Piston trouble...

JoeOffRoad · 01-29-2007, 09:04 PM

Okay.. Im in the process of trying to figure out what did this:

The number 2 and 3 have the same little in-dent in them... not cracked or broken.. almost looks molded that way... the rings arnt broken either!??!?!

The head looks great... To get it running would be about 150.

Im now debating weither to just replace the 2 pistons and run it till it drops.. OR yank and rebuild... OR ??

Total investment so far 7.50 (actual $$) IN THE ENTIRE RIG!

what do you guys think? It is a HO engine, 5spd... It needs some love.

What I started with:

(only pre-purchase photo)

today so far...

jmundale · 01-29-2007, 09:08 PM

if it were me id just get it running and have a ball... as a matter of fact there is this SWEET video of these kids and an old xj....

**kg4kzv** · 01-29-2007, 09:33 PM

Are those dents from wrong spark plugs? Was the engine running before you took the head off if so did it show any signs of a bent rod? Does the dent get into the rings or is the any signs that the dent is causing any interference to the cyl. Wall. Lastly is there any cracking on the piston. You know which answer is right for each ? If all looks good then sling that puppy back together and have fun.

If something looks wrong to you chances are your right and then rethink your plans.

Good luck.

Chris

Rock Kustoms · 01-29-2007, 09:44 PM

no... dont put it back together, replace the pistons.....

looks like detenation issues

**alexrule123** · 01-29-2007, 09:44 PM

time for a stroker?

xj 98/yj 94 · 01-29-2007, 09:51 PM

Stroke It!

JoeOffRoad · 01-29-2007, 10:24 PM

stroking uses a 258 crank??

AZ Jeff · 01-30-2007, 09:47 AM

Quote:

Originally Posted by tealcherokee

no... dont put it back together, replace the pistons.....

looks like detenation issues

Agreed. It looks like spark knock damage to those two pistons. YOu can see the top of the first piston ring on at least one of the pistons in the photos.

Replace the pistons, and if you don't, you can expect major engine problems shortly after you button that thing back up.......

bee guz · 01-30-2007, 10:02 AM

Thats quite a gouge in the cyl. wall, I depends how deep it is if it can be honed out, fine if not it wont do rings any good or your compression either.

If you just want to run it till it stops, I wouldn't waste the money on that engine if you are not going to do something with the gouge, you would be better off with another engine. Or some time in a machine shop.

**VDoubleUVR6** · 01-30-2007, 10:07 AM

Quote:

Originally Posted by tealcherokee

no... dont put it back together, replace the pistons.....

looks like detenation issues

Looks similar to a friends VW after he up'ed the boost with a smaller pulley on his G60 swap...

**XJH-007** · 01-30-2007, 10:41 AM

Hmmmmm............deff. spark related but I think it could be one of three things.

First check your plugs, make sure they are of the correct heat range. A plug that's too hot could slowly eat a piston up.

Second, replace your injectors/clean the fuel rail. If the injectors are producing a goofey/lean spray...that could eat your pistons up.

Third, double check your rings, if there's a gap...the excaping exhaust gas could eat your piston up...eventually.

But I tell you what.....I've seen alot of high mileage 4.0's and 4.2's and yours looks cooked. Cylinder walls are in terrible shape, and your pistons should be much cleaner than that (carbon) no matter how many miles you have on the thing. My 258 looked way better then your pics after 280K...and it's carburated.

You're this far in............atleast hone, re-ring and do the valves.......I think you have massive blow-by.

**alexrule123** · 01-30-2007, 11:46 AM

Quote:

Originally Posted by JoeOffRoad

stroking uses a 258 crank??

yes....if you are asking a question

bee guz · 01-30-2007, 12:25 PM

Dont waste you money on that block, unless you plan on haveing the bore cleaned up, if you want to put pistons in that you might as well send me the money, it will do the same thing, you will just be throwing away money.

look for a different motor or have that block cut for new pistons, but if you put that back together your looking for trouble, and you will paying for nothing, even used pistons wont help with that gouge in the wall, if it is just melted piston and not a gouge, you can clean it up...other than that.... well its easy to say get another motor with someone elses money,if it has big miles on it you need new pistons anyway, the ring groves are probaly pretty wobley, have someone look at the block, and check the crank, before you spend any money on it, other wise you loose big time...

Rock Kustoms · 01-30-2007, 04:22 PM

Quote:

Originally Posted by VDoubleUVR6

Looks similar to a friends VW after he up'ed the boost with a smaller pulley on his G60 swap...

that engine was overheated to the point that the heat was detonating the a/f mixture b4 the plug... again preignition is deadly to a motor

Rock Kustoms · 01-30-2007, 04:23 PM

Quote:

Originally Posted by JoeOffRoad

Okay.. Im in the process of trying to figure out what did this:

The number 2 and 3 have the same little in-dent in them... not cracked or broken.. almost looks molded that way... the rings arnt broken either!??!?!

The head looks great... To get it running would be about 150.

Im now debating weither to just replace the 2 pistons and run it till it drops.. OR yank and rebuild... OR ??

Total investment so far 7.50 (actual $$) IN THE ENTIRE RIG!

what do you guys think? It is a HO engine, 5spd... It needs some love.

What I started with:

(only pre-purchase photo)

today so far...

click free

01-29-2007, 10:24 PM	#7
JoeOffRoad Registered User Join Date: Nov 2006 Location: Vancouver, WA Posts: 58 Profile Gallery Classifieds My Jeeps	use.. stroking uses a 258 crank??

01-30-2007, 10:41 AM	#11
XJH-007 I drank what? Join Date: Mar 2005 Location: Morrison, Colorado Posts: 4,674 Profile Gallery Classifieds My Jeeps	Hmmmmm............deff. spark related but I think it could be one of three things. First check your plugs, make sure they are of the correct heat range. A plug that's too hot could slowly eat a piston up. Second, replace your injectors/clean the fuel rail. If the injectors are producing a goofey/lean spray...that could eat your pistons up. Third, double check your rings, if there's a gap...the excaping exhaust gas could eat your piston up...eventually. But I tell you what.....I've seen alot of high mileage 4.0's and 4.2's and yours looks cooked. Cylinder walls are in terrible shape, and your pistons should be much cleaner than that (carbon) no matter how many miles you have on the thing. My 258 looked way better then your pics after 280K...and it's carburated. You're this far in............atleast hone, re-ring and do the valves.......I think you have massive blow-by. __________________ Scott-Crawlorado Native I have an addiction..... 00' XJ_T-n-T Y-Link/6" RE_OME's_33" KM2's Tera 4:1 / 4:56's_Elec. Locked D44 84' CJ7 4"BDS 33's **02 WJ Overland

01-29-2007, 09:44 PM	#4
Rock Kustoms Registered User Join Date: Feb 2005 Location: Wolcott, CT Posts: 3,848 Profile Gallery Classifieds My Jeeps	no... dont put it back together, replace the pistons..... looks like detenation issues

01-30-2007, 10:02 AM	#9
bee guz Registered User Join Date: Jun 2006 Location: wilkes-barre Pa. Posts: 1,117 Profile Gallery Classifieds My Jeeps	Thats quite a gouge in the cyl. wall, I depends how deep it is if it can be honed out, fine if not it wont do rings any good or your compression either. If you just want to run it till it stops, I wouldn't waste the money on that engine if you are not going to do something with the gouge, you would be better off with another engine. Or some time in a machine shop.

01-30-2007, 12:25 PM	#13
bee guz Registered User Join Date: Jun 2006 Location: wilkes-barre Pa. Posts: 1,117 Profile Gallery Classifieds My Jeeps	Dont waste you money on that block, unless you plan on haveing the bore cleaned up, if you want to put pistons in that you might as well send me the money, it will do the same thing, you will just be throwing away money. look for a different motor or have that block cut for new pistons, but if you put that back together your looking for trouble, and you will paying for nothing, even used pistons wont help with that gouge in the wall, if it is just melted piston and not a gouge, you can clean it up...other than that.... well its easy to say get another motor with someone elses money,if it has big miles on it you need new pistons anyway, the ring groves are probaly pretty wobley, have someone look at the block, and check the crank, before you spend any money on it, other wise you loose big time...