Short Block Assembly

 

   The "short block" refers to everything contained in, and including the engine case (crank, rods, cam, lifters, etc).  Before you start the assembly you should have your case fully inspected and align bored if necessary, your crank, rods, cam & lifters inspected and re-ground or re-built as necessary.

   The first thing I do is to test check ALL the bearing clearances with Plastigage.   

CAUTION - Never touch bearing surfaces with your bare hands.  Oils on your hands will begin the corrosion process and shorten their life.

    Once you've made any adjustments on the bearings, it's time to assemble the cam and distributor drive gears onto the crankshaft. 

   Once you've gotten the crankshaft assembled, it's time to hang the rods on the crankshaft.  I always use liberal amounts of assembly lube on ALL wear surfaces.  You can also use motor oil to pre-lube all surfaces.  The rods must be assembled with the forge mark facing UP.  Be sure the numbers on the rod caps are on the same side of the rod as the number on the rod it's self.   These number MUST match too.    Prior to putting on the nuts, they should be peened to ensure they don't come loose.  After you've gotten them all on, torque them to the proper torque.  DO NOT exceed this specified torque.  It's NOT BETTER to "give it a little more" because you will be exceeding the capability of the threaded bolt.  Too much torque and bolts tend to stretch and/or break.  

     Now you can install the the all the little dowel pins into the main bearing saddles.  If you have a few extra dowel pins, try and use the tightest fitting ones.  You don't want loose pins holding your bearings in place!!  Here's a photo of my assortment of pins (with a standard 8 X 13mm nut for size perspective).

dowel-pins.jpg (32060 bytes)

    Next install the split #2 main bearings into their respective saddles and apply assembly lube or oil to the wear surfaces.  Now you need to apply assembly lube to the thrust bearing and the crank's thrust bearing surface and carefully slide it into place.  Note which side the dowel pin hole is on and ensure it is in the correct location for assembly.  Now you are almost ready to install the crankshaft assembly into your fresh case.

     At this point it's good to have an engine stand to bolt your engine case half to.  If you don't (like me), you can do what I do and install the bottom 4 cylinder studs into the case and tip it over on it's side.  This gives you plenty of angle to keep things from falling out while ensuring your rods don't hit the work bench.

    Grab the rods for pistons #1 & #2 and carefully lower the crank into place.  When the crank is resting in the bearing saddles, you must now carefully rotate the three bearings and line up the dowel pin pockets with the dowel pins in the case.  This may seem easy, but it can prove frustrating at times.  One way I have found to keep the frustration down to a minimum, is to pre-mark all the bearings by using a marking pen where they sit once they are fully seated with the dowel pins.  If you use this method, it's more or less a matter of lining up the lines on the underside of the bearings and watching it fall into place.   You can often just feel the bearing lock onto the dowel pin.  once you feel them all drop into place, apply even pressure on both ends of the crank and seat the bearings in the saddles.  If it doesn't seat properly, you still have a bearing out of place.  Find it and correct the problem before going any further.  Below is a photo of a properly seated thrust bearing.

thrust-bearing-seated.jpg (59985 bytes)

    Now you're ready to install the lifters and cam.  I apply assembly lube to the lifter bores as well as the lifters.  Slide them into their bores (all 8 of them).  You should also apply assembly lube to ALL the cam's wear surfaces INCLUDING all four lubes.  Since you already checked the thrust clearances and modified your case for double thrust cam bearings (if used), you will now need to locate the two small timing marks on 2 of the crank's cam drive gear teeth and position the marked gear tooth on your cam gear between them as pictured.  Then rotate them together until the cam is properly seated in it's bearings.

cam-gear-timing-marks.jpg (31775 bytes)

    Now it's time to install the distributor drive gear and washers.  Ensure that you have 2 (TWO) washers (as pictured) under the pinion prior to installing.  This can be done AFTER the engine is assembled, but you really need a special drive puller tool which most folks don't have (including myself), so I advise doing it now.  With the #1 rod in firing position, the slot in the end of the drive pinion should be in this position:

dist-drive-washers2.jpg (36567 bytes)             dist-drive-position.jpg (18814 bytes)

    Now you need to dig into that new engine gasket set and pull out the 6 large rubber "o-rings" and slide one down each of the large case half studs.  It's also a good idea to lubricate these with some motor oil prior to installing them to ensure they don't end up rolled when they are slid down the main bearing case studs.  You should now almost be ready to assemble the two halves of the engine case.  Before you do, you will need to apply a sealant to the case halves.  I prefer to use the liquid Permatex type.  I can't remember the number for sure (I think it's 3B??).  But since I'm here in Central CA, I can't seem to locate any.  So for this engine I used Permatex 2B which is basically a thicker version of the previously mentioned stuff.  The key to finding a good sealer for the case halves, is to get a NON-HARDENING sealant.  Other recommended sealants are Loctite 518 and Yamaha's "Yama-bond".  DO NOT USE RTV TYPE SEALANTS.  There are lots of great uses for RTV sealants, but THIS IS NOT ONE OF THEM.  You do not want a chunk of that hardened RTV to someday break free and be sucked into your oil pump where it can be plumbed into an oil galley restricting flow to one of your bearings, do you??  Save that RTV for later.  Below is a photo of one of the two case halves with sealant applied.  Remember, you're not painting a battleship, so just a thin film is all that's required.

case-half-sealant.jpg (46404 bytes)

   Now you're ready to mate the two halves. . . ALMOST!!  DON'T FORGET THE CAM PLUG!!  I always install the plug with the with the flat center toward the outside of the case.  That will protect the plug from the odd chance of wearing on the end of the cam as the engine wears.  

cam-plug.jpg (49941 bytes)

    With that installed in one case half, carefully slide the other half down the large main bearing case studs until the two halves are properly seated.  If you can't get them seated with your hands, chances are that you may have a bearing dowel pin unseated.  That will be a SERIOUS PROBLEM if not corrected now.  So find out what the problem is prior to installing or applying torque to any case bolts!!  You will ruin a bearing or worse if this is the problem. 

   With the case halves properly seated, install the case-half nuts and bolts finger tight. 

   You're almost done now.  It's now time to install the oil pump housing.  You should apply some non-hardening sealant to the back side of the pump housing as well as the same area on the case where these two surfaces come together.  Before installing the pump housing, place the proper paper gasket onto the case.  Now install the pump housing into the case seating it firmly by hand.

    With the pump housing in place, start by torqueing the 8mm stud closest to the thrust beating to 14 ft. lbs.  Then torque the six 15mm nuts to 25 ft. lbs.  Once those are torqued you can then torque the other 13mm nuts to 14ft. lbs.  I usually go over all the nuts again to ensure I didn't miss one.  Again, DO NOT over torque these nuts; especially the 15mm ones.  These provide an exact amount of "crush" to the bearings for that given torque.  More torque could cause excessive and/or premature wear to your crankshaft & camshaft wear surfaces.

   Now you can install the oil pump gears into the pump housing.  Ensure that the drive gear is fitted properly into the detent in the front of the cam (when properly engaged, the gear will drop about 1/8" as it slips into position).  When it's in place, try and give the gears a spin.  If they spin, you're probably using a early style "flat" pump with a later style "dished" cam.  These are NOT compatible because your oil pump will not be driven by the cam.  Once you've determined that everything is in order, place the other paper gasket onto the pump case and install the pump cover.  Again, I use a very thin layer of non-hardening sealant to both areas prior to installation.  Torque those bolts also to 14 ft. lbs.

   Now comes the moment of truth.  Slowly turn the crank by hand.  If everything spins without any binding or making any funny noises, you're done!!  If when you turn the engine, you feel ANY binding whatsoever, you need to tear it all back down or somehow determine what is binding and fix the problem before going any further.

   Now pat yourself on the back because you now have a short block!!  That wasn't as hard as you thought it would be, huh??

CONGRATS!!

 


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