Help , 0 compression in #5
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Seems like you got the green light 
Just because it's new doesn't mean you won't be messin' with it...
Day 2 of ownership (2013 GS, left the dealer with 3 miles on the odometer):
Old console...
New console...
Day 7 of ownership:
Prepping for front splash guards and carbon fiber side skirts
Day 45 of ownership...my own wireless exhaust controller (why spend $100 when you can build your own?)
Last weekend, changed the oil. This weekend I'm changing transmission fluid.
Let her think you'll be bored
Just because it's new doesn't mean you won't be messin' with it...Day 2 of ownership (2013 GS, left the dealer with 3 miles on the odometer):
Old console...
New console...
Day 7 of ownership:
Prepping for front splash guards and carbon fiber side skirts
Day 45 of ownership...my own wireless exhaust controller (why spend $100 when you can build your own?)
Last weekend, changed the oil. This weekend I'm changing transmission fluid.
Let her think you'll be bored
Thread Starter
Pro
Joined: Dec 1999
Posts: 673
Likes: 0
From: Venetia,Pa,USA
Thanks guys. I race this car in NASA ST2. I was always under rules by 40 HP so next year I was planning on ST3 where I'd be closer to the limit. One of my friends I race against in NASA has a new set of heads off the new ZZ4 crate motor he bought. He pulled them and replaced them with a set of modified heads. The heads I've been using are AFRs.
He of course is giving me one of the heads to bolt on and pressure test.
I'm going to be very upset if I find the NEW SHORT BLOCK is bad.
I appreciate all the suggestions. I'll keep posting as things progress.
He of course is giving me one of the heads to bolt on and pressure test.
I'm going to be very upset if I find the NEW SHORT BLOCK is bad.
I appreciate all the suggestions. I'll keep posting as things progress.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Thanks guys. I race this car in NASA ST2. I was always under rules by 40 HP so next year I was planning on ST3 where I'd be closer to the limit. One of my friends I race against in NASA has a new set of heads off the new ZZ4 crate motor he bought. He pulled them and replaced them with a set of modified heads. The heads I've been using are AFRs.
He of course is giving me one of the heads to bolt on and pressure test.
I'm going to be very upset if I find the NEW SHORT BLOCK is bad.
I appreciate all the suggestions. I'll keep posting as things progress.
He of course is giving me one of the heads to bolt on and pressure test.
I'm going to be very upset if I find the NEW SHORT BLOCK is bad.
I appreciate all the suggestions. I'll keep posting as things progress.
Last edited by 96GS#007; Nov 16, 2012 at 03:58 PM. Reason: fix my technical boo boo
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
I wouln't even bother with bolting on a new set of heads. It has to be the piston or no rings. With the valves closed, you have air escaping into the crankase. It has to be going by the piston. Even a bad hone job as suggested will give you some compression. If you get the head off, slip a feeler gauge alongside the piston and see if you hit the top ring. Odds are you won't.
Racer
Joined: Oct 2011
Posts: 312
Likes: 0
From: state of insanity
I wouln't even bother with bolting on a new set of heads. It has to be the piston or no rings. With the valves closed, you have air escaping into the crankase. It has to be going by the piston. Even a bad hone job as suggested will give you some compression. If you get the head off, slip a feeler gauge alongside the piston and see if you hit the top ring. Odds are you won't.
Le Mans Master
Joined: Feb 2005
Posts: 6,485
Likes: 566
From: Clearwater Florida
........... The only way to get a Chevy piston out by pulling the oil pan is if the piston is IN the oil pan ... and if thats the case , you can check its condition by looking thru that big hole in the side of the block ... Sorry , but the head has to come off ................
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
........... The only way to get a Chevy piston out by pulling the oil pan is if the piston is IN the oil pan ... and if thats the case , you can check its condition by looking thru that big hole in the side of the block ... Sorry , but the head has to come off ................
Meant to restate my original post to drop the pan and inspect from below. Piston or ring issues will show up as parts in the pan or scuffing on the cylinder bore. Way easier to do that than pull the heads.Having said that, subsequently the OP says it's an ST2 car. So what's on the engine? If it's an alternator and a ps pump, all the HVAC stuff is cleared out including back by the firewall, easy to remove headers, etc....things start to look a little quicker regarding a head R&R. A pic or two would certainly come in handy but it's far easier to ask for data-free analysis and advice. Just sayin'
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Thread Starter
Pro
Joined: Dec 1999
Posts: 673
Likes: 0
From: Venetia,Pa,USA
Found problem. A missing piece of piston at about 11 oclock. Also it appears that the top ring is also cracked. If anyone is interested in seeing a picture E Mail me at orawiecs33@comcast.net and I'll send it to you. Don't know how to post a picture here.
Safety Car
Joined: Feb 2000
Posts: 4,564
Likes: 110
From: Austin Texas
Found problem. A missing piece of piston at about 11 oclock. Also it appears that the top ring is also cracked. If anyone is interested in seeing a picture E Mail me at orawiecs33@comcast.net and I'll send it to you. Don't know how to post a picture here.
More fun...
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
at 71 ?
hell, he's got over a decade on me and I sit here trying to decide which kidney to sell so I can pay someone else to do what I can't anymore...
I'd say the OP is doing pretty good...
regarding the engine....a mechanics scope would be helpful....a peek in that cyl at the cyl walls might be very informative ! If there is/are broken/missing rings there will be some scratching on the walls.
He can also get some heavy oil in that cyl and try the comp test again...IF the pressure comes up, that indicates a ring/sealing issue. If this changes nothing the problem is heads. Almost a sure thing. Heavy oil...gear oil. Something very thick that will seal temporarily.
I see you figered it out....echo "that sucks.." new engine, new build, worst case. Time to see the engine seller and what they'll do to help make it right.
hell, he's got over a decade on me and I sit here trying to decide which kidney to sell so I can pay someone else to do what I can't anymore...
I'd say the OP is doing pretty good...
regarding the engine....a mechanics scope would be helpful....a peek in that cyl at the cyl walls might be very informative ! If there is/are broken/missing rings there will be some scratching on the walls.
He can also get some heavy oil in that cyl and try the comp test again...IF the pressure comes up, that indicates a ring/sealing issue. If this changes nothing the problem is heads. Almost a sure thing. Heavy oil...gear oil. Something very thick that will seal temporarily.
I see you figered it out....echo "that sucks.." new engine, new build, worst case. Time to see the engine seller and what they'll do to help make it right.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Thats bizzare !
is that from a hot plug? pre-ignition? It does not look broken off, but more like its been burned off. Rings are chrome-moly and take a LOT more heat than aluminum pistons will....I've seen "holed" pistons in semi hemi heads in the middle of a dome or dish but is this where the angled plug is aimed?
wow...sorry for your loss !
is that from a hot plug? pre-ignition? It does not look broken off, but more like its been burned off. Rings are chrome-moly and take a LOT more heat than aluminum pistons will....I've seen "holed" pistons in semi hemi heads in the middle of a dome or dish but is this where the angled plug is aimed?
wow...sorry for your loss !
Last edited by leesvet; Nov 23, 2012 at 02:18 PM.
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
OUCH! That explains why it won't squeeze.
Even then....I am baffled. Never seen anything like that in such a short run time.
Thread Starter
Pro
Joined: Dec 1999
Posts: 673
Likes: 0
From: Venetia,Pa,USA
After my back recovered this morning I checked with a magnifing glass and light and it is indeed melted. The top ring in the area of missing piston is cracked also. The spark plug is almost 180* from the failure.
I'm hoping GM PARTS will cover it under warranty ?????????????
Additional comments appreciated.
I'm hoping GM PARTS will cover it under warranty ?????????????
Additional comments appreciated.
Safety Car
Joined: Feb 2000
Posts: 4,564
Likes: 110
From: Austin Texas
After my back recovered this morning I checked with a magnifing glass and light and it is indeed melted. The top ring in the area of missing piston is cracked also. The spark plug is almost 180* from the failure.
I'm hoping GM PARTS will cover it under warranty ?????????????
Additional comments appreciated.
I'm hoping GM PARTS will cover it under warranty ?????????????
Additional comments appreciated.
I found it was MUCH easier to work on the C4's engines by jacking the front up to a comfy height and removing front wheels. Stand inside wheel well straddling the control arms.
Bending over the tire killed my back
Le Mans Master
Joined: Sep 2005
Posts: 6,551
Likes: 36
From: Jenks OK
Ha, I just start at the tire on the opposite side that I want to work from and lay across the whole thing, yeah leaning across the tire will ruin you fast.