Hello guys,

So I did a compression test for the first time and the numbers are:
#1: 145.5
#2: 135.5
#3: 145
#4: 145

They are almost identical except #2 but later I found the numbers are inaccurate. Yes, I forgot to ask my wife to hold the gas pedal wide open while I was holding the gauge. So here is a newbie question. Does the compression usually go up with the throttle wide opened?

Thanks in advance.

kkid

Hey KKID,
Short answer: YES!!! Open vs. closed throttle can make a BIG difference in your compression check numbers. So, make sure the battery is charged, pull all the plugs, JAM the trottle open with a screwdriver or pliers or whatever will work and take another check on #2.

I'm sure it will be better. That said, unless you are prepping for the National Runoffs, even the 10lbs difference you found should be fine for a daily driver.
You can always make it PERFECT in another 60k - 80k miles....

The question I have: What engine configuation are you running? It seems to me that the 145.5 lbs/in3 is pretty darn good for a 9:1 CR motor. Also, I'm guessing you are running a stock or mild cam.

NO WORRIES, you have a great engine!

Terry

Hey Terry,
Thanks for the positive perspective.

I was just not sure if it's in good condition. I am beginning to feel my car seems slow for a 2.0L car lately. I have to rev higher than 3000rpm at all times to keep up with other traffic. And the car is working very hard to do this task. BTW my car is stock with D-jet and its motor was rebuilt 25k miles ago, but I don't know about the current CR.

I will definitely test it again probably tomorrow.

kkid

I think 3k is pretty normal... My car seems to almost always be between 3 and 4K and it is a 73 2.0 with D-Jet. These cars like to rev.

It could be the clutch.. do you have hard time taking off/

Did you change tire size?

At 140 psi per cold /closed throttle, I wouldn't worry a bit.

...KKID.....The first thing to check...If your car seems a little slugish, and you need to rev it up higher than you think it should have too.....to get it to have some power.....CHECK the IGNITION TIMING...check and insure the rotor moves freely that the advance in the distributor works smoothly, and does not stick,...Check the point GAP., check the cap and rotor for"carbon build up".If in doubt just get a new cap and rotor. If your Ignition is not working properly, or set properly, you can chase your tail forever....Your compression numbers appear to be less than a 10% variation between cylinders. This is perfectly acceptable for a street engine.

Yes, you maybe right. It is not as smooth as other cars to engage/disengage clutch. I can barely take off by slowly engaging the clutch at idle(900-950rpm). It vibrates so I have to rev a little to get it going.

What is wrong with the clutch?

I haven't changed the tires nearly 3 years.

It looks like it's not a motor.

Yeah, I will definitely recheck the timing since I did it all alone last time. I disconnected a hose from TB(has only one from there) but did not plugged or pinched it when the timing was measured. Wondering if it does matter...

I have an electronic point less ignition in the dizzy and plugged a retard port on both TB and vacuum can permanently since I have heard these are equipped for an emission purpose only.

Will clean the rotor and cap as well as oiling the felt pad to ensure the spring action.

Thanks,

kkid

My car may have an original clutch as far as I can tell from the receipts. Does the original clutch fail just by the age?

kkid

.....I 2nd that 1.........yes they do!(please don't baby her)
(if those readings are correct, you're good!!)

OK, I won't baby her anymore.
What about the clutch?

if the clutch was slipping much, youd'd be able to hear it, and smell it more than likely


check timng, and make sure the mixture is correct, mixture can be off if the head temp senodr is off, wires bad, pressure sensor bad, etc.... look for vacuum leaks also. if your donw on power and your enigne is mechanically ok (compression good, valve adjusted) echkt teh tunning things like mixture and timing.