Cold compression ratios for a 5.0?
03-01-2009, 09:14 PM
#1
Thread Starter
Join Date: Mar 2009
Location: NJ
Posts: 4
Cold compression ratios for a 5.0?
My dad's friend's son has a 1991 Ford Mustang 5.0 that has a blown engine. He currently has another engine in the garage.
I was wondering if anyone information regarding cold compression ratio numbers? I really don't feel like dropping in the motor only to find out its a lump of poop.
Also if the motor was a lump of poop, what do you guys recommend me dropping in there? The same motor or a 351?
BTW: The car is an automatic
I am not to familiar with V8's as I have only worked on imports. Sorry guys.
I was wondering if anyone information regarding cold compression ratio numbers? I really don't feel like dropping in the motor only to find out its a lump of poop.
Also if the motor was a lump of poop, what do you guys recommend me dropping in there? The same motor or a 351?
BTW: The car is an automatic
I am not to familiar with V8's as I have only worked on imports. Sorry guys.
03-02-2009, 01:13 PM
#6
Banned
Join Date: Oct 2006
Location: Mount Laurel, NJ
Posts: 1,206
cylender pressure check much?
good luck CHECKING compression ratio after you're all assembaled.
you can do some math to find it out, but I have never heard of checking it. Enlighten me if I am wrong.
Last edited by Slo5oh; 03-02-2009 at 01:16 PM.
03-02-2009, 01:36 PM
#7
Join Date: Feb 2009
Location: Arizona
Posts: 48
I think there is some confusion of terms. Compression ratio is determined mathmatically, a compression test is done in the real world, and can be done on a motor lying on the ground, so long as it has the heads on it and a starter bolted to it. Just open the carb or TB to wide open, screw in a compression guage, and take a battery (freshly charged) and jump the starter motor to make the engine turn over 5 or 6 revolutions (make sure you strap the thing down!). You should get a minimum of 90 psi. More important is that the value be consistant among all the cylinders - if it varies more than 15% then there is a problem with the motor. Keep in mind too that if you squirt some oil in the cylinder it will read much higher, especially if there is a problem with the rings and/or cylinder scoring.
03-02-2009, 07:39 PM
#9
1st Gear Member
Join Date: Feb 2009
Location: nc
Posts: 63
i have a question aswell hope yall can help i got oil on 2 of my plugs but whn i bought it has way to much oil in the engine could that be the cause of to much oil is y ive got oil on two of my plugs?ima change it whn it gets warmer until thn im not driven it but to my mecahnic to get my carb rebuilt and get my lokar bracket and throttle and kick dwn cable put on.
03-02-2009, 08:18 PM
#10
Thread Starter
Join Date: Mar 2009
Location: NJ
Posts: 4
i have a question aswell hope yall can help i got oil on 2 of my plugs but whn i bought it has way to much oil in the engine could that be the cause of to much oil is y ive got oil on two of my plugs?ima change it whn it gets warmer until thn im not driven it but to my mecahnic to get my carb rebuilt and get my lokar bracket and throttle and kick dwn cable put on.
And I not talking about compression RATIO, I am talking about compression NUMBERS like when you check a motor in every cylinder and measure the peak pressure after cranking a number of times.
I guess no one knows then. I will assume less than 10% difference between cylinders is good enough to know if the motor is good.