Compression test help??

latham83 · Dec 26, 2003

Hey I want to do a compression test here and I know the basics of what to do , but my chiltons manual doesnt tell you ****...it really pisses me off... Like ok I know all i have to do is take all the plugs out..have someone open the butterfly all the way, and crack it over manually..
now how do I crank it over?! I have no idea where to find the electronics for this or what to do..no one tells you...I have the gauge already....other then this, do i have to disconnect any sensors??? Chiltons says nothing..although i read somewhere that u are suppose to disconnect a crank posiition sensor or disconect the coil packs so it wont produce spark ??? is this true? someone please help me..i wish these books would actually explain how to do things...

Grandmaster · Dec 26, 2003

Here are the basic steps from the Haynes manual.
Run engine to normal operating temperature. Make sure batery is fully charged. Remove the spark plug wires. Use compressed air or wire brush to clean around spark plugs, then remove all spark plugs. Block throttle wide open. Disconnect the coil wire from the center of the distributer cap. Use a jumper wire with alligator clips to ground that wire (to the block for example). Install compression guage in cylinder one. Crank over 7 compression strokes. Record results. Repeat for the 7 remaining cylinders. And then there are procedures like squirting oil in the hole and see what it does to diagnose any problems but i'm sure chiltons has that in it if you need reference. I just did this yesterday. It was a real pain, but i'm glad i got it done. Hopefully more knowledgable people can help if this doesn't, just trying to do what i can.
-Grand
p.s. this is for an efi car. I think the only difference is, if the car is carbed, the choke valve must be all the way open (which it should be if the engine is warm anyways).

Fox Saleen 163 · Dec 26, 2003

Sounds right to me. The instructions that came with my compression gauge said the same thing. I used "the club" to stick between the seat rail and the gas peddle to keep the thottle wide open. I only had two hands.

Grandmaster · Dec 26, 2003

so what's the right way to crank the motor over? I think thats the main thing he is wondering, i just didn't want to answer and be wrong.

Fox Saleen 163 · Dec 26, 2003

Oh, turn the key! 7 compression strokes on each cylinder.

Fox Saleen 163 · Dec 26, 2003

Just make sure to take your coil wire off at the distributor and ground it, or there will be lots of electrical current looking for a place to go. You don't want a plug wire to arc on the electronics under your hood and fry everything.

Grandmaster · Dec 26, 2003

ok lol, thanks, thats what i thought, i just didn't want to answer and be wrong hehe.

Fox Saleen 163 · Dec 26, 2003

Haha yeah. Well, turning it by hand at the crank would get pretty tiring after doing all 8 cylinders. That's why the manual says "make sure battery is fully charged".

latham83 · Dec 26, 2003

hey thanks alot guys!! so just make sure i ground that plug wire for the distributor, and then i can just turn the key? how do u know how many cranks u turned..does it do it slow?

Fox Saleen 163 · Dec 26, 2003

No it's actually kind of fast. Just listen real good and you will hear how it cycles. You ground the COIL wire. Take coil wire off of distributor, leave connected to coil on other end, connect end of coil wire to ground using some time of alligator clip.

latham83 · Dec 26, 2003

thanks guys...so ya know...i have 165000 on her...
if the test turns out pretty good...i think i wanna get new heads, headers, and a new manifolds...any suggestions?
also what numbers should i have

Fox Saleen 163 · Dec 26, 2003

Well, I have 135k. All of my numbers were 150, plus or minus 4. I want to get heads too, but I may wait and just get a complete longblock. The Trick Flow package should work nicely, and you know it's matched so you can't lose.

latham83 · Dec 26, 2003

whats the trick flow package???

Fox Saleen 163 · Dec 26, 2003

Also, before throwing H/C/I on there you may want to have a leak down done. But if you're not burning oil there is a good chance your rings are good. Another thing you can do is listen for air bleading out of the cyclinder.(while it's still got air compressed in it) It could go into the intake, headers, or oilpan. It has to be really quiet for this to work.

Fox Saleen 163 · Dec 26, 2003

Trick Flow package... it's in the new Summit catalog. Twisted Wedge heads, Track or Street heat intake, Trick Flow stage 1 cam, and everything you need to install it. Gaskets, roller rockers, push rods, valve covers, ect. Cost is $2000 I believe. Of course you will have to buy bigger injectors and such.

Grandmaster · Dec 26, 2003

I'm not really sure what the numbers should be, hopefully someone else will. As for selecting heads etc, it really depends on what you aim to accomplish with the car:
Is it a racer? Street? Both?
What kind of racing?
How fast do you want to go? (like if you drag, what do you want to run)
It really just depends on your goals and how much you are willing to spend.

latham83 · Dec 26, 2003

well i have no intentions on track racing..i just want a good, quality street car that is fun to drive..meaning i want torque..neck snapping launch..high end isnt a factor for me..so..im looking for just at set of heads, intake, and shorty headers that will do that for me....and thats all i wanna buy..those 3 things..i dont need a cam or anythign else..now if i put those 3 things on my car..i dont HAVE to get bigger injectors and all do i...or anythign else? like fuel pump and ****..can i leave it be

Grandmaster · Dec 26, 2003

Hmm...
I'm not sure what you mean by neck snapping torque, because to some people a 13 second car is fast to others a car isn't fast unless its in the 11s etc, but for a strictly street car, you should be fine with probably thumper heads and a tmoss intake. Also if your car has stock gears you should change those out, that makes a huge difference. You might want to start a new thread asking for ideas on the subject also.
EDIT: also, if you go the thumper/tmoss route i dont THINK you have to upgrade the fuel system but i'm not sure.

tmoss · Dec 28, 2003

Grandmaster said:
Hmm...if you go the thumper/tmoss route i dont THINK you have to upgrade the fuel system

That's correct. No need to change up to about 300HP.

bock · Dec 28, 2003

I would crank the motor by jumping the selenoid.... like this you wont trought fuel in for each 8 cyl... you do this with the keys in your pockets..

Compression test help??

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