Not much power

[T-stone]

set up- 1972 240z l24 block N47 head, schneider cam Intake Valve Lift 48

Exhaust Valve Lift 480 duration 274

header 6-1 2.5 inch outlet

aluminum 3 row radiator, stock dizy new points, condensor balest resistor, rotor butten, new dis cap.

ngk copper plugs, ngk plug wires.

stock coil.

timing set good, point gap set 16, carbs balanced and tuned.

Took the car to my uncles house, he has had many 240's some stock and others built.

Let him drive ther car, he says it has about half the power of what it should, i have just now got the car relable, it has had manny problems in the past.

the car runs good and sounds strong, but feels like it is lacking power.

droping the clutch from about 5 grand from first to second i get a little bark, fulles steady through all gears and off take off.

ran a compression test, 1-6 cylinders were at 90psi across the board.

i was looking up compression numbers, it was said they should be anywhere from 160 and up.

not so how accuret this is?

is this what i should excpect from the motor or am i really lacking in power?

[FastWoman]

Sounds like your motor is pretty worn to only get 90 psi. What are your compression numbers when you squirt a bit of oil in the cylinders?

[tlorber]

yeah, are you sure you had the throttle open when you did the compression test?

[spdcrazy]

i'm not that familar with running compression tests on the early Z's. but it is a good sign that they are all about the same. but 90 is quite a bit low. hopefully you forgot to stick the throttle open....

[Zs-ondabrain]

Disconnect the coil wire

ignition switch off

(Wide Open Throttle) Throttle open (Butterflies open) Carb Piston propped up so everything can breathe, thru the carb and butterflies)

remove only the spark plug of the cylinder that you're testing, leave the others in.

Spray some WD-40 down into the cylinder, thru the spark plug hole.

Attach the compression tester, zero out the gauge.

Use a starter motor jumper to engage the motor for about 3 seconds.

write down your results, test again, write it down, then move on to the next cylinder after reinstalling the spark plug of the cylinder you just tested

This is the way I tested mine, worked great. if anyone here sees something wrong in my instructions, PLEASE advise before he actually does the test.

Dave

[olzed]

Like Dave---oops

Edited February 23, 2011 by olzed

[olzed]

Like Dave said, only I remove all the plugs so engine spins easily, and warm up the engine first. I had 140-150 on all.

[Jennys280Z]

Tstone: How many miles are on your motor? Maybe you didn't do/see the compression test right? Did you use a threaded tester?

[FastWoman]

Yeah, I do mine just like Zs said, except with the sparkplugs removed. A bungie cord is great for holding the throttle open.

[racer88]

I am not sure how much overlap the cam has but a performance cam with lots of overlap will have lower cranking compression, but probably not as low as 90psi. The other thing that can affect cranking compression is cam timing. Just some things to think about

Bob

[Zed Head]

If you're using the adapter tube that comes with many testers, it will lower the value at the gauge. The adapter/extension tube in my set lowered the reading from 180 psi to 120 psi. It adds volume.

[T-stone]

I did not opent the threttle while doing the compression test, dint even cross my mind to do that.

I will run test as recomended tomorrow and update.

Im a little iffy on the cam timing, i am running the stock cam gear, numbers on the gear run from 1-3 i have mine set on 2.

i have heard that each mark advances or retards by about 4 degrees, im not sure if i have mine set to how it should.

i looked up videos and pictures to try and find the correct way to set, even the old service manual was mum on this.