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L20 motor dissasembly method


Curt

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Hello all you knowledgeable folks. I picked up an 80 excab 720 with a L20b/w58 head (looks original) that I want to rebuild for my 620.

This will be my first motor disassemble and I'm looking for some pointers. Like things to disassemble while still connected to the trans or little tricks to get things apart. A link to a guide or something would be awesome if there are any.

 

I was dreaming of doing the 2.3 "big bore" but after reading about it( I would need another block n pistons) I think a more stock rebuild would be better for my first motor rebuild.

So, my second question is the usual, what bang for buck should I look into for the bottom end. I would like to do side drafts, port n polish and a cam eventually.

I want it to be street-able as we will be driving it to work and what not. Hardly any traffic where we live so it can be on the "more fun" side of things but nothing crazy.

My 620 already has the low rear end and a 5 speed 720 trans.

Thanks folks, I hope this is enough info here and written well enough.

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Trick one is to loosen the crank pulley bolt before removing the engine (trans in gear, parking brake set).  Almost necessary if you don't have an impact wrench.

 

Trick #2:  Buy a 12mm universal (swivel) socket.  It makes getting the manifold nuts out much easier (particularly the lower inner ones).

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Dr. Feltersnach, It is more about me wanting to disassemble/assemble a motor. I grew up handing wrenches for race cars and hot rods but never had the chance/took the time to build one myself. I've seen a dozen or more motor rebuilds growing up and now I have the time and space to be able to try one out myself.

 

Datsunaholic, thanks a ton. That is exactly the stuff I'm talking about.

 

Things I have in stock so far. Stock L18(in truck), Stock L20b(in donor truck), Weber 32/36. I could probably gather the parts for the 2.3 but I'm kinda intimidated doing it as my first motor.

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Not a crazy amount. What does a typical rebuild end up costing?

I'd like to stick with rebuilding the L20b. I have no idea if it runs. It was sitting for 4 years. I could hear crustys in the lower rad tube when I squeezed it so I'm amusing it is bone dry. It had been sitting in a neighbors yard and I got it for almost nothing so I took the risk in buying a non running motor.

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STOP!!!!!!

 

 

Pull the dipstick.  Is there oil on it?  if so, put dipstick back in.

Can you turn the engine with wrench on the crank pulley, if so go on to next step.

Hook up a good battery to the starter, and try to crank it.  If it cranks, listen to it.  Does it spin freely, or is does it have a rhythmic sound, as each piston comes up on compression?  If it has a nice rhythmic sound, do a compression test.  

If above 140 to 150 on all four, hook up ignition, and pour a little gas in the carb throat, see if it fires.

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Well, i opened the valve cover to find the rustiest shit ever so i decided not to fire it and to just start disassembling it. Pulled the head and there is rust in the cylinders and some pitting on the walls and the rings are seized up too. Soaked it for a couple days with PB. Rocked the shit out of it in gear to try and free it up but nothin...

Should I even pull the motor out to examine the bottom end further? Or scrap it altogether and find a "running" bottom end.

I do have a set of nos L20b pistons that are .75 larger (.o30) so my hope was it would bore out. The pistons are stock so its stock bore now.

I'm kinda stuck at this point mentally about this project and what path to take.

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STOP!!!!!!

 

 

Pull the dipstick.  Is there oil on it?  if so, put dipstick back in.

Can you turn the engine with wrench on the crank pulley, if so go on to next step.

Hook up a good battery to the starter, and try to crank it.  If it cranks, listen to it.  Does it spin freely, or is does it have a rhythmic sound, as each piston comes up on compression?  If it has a nice rhythmic sound, do a compression test.  

If above 140 to 150 on all four, hook up ignition, and pour a little gas in the carb throat, see if it fires.

Great advice. I never tear into something without seeing how (or if) it runs first.

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L20s come up cheap sometimes . I got mine free a guy was going to throw it away.

 

key is ck for cracks in the L29 in the center where the water passage is. alot crack there.

 

 

putting new piston in is the real cut of the machine shop/ when all said and done its going to be a 1500 motor.

 

but you can wait it out and find a running L20 for Free to 150-300. as most need cash fash cause thy want to put that KA/SR in their car FAST(5yrs later might be done)

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I checked out the cylinders pretty well so far. No cracks that I can see in the top half of the 2 and 3 cylinder or water passages. The only reason I've kept at this seized motor is the block looks pretty decent so far. I've kept an eye out here for an l20b for the last year or so but they usually look hammered upon or rebuilt by turkeys. I think I've seen two in the last year for sale. I expected to spend money on the rebuild. If the block is toast when I get it checked I may just rebuild the L18 that is in it, since that would ultimately be the cheapest quickest route.

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The crack Hainz is referring to is usually on either side of the center head bolt hole. It is usually very faint and hard to see. Clean the deck good, and don't use power tools for this. I hate seeing people use those Roloc discs to clean gasket surfaces... Use a block and light sandpaper (after cleaning off the old gasket) and the crack should show up, if it's there.

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It does have a bit of rust near there in the cooling hole location. Anyone have a picture of said crack? lol. Or!... Is someone willing to point the area out with a pic? If I didn't notice anything obvious I was gonna have it checked out.

I pulled it out today and that went quite smooth, way easier than I thought it would be.

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