compression on rebuilt motor before break-in

[Mattvichuck]

i have just recently fired up my 92 talon for the first time sience the rebuild and did a comression test. i found 128-128-128-128 and was wondering what it should be like, also what is it supposed to be after break in? also the two cylinders on the opposite side of the timing belt appear to not be firing as in the plugs are clean yet the car idles fine and doesnt sound like it is runing on two cylinders ?
-mattkay

 

[anteversion]

when you say that you have rebuilded your engine , it involve in what?? just putting new pistons and rings?? or have the sleeve bored too?

 

[TOONAH]

Matt, I have to say that 128 psi is too low. Something is wrong. How quickly does the gauge
leak down? Did you replace the pistons and rings?. Did you measure the end gaps?
The readings should be at least 150 psi for 8.5:1 pistons and more for higher compression ratios. We do need more info to help you.

 

[webconnect]

What is your elevation in Canada?

 

[Freerevving]

seems okay to me, maybe a little low, but after break in you'll be around 150

 

[97 4G63]

Run it for a couple of days and break it in and then do another compresion test.
Do this.
Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power

 

[->PrOjEcTGS<-]

Compression is most always lower than expected on a new rebuild. Compression generally goes up a little during break in. Wait for the rings to seat properly and then check the compression again.

 

[91tizzy]

Run it for a couple of days and break it in and then do another compresion test.
Do this.
Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power

+1 I am a firm believer in this method....run it how its gonna be driven and DONT BE SCARED OF THE THROTTLE....and I agree compression should go up once the rings have seated....let the motor see alot of vacuum as well.

 

[LTUDSM]

when i rebuilted my motor,.20 bore eagle rods and wiseco pistons.the compression that i had,was 130 across the board,now i got 600 miles on the motor,and my compression is 150 across the board

 

[anteversion]

so your comp is now ok and in the spec range. nothing's wrong with your engine

 

[anteversion]

do some research please before asking question like that, it sure that comp ratio are lower than expected right aftr the rebuilt, it took at least 600 miles to get the rings to seat properly like it was said before. you were supposed to know that if some research was made before the post

 

[Mattvichuck]

sorry for the noob question but i just thought that 128 was low. when i said rebuilt i mean completely rebuilt. another issue i am having is on the spark plugs the two closest to the timing belt look like they are fine not fowled but you can tell its running, but the two furthest away from the timingbelt look almost exactly the same as when i took them out of the box. The car is running fine ,as in not on two cylinders. I dont really know why.

 

[->PrOjEcTGS<-]

How many miles have you put on it? I think you are paranoid. Run it. Do your frequent oil changes during break in. Remember, use conventional oil for break in. Every time you change the oil check the plugs. If it is running fine don't worry about it. Do a compression check at every oil change. Trust me, on a new rebuild you will get better numbers as miles get put on it and the rings have seated.

 

[Mattvichuck]

yeah i guess i am just a little bit paranoid, i just dont want to mess up the fressh motor thanks for the reasurance.