Jeep Engines - Oljeep

l- -1‘1136 MOPAR PERFORMANCE PARTSFirst, we strongly recommend that the engine builder readcompletely this chapter before any engine work is started.Before the engine is assembled, all the basic parts (block,crankshaft, head, etc.) should be cleaned, and then cleanedagain! The bearing clearances should be checked withPlastigauge (P42868 19) or micrometers (inside and outside).Before reassembling, gather all the chemical productslikely to be needed such as RTV, Loctite, etc. If any partsare to be stored after they are machined and/or cleaned,they should be sprayed with a rust preventive, wrapped innewspaper and covered with plastic bags.When the camshaft and lifters are installed, a camshaftbreak-in oil should be used on the camshaft lobes andjournals and the outside of the lifters. The camshaft breakinoil should come with the camshaft kit. If you needcamshaft break-in oil, order Lubrizol.Before totally disassembling the block, check the deckheight of the pistons. Deck height is the distance from thetop of the piston to the top of the deck surface of the block.This is an important dimension since it has a direct influenceon compression ratio. If the piston is a flat-top type, it willusually be below the deck and this is the distance that mustbe measured. A domed piston will stick up above the decksurface and the distance is measured from the deck to theflat of the piston, not the top of the dome. Mark this figuredown for future reference and completely disassemble theblock. On a new block, wait until the block is bored to sizebefore measuring the deck height.When all machine operations are complete, the blockshould be thoroughly washed out with solvent. Use bottlebrushes of suitable size to clean out all bolt holes, oilpassages, etc. Finish off with another thorough washing,using a good, common detergent and warm water. Blow orwipe dry and oil to prevent rust. Engine parts can’t be tooclean. Many early engine failures can be traced to dirt orforeign objects (metal chips, etc.) that were left in theengine when it was reassembled.MAIN CAPSHardened Washer SetsFor use with head bolts and main cap bolts.P4 120456P4 120457P4 1204S8Comprised of: (20) - 3/8” washers.Comprised of (20) - 711 6” washersComprised of: (20) - 1/2” washers.Let’s assume your main caps are O.K. and you have themall. We’ll also assume that you are building a race or highoutput engine. The problem with main caps is that they aretoo simple. If they look like the right caps and we haveenough, then we’ll probably use them even if they aren’tfrorn this particular block. We have already stepped overthe line in this last sentence. We’ll explain shortly.You1 may be asking, “If my caps aren’t broken and I haveenough, why should I change?‘’ or, “Why should I install newcaps?’ These two questions are not the same! First, rememberthat if the main caps are changed, then the block MUST bealign-bored. Always! If you are building a race engine, youalso MUST align-bore the engine. (The only exception is ifthe engine was align-bored on its last rebuild, then it shouldbe alright.) Remember our “over-the-line” sentence regardingusing caps that weren’t from our particular block? In this casewe must also align-bore the block.Remember that a weak cap doesn’t necessarily fail itself.An engine failure will more likely occur with the bearings,crankshaft, bolts, or even the bulkhead. A cap failure wouldonly occur in the most extreme cases. But it does occur.You’d like to find it when you are routinely checking thebearings, but you don’t always get that lucky!Note: It is recommended that new main cap bolts alwaysbe used (if possible) when rebuilding an engine.FREEZE PLUGSEvery block used in production uses freeze plugs. They arepressed into the sides and ends of the block. If they do theirjob correctly, you will probably never know they are there.If they fail, things can go wrong very quickly.If you are building a race engine, it is highly recommendedthat the block be thoroughly cleaned before you start. Toclean a block thoroughly, you need to remove the freezeplugs. If you have the block hot-tanked, then the freezeplugs MUST be replaced because they have lost their“press” and will fall out as soon as there is any pressure inth8e water jacket.Freeze plugs can’t be re-used, so once you take them out,you need a new set.We all know an engine must have a set of main caps tofunction. If you have a used engine block, it probably hasits own main caps, but some blocks may have broken or lostcaps. Main caps should be replaced in sets. Most usedengine blocks should have the mains align bored before theengine is assembled into a “race” engine.