i recently got a built b16 motor with low compression pistons eagle rods,ect...i did a compression test and i just wanted to know what you guys think. are the numbers too low or ok?

#1 125psi
#2 147psi
#3 125psi
#4 125psi

i did the test again and this time i put a few drops of oil in each cylinder.
#1 150psi
#2 150psi
#3 150psi
#4 150psi

is that much of a jump ok??

thanks

 

did you perform the test with the throttle body open?? those are like 8:1 compression numbers

 

number 2 is pretty high off from the others.. also do as he just said. was your throttle body wide open. also motor cold or hot?

 

how did you perform the test? Compression test needs to be done on a hot engine, with throttle plate fully open and let it crank over 5-6 times to get the most accurate reading. but if its low compression then most likely it has 8.4:1 or somewher in that area so 130-150ish is going to be par for the course

has this engine been run? if so how does it run? with 3 being 125 and one being 147 sounds like a leak down issue also. on a cold motor check yoru valve lash specs. Also line up timing marks and be sure yoru not a tooth off but i dont think you are seeing one is at 147. just check the valve lash and then do comp test on hot engine and see what you come up with

 

i did the test on a warm motor and i did open the throttle body all the way.
i let it run for about 15 min before doing the test. the car runs and drives great, the motor feels solid but the numbers had me a little worried. its on b base map so i haven't hit boost. car starts up every time on the first try. the only weird thing is that itll smoke on startup but doesnt burn any oil,.
i cranked the motor 7-8 times on each cylinder but im going to do #2 again because i THINK i cranked that one more than the others.

 

the smoke on start up is either fuel, or valve guide seals IMO. I usually crank 8-10 times. how many miles are on the build??

 

i was told its around 30k on the motor

 

so do you guys think the numbers are ok or low??

thanks

 

what is your valve lash on cold motor both intake and exhaust?

 

i don't know what my valve lash is....

 

well then measure it on a cold motor. they could be to tight and it will run good but will give you low readings on comp test. do you have a leakdown tester?

 

i dont but i am trying to get a hold of one... my main concern is the smoking on startup....

 

im pretty sure that if his lash was out then the numbers wouldnt have changed when he added the oil during the compression test. Correct me if im wrong.

 

yes they would still change. the oil takes up space ion the gaps hence giving higher readings if there is leakdown. if the valve lash adjustment is just a hair tight it will run and drive fine but still give low test numbers and will bump up some with oil added. IMO only true way to tell is with a leakdown tester. and or measure the valve lash .

smoke on start up can be many things, valve stem seals to bad turbo seals to to much fuel to coolant.

what color, what does it smell like?