300zxhks

iTrader: (1)

I have a brand new motor runs perfectly fine, but I just decided to check the compression the other day and I got some weird numbers... All 4 cylinders are between 75-80psi which is extremely low.

I double checked the timing and it was dead on. Also checked the dipstick tube and that was tight also. The car was warmed up and at WOT when i tested it. I put a little oil into the cylinder also and there was no change in any of the numbers. I thought it was weird that Im getting such low numbers and the car still starts and runs fine.

I just put a 2.4 block in the car with an evo crank with long rods and 9:1 pistons. cometic head gasket. It also has AEM adjustable cam gears that are both set to -4* (thats what they were set at before I got the car and it ran fine...) If somebody also has some input on these cam gears specifically that would be awesome, car has 264's installed as well.

Anybody have any ideas? I am thinking about setting the cam gears back to 0* and see what happens with that.

okevolutionVIII

iTrader: (71)

Did you break in the rings properly? If you didn't within the first few minutes and miles that the engine was running then you have to pull it apart, hone the cylinder walls, install new rings and do it again.

todd6027

iTrader: (10)

first try another compression tester then get a leak down test done

JohnBradley

iTrader: (30)

^^^ This. They are even between each other and you say it runs fine. You need a compression guage.

fteofbeary

Did you break in the rings properly?

LetsGetThisDone

iTrader: (1)

Even poorly seated rings won't have comp numbers that low. Get a different compression tester and go from there.

300zxhks

iTrader: (1)

I set both cam gears to 0* and the compression went up to around 115/cylinder. I did the test the same way as before. Same gauge I havent gotten a chance to get a new one..

Ive also read somewhere that the way I built my motor I should see different from stock numbers.. (2.4 block, evo crank, long rods, etc) is this true, if so what kind of numbers should I be looking for?

LetsGetThisDone

iTrader: (1)

what length rods? should be 162mm rods with a 88mm crank in a 4g64, with (I THINK) standard compression height pistons.

300zxhks

iTrader: (1)

Also.. how long does it take for rings to even seat? The motors probably only got 2 miles on it and maybe an hour of run time...

300zxhks

iTrader: (1)

The rods are 162mm I believe. . The pistons are wiseco K627M87. With a 1.13 comp height. I vaguely remember the shop I ordered them from saying something about them being shorter?

300zxhks

iTrader: (1)

Another thing too, after i crank the engine and it gets to 115, highest it will go, I watched the gauge and none of the cylinders loose pressure

todd6027

iTrader: (10)

go drive it and stop worrying

LetsGetThisDone

iTrader: (1)

I would put some miles on it. Break it in properly, then go from there. Would probably still try a new gauge...

300zxhks

iTrader: (1)

Lol im not the one worrying about it. I think its running just fine lol... the kid whos buying it is scared about it.