Compression test Qs

HISSIN50 said:

Chris, you're stuck with me posting on your thread again.

1). I'd use 6 amps.

2). I suppose you could (I haven't done it like that - perhaps others have) because I dont like for the coil to have no where to dissipate the energy it produces.


3). When you do the dry and then wet test, that can suggest to you how the rings are doing (the comparison is what allows this). I suppose the Corral guy figured that deductively the valve guides were what is left as the source of leakage (if wet and dry are the same), which I disagree with. That would be where the leakdown test comes into play - it allows you to pinpoint the source of issues in the motor much better.

You can have decent compression numbers but the leakdown is disappointing. But in your case, we're not really lookin for finding out exactly how the engine is sealing, but rather finding what the issue is with your car (so it runs well - you can make a leakdown tester at your leisure if you desire once it runs better). In other words, the comp. test should provide adequate data for this situation.

Do have the motor be hot. It's not as critical on a hypereutectic-slugged mill as it is on forged (coefficient of expansion) but it's more accurate when hot.

Good luck bud.

Click to expand...

HISSIN50 said:

Chris, I forgot - thank you for the kind thoughts in an earlier post. I feel the same way about almost everyone on here who replies to my questions too !

I might be missing the boat a bit but my couple thoughts...............

A leakdown test is great to check the condition of overall sealing in a motor - it's awesome to do before bolting on a blower to make sure it can take the extra cylinder pressure.

Now you had something go haywire and start making chitty noises. Without hearing it and just being there (it's hard enough to diagnose stuff like that in the flesh), it's hard to say what it could be or where I'd start. But for an issue like that, I dont think a leakdown test is going to help.

On your Corral thread, people saw your compression numbers but perhaps didnt know the underlying reason for checking compression, so they mentioned doing a leakdown test (I would have too, if you simply were wondering how the motor's sealing up, absent knowing of an underlying issue for the testing).

I think you had a ticking/pinging noise but it wasnt like detonation (it wasn't knocking, was it)?

My next step might be to drain oil and check for bad things in it. If you can cut open the filter, that's not a bad idea. I'd do that if you think a hard part took a dump.

If you think a rocker or something let go, well, I'd check that up top.

It's been a couple days since I read your thread and I just got back in from working outside for hours, so I'm a little dingier (word?) than normal. Grady and the other wise folk might have some better ideas for ya. I just start checking everything that I can think of (that isnt a royal pain to do) to look for clues.

Does it still make noise (like when you warmed it up for the comp. test)?

Good luck and bump Chris.

EDIT: I'm not sure I'd look at the oil control as being the issue if you've been drinking oil for a bit now and didnt have the pinging issues. I would certainly address that at some point, but it might not be a primary cause of the noise (though excessive oil in the chambers can cause detonation..............).....

Click to expand...