What is a good compression reading for an sr20 - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

240sx23 · 12-26-2011, 10:19 AM

Just curious lmk thanks

EsChassisLove · 12-26-2011, 10:50 AM

Not sure but mines 170, 170, 155, 170 after a rebuild and 9:1 compression.

I can't imagine anything under 140 being too good even if its consistent numbers with all the cylinders.

Edit-pretty positive this has been covered before.

clutch187 · 12-26-2011, 11:35 AM

i know all cylinders should be +or- 14 psi of each other. most will probably say time for another rebuild

i accidently responded to EsChassisLove thinking he was the OP, sorry

jr_ss · 12-26-2011, 12:07 PM

Factory spec is 156psi, with 128psi being the minimum. 14psi difference between cylinders is the max allowable per the FSM. The important part is that they are consistent between cylinders. There are many variables that can create comp differences, rings, valves, and head gaskets are the most common. A leak down test will give you a better idea of how healthy your engine is.

jr_ss · 12-26-2011, 12:10 PM

Quote:

Originally Posted by EsChassisLove

I can't imagine anything under 140 being too good even if its consistent numbers with all the cylinders.

This varies, lower compression motors aren't going to yield high comp numbers. Changes in head gasket thickness, piston compression ratio's and ring gaps will all play a role in different comp readings. Just because it "reads low" doesn't mean it's in bad shape.

Kingtal0n · 12-27-2011, 05:10 PM

most important thing is that they are all very similar to each other. if one cylinder is notably lower than the others that is an indication that something is wrong. could be anything- from a piece of carbon stuck in a valve, to a broken piston ring.

12-26-2011, 10:19 AM	#1
240sx23 Zilvia Member Join Date: Oct 2011 Location: ny long island Age: 35 Posts: 283 Trader Rating: (3) Feedback Score: 3 reviews	What is a good compression reading for an sr20 Just curious lmk thanks

12-26-2011, 10:50 AM	#2
EsChassisLove Nissanaholic! Join Date: Jan 2011 Location: San Diego Age: 36 Posts: 2,090 Trader Rating: (26) Feedback Score: 26 reviews	Not sure but mines 170, 170, 155, 170 after a rebuild and 9:1 compression. I can't imagine anything under 140 being too good even if its consistent numbers with all the cylinders. Edit-pretty positive this has been covered before. __________________ IG/TikTok-ThatS14_Z06guy

12-26-2011, 12:07 PM	#4
jr_ss Post Whore! Join Date: Dec 2005 Location: Pa Posts: 6,415 Trader Rating: (35) Feedback Score: 35 reviews	Factory spec is 156psi, with 128psi being the minimum. 14psi difference between cylinders is the max allowable per the FSM. The important part is that they are consistent between cylinders. There are many variables that can create comp differences, rings, valves, and head gaskets are the most common. A leak down test will give you a better idea of how healthy your engine is. __________________ My SR20VET Does your VTC gear rattle in your S14/15 SR? PM me.

12-26-2011, 11:35 AM	#3
clutch187 Join Date: Nov 2011 Location: indiana Age: 38 Posts: 8 Trader Rating: (0) Feedback Score: 0 reviews	i know all cylinders should be +or- 14 psi of each other. most will probably say time for another rebuild i accidently responded to EsChassisLove thinking he was the OP, sorry

12-27-2011, 05:10 PM	#6
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	most important thing is that they are all very similar to each other. if one cylinder is notably lower than the others that is an indication that something is wrong. could be anything- from a piece of carbon stuck in a valve, to a broken piston ring.