get;

#1 - 175
#2 - 175
#3 - 175
#4 - 150

I tried #4 three times and got 150 everytime. What do you guys think? I have 30day on block and head from the company I got it off of (which I have had no problems with, everything went smooth and fast shipping too). The guy over the phone said it had pefect compression etc (which all salesmen say I would think). I just want a decent bottom end, like Im planning on redoing the top end ONLY and cant afford to spend more.

drftwerks · 02-27-2007, 10:03 PM

you do know oil bumps compression up if it is low, i dunno get it checked out, R.O.T lowest cyl should be within 75% of highest.

i dunno

BLITZZZ · 02-27-2007, 10:07 PM

I'd do a leakdown test to the motor, if you don't know how search it on google. figure out if its the rings or head...

I've driven sr's with more than 30psi off in one cylinder and they ran like a charm... you may be perfectly fine man..

also the 4th cylinder gets the hottest so its not surprising it has lowest comp..

Realnez · 02-27-2007, 10:23 PM

yea I agree,

I will check how to do a leak down test asap. I would really like to start taking it apart and replacing stuff, but like I said I really want a solid bottom end.

If oil bumps up the compression then I wonder what that cylinder is really at

anyone else have and advice?

SC_S13 · 02-27-2007, 10:32 PM

if you can spare the cash, maybe just give the block a rebuild. might save you trouble in the near future?

Realnez · 02-27-2007, 11:15 PM

cant spare I dont sell crack anymore lol

CoasTek240 · 02-27-2007, 11:26 PM

well with those numbers, that seems alright. Youd get a better idea from a leakdown. but those seem good actually. 160 across would still be good.
you do need to check the level of your oil cuz like someone (above) said that can raise compression.
I recomment the rebuild. Ive dealt with used motorsets b4 and theres always a lil bit of doubt there. Id recomment a mild rebuild/freshen up with block cleaning. milling and gaskets and rings...and maybe bearings.
good luck.

JDMClifford · 02-28-2007, 04:21 AM

did you take your intercooler pipe off and hold it at full open throttle when you tested it?

Realnez · 02-28-2007, 05:59 PM

well I called him today and he told me;

The engines sit for a long time and I need to put the motor in and run it, then the compression will even itself out. Also the oil is there for storing purposes and it will burn out when I start the motor.

Does this make sence? I guess Im gonna do what he says and if its still fucked Im gonna take it out. (big waste of time)

Here are pics of the spark plug holes.

CYL #1

CYL #2

CYL #3

CYL #4

Spark plugs

02-27-2007, 10:32 PM	#5
SC_S13 Zilvia Addict Join Date: Nov 2006 Location: - Posts: 936 Trader Rating: (15) Feedback Score: 15 reviews	if you can spare the cash, maybe just give the block a rebuild. might save you trouble in the near future? __________________

02-27-2007, 11:15 PM	#6
Realnez Zilvia Junkie Join Date: Jan 2006 Location: Burnaby Posts: 322 Trader Rating: (0) Feedback Score: 0 reviews	cant spare I dont sell crack anymore lol __________________

02-28-2007, 04:21 AM	#8
JDMClifford Zilvia Junkie Join Date: Nov 2006 Location: Santa Cruz Posts: 376 Trader Rating: (0) Feedback Score: 0 reviews	did you take your intercooler pipe off and hold it at full open throttle when you tested it? __________________ Parking lot pimping

02-28-2007, 05:59 PM	#9
Realnez Zilvia Junkie Join Date: Jan 2006 Location: Burnaby Posts: 322 Trader Rating: (0) Feedback Score: 0 reviews	well I called him today and he told me; The engines sit for a long time and I need to put the motor in and run it, then the compression will even itself out. Also the oil is there for storing purposes and it will burn out when I start the motor. Does this make sence? I guess Im gonna do what he says and if its still fucked Im gonna take it out. (big waste of time) Here are pics of the spark plug holes. CYL #1 CYL #2 CYL #3 CYL #4 Spark plugs __________________

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02-27-2007, 10:01 PM	#1
Realnez Zilvia Junkie Join Date: Jan 2006 Location: Burnaby Posts: 322 Trader Rating: (0) Feedback Score: 0 reviews	Just did a compression test on my blktop Ok so I just got my blktop shipped in and obviously the first thing Im gonna do is a compression test. So I take off the cover and plug wires and I notice on cly #1 there is a bit of surface rust inside where the spark plug is (maybe from sitting i dunno). Anyways I take out the first spark plug and its covered in oil and I look inside and notice its all covered in oil too. Same goes for each cylinder, all coated in oil. I do the compression test and get; #1 - 175 #2 - 175 #3 - 175 #4 - 150 I tried #4 three times and got 150 everytime. What do you guys think? I have 30day on block and head from the company I got it off of (which I have had no problems with, everything went smooth and fast shipping too). The guy over the phone said it had pefect compression etc (which all salesmen say I would think). I just want a decent bottom end, like Im planning on redoing the top end ONLY and cant afford to spend more. __________________

02-27-2007, 10:03 PM	#2
drftwerks Nissanaholic! Join Date: Mar 2004 Location: california Posts: 2,343 Trader Rating: (1) Feedback Score: 1 reviews	you do know oil bumps compression up if it is low, i dunno get it checked out, R.O.T lowest cyl should be within 75% of highest. i dunno __________________ giantroboteyes.wordpress.com/

02-27-2007, 10:07 PM	#3
BLITZZZ BANNED Join Date: Jan 2007 Location: Richmond, VA Posts: 134 Trader Rating: (0) Feedback Score: 0 reviews	I'd do a leakdown test to the motor, if you don't know how search it on google. figure out if its the rings or head... I've driven sr's with more than 30psi off in one cylinder and they ran like a charm... you may be perfectly fine man.. also the 4th cylinder gets the hottest so its not surprising it has lowest comp..

02-27-2007, 10:23 PM	#4
Realnez Zilvia Junkie Join Date: Jan 2006 Location: Burnaby Posts: 322 Trader Rating: (0) Feedback Score: 0 reviews	yea I agree, I will check how to do a leak down test asap. I would really like to start taking it apart and replacing stuff, but like I said I really want a solid bottom end. If oil bumps up the compression then I wonder what that cylinder is really at anyone else have and advice? __________________

02-27-2007, 11:26 PM	#7
CoasTek240 Post Whore! Join Date: Jan 2002 Location: VA Age: 40 Posts: 3,034 Trader Rating: (3) Feedback Score: 3 reviews	well with those numbers, that seems alright. Youd get a better idea from a leakdown. but those seem good actually. 160 across would still be good. you do need to check the level of your oil cuz like someone (above) said that can raise compression. I recomment the rebuild. Ive dealt with used motorsets b4 and theres always a lil bit of doubt there. Id recomment a mild rebuild/freshen up with block cleaning. milling and gaskets and rings...and maybe bearings. good luck.