compression

thethirdmurph · April 4th, 2008, 10:41 PM

what is the compression on a 351w supposed to be? psi not ratio.. I just put this motor back together and dropped it in. and now it sounds like there is no compression it is just turning over without firing at all.
Thanks guys

ScratchinFerTraction · April 4th, 2008, 11:03 PM

I would say for a fresh motor look for around 175 PSI, remember to hold the throttle body open while cranking the engine. A worn out engine is down to like 130 PSI or so, all variable depending on the CR of what you are running.
Stan

jrh_1980 · April 5th, 2008, 12:47 AM

sounds like timing is off. your intake valve is opening before you reach TDC and allowing compression to escape back though the intake

thethirdmurph · April 5th, 2008, 02:56 AM

thanks guys.. I was getting 0psi..apparently l had the rockers adjusted too far down. backed them out one cylinder at a time and now I'm up to 150 per cylinder..

April 4th, 2008, 10:41 PM	#1
thethirdmurph Newbie Join Date: May 2007 Posts: 37 iTrader: 0 reviews	compression what is the compression on a 351w supposed to be? psi not ratio.. I just put this motor back together and dropped it in. and now it sounds like there is no compression it is just turning over without firing at all. Thanks guys

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April 4th, 2008, 11:03 PM	#2
ScratchinFerTraction Newbie Join Date: Mar 2007 Posts: 41 iTrader: 0 reviews	I would say for a fresh motor look for around 175 PSI, remember to hold the throttle body open while cranking the engine. A worn out engine is down to like 130 PSI or so, all variable depending on the CR of what you are running. Stan

April 5th, 2008, 12:47 AM	#3
jrh_1980 Regular 89 Mustang LX 7.90@90mph 8th Join Date: Feb 2008 Location: Macomb, Illinois Posts: 151 iTrader: 1 reviews	sounds like timing is off. your intake valve is opening before you reach TDC and allowing compression to escape back though the intake

April 5th, 2008, 02:56 AM	#4
thethirdmurph Newbie Join Date: May 2007 Posts: 37 iTrader: 0 reviews	thanks guys.. I was getting 0psi..apparently l had the rockers adjusted too far down. backed them out one cylinder at a time and now I'm up to 150 per cylinder..

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