Re: [Chrysler300] Engine/Compression question

["Laurence G. Johnson" <laurence_g_johnson@xxxx>]

Johnathan,
The only thing I can think of that would cause low compression readings in 
two cylinders would be something like a rag left in the intake during 
assembly. This would choke off multiple cylinders and give low compression 
readings because limited air reaches the effected cylinders.

Other that something like that, you have a compression leak. The easiest way 
to find such a leak is to pressureize each cylinde with compressed air. You 
can buy adaptors to screw into the sparkplug holes and attach the hose from 
your air compressor. The trick is to locate the piston at the TOP of the 
stroke on the firing position. This must be done accurately or the air 
pressure from the compressor will just push the piston down the bore until a 
valve opens. If you are on TDC on the overlap stroke, both valves will be 
cracked open and you will not develope any pressure in the cylinder. After 
you get #1 set to TDC and firing, connect the air hose to the adapter with 
100-125psi and pressureize the cylinder. Listen for air hissing out of the 
engine at the intake for intake valve leak, exhaust pipe for exhaust valve 
leak. These should not leak at all. Take the oil filler cap off and listen 
for crankcase (ring) leakage. All engines will leak a small volume past the 
rings. If the airstream coming from the filler will disturb cigarette smoke, 
be suspicious. Head gasket leaks will usually show up as air bubbles in the 
radiator, take radiator cap off and look. Check a couple of the "good" 
cylindres to get a baseline and develope some "feel", then check the bum 
cylinders and see what shows up abnormally. Good luck, Larry Johnson


> From: Jonathan Sacks <jwsacks@xxxx>
> To: Chrysler300@xxxxxxxxxxxxxxx
> Subject: [Chrysler300] Engine/Compression question
> Date: Fri, 16 Nov 2001 11:19:14 -0800 (PST)
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>
> Hi all,
>
> Quick question about compression:
>
> I just had my 413 rebuilt along with the carb.
> Replaced/rebuilt a lot of the other engine components
> at the same time.
>
> Unfortunately, after putting it all together and
> starting it up I find that I have low compression in
> two chambers. Around 30 when of course it should be up
> around 90.
>
> Now I've heard differing views on this, but my
> question is, can the compression problems be anywhere
> besides inside the chamber. Like in the carb, maybe?
> Or does it have to be either the rings or how the
> valves are seated?
>
> I guess what I'm asking is, am I going to have to pull
> the engine off and get the rebuilders to take it apart
> again?
>
> Always grateful for the advice,
> Jonathan
>
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