Re: [Chrysler300] Engine/Compression question

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

Johnathan,
I thought about your low compression problem a bit more and realized that 
lobes wiped off the camshaft would also starve the engine for air and give 
low compression readings. A flat tappet cam will wipe in the first few 
minutes of operation if its going to, so don't dismiss the possibility 
because the engine is freshly rebuilt.

Take the rocker arm covers off and the spark plugs out. Have someone turn 
the engine over with a 1 1/4" socket and ratchet on the crank snout. Watch 
each valve in turn and look for any that barely lift. A bad exhaust will 
also effect cranking compression so look at both intake and exhaust valves. 
Incidently, the rag in the intake was not ment to sarcastic, I did it once 
myself. Good luck. LGJ


> From: "Laurence G. Johnson" <laurence_g_johnson@xxxx>
> To: jwsacks@xxxx, Chrysler300@xxxxxxxxxxxxxxx
> Subject: Re: [Chrysler300] Engine/Compression question
> Date: Fri, 16 Nov 2001 17:46:42 -0500
> 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 cylinder 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


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