Mechanics

JEEP WRANGLER PISTON PROBLEM

1997 Jeep Wrangler • 999,999 miles

Hi I have a question that I bnen trying to figure out for a while when rebuilding an engine when buying pistons and rods I wanna rebuilt my engine and machine my block cylinder walls.10 over I wanna buy new pistons and rods. How do u buy them do what do I ask for? Like the specs do I have to tell them the stroke and pistons exact diameter I want or how?
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Guest
February 7, 2013.




Well you have to take the engine apart first to see if.10 over will be adequate for your pistons. You may have to go larger than that if they are worn out farther or scored. You will have to let a machine shop clean up the bore and then measure it to determine what size piston will be necassary. The rods will be the same thing as will the crank journals. You may have to have them both machined down and measured before you can know what size bearings to [purchase. A short block does not cost too much for a mahcine shop to do and that will solve all your problems. That is my best suggestions. You can bolt on the heads, etc. Without issue as long as the heads are not warped.
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JUST TO ADD A LITTLE MACHINE SHOP JARGON

'ROUND HERE, MANY TIMES THE MACHINE SHOP WILL ORDER THE PARTS FOR YOU----THEY WILL GIVE YOU CHOICES ON THE "BRANDS" AND THEIR EXPERIENCES WITH WHICH ARE THE "BETTER PARTS"

IF YOU ARE USING AN ESTABLISHED SHOP. REMEMBER THEY DO THIS STUFF ALL OF THE TIME. THE CRAP THAT YOUR BUDDY READ OR DISCUSSED WITH THE "MODIFICATION CROWD", MAY NOT APPLY FOR WHAT IS BEST FOR YOUR ENGINE!

SOMETIMES THEY WILL ASSEMBLE YOU A "KIT". BASICALLY THE "WHOLE NINE YARDS". PISTONS THRU GASKETS

AS FAR AS WHAT THEY WILL BE TALKIN'

. THE PISTONS WILL BE FACTORY BORE OR "STANDARD"

THE ONLY WAY YOU GO FROM THERE IS A BIGGER SIZE. LIKE ".010 OVER" (10 OVER) ".020 OVER" (20 0VER) AND SO ON. GENERALLY "060 OVER" (60 OVER) IS THE LIMIT. SOME ENGINES SUCH AS MY 1946 WILLYS L-134 CID MAY GO TO ".080 OVER" (80 OVER)

AS DrCranknWrench SAID, THE SIZE IS DETERMINED BY HOW MUCH "MEAT" THEY MUST REMOVE TO GET A USABLE SURFACE---OR IF DESIRED MAKE THE BORE LARGER FOR THEM RACING KINDA FELLERSAS THE "NORM" THE LESS TAKEN OUT, LEAVES ROOM FOR ANOTHER FUTURE REBUILD WITHOUT SLEEVING OR BUYING ANOTHER BLOCK. KINDA LIKE TURNING YOUR BRAKE ROTORS

AS FOR THE ROD SURFACES AND MAIN SURFACES ON THE CRANKSHAFT---THE SAME APPLIES, TAKE OFF THE LEAST AMOUNT OF "MEAT" TO MAKE THE SURFACE USABLE. EXCEPT THIS TIME WE WORK FROM "STANDARD". DOWNWARDS ".010 UNDER" (10 UNDER) ----(20 UNDER)---(30 UNDER).I THINK YOU GET THE PICTURE!

PISTONS AND BEARINGS ARE NORMALLY SOLD IN SETS----ALL THE SAME SIZE----SO THE MACHINE SHOP WILL BORE OR GRIND EVERYTHING TO THE SIZE OF THE "WORST" CYLINDER OR JOURNAL IN THE BLOCK OR CRANK. THIS KEEPS EVERYTHING SORTA BALANCED OUT AND YOU WON'T HAVE MIS-MATCHED PARTS TO GO BACK IN

IF YOU ARE DOING THE BUILDING---IN MOST CASES THE PISTONS WILL BE INSTALLED "CORRECTLY" ONTO THE RODS BY THE MACHINE SHOP USING A HEATING PROCESS, AS YOU MOST LIKELY DON'T HAVE THE TOOLING TO DO SO (WITH MY WILLYS JEEP, THE WRIST PINS GET SQUEEZED BY BOLTS RUNNING THRU THE ROD, THIS CAN BE DONE "AT THE HOUSE!")

I DON'T KNOW IF IT'S AVAILABLE ON YOUR RIG, WITH MY CJs, I ALWAYS INSTALL A HIGH VOLUME OIL PUMP, WHEN I BUILD, THIS SEEMS TO EXTEND THE LIFE OF MY ENGINES, ALONG WITH A "SERIOUS" MAINTENANCE SCHEDULE!

ANY MORE INFO. JUST KEEP ASKING HERE

THE MEDIC


CJ MEDEVAC
Feb 7, 2013.

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