I knocked the top of my piston off! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

pritch · 06-25-2006, 12:52 AM

I was driving down the freeway today and all of a sudden comes a strange vibration and a general decrease in power. I was still a few miles from the house, and I figured the damage was done, so I limped home and into the shop. The motor sounded real bad, but a noise I hadn't really heard before, coming from either #3 or #4 (straight 6). I pulled out #3 spark plug and checked compression, and it was fine, so I checked #4-and ZERO! I stuck a drink straw in the plug hole and cranked it over-no movement detected. I really thought I threw a rod, but there is no water in the oil, and no hole in the side of the block, so I pulled the head and this is what I found:

I guess I'll pull the bottom end out tomorrow and see what all happenned. I only found half of the lower compression ring, and none of the oil ring so I guess they are down in the oil pan.
Bummer.

TugOwar · 06-25-2006, 12:57 AM

how the hell?

jrb71c20 · 06-25-2006, 01:01 AM

how the hell?

Thats exactly what I'm wondering??? It pratically grenaded

pritch · 06-25-2006, 01:05 AM

Yeah-I've blown up lots of motors but never had one do this. From what I can see of the cyl. wall, it looks OK. No visible damage to the head, but I have a different one I wanted to put on anyways. I'll know more in the morning.

Fred T · 06-25-2006, 01:28 AM

Probably had a crack in the top when it was cast. It's not uncommon in older engines. With enough stress from combustion, the crack finally grew until the piston failed.

RSRXION · 06-25-2006, 09:15 AM

It didn't drop a valve ??!?!?!?!?!? I've seen that kind of damage from valve train failure but I don't think I've ever seen anyone pull a piston in two. Were they cast or forged ? I suspect the manufacturer of those pistons would probably like to see it for evaluation. You might send them a note and some photos. If I'd made it, I'd want to know why it failed. Smells like a good opportunity to slide a big block in there ! JMHO, Dean

**Palf70Step** · 06-25-2006, 09:38 AM

I had a 280Z in Japan do the same thing, but I knew what caused it....water got sucked up through the tailpipe and the cold water hot engine went boom. Hopefully you can still reuse the block. On my z it damaged the walls to bad to correct.

*hoser* · 06-25-2006, 09:58 AM

New or used pistons?

OEM pistons?

How many miles?

Sux that it happen I hope its a easy fix...

If it were my engine I would replace the rest of the pistons.

FRENCHBLUE72 · 06-25-2006, 10:25 AM

Wow thats one for the hey guys look what I blew up wall..

TugOwar · 06-25-2006, 11:58 AM

Quote:

Originally Posted by FRENCHBLUE72

Wow thats one for the hey guys look what I blew up wall..

lol, yup. That would have it's very own display case on the shop wall, lighted even! hehe

pritch · 06-25-2006, 01:30 PM

Well I got that rod out. I guess I was pretty lucky, the cylinder looks OK. I would be alot more concerned if I had any plans of keeping this motor. I remembered that when I first bought this Panel, it had a broken piston. I think a PO rebuilt it with the cheapest parts he could find. I'll be putting in a 327 when all is said and done. That's what drives me crazy-the big frame off starts this fall, I just wanted to drive it a little bit this summer but I had to put in a new clutch last weekend just to do that. So I'll slap in a new piston and hope it lasts 'till the road salt flys.

PS-I'll go ahead and keep it on the wall of shame along with some others.

Green Machine · 06-25-2006, 03:34 PM

In the first pic, does it look like the balance pad on the rod is twisted or not quite square with the block ? Maybe it is the picture angle, but if the rod was twisted before it might stress the piston, but maybe the twist happened when it broke ?

chevymad · 06-25-2006, 07:04 PM

My brother did that to 6 of the 8 pistons in his 327 impala. There were full ring sets laying in the bottom of the pan, unbroken. No block damage. As with yours the lower portion of the piston held the rod so it didnt rub the cylinder walls. Hard to believe but this engine actually ran into the garage that way. After taking it all apart, we figured it was the huge cylinder ridge and ton of cylinder taper, along with a kid revving an old engine to the moon, that broke the pistons.

A few years ago we also had a Case diesel tractor do that. Cast iron piston. Piston pin almost wore through the cylinder liner. Was a very weird sounding motor. The rings stayed on the piston top and the rod would "throw" the piston top up against the head. .then fire. The top would come slammin down on the rod again. Didnt even bend any valves. I ended up just replacing the one cylinder sleeve and piston.. I'm sure its very well balanced now.. the new piston is aluminum!

**truckdude239** · 07-01-2006, 04:03 PM

wow never seen that before

phantom dually · 07-01-2006, 04:57 PM

Never saw that happen either!

LUV2XCLR8 · 07-01-2006, 06:16 PM

Ouch, was this before or after the other post?

89 crew · 07-02-2006, 03:37 AM

My brother had a 79 k30 he bought that was rebuilt with imported pistons. 1 piston broke the center of the top, the other 7 when checked had collapsed at least 40 thousandths and up to 120 thousandths. I think his po and yours bought parts from the same place! Oh and to make you feel worse, buying that crap saved $47 for a 400 small block!

grayw0lf · 07-03-2006, 08:31 AM

I burnt the left side off of the #2 piston in my 2.5L, leaving much of it fused to the cylinder wall. But I've never seen the piston seperate.

pritch · 07-03-2006, 11:14 AM

The old machinist I go to said maybe I didn't have enough end gap on the rings and maybe one of them put the squeeze on the top of the piston. That's something I'm always carefull to check when I put a motor together, but who knows. Maybe I missed one.

06-25-2006, 12:52 AM	#1
pritch Registered User Join Date: Mar 2004 Location: Hoytsville, Utah Posts: 3,365	I knocked the top of my piston off! I was driving down the freeway today and all of a sudden comes a strange vibration and a general decrease in power. I was still a few miles from the house, and I figured the damage was done, so I limped home and into the shop. The motor sounded real bad, but a noise I hadn't really heard before, coming from either #3 or #4 (straight 6). I pulled out #3 spark plug and checked compression, and it was fine, so I checked #4-and ZERO! I stuck a drink straw in the plug hole and cranked it over-no movement detected. I really thought I threw a rod, but there is no water in the oil, and no hole in the side of the block, so I pulled the head and this is what I found: I guess I'll pull the bottom end out tomorrow and see what all happenned. I only found half of the lower compression ring, and none of the oil ring so I guess they are down in the oil pan. Bummer. __________________ '68 Panel Project Boogie Chillin' '68 C-10 Ol' Green Last edited by pritch; 06-25-2006 at 12:56 AM.

06-25-2006, 01:28 AM	#5
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: I knocked the top of my piston off! Probably had a crack in the top when it was cast. It's not uncommon in older engines. With enough stress from combustion, the crack finally grew until the piston failed. __________________ Fred There is no such thing as too much cam...just not enough engine.

06-25-2006, 09:15 AM	#6
RSRXION Senior Member Join Date: Jun 2006 Location: Arkansas Posts: 227	Re: I knocked the top of my piston off! It didn't drop a valve ??!?!?!?!?!? I've seen that kind of damage from valve train failure but I don't think I've ever seen anyone pull a piston in two. Were they cast or forged ? I suspect the manufacturer of those pistons would probably like to see it for evaluation. You might send them a note and some photos. If I'd made it, I'd want to know why it failed. Smells like a good opportunity to slide a big block in there ! JMHO, Dean

06-25-2006, 09:38 AM	#7
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,251	Re: I knocked the top of my piston off! I had a 280Z in Japan do the same thing, but I knew what caused it....water got sucked up through the tailpipe and the cold water hot engine went boom. Hopefully you can still reuse the block. On my z it damaged the walls to bad to correct. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

06-25-2006, 09:58 AM	#8
hoser Account Suspended Join Date: Nov 2005 Location: ILLINOIS Posts: 145	Re: I knocked the top of my piston off! New or used pistons? OEM pistons? How many miles? Sux that it happen I hope its a easy fix... If it were my engine I would replace the rest of the pistons.

06-25-2006, 12:57 AM	#2
TugOwar Registered User Join Date: Sep 2004 Location: Pleasanton, TX Posts: 1,723	Re: I knocked the top of my piston off! how the hell?

06-25-2006, 01:01 AM	#3
jrb71c20 Registered User Join Date: Mar 2005 Location: Claremore, OK Posts: 486	Re: I knocked the top of my piston off! how the hell? Thats exactly what I'm wondering??? It pratically grenaded __________________ 93 Sonoma 2.8/5spd 75 Malibu Classic 350/350 If it don't have round headlights and a carb, I don't trust it!

06-25-2006, 01:05 AM	#4
pritch Registered User Join Date: Mar 2004 Location: Hoytsville, Utah Posts: 3,365	Re: I knocked the top of my piston off! Yeah-I've blown up lots of motors but never had one do this. From what I can see of the cyl. wall, it looks OK. No visible damage to the head, but I have a different one I wanted to put on anyways. I'll know more in the morning. __________________ '68 Panel Project Boogie Chillin' '68 C-10 Ol' Green

06-25-2006, 10:25 AM	#9
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,606	Re: I knocked the top of my piston off! Wow thats one for the hey guys look what I blew up wall.. __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

06-25-2006, 01:30 PM	#11
pritch Registered User Join Date: Mar 2004 Location: Hoytsville, Utah Posts: 3,365	Re: I knocked the top of my piston off! Well I got that rod out. I guess I was pretty lucky, the cylinder looks OK. I would be alot more concerned if I had any plans of keeping this motor. I remembered that when I first bought this Panel, it had a broken piston. I think a PO rebuilt it with the cheapest parts he could find. I'll be putting in a 327 when all is said and done. That's what drives me crazy-the big frame off starts this fall, I just wanted to drive it a little bit this summer but I had to put in a new clutch last weekend just to do that. So I'll slap in a new piston and hope it lasts 'till the road salt flys. PS-I'll go ahead and keep it on the wall of shame along with some others. __________________ '68 Panel Project Boogie Chillin' '68 C-10 Ol' Green Last edited by pritch; 06-25-2006 at 01:32 PM.

06-25-2006, 03:34 PM	#12
Green Machine Senior Member Join Date: Jul 2004 Location: Estherville, Iowa Posts: 3,371	Re: I knocked the top of my piston off! In the first pic, does it look like the balance pad on the rod is twisted or not quite square with the block ? Maybe it is the picture angle, but if the rod was twisted before it might stress the piston, but maybe the twist happened when it broke ? __________________ 1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0

06-25-2006, 07:04 PM	#13
chevymad Registered User Join Date: Jan 2001 Location: skamokawa, WA, USA Posts: 527	Re: I knocked the top of my piston off! My brother did that to 6 of the 8 pistons in his 327 impala. There were full ring sets laying in the bottom of the pan, unbroken. No block damage. As with yours the lower portion of the piston held the rod so it didnt rub the cylinder walls. Hard to believe but this engine actually ran into the garage that way. After taking it all apart, we figured it was the huge cylinder ridge and ton of cylinder taper, along with a kid revving an old engine to the moon, that broke the pistons. A few years ago we also had a Case diesel tractor do that. Cast iron piston. Piston pin almost wore through the cylinder liner. Was a very weird sounding motor. The rings stayed on the piston top and the rod would "throw" the piston top up against the head. .then fire. The top would come slammin down on the rod again. Didnt even bend any valves. I ended up just replacing the one cylinder sleeve and piston.. I'm sure its very well balanced now.. the new piston is aluminum! __________________ 70 C10 long fleet, 355/200 4r, 6 lug disc conversion, 3" drop 70 gmc changed to 67/8 chevy, 454 with voodoo cam, th400, all 74 running gear.. in progress

07-01-2006, 04:03 PM	#14
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,238	Re: I knocked the top of my piston off! wow never seen that before __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

07-01-2006, 04:57 PM	#15
phantom dually Project92 SWB stepside Join Date: Feb 2003 Location: Louisville KY Posts: 4,792	Re: I knocked the top of my piston off! Never saw that happen either! __________________ 92 C1500 stepside 496 Stroker Competiton Engineering Ladder bars/QA1 coilovers. Dana 60 rear with 4.10 gear and posi. Bonspeed Palisade 20x12 in rear w/335/30/20 and 20x8.5 front w/245/40/20. 5/8 drop with Belltech springs/DJM spindles/drop shocks. WWS Progress thread http://67-72chevytrucks.com/vboard/s...d.php?t=140448

07-01-2006, 06:16 PM	#16
LUV2XCLR8 The LuvShack Garage Join Date: Jan 2004 Location: Maple Grove, TN (West Side) Posts: 30,468	Re: I knocked the top of my piston off! Ouch, was this before or after the other post? __________________ Owner/Op: "TN Classic Transport Carriers" The Toy: "Square Vette" 72 Hybrid Blazer Toy Barn: "LuvShack" 40 x 60 x 20 Shop Tow Piggy:"Maddy" 88 Silverado 3500 Hauler: "Feathers" 14 Aluma 8218T



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07-02-2006, 03:37 AM	#17
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: I knocked the top of my piston off! My brother had a 79 k30 he bought that was rebuilt with imported pistons. 1 piston broke the center of the top, the other 7 when checked had collapsed at least 40 thousandths and up to 120 thousandths. I think his po and yours bought parts from the same place! Oh and to make you feel worse, buying that crap saved $47 for a 400 small block!

07-03-2006, 08:31 AM	#18
grayw0lf Registered User Join Date: Apr 2004 Location: Clanton, AL Posts: 1,253	Re: I knocked the top of my piston off! I burnt the left side off of the #2 piston in my 2.5L, leaving much of it fused to the cylinder wall. But I've never seen the piston seperate. __________________ 85' CUCV M1009!!! The newest addition! 6.2diesel, Th400, NP208, & only 36k miles! 70' C-10 LWB Fleetside - Looking good these days! 05' Dodge Neon 88' Winner Escape Sport 1750 - 4.3v6 94' Seadoo SP 84' Honda TRX200, bare nekkid. Just a frame & tires. Always looking for another project or any good deal!

07-03-2006, 11:14 AM	#19
pritch Registered User Join Date: Mar 2004 Location: Hoytsville, Utah Posts: 3,365	Re: I knocked the top of my piston off! The old machinist I go to said maybe I didn't have enough end gap on the rings and maybe one of them put the squeeze on the top of the piston. That's something I'm always carefull to check when I put a motor together, but who knows. Maybe I missed one. __________________ '68 Panel Project Boogie Chillin' '68 C-10 Ol' Green

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