piston rings... Q
- Thread starter DavidT
- Start date
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Machspeed
Former 1991+ owner
You would have to have the pistons all the way out for a ring job. Im not sure if you could get them in and out from the bottom. Id think youd have to take the heads off.
Off Road SHO
Moderator
It's a lot more work, and yes they come out the top, after you remove the head and the rod bolts.
They have to go back in through the top also.
What makes you want to undertake such a daunting task?
Tom
They have to go back in through the top also.
What makes you want to undertake such a daunting task?
Tom
well, assuming THEY are the cause of the lousy compression readings I had...
I am going to add a bit of oil in each s. plug hole and recheck each cylinder.
The sho is no fun to drive unless it is at full running power. If it is, boy is it a blast!
Heres my story (short version):
Got sho at 145K
Dynod at 99 HP
Full 60K, still no better
Replace exhaust... WOW! (had broken up cat blokage) Power gains were enormous.
Over time (about a year) noticed more oil loss (leakage and assumed consumption)... and doesn't seem as FAST as it DID... could be only imagined though.
Back to dyno:160 HP 170 ft.lbs TQ.
10.2 sec @ 69 mph at track. (1/8 mile)
I am wondering if the new found free flowing exhaust has erupted the effects of a blocked exhaust for who knows how long.
Yes, I drove it hard, but not THAT hard.
I have also noticed a loud ticking under the rear valve cover in the past year or so. I am assuming T.C. tensioner. Could that also be a result of blocked exhaust?
I have come to the decision that I either want my sho healthy, or I am selling it.
I am NOT mechanically inclined, but I have another vehicle... I am willing to TRY to fix it... shrug
I am going to add a bit of oil in each s. plug hole and recheck each cylinder.
The sho is no fun to drive unless it is at full running power. If it is, boy is it a blast!
Heres my story (short version):
Got sho at 145K
Dynod at 99 HP
Full 60K, still no better
Replace exhaust... WOW! (had broken up cat blokage) Power gains were enormous.
Over time (about a year) noticed more oil loss (leakage and assumed consumption)... and doesn't seem as FAST as it DID... could be only imagined though.
Back to dyno:160 HP 170 ft.lbs TQ.
10.2 sec @ 69 mph at track. (1/8 mile)
I am wondering if the new found free flowing exhaust has erupted the effects of a blocked exhaust for who knows how long.
Yes, I drove it hard, but not THAT hard.
I have also noticed a loud ticking under the rear valve cover in the past year or so. I am assuming T.C. tensioner. Could that also be a result of blocked exhaust?
I have come to the decision that I either want my sho healthy, or I am selling it.
I am NOT mechanically inclined, but I have another vehicle... I am willing to TRY to fix it... shrug
Ishodu
SHO Member
You are defiantly lacking some power. With the same Y-pipe as you I go 42 more Hp at the wheels. If you are going to spend that much money to replace the rings, then your going to spend alot of $ in gaskets and parts. Why not get another engine? 3.2L? This could be a cheaper route.
<small>[ November 24, 2003, 09:05 PM: Message edited by: Ishodu ]</small>
<small>[ November 24, 2003, 09:05 PM: Message edited by: Ishodu ]</small>
Off Road SHO
Moderator
It WILL be a cheaper route. Re-building these motors is expensive.
Now if you just fix what is broken and reuse everything you possibly can, then you might be able to do it cheaper than another junk yard motor.
Tom
revhardSHO
SHO Member
Time for a new motor if you want full compression back. Im almost sure you sucked that bad cat up into your engine cylinders. Problably damaged the factory bore, scored the cylinder wall, and damaged the piston(s) & rings. hence the low compression readings and low dyno #s. Get your self a used motor of ebay...perhaps even a 3.2L?
IMO its not worth dealing with that.
IMO its not worth dealing with that.
Hack
...............
It was common a long while back (when a lot of Gen 1 cars first began approaching 100K miles) for the cats to break up. Tiny pieces of the catalyst material would then get sucked back up into the combustion chamber. They would then score the cylinder wall creating the condition that you currently have. I think that this problem is not as common as it once was due to so many people upgrading their catalytic converters/y-pipe assembly.
I would agree with what many others are saying. Try to find a low mileage complete engine. It will definately save you some money. Good luck with whatever plan you decide to go with.
93EmeraldMTX
New Member
i was told perfect seal rings are about the best in the buisness. however, i dont know what parts store i can buy them at. anyone know?
keli
New Member
What is the stock compression on an SHO supposed to be?
thanks for all the replies, but in all reality, isn't swapping a motor a 'lil more complex than the avg. Joe can do?
A 3.2 would be a dream though
P.S. A previous owner apparently tried to gut the cats. I assume this due to each cat having "weld spots" on them. The blockage was found at the end of the resonator, near the bends around the gas tank. The size of a baseball. eek!
A 3.2 would be a dream though
P.S. A previous owner apparently tried to gut the cats. I assume this due to each cat having "weld spots" on them. The blockage was found at the end of the resonator, near the bends around the gas tank. The size of a baseball. eek!
Ishodu
SHO Member
If you have the courage to change the piston rings you should have no problem changing a motor.DavidT:
thanks for all the replies, but in all reality, isn't swapping a motor a 'lil more complex than the avg. Joe can do?
A 3.2 would be a dream though
P.S. A previous owner apparently tried to gut the cats. I assume this due to each cat having "weld spots" on them. The blockage was found at the end of the resonator, near the bends around the gas tank. The size of a baseball. eek!
rangerj
Active Member
David T,
It is far more likely that you need a valve job and that poor valve sealing is the cause of your compression problems than poor piston rings.
That having been said, we are all guessing.
You could and should go to a garage that has the equipment to look into your cylinders with a camera and determine the condition of the cylinder walls and the valves.
There is a lot more to an engine "Rebuild" than just throwing a set of rings and bearings in it.
The engine should be pulled, disassembled, and every piece gone over with a micrometer.
Cylinders that are not perfectly round and perfectly straight up and down need to be bored and trued. The crankshaft usually needs to be ground true and rebalanced. Then the rods, wrist pins, and pistons need to be repaired or replaced.
Before doing any of the above, everything should be magnafluxed for any cracks.
The point here is to do some diagnostics and determine what the problems are. Then determine which is the most economically feasable thing to do -repair, replace, or rebuild.
Just some food for thought! rangerj
It is far more likely that you need a valve job and that poor valve sealing is the cause of your compression problems than poor piston rings.
That having been said, we are all guessing.
You could and should go to a garage that has the equipment to look into your cylinders with a camera and determine the condition of the cylinder walls and the valves.
There is a lot more to an engine "Rebuild" than just throwing a set of rings and bearings in it.
The engine should be pulled, disassembled, and every piece gone over with a micrometer.
Cylinders that are not perfectly round and perfectly straight up and down need to be bored and trued. The crankshaft usually needs to be ground true and rebalanced. Then the rods, wrist pins, and pistons need to be repaired or replaced.
Before doing any of the above, everything should be magnafluxed for any cracks.
The point here is to do some diagnostics and determine what the problems are. Then determine which is the most economically feasable thing to do -repair, replace, or rebuild.
Just some food for thought! rangerj
Off Road SHO
Moderator
I'm not advising you to do a motor rebuild in any way, but there is an easy way to determine whether your low compression is from valves or rings.
Pick one of the low compression cylinders on the front bank (the easy ones to do). Squirt about a teaspoon of clean motor oil into the spark plug hole and re-attach your compression tester.
( Assuming you have all of the rest of the spark plugs out) crank over the engine for 6-10 revolutions.
If the compressions comes up alot higher than it was before the oil, it is bad ring seal on the cylinders.
If the compression does not come up at all, you have a bad valve seal.
Oil will temporarily help to seal bad rings but not bad valves.
Judging from your prior information, I'm guessing bad rings.
Tom
PS Just get another motor that was compression tested by the junk yard before removal and comes with a garanty (sp?).
Tom
<small>[ November 26, 2003, 09:52 AM: Message edited by: Off Road SHO ]</small>
Pick one of the low compression cylinders on the front bank (the easy ones to do). Squirt about a teaspoon of clean motor oil into the spark plug hole and re-attach your compression tester.
( Assuming you have all of the rest of the spark plugs out) crank over the engine for 6-10 revolutions.
If the compressions comes up alot higher than it was before the oil, it is bad ring seal on the cylinders.
If the compression does not come up at all, you have a bad valve seal.
Oil will temporarily help to seal bad rings but not bad valves.
Judging from your prior information, I'm guessing bad rings.
Tom
PS Just get another motor that was compression tested by the junk yard before removal and comes with a garanty (sp?).
Tom
<small>[ November 26, 2003, 09:52 AM: Message edited by: Off Road SHO ]</small>
MGidish
SHO Member
Question about the cats. Is there still a need to worry about the ceramic getting sucked back up with an aftermarket y-pipe. I have been getting some rattling lately which is making me wonder about the cats.
rangerj
Active Member
OFF ROAD SHO is absolutely right. Any time a compression test is done any, or all, cylinders that come up with low compression readings should be retested as Tom describes.
This will tell you if the rings are worn out, or if the valves are not sealing. It is part of doing the diagnostics. Good catch Tom.
As for the rattle in the cats, why risk further problems. Pull the cats and see if the guts fall out. If it does, replace the cats! rangerj
This will tell you if the rings are worn out, or if the valves are not sealing. It is part of doing the diagnostics. Good catch Tom.
As for the rattle in the cats, why risk further problems. Pull the cats and see if the guts fall out. If it does, replace the cats! rangerj
SHOguy 92
New Member
About how Tom described the compression test. What if its bad valve guides? Will it also come up with no compression then also?
Off Road SHO
Moderator
No, bad valve guides will just give you smoke from sucking oil into the combustion chamber or blowing cylinder gasses into your oil pan. The valve guides are not in the compression area, just the valve seats and piston rings.
Tom
Tom
SHOguy 92
New Member
Oopises, Well How would I check if my valve guides or valve seals are whats causing the burning of oil? The car just feels weak it has sense I got it 125mph is about tops for it, it already leaks oil and sometimes I see blue smoke.
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