compression test results

[nazthug]

well did a thourough compression test today and got these results:

with 5 cranks, fuel pump off, gas pedal down, fresh battery, i got:

170,150,168,168

I added oil into cyl 3 and got up to almost 180

So...now im a bit worried. Seems like cyl 3 is taking the most beating and the piston rings are wearing????

What should i do and how worried should i be?

Should i be worried about boosting up my new t3/04b and running it hard? Its tuned fairly safe now, a/f in the high 10's, no knock on the dsmlink, car runs pretty strong...

also, can i just replace the piston ring on cyl #3?

See, i have a 99gst and supposedly they are less prone to crankwalk and i think the engine otherwise is in good shape and if i rebuild it, i want to probably use the same block and just build it as a 7bolt

Are piston rings something you can just change or what?

Is there any additive i can run to help the piston rings out?

 

[DSMeclipse4G63]

do a leak down test, youll find the 150 to have a higher leak then the others. how many miles are on the motor, as that may affect the compression with carbon deposites. the 150 cylinder may really have alot less compression and only due to carbon deposties on the cylinder its up to that. yes you could JUST replace the rings on one cylinder, but that like replacing half the suspension, why not do it all and do it right while your at it. the little extra time and money will be worth the peace of mind....

 

[gixrman]

A leakdown test is your best bet at finding the real problem, it could be a burnt valve, failing head gasket. #3 cylinder is were the HG usually goes.

 

[aero_sallee]

I agree he should still do a leakdown test. But adding oil already points mostly to the rings. Oil would not help any other part of the cylinder seal much better.

 

[nazthug]

yeah i figured leak down test is only if the oil test fails

the engine has almost 80,000 miles on it, 20,000 of which have been with a non stock turbo and tuning

but adding a drop of oil to #3 brought it up to 180!!! which is over new specs, so i figured if it seals it that well, there is no leak anywhere else

Changing a ring vs doing a full bottom end rebuild is a huge difference to me, and i cant afford that now, but i do have mechanics class in college im taking and we are working on rebuilding engines(just spare blocks we are rebuilding around the shop) and i could probably do it there(hell, i can rebuild the engine there, but i rather have someone else do it)

What is involved in changing the rings? DO i have to still hone the block or can i get away with just pulling the rod, piston, changing the rings, and throwing it back in?

 

[Batty200]

I would just run it as is and save up and build a 6bolt in the meantime. I know I ran a low compression motor for months at high boost and still had a descent running car.

Later

 

[nazthug]

how bad is 150 in one cylinder? And is there anything i can do to prolong the engine life?

I rather not do a full 6 bolt anytime soon, if i build it, again, i rather build this 7bolt, since its 99, it shouldnt have problems with crankwalk, and its a strong engine and its easier for me to build it since i already have it and i dont have to do any mods to run a 6 bolt, it still has to pass smog as well, im in california

so back to my question, can i just change the rings for some new oem piston rings without any block work?

 

[rsunahar]

how bad is 150 in one cylinder? And is there anything i can do to prolong the engine life?

I rather not do a full 6 bolt anytime soon, if i build it, again, i rather build this 7bolt, since its 99, it shouldnt have problems with crankwalk, and its a strong engine and its easier for me to build it since i already have it and i dont have to do any mods to run a 6 bolt, it still has to pass smog as well, im in california

so back to my question, can i just change the rings for some new oem piston rings without any block work?

it's the juxtaposition that you have to look at.

150 in one cylinder is still actually not too bad. I'm running about that, but then again, I have a 1g 7bolt with 7.8:1 compression.

You can definitely re-ring with engine in car. It's a lot of work, and the results would be iffy, but I've seen it done successfully. The most important point is to be as meticulous as possible. You'd have to pull the head and the oil pan. Unbolt the rod bolts etc...shove piston through top of motor after sanding the ridge down if there is any. Tape up the crank journals, and either hone the cylinders or sandpaper them slightly.

Rering the piston, tape up the rod ends and shove the piston through...

Most people will tell you to do just pull the block and take it a machine shop and do it right the first time, but I can understand having no downtime and such.
Not everyone has a spare block to build or a spare car to drive.
This can be done with help in a weekend and will probably last a year or two or maybe even longer depending on how meticulous you are with the ghettoness

In the meantime, you can search for a 6bolt short block to build.
That's an option....


But this type of fix won't last nearly as long as a properly machined, balanced and built long block.
But all of that depends on time and money.

 

[BlackHalo]

well did a thourough compression test today and got these results:

with 5 cranks, fuel pump off, gas pedal down, fresh battery, i got:

170,150,168,168

I added oil into cyl 3 and got up to almost 180

So...now im a bit worried. Seems like cyl 3 is taking the most beating and the piston rings are wearing????

What should i do and how worried should i be?

Should i be worried about boosting up my new t3/04b and running it hard? Its tuned fairly safe now, a/f in the high 10's, no knock on the dsmlink, car runs pretty strong...

also, can i just replace the piston ring on cyl #3?

See, i have a 99gst and supposedly they are less prone to crankwalk and i think the engine otherwise is in good shape and if i rebuild it, i want to probably use the same block and just build it as a 7bolt

Are piston rings something you can just change or what?

Is there any additive i can run to help the piston rings out?

Just run the new turbo and forget about it... The motor is just old and look for a 6bolt in the mean time. If the car runs fine i wouldnt worry about it and would just drive it until it decides to give up.

 

[gixrman]

but adding a drop of oil to #3 brought it up to 180!!! which is over new specs, so i figured if it seals it that well, there is no leak anywhere else

are you serious, one drop? I would do the compression test again I don't see how ONE DROP would seal the rings. Might be ripping your motor apart for nothing.

 

[nazthug]

sorry, by a drop , i meant 1/2 capful of oil, not huge amount, but definetly more then a drop,

I was just surprised since i see all these guys running their 1g stock engines, with 150K+ miles, with mods and still running strong

My car is only 5 years old, almost 80,000 miles and 60,000 of those were stock


Oh well, i have a machine shop 2 days a week, 3 hours each, i might do something in there

meantime, where can i get a decent BARE 6bolt block to start at least machining in my class

Whats the best way of finding a good 6 bolt bare block, i can do alot of hte work in class, i have a whole semester

Also, who can list of the parts i need to purchase to do the swap because its going in a 2g

 

[95GSXBLUR]

six bolt block are all over... people on this site have them in quanity.

I have a block, with pistons and crank it iit, that's it... PM me if you want it. we'll work something out.

 

[1fast97gsx]

just rering it ... it'll cost you $300 if you do it yourself for everything. ( and for gods sake do all 4 cylinders while you're in there! )

 

[Defiant]

well did a thourough compression test today and got these results:

with 5 cranks, fuel pump off, gas pedal down, fresh battery, i got:

170,150,168,168

I added oil into cyl 3 and got up to almost 180

Yeh. You're fine.

What should i do and how worried should i be?

Drive it, and none.

Should i be worried about boosting up my new t3/04b and running it hard?

Well, yeah. But you should have been worried about that before it got installed. Not much point in it now.

also, can i just replace the piston ring on cyl #3?

We'll pretend you didn't just ask that question.

See, i have a 99gst and supposedly they are less prone to crankwalk and i think the engine otherwise is in good shape and if i rebuild it, i want to probably use the same block and just build it as a 7bolt

How about you worry about crankwalk if you ever get it?

Are piston rings something you can just change or what?

Yeah, you can do a ring-and-valve, or top-end rebuild (do they teach you anything in that college class?

Is there any additive i can run to help the piston rings out?

There are no mechanics in cans nor bottles. And you don't need one even if there were.