question about compression

[KA24boi]

im looking at a good deal on a ka-t for $1500

but the only down side is that the third cylinder has no compression and the guy says that all that needs to be changed are the rings and the engines got less than 10miles

i know what the compression ratio is, but i need to know it in pounds (if that makes sense, idk the right term). the rest of the cylinders have 120-130 lbs of compression. is that right?

and i have experience working on cars, just not a whole lot but would it be difficult to change the rings and how long would it take about?

its a 1993 240sx

any help would be appreciated

[4sfed180]

you usually cant just change the rings. the old rings wear themselves in the bore a certain way. to do this you need to take the motor apart and have that one cylinder light hones to roughen it up.

this will make sure that the rings break in and seat properly.

if it truly has only 10 miles then you might be able to get away with simply reringing that cylinder. 10 miles is not enough time to have the rings seal properly.

the number you provided IS in pounds. 120-130 seems kinda low. i have worked on a KA but from other engines its low.

my 2jz with 150K has almost 180.

[KA24boi]

ok, thanks for the advice

but i was trying to figure out the right amount of compression in lbs that it's suppose to be

[4sfed180]

you can look up the proper compression numbers in the factory service manual.

[murda-c]

should be 150-180 on a stock compression motor.

How are the rings bad if it only has 10 miles?

[KA24boi]

well, i dont have a manual

but thanx murda-c for the numbers

[KA24boi]

so do you guys think its a good deal?

"the good
clean body clean title
5 speed trans
brand new clutch stage 2 6 puck disk
new valves and head rebuilt new timing chains
new set of crank bearings
full turbo kit with large front mount
stainless steel tubular manifold
engine has less than 10 miles on it

the bad
...we put the car together and it has no compression on cylinder number 3 it needs new rings in that cylinder all the other cylinders have 125-130 LBS of comprs. it starts and runs but it runs like it has a miss due to number 3 cylinder we did a cylinder leak test it does not leak any air from seals or valves so it just need new comp. rings . $1500 OBO will also include another compelete short block and an extra head with cams so you can do the cam swap for two exhaust cams if you wanted to"

oh yea, and how long should it take for the rings to break in after all?

[fliprayzin240sx]

No compression on a bad ring with less than 10 miles on it? Sounds suspect. Usually, even with a bad ring, you should still get some kind of compression. 0 compression usually means valves not seating/sealing properly. Im leaning on valves, unless the damn piston got a fucking pin hole in it.

[S14DB]

Sounds like a bad rebuild not a ring problem. I would lean more to them fucking up the HG or the decking not the rings.

If the pressure comes out the PCV/Breather then it is blow by. But, I'm willing to bet to get to 0 compression and low on the others the HG has to have gone.


Might not be a bad deal for a shell with 2 motor sets if the shell is in good condition.

[KA24boi]

"Sounds like a bad rebuild not a ring problem. I would lean more to them fucking up the HG or the decking not the rings."

what do u mean by HG?

[at23]

head gasket dude.

[jspeedm]

the only way you should have less than 150psi is if you have low compression pistons, or more problems than you want to deal with after paying that much moneey. when you checked the compression was the throttle wide open? if not you will get low readings.

[KA24boi]

well i havent seen the car yet, idk if i wanna get it now, i think i need to get something less complicated

[jspeedm]

i say go for it though. you still get a chasis and turbo kit for 1500. then you can find good used motors for 500 all day long on here.

[lost240soul]

u could always do a cylinder leak down test to see were the leak is coming from..

[4sfed180]

if the car is clean then its a decent deal. half the time you can find a stock KA for free and its not even hard to find them either.

Touge Factory use to give them away or straight up throw them out back in the day after doing swaps. :)

do it!!!