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knock, rpm, engine vaccuum?

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gsxtrev

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Discussion starter · #1 ·
I have a 98 gsx cant figure out whats going on, it was at perfect idle with a slight knock coming from the drivers side part of the head but the car had power loss. The car wont go past 3500 rpm while driving and now the knock has gotten alot worse could it be lifters i rebuilt the engine which has 3000 miles on it and i havent done any work to the head except having it pressure checked, milled and cleaned. i couldnt figure it out so i had mitsubishi look at it and they checked the timing which was good and they mentioned the engine vaccuum was at 14psi and should be at 18-20 whats does that mean. thanks


Trev
 
Discussion starter · #4 ·
When you say it is measured in the hg what does that mean? the car is stock basically how do you measure the vaccuum and or what problems will you have if it isnt running at 18-19 psi also what are the causes of a low reading.


TREV
 
#5 ·
gsxtrev said:
When you say it is measured in the hg what does that mean? the car is stock basically how do you measure the vaccuum and or what problems will you have if it isnt running at 18-19 psi also what are the causes of a low reading.


TREV
Click to expand...
18-19 in.HG, its a measurement of atmosphere. Basically its when your engine is sucking in air. PSI is when you're compressing air that is going into the engine. Thats about the extent of my knowledge.. It'd be nice if someone could come in and explain what problems poor vacuum causes and stuff......
 
#6 ·
Poor vacuum is caused by a few different things. Vacuum leaks some where along the intake side which would be a boost leak, timing being off causing the valves to open at the wrong time and let the compression out the cylidners.
 
#7 ·
I kind though that's what it was.. one time I was driving and the line going to my boost gauge popped off and my car drove fine.. I was kind of surprised considering my vac source is from the FPR.. Anyways here's a little info from 1000q.

PSI (or P.S.I, psi or p.s.i) is an acroynm for pounds per square inch, a measurement of pressure that is often used in automotive circles. The metric equivalent for psi is the Pascal, although most psi measurements equate better to kiloPascals (kPa). Other units for pressure include the bar and the atmosphere (atm). For the mathematically minded, 1 bar = 14.504 psi = 100 kPa = 0.9869 atm.

'Hg' is the chemical symbol for mercury. It is sometimes used as an incorrect version of inches of mercury (inHG) or millimeters of mercury (mmHG), the unit of measurement for vacuum. This unit was derived from the technique of measuring vacuum by pulling mercury up a glass tube. Vacuum, which is simply negative pressure, is also commonly measured in bars, inches of water (inH2O), and Pascals (Pa). In this case, 1 bar = 29.53 inHg = 401.463 inH2O.
 
Discussion starter · #8 ·
The timing is fine set to stock standards. i did a compression test and i am at 167-170-171-173 on the cylinders so im not sure where the knock is at but could a lifter cause the car to not go past 3500 rpms or would that be a bad rod even though they were replaced 3000miles ago.


Trev
 
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