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Posted

I have a knock in the engine on the D45.  I was concerned about a bad rod bearing or loose wrist pin.   I picked up a pan gasket at Hershey from OLSONS Gaskets ( great people to work with).  I dropped the pan and checked #1 cylinder wrist pin for tightness and dropped the rod cap and tested with plastigage.  Clearance is just under .004".  surfaces look good on the journal and bearing.  Should I surface grind the cap spacers (.101 Thickness) to reduce the clearance?  What is the acceptable clearance range?  What is a good torque spec for the rod bolts?

 

Also, I removed the oil pump and check the gears.  They show almost no wear and there is only about .001 wear on the bottom plate.  What are the clearance limits on the gears to the bottom plate?

 

Thanks for any assistance.

 

Bob Engle

 

 

 

Posted

The old rule of thumb was .001" per inch of journal diameter.

Posted

Thanks for your responses.  I'll have to take the 1/10" thick shims and mark each for surface grinding to get  the clearances tighter.  Nothing extreme, but .001 to .0025  removal.

 

Bob Engle

Posted

Bob

 

How 'round' is the worn rod bearing hole?

If you file the spacers down, then you will only be reducing the diameter in one direction and might still have .004 wear in the other.

That's a lot for a 2" rod bearing ( i'm guessing here!)

Not familiar with early Buicks but I'm guessing the D45 isn't a pressure fed oil system so it might not be critical like it is with pressure fed bearings.

 

Brad

 

Posted

It is a dipper connecting rod fed oil from troughs in the pan which is gravity fed from the oil pump.  the rest  of the bottom end is splash oiled.  To the best of my knowledge, all cast babbit bearings have their clearances set with shims on the camps.  This controls the clearance in the major load direction.

 

Bob Engle

Posted

I haven't checked the mains yet.  I am still trying to decide what to do with the rod bearings.  All wrist pins are tight and centered in the piston.  I get tempted to pull the pistons just to see what they look like, but I don't know if I want to fool with trying to get them back in the bores from the bottom.

 

Bob 

Posted

I have never found it difficult to insert the pistons from the bottom. Sometimes I used a ring compressor, but I was also able to "wiggle" the pistons in, the taper at the bottom of the bore was enough to compress the rings.

The original thick rings are probably more compliant than if you have newer pistons with the thinner rings.

 

However, if you dont need to pull the pistons you probably shouldnt. Removing shims to get clearances is pretty straight forward.

 

The main lubrication on these engines is a bit problematic in my mind. There is a "trough" with a hole in the upper crankcase that feeds the mains. That trough must be filled by the oil splashing. If the hole gets blocked, the main can starve.

I also find that if my car sits for a very long time, it will knock some until the oil gets everywhere, then it quiets down.

  • Like 1
Posted
3 hours ago, DonMicheletti said:

I have never found it difficult to insert the pistons from the bottom. Sometimes I used a ring compressor, but I was also able to "wiggle" the pistons in, the taper at the bottom of the bore was enough to compress the rings.

The original thick rings are probably more compliant than if you have newer pistons with the thinner rings.

 

However, if you dont need to pull the pistons you probably shouldnt. Removing shims to get clearances is pretty straight forward.

 

The main lubrication on these engines is a bit problematic in my mind. There is a "trough" with a hole in the upper crankcase that feeds the mains. That trough must be filled by the oil splashing. If the hole gets blocked, the main can starve.

I also find that if my car sits for a very long time, it will knock some until the oil gets everywhere, then it quiets down.

 

The buick may have a similar setup to my cad which actually is designed so you can put them in from the bottom, it basically has a taper at the bottom of the bore to compress the rings for you as you push it up. I'm guessing they did that because ring compressors hadn't been invented yet. They go in really easily when the rings are the correct size (and shower you in bits of piston ring if they're not) 

Posted (edited)
On ‎10‎/‎11‎/‎2017 at 11:54 AM, Bob Engle said:

I have a knock in the engine on the D45.  I was concerned about a bad rod bearing or loose wrist pin.   I picked up a pan gasket at Hershey from OLSONS Gaskets ( great people to work with).  I dropped the pan and checked #1 cylinder wrist pin for tightness and dropped the rod cap and tested with plastigage.  Clearance is just under .004".  surfaces look good on the journal and bearing.  Should I surface grind the cap spacers (.101 Thickness) to reduce the clearance?  What is the acceptable clearance range?  What is a good torque spec for the rod bolts?

 

Also, I removed the oil pump and check the gears.  They show almost no wear and there is only about .001 wear on the bottom plate.  What are the clearance limits on the gears to the bottom plate?

 

Thanks for any assistance.

 

Bob Engle

 

 

 

Mr. Tinindian is right, it doesn't make any difference what engine, the setting is .001-00 per inch of shaft. A 2 inch shaft will need .002-00 clearance Minimum, and or  another .000-50 thousandths, Maximum.

 

Herm.   Kohnke RebabbittingService.com

Edited by herm111 (see edit history)
Posted

One thing. When you start removing shims, do one rod and then crank the engine by hand to insure there is no bind. Do one rod at a time. If you do them all at once, if you do have a bind you wont know which one is the problem.

 

Another way to isolate a knocking rod is to short out the plugs one at a time. The bad actor would stop knocking when the plug is shorted.

 

However, you may be well past that point to test now.

  • Like 3
Posted

I got back to work on my rod bearings today.  I checked all the shims for the rod caps.  I am used to working with engines that had a stack of shims form .0005" to .0100" thickness installed when the bearings were new.  As the engine wore, shims could be removed to keep the desired clearance.  This engine has a single thick stamped brass shim on each side of the cap.  They vary in thickness from .0999" to .1060" thick.  They are stamped pieces as one side has rounded edges and the other  has sharp edges,  They are not of uniform thickness as they vary about.001" across their length.  

 

I am considering surface grinding them all to a common thickness and then adding shims  to get the desired gap. The crank journals are a nominal 1 3/4" Dia.  so according to the above posts  a target of  .002" should be ideal.

 

A couple other things I found were the hex castle nuts were torqued to about 35ft- #.  Specs for a #2 fine fine Thread 3/8" rod cap bolt should be about 17 ft-#.  The rod caps had mushroomed  at the bolt holes, so I reamed the holes to remove the collapsed metal.  I will install new hex castle nuts and torque to 17 ft-#.  

 

I would appreciate any thoughts on this plan.

 

Bob Engle

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Posted

I double checked again.  They are definitely on piece brass.  not a stack of laminate shims.  

 

It's hard to believe that model A shim would fit the shape  of this Buick. I'll check with some local shops to see if they have some  similar shims.

 

 I hate the thought of having to make a batch of  shims to the current profile.  

 

Bob Engle

Posted

Don:  That's the best explanation so far.  I taped two planer blades to my granite plate and put the shim between the two and filed them down to 1.001"  I have ordered some shim stock at .0005", .0010". .0015" and .0002",  I will make two steel pieces and clamp the shim stock between them for trimming.  Then it's back to plastigage, torque, remove cap and add shims to get .0002" clearance.  Once the rods are all set, I'll remove the main caps one at a time and see what I have there.  If  I am correct, to remove the front main cap, I must remove the cast piece that is also  the lower water pump/starter-generator gear pan.  If this is correct, I'll get to inspect the gears for their condition. 

 

Bob Engle

Posted

Yes you re right about the front bearing cap.  I'd hesitate to go to that much trouble unless you find the other bearings have excessive clearance.

As far as the gears go, I have seen both steel and fiber gears on the cam shaft.

It is a real PITA to remove the front cover since it is also the front motor mount. And I think the "nose" goes through a hole in the radiator. (It has been a while).

 

By the way, what are the worse and best rod clearances that you have found?

 

 

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