Topic: 93 YJ Newbie Question..Engine Noise...

[tjjohn]

engine noise ahh.   I work in a speed / machine shop and have found that the 2.46 or more common 2.5 is kinda just thrown together from factory, Not good many of the noisy ones have defect pistons in them from the start , mine did .003 smalled than rest so it made a scraping sound until piston skirt broke then it got bad. so punched .030 over and got an master kit from eng pro with teflon coated pistons and molly rings my 2.5 runs smooth no rattel or shakes .   

[erock0010]

did the rebuild/fix improve any of the power...?

[jdarg]

tjjohn is right...sounds like piston slap. I recently "refreshed" my motor with new bearings, cam, lifters, etc. but I didn't do any machine work on the block or heads. It had slap + one lifter ticking really loud before, now it just has the slap. The pistons were slightly out of spec but the bores were still good w/ no ridge at the top at all. I figured if it made it 120K like that already, it will be fine for the conceivable future since it isn't a 70 mile/day DD anymore.

[tjjohn]

Yes! no rattle or slap runs strong better than new.

[tony_dt]

Right on John,

I thought I had lifter noise and then I found an cracked exhaust between 2/3. I kept trying to figure out where the noise was coming from. 

It turned out to be the #2 piston. The skirt broke and broke my motor. I had to replace the block and head.
The motor was perfect exept that #2 piston. The crank and bearings were fine even though around 130,00 mi. The other pistons looked fine. 

Runs fine now with the Banks Header. Gets better gas mileage than when it had 12,000 miles on it.
It is stock other than overbore, air raid, and header. It's again my DD.