I have acquired a few compression testers over the years, 1 that is the rubber stopper type where the tester is held by hand while the engine is turned but not sure how accurate these types of testers are? I have a couple of other generic brand testers where the needle no longer sets at the zero marks. My most recent tester is again generic but the gauge and the hose are connected, no quick disconnect, and find inserting the spark plug connector with the hose attached can be a pain in the backside. I am looking to replace these testers for a quality replacement that includes a quick disconnect feature, I came across a 'leak down' tester and not clear if it would be a better option if it can be used for both functions and if so would appreciate any suggestions!!

Comments/Suggestions appreciated.

 

I don't have or ever used a leak down tester so cant say if it could be used as a compression tester but I don't think it can.

With any compression tester you are looking to see what the spread is between all cyl. and if any of the ones you have that are not at 0 can do this then I don't see why the need to replace.
You could take all of them to a motor that you know is good and run a test to see if they read different from each other and go from there on what to do.
But if 1 reads say 150 on all holes and the next is 120 on all holes and the 3rd 140 I would not worry as they all rear the same across all holes just at different highest levels but again I look for the spread across ALL HOLES and I am not seeing that with the above reading I posted.

As for the disconnect and hose where do you want this disconnect?
On some motors you need the hose just to get to the plug holes like on a hemi and some other where the plugs are down in the valve cover.
I have both the type with the hose, no disconnect, and the rubber stopper and I use the stopper type way more than the other, just easier for me.
It works great as long as you get it to seal and you can hear that when cranking the motor over.
Dave ----

 

Just my opining but those hand-held testers can't be that accurate. Seems without the test port being seated and sealed in the spark plug hole any results you see wouldn't be reliable.

OTC's line of imported test gear has a lot of useful features you might find suitable--look for their deluxe test kit #5605. I believe that kit has a Triton motor specific connector for an easier connection inside the plug well. If not included it could be ordered separately.

HTH

 

A leak-down test is more consistent, more accurate or reproducible, because it removes some of the variables compared with a standard compression test. A compression test assumes that both the battery and starter are at 100%. But a leakdown test requires a source of Shop air of at least 100 psi. and they cost a little more than a compression gauge. The cylinder to be tested, the piston is placed at TDC and the air is normalized at 100 psi. So it's more of a precision test. But a compression test is always the first thing done during a proper Tune-Up.

 

Has any one done the compression test as it should WOT and then with it closed to see what difference you get?
I have not and the testis with throttle closed, again I am looking for the spread between all holes and it should not make a difference at that point open or closed.

If you had a motor with a miss and ran a test and had 125, 120, 125, 75, 120, 120 with the throttle closed do you think with it open you would get that 75 hole up to 120 or even 100?
I don't think so.
Then you can run the leak down test if you wanted but just putting air in the hole would tell you where the issue is.
Air out the carb bad intake valve, out the tail pipe bad exh valve, pull the head(s) for a valve job is needed.
Out the oil cap bad rings or piston but either way the motor is coming apart for a rebuild.

For a guy working in his drive way / garage on a street motor how dead on dose the testing have to be to tell something is wrong and where?
Now if this was a race motor that is a different story and my thinking you is it would not get that bad to need a compression test and just go right for the leak down test.
Just my .02 and has worked for me.

BTW my 2 compression testers I have had since the late 70's and I used 1 of them 4 years go on my trucks 300 six to make sure the miss was not a dead hole, they all tested good, put a set of plugs in and it ran great so I pulled the truck apart for a cab off frame rebuild.
Dave ----