2F Build, Tight rod clearance. Any ideas? (1 Viewer)

[Toyrod]

2F Build, Tight rod clearance. Any ideas? SOLVED

I'm building a 2F out of an 85 FJ60 for my 40 project. The crank has been turned and the bearings are .25 mm. The crank measures 2.115 inches with a micrometer which is within spec. I checked the rods and mains with plastigauge when I first assembled it. Rods were .002 inches at 35 lbs/ft torque. (Final torque was 55 lbs/ft. I noticed that there was no side thrust on the rods and the motor got harder to turn over as I went. By the time I got it assembled, it was all I could do to turn it over by hand with the dampner. Filled it full of oil, primed the pump, and then turned the motor over with the starter, (distributor and oil pump engaged) The gear reduction started acted like it was straining and it seemed to get harder to turn over the second and third times.

Drained the oil and pulled the pan. Took #2 and #5 rod caps off and rechecked the clearance. At 35 lbs/ft., the clearance was .002 inches across the rod journal. At 45 and 55 lbs/ft., the clearance was .0015 at the outsides of the bearing and .002 in the center. No side to side thrust at any torque. Backed off all the rod caps to just snug, 5-10 lbs/ft., and the motor turns over easy by hand.

Any ideas? The bearings don't have any spots that look like there was uneven pressure or anything else unusual. Bearing brand was Clevite.

 

[amaurer]

I've gotten myself into trouble assuming that the 2F and the 3B are similar before... HOWEVER... big end oil clearance spec for a 3B is .0012 to .0028. When I checked it at 150,000 mi, most of my rods measured close to 0.001".

Now, if a 2F is wildly different then ignore me. But otherwise I don't think it sounds like this is terribly wrong.

 

[Pin_Head]

Did you have your machine shop resize the rods to make sure that the big end is round?

 

[Mark W]

no question of swapped rod caps.... or caps installed backwards?


Mark...

 

[ken_79-fj40]

I just assembled my 2F last week and I recall the rod bearing cap torque spec being 45 ft lbs. If they didn't bind at 35 but bind at 55 maybe they are too tight? I would think the caps would bottom out on the rods and it wouldn't really make much difference, but it might. Also I had asked last week because I was surprised that the notched ends of the bearings went on the same side. For some reason I recall the last Toyota motor I built (a 4AGE 12 years ago) had them opposite one another. If you think like me perhaps the bearing caps are backwards.

 

[Toyrod]

Did you have your machine shop resize the rods to make sure that the big end is round?

This was a running motor that was rebuilt and had less than 10k on it. The PO had started it to warm it up after it had sat for about a month. It had a funny noise so it was shut down and towed to the shop that did the rebuild and oil changes. They found that the motor was out of oil.

When I got the motor, it was a little tight but you could turn it over. I totally disassembled it and the only damage I could find was that the rods bearings had just begun to smear. Mains were fine and cam bearings looked good too. I had a machine shop replace the cam bearings purchased new rods and mains. The crank had some slight transfer of bearing material on the rods journals so I had all rods and mains polished.


There was no evidence of heat discoloration on anything and the bearings had not spun.

I didn't have the rods resized because I thought that with the above findings, they should be fine.

 

[Toyrod]

no question of swapped rod caps.... or caps installed backwards?


Mark...

The rod caps are stamped 1-6. I installed them so that the number on the rod and cap have the numbers lined up. I will check that to make sure lining up the numbers is right.

 

[dargreg]

no question of swapped rod caps.... or caps installed backwards?


Mark...

That would be my guess is the rod caps are swaped ,VERY important ,I,ve found that if they are not no.d is to try swaping those two caps, make sure they are not backwards

 

[CruisinMT]

were there any shims on them? When I had my F135 apart it had small shims on the rod caps. I don't know if the 2F's had these or not.

 

[bsmith123]

Taper

The difference between the widest reading and the narowest is the taper---should be a spec for allowable journal taper in your manual.

but with the smaller clearances on the outside than the inside this sounds like it might have to do with the size bearing you have. The bearings stick up a little above the journal ---this is called the crush height and as you torque it down it changes the clearance

you could also measure the jounals across the face front to back to make sure they are the same size all the way across but since you had .002 all the way across with less torque I suspect maybe the bearing is the source of the prob

You could remeasure the the journals and the crank and figure the correct bearing size that way

Just google measuring conrod bearing size you should get a bunch of hits on how to do it

 

[Fuzzy Logic]

The bearings stick up a little above the journal ---this is called the crush height and as you torque it down it changes the clearance

Where in the HELL did you come up with that line of s***??

 

[amaurer]

Where in the HELL did you come up with that line of s***??

You're a delicate creature, aren't ya??

Maybe he got it here:
Dictionary of Automotive Terms Abbreviations

Crush height
The precision insert bearing must fit the bottom end of the connecting rod in order to transfer friction heat to the connecting rod. The insert will protrude a small amount above the rod bore parting surface. This distance is called the crush height. When the rod halves are drawn together, the inserts touch before the halves, thus forcing the inserts tightly into place.

Or here:
POWER ENTERPRISE USA

When the caps were installed and properly torqued, the amount of crush height create a tension on the bearings toward out side of the housing, resulting in enlarging the clearance. Some extreme case happens with RB26 engine's crank main, the crush height create as large as 0.020mm enlargement.

(I'll point out that those were the first two links on google, so this doesn't appear to be a secret.....

 

[joeyg1973]

Use LOTS of assembly lube. It looks like you have hardly any in there. Remember till the motor is running for a bit, this is the only protection you have. The bearings should never actually touch the journal as they should be hydraulically suspended by the oil.

 

[bsmith123]

clearances

the crush height stuff I think I read on the plastigage site and a couple of other sites on problems with getting clearances right by engine builders

Ive done a few engines and used plastigage and never really had a prob but the sites said sometimes two different size bearings are required to get it right with the thicker one installed on top

The clearance will affect oil pressure in the end but the worse case scenario is ruining the build by spinning a bearing or something

heres the definition in full

When journal bearings are assembled, each insert installed either in a semi-circular bore in the block (or rod), or a similar area of a bearing cap. When assembled into the cap and the bore section of the block, the ends of the inserts stick out slightly. When the cap is put in position, the ends of the bearing inserts butt up against one another before the cap actually seats against the block. In this position, the inside diameter of the bearing will be slightly greater when measured between the centers of the inserts than when measured between the two ends of either insert. The difference between these two diameters is the bearing crush. The crush is removed when the main cap bolts or connecting rod cap bolts are torqued.


but I am also wondering why he has a such a different reading across the face of the journal

with a small gap at the edges and a bigger in the middle it seems the bearing is pressing in the middle and not contacting so good towards the edges when he applies the full torque --at the lesser torque it was ok

Wouldn't have a smaller width of plastigage at the edges mean excess clearance and allow oil to escape and lower the overall oil pressure?

seems to me this may warrant re-measuring everything to look for probs

 

[Pin_Head]

I didn't have the rods resized because I thought that with the above findings, they should be fine.

I always have the rods resized as it is cheap insurance. If you had .002 clearance all the way around you wouldn't be having this problem. I learned this the hard way, so it stuck.

 

[dargreg]

The only real fix ,which usually is not nessesary is to have the rods line checked at torque .Usually if a machinist takes the crank down 10 or 20 thou. he orders the bearings ,checks them and thats it.The only time ive had an engine do this is when I had no. 5 look like 6 and visa vesa (poor stamping on my part) but it came up solid apon assembly. reversed them all was good.

 

[Toyrod]

My next step is to pull one or two rods and check the bearning id. with the cap torqued. I'll also double check the rod caps to see how they fit reversed.

Thanks for all the sound advice so far.

Brian

 

[dargreg]

What a machinist will do is take each rod ,fit a cap. check it ,and then number it. Like a small block chev 1357are oposite of 2468 so in my case no. 5 rod and 6 rod caps were on backwards.I guess my point is that somehow a rod cap got mixed up,Clevit is a good brand,make sure you got the right bearings eg. you didnt get 30 over for a 20 over crank and use lots of essembly lube.

 

[Toyrod]

What a machinist will do is take each rod ,fit a cap. check it ,and then number it. Like a small block chev 1357are oposite of 2468 so in my case no. 5 rod and 6 rod caps were on backwards.I guess my point is that somehow a rod cap got mixed up,Clevit is a good brand,make sure you got the right bearings eg. you didnt get 30 over for a 20 over crank and use lots of essembly lube.

Verified the cap alignment. All 6 are matched with the rods and are not swapped. I mic'd the crank in several spots around rod journals. It is 2.115 all the way around on each journal. I took #1 and 6 rods out, cleaned everything up, and retorqued the caps at 45#. The i.d. is 2.117 at the bearing split. The i.d. from top to bottom is 2.115. I also found a slight shiny mark on the bearings at the top and bottom, at the outermost point.

I think the next step is to take all the rods to the machinist and have them resized and get a new set of bearings.

 

[dargreg]

Your best bet . Good luck