Compression

[ItsA5Spd]

Hi all, I'm going to to a compression test here soon and want to know what kind of PSI I should be lookin for. I think that it should be in the 110-130 PSI range, is that right? any help is great. Thanks!!

 

[Wicked_Sludge]

more important than the actual number is the ratio between the cylinders. you want all cylinders to be within 30-40 PSI or so of each other. if you have a lot of variation between cylinders, or one cylinder is much lower than the rest, you have a problem.

 

[shadetree]

You do want some pressure. I like 120 and above. Readings between cylinders should be within 15% of each other.

Take the readings with the engine warm. All plugs out, and disconnect the electrical connection to the fuel injectors. Turn the engine at least 4 revolutions.shady

 

[ItsA5Spd]

OK, thanks guys. Oh, where is the connection for the injectors? Also, will parts off of a 93 STX fit my truck?

 

[Wicked_Sludge]

just hold the gas pedal to the floor while you crank it. this will cut the injectors and supply the cylinders with more air to compress (give you a better reading).

 

[ItsA5Spd]

just hold the gas pedal to the floor while you crank it. this will cut the injectors and supply the cylinders with more air to compress (give you a better reading).

OK, so I don't need to unplug anything?

 

[Wicked_Sludge]

just the spark plugs to keep the engine from trying to start.

 

[ItsA5Spd]

just the spark plugs to keep the engine from trying to start.

Right, I knew that. OK sounds good, I'm gonna do it here soon. One quick question what is the biggest tire I can fit stock and the biggest tire if I level it? Thanks

 

[Wicked_Sludge]

biggest stock is 31x10.5. leveled could probably stuff 32's.

 

[ItsA5Spd]

ok, awsome, thanks for all the help guys!!