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Jeep Wrangler YJ
YJ General Discussion
Time to rebuild my 258 /4.2 engine and I'm wondering those of you here who have done it what would you do again what not to bother with?
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<blockquote data-quote="Stoopid Jeep" data-source="post: 434442" data-attributes="member: 20049"><p>I've never built a 4.2 but I have probably built enough motors to weigh in on this.</p><p>First thing is make sure you calculate your <u>compression ratio</u> and <u>quench</u> before you do anything. Quench is one of the most important factors that dictates how your new engine will run. (it is also one the most commonly forgotten). make a plan before you have the block machined and know what thickness head gasket you're going to use.</p><p>You can get by with inexpensive cast pistons, they will run just fine in your application, guaranteed.</p><p>Never cheap out on bearings, timing sets, oil pump, or rings. Buy the best available.</p><p>Same deal with gaskets, stick to Felpro, Mahle, or Mopar. Don't cheap out on gaskets.</p><p>There have been libraries written on cam selection.</p><p>Just make sure you match the cam specs to the compression ratio and the <u><strong>RPM range that you will actually be driving</strong></u>. Nothing worse than driving a motor with too much cam. Ignore the peak numbers and focus on useable power range under 4000 Rip'ems.</p><p>Let's be honest, how much time do we actually spin our motors 6000prms? Personally, my engine has never seen 4500rpms, so any power gains over that point effectively are unuseable, and worse it hurts the low end power.</p><p></p><p>Make a clean organized work space.</p><p>Measure EVERYTHING!</p><p>If you can't measure it yourself, have the machine shop assemble it.</p><p>Have fun, I love building motors.<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite4022" alt=":geek:" title="Geek :geek:" loading="lazy" data-shortname=":geek:" /></p></blockquote><p></p>
[QUOTE="Stoopid Jeep, post: 434442, member: 20049"] I've never built a 4.2 but I have probably built enough motors to weigh in on this. First thing is make sure you calculate your [U]compression ratio[/U] and [U]quench[/U] before you do anything. Quench is one of the most important factors that dictates how your new engine will run. (it is also one the most commonly forgotten). make a plan before you have the block machined and know what thickness head gasket you're going to use. You can get by with inexpensive cast pistons, they will run just fine in your application, guaranteed. Never cheap out on bearings, timing sets, oil pump, or rings. Buy the best available. Same deal with gaskets, stick to Felpro, Mahle, or Mopar. Don't cheap out on gaskets. There have been libraries written on cam selection. Just make sure you match the cam specs to the compression ratio and the [U][B]RPM range that you will actually be driving[/B][/U]. Nothing worse than driving a motor with too much cam. Ignore the peak numbers and focus on useable power range under 4000 Rip'ems. Let's be honest, how much time do we actually spin our motors 6000prms? Personally, my engine has never seen 4500rpms, so any power gains over that point effectively are unuseable, and worse it hurts the low end power. Make a clean organized work space. Measure EVERYTHING! If you can't measure it yourself, have the machine shop assemble it. Have fun, I love building motors.:geek: [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Time to rebuild my 258 /4.2 engine and I'm wondering those of you here who have done it what would you do again what not to bother with?
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