Bad compression..runs great

[iBoostDSM]

As the title says my car has been running great but I decided to check compression just to be sure. Sure enough did a compression test at operating temp with an Autozone test and here are my result. 1st-4th 62-82-85-100. Not very good. Put oil in and got 140 across the board. What should I do? As I said it runs great, timing is dead on, just redid it last week. Suggestions?

 

[coryd21]

You did the compression test with the engine off and the valves sealed correct?

If so then when your able to raise the compression by adding oil to the cylinder that usually points toward worn piston rings. You could also do a cylinder leak down test to verify if the rings are bad b/c you will be able to hear air in your oil dipstick tube when you are doing the test.

http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-leak-down-testing.html

This should help.

 

[rx7ttlm]

As the title says my car has been running great but I decided to check compression just to be sure. Sure enough did a compression test at operating temp with an Autozone test and here are my result. 1st-4th 62-82-85-100. Not very good. Put oil in and got 140 across the board. What should I do? As I said it runs great, timing is dead on, just redid it last week. Suggestions?

6 bolt swap time . Assuming your running the 2g engine still 140 is low. I think 135 is the min IIRC My original 2g engine had 195-130-175-195 and it ran like balls . Now with 6 bolt its 175 across. (lower compression)

 

[iBoostDSM]

Yes the engine was off. How would I go about sealing the valves?

The instructions in the link were the ones I followed.

 

[silvreclips]

Heres how to do a proper compression test. Remove plugs and unplug coil pack. Unplug the fuel pump relay. Make sure engine is warmed up to operating temp first. Insert compression gauge and turn motor over at WOT until the gauge no longer moves.

I dont know what coryd21 is talking about the valves being sealed. Sounds like hes talking more about a leak down test.

 

[iBoostDSM]

Heres how to do a proper compression test. Remove plugs and unplug coil pack. Unplug the fuel pump relay. Make sure engine is warmed up to operating temp first. Insert compression gauge and turn motor over at WOT until the gauge no longer moves.

I dont know what coryd21 is talking about the valves being sealed. Sounds like hes talking more about a leak down test.

That's exactly what I did except I didn't unplug the coil pack. Would that make my results any different?

 

[crusada]

run a quart of resinol through it and see if that helps it at all i had a friends gst do this he ran resinol through it and the compression stayed up he ended up 6bolting it a month later but its worth a shot to see if it would help. just my 2cents But i do agree 6bolt swap time

 

[iBoostDSM]

^^ I'll try that out. Still need to know if unplugging my coil pack would change the results. If not it's 6 bolt time.

 

[Calan]

You unplug the coil pack to prevent plugs from firing or to keep the plug wires from shorting to something.

Sometimes you can loosen up sticky rings, usually in a motor that has set for a while. That sounds like what happened in the post above.

 

[iBoostDSM]

Ok. And one thing after doing a wet test and starting the car I noticed white smoke coming from near the exhaust Manifold. Would that be just the oil burning off or something to look at? It has never done that before.

 

[Calan]

Ok. And one thing after doing a wet test and starting the car I noticed white smoke coming from near the exhaust Manifold. Would that be just the oil burning off or something to look at? It has never done that before.

Sounds like you had enough burning oil in the cylinders to show up as an exhaust leak.

Run some Seafoam through it to clean the oil residue and carbon out of the cylinders and locate the exhaust leak(s).

 

[iBoostDSM]

Thanks for the help calan. Would you suggest getting a new/different 6 bolt block sooner rather than later or just run with it as is. Like I said it drives great with virtually no problems...that I can notice.

 

[Calan]

Thanks for the help calan. Would you suggest getting a new/different 6 bolt block sooner rather than later or just run with it as is. Like I said it drives great with virtually no problems...that I can notice.

First of all, if it "it drives great with virtually no problems", then those initial compression numbers you saw (62-82-85-100) were probably not accurate.

I personally don't like tearing down a motor unless it needs it. If it were me, I would do a leak-down test on it to determine exactly what shape it is in, and where any problem areas may be. That would give you a lot more information to base your decision on.

BTW - There are LOTS of people making big numbers and running fast times on 7-bolt motors. The 6-bolts were stronger from the factory, but the whole "6-bolt swap" thing is a bit overrated IMHO. It's mostly a matter of funds and how much time you want to spend swapping it out vs. building the 7-bolt...if it needs it in the first place.

 

[iBoostDSM]

I've never done a compression test before so I'm hoping that I didn't do it correctly. I read up on it and followed the instructions but I don't know.

I might take it some where to be checked out, bothe compression and leak down test, or get a local to help me out. I don't think I want to base my decisions on what I did because as I said this was my first time.

I was also leaning towards the 7 bolt side because I won't have much time to have it down because it is my daily driver.

I'll see if I could get it tested again, by someone with experience.

 

[Calan]

The most common mistake that people make when doing a compression test is to use a crappy tester, or to not get the adapter sealed in the spark plug hole. Any decent tester (even a $20 one from Walmart), will have a couple different adapters with o-rings on them for sealing.

Match one of your spark plug's threads up with the adapters until you find the right one, and then screw it into the plug hole. If the cylinder plug holes are clean and have good threads, and the tester's adapter has a good o-ring...you can usually tighten the hose/adapter by hand enough to seal. (I can't really remember the last time I had to tighten a compression tester into a plug hole with anything other than my hand and just twisting the hose). Using a little clean oil on the adapter threads and o-ring can help too.

It just takes doing it once or twice. As soon as you "get" it, it's a piece of cake and quickly becomes second nature. You'll know immediately if the numbers make sense or if you did something wrong.

 

[iBoostDSM]

Thanks for the help and advice. I'll get it tested out again and then run it till it blows I guess or I feel it's super messed up.

 

[Calan]

Well... get it tested. If it needs to be rebuilt, then cross that bridge when you get there.

 

[dsmornothing]

^^ I'll try that out. Still need to know if unplugging my coil pack would change the results. If not it's 6 bolt time.

Well if you drive a 98 and swap to a 6 bolt you deserve a kick in the gonads.

 

[j_biggz]

very informative post. Thanks guys