did the compression test

TxCobrA98 · Feb 18, 2008

...today and the results are awesome. hopefully i did everything right!

Cylinder 1 - 186psi
Cylinder 2 - 186psi
Cylinder 3 - 180psi
Cylinder 4 - 180psi
Cylinder 5 - 177psi
Cylinder 6 - 185psi
Cylinder 7 - 175psi
Cylinder 8 - 175psi

My car wasn't VERY warmed up but it had only been sitting for like 1 hour - 1.5 hours and i could easily still feel the heat coming off the engine. We kept all the spark plugs in and did one at a time. cranked it a few times and got these numbers. Let me know what you guys think and tell me if we did everything right.

Also got the TPS sensor in and the car runs way smoother and got the new plugs put in. My car actually feels powerful now. Next weekend we are doing the oil and hopefully putting in the aftermarket bump stop we forgot to put in a year, year and a half ago when the springs went in.

realitygt · Feb 18, 2008

if those are your numbers you don't need a new engine. that compression is great and all of them are right around the same numbers. did you keep the throttle w/o?

TxCobrA98 · Feb 18, 2008

oh yeah we left it wide open. forgot that part. :thumb:

realitygt · Feb 18, 2008

weren't you planning on rebuild your engine because it burned oil or something? with those numbers I would look at something else besides the piston rings being worn cause that compression is good.

TxCobrA98 · Feb 18, 2008

yeah i think its the valve seals that are worn. i dont now if that would be show up in a compression test or not.. maybe thats why im askin what ppl think.

and we are rebuilding this motor. but i have a whole other 4.6 DOHC engine with forged everything, i just have to go pick it up. my motor is going into the other cobra and taht motor is going into my cobra. i may keep my motor though and build this one and just sell the other engine. idk yet. :thumb:

TxCobrA98 · Feb 19, 2008

bumppppppppp anything you guys??

realitygt · Feb 19, 2008

replace your valve seals? :dunno:

MeanGrn Gt · Feb 21, 2008

they say you want to be within 10% on all cylinders so you are close. To see if it is a valve or rings do it again and this time squirt a little 30 wt motor oil in the cylinder and retest. if its higher the 2nd time then its the rings/cylinder that is leaking if not then its a valve(or could be a headgasket).

or you could do a leakdown test and it will be much easier/more accurate as to where you problem is.