Last fall I put in a new crank, line bored it and set bearing clearance to approx. .002 - .003 thousands of an inch. Started it and after running for approx. half a minute, it started having a pretty high pitched squealing... Tonight I loosened and lightly re-snugged the nuts that hold the first (from radiator end) and second bearing caps in place and no more squealing!! Can anyone recommend how much more shim thickness I need to stick in there??? Also if the third main ends up needing more shimming, will I need to pull the engine to get to those bolts???
Thanks in advance for any help!!!
Rodney, you need to determine the clearance. IMO the best way is to use Plastiguage You can get it at your local parts store for a few bucks. Be sure to remove the oil on the pin and bearing as oil make the Plastiguage lie. Another method is to cut a 1/2 strip of cheap AL foil and lay it in the bearing tighten the bolts and turn the crank. if it turns without a great deal of effort remove shims until it's hard to turn. Then remove the foil, oil the bearing and assemble. Without the foil it should crank over as normal. Questions, call me at 903 824 1949.
Rodney -- Three thou is a bit much , so you don't want to add more shims. One-and-a-half is ideal, and 1-1/2 to two thou is pretty good. I don't know what caused the squealing. Working on the rear main with a 3-dip pan is a pull-the-engine kind of deal.
p.s. -- You don't "lightly re-snug the nuts" on the main bearing caps. You make those just about as tight as you can.
It should be about .0015 inch to .002 inch. It might be that the caps were not on straight. When you tighten the cap before you get it all the way tight it should be tapped lightly from each side so that the cap centers on the crankshaft. Then torque down the bolts. If you didn't do that, it could be binding in one place. The third cap is easier to remove and replace with the engine out of the car and the crankcase removed.
I would rather you set the bearing clearance at .0015 to .002". They will get to .003 soon enough.
Why would it squeal? Did you put oil in the engine?
Lightly re-snugged? They gotta be TIGHT.
Sounds like you need to pull the engine off the pan and check the mains again.
When you put the plasti-gage strip about a half inch long on the crank you need to have the crank oiled and tighten the main cap to around 70 lbs.
Being careful not to turn the crank remove the main cap and measure the plastic strip.
If it is between .001 and .002 go on to the next.
If it is tighter than one but you can still turn the engine over easily just leave it alone.
If it is looser than 2.5 thousandths I would lay the main cap on a large flat file and run it back and forth until the whole surface of the cap that touches the block has been filed.
You do not adjust clearance by tightening the main cap nuts.
They gotta be tight. I think at least 70 to 80 lbs. is good.
If you are one of the guys that likes to lube his engine with oil that is slightly heavier than roofing tar I would consider switching to oil no heavier than 15-40 and I would recommend 5-30 or 10-30.
If the flywheel is churning up the oil enough so it runs down the oiler tube to the timing gear and then runs back under the front main cap into the front rod dip then it is splashing into the mains.
There should be no squeeling even if every bearing has zero clearance.
I have been around many an engine that seized after running a few minutes from lack of clearance and have never heard one squeal with oil in it.
Let us know what you do and the results.
Sorry to say the same as others above said, but when I started typing there were no other posts yet.
I guess we all agree on what the ideal clearances should be!
are you sure the noise came from the mains? how about a new rear cam bearing? was that replaced on rebuild? if it is to tight it will chime in also.
Originally I used plastigauge and had tightened nuts as tight as I could... the reason for "loosening" them slightly was to see if made any difference with the squeeling which it did, leaving me with a pretty good idea that the noise was from "too tight" bearing caps.
Now that I think about it, in the early 70's I had a guy working for me that rebuilt the engine in his Alfa.
When he started it it had a squeak-squeak.
We ran it with the pan off and decided the squeak was coming from the front piston.
He pulled off the head and took out the two front pistons.
So I think he honed the cylinders with very light pressure on the hone and put it back together.
It did not squeak as much but stopped squeeking altogether in about 10 minutes, as I recall.
If you could still turn the engine over with the hand crank it was NOT too tight.
Also, yes, I did oil everything before putting back together and am running a straight 30w oil in it..
Another thing it did, was after the squeeling got fairly loud, the engine started turning "hard" so I shut it down right away...
Yup, no problem hand cranking the engine..
Joe, I didn't replace the cam bearings during the rebuild...
Was oil galleries cut from the oil holes in the new main babbitt?
Actually Kerry, all the bearings were in good condition, so I was able to re-use original ones... the crankshaft I put in was a new Skat crank and it was very snug at first fit.. even had to shim all the mains to get get enough clearance to turn crank. Did the lineboring after there was barely enough clearance to turn by hand.
line bore off? Try some bearing bluing and turn it over by hand. Then look at the pattern.
Just a thought.
I have witnessed squealing from a freshly-built (not by me!) T engine that turned out to be oil-starved triple gear bushings.
I think it is unlikely that a squeal would have anything to do with the babbitt. If you can turn the engine over by hand okay, then what could change when it was running?
How did you set the line bore outfit up on the block so the gears would be the proper distance apart? Did you measure, or use "spacers", or "eyeball" it? Gears that are too close together could cause a squeal from the front cam bearing...
If there was an interference on the main bearings that was bad enough to make a squeal noise, then you should be able to see where the interference is just by looking at the bearings... You should see shiny or "wiped out" babbitt at the spot.
Could also be: Cam gear or crank gear or crank pulley could be binding against the front cover or block. Line bore could be "out of line". Cam bearing/s could be improperly fit. There could be some sort of contamination in the engine. The noise could also be coming from the front of the drive shaft or the ball cap.
If you are in neutral when the engine is running, the triple gear bushings could be too tight. Run the engine with the rear axle on jack stands and the transmission in high gear and see if the noise is gone. That could prove a triple gear problem...
Is your starter properly disengaging when the engine starts to run? Is the squeal coming from a bearing on the generator?
Check a main cap for signs of rubbing at the cheeks.
An incredibly small high spot can cause trouble.
Just another thought, you didn't mix up the front and center main caps did you?
Just a thought ,you do know the skat cranks are ground at 2.250 not the original 2.248 what size did you line bore your mains?
Colin, that would be 1.250 and 1.248, right? I don't believe this makes a difference if the bearings were clearanced before running.
Yes James I had a hard day
1.250 and 1.248
It is possible that the pistons are too tight. If it sounded OK when it was first started, but then made a squeak as it warmed up and got to turning tight. Then after it cooled off thoroughly, it was quiet again. In that case, the pistons expand with heat and will seize up if it is continued to run. You can test them with a feeler gauge without pulling the engine. Pull off the inspection plate under the crankshaft and rotate to where the piston is at the bottom of the cylinder and use a feeler gauge. With aluminum pistons it should be about .005 inch. If less, it will expand with temperature and that is not good. Unfortunately, the same can happen if the ring gap is too tight, but you will have to pull the pistons out to check for that.
The 3.875" pistons I ordered from Egge for my '25 Dodge came sized with .0035 clearance. They are, of course, cam ground pistons.
I was going to turn the skirts to give them .005" but figured if Egge doesn't know they are doing by now they'd be out of business so I left them alone.
Glad I did too.
I would love to see the vendors carry precut shims for the mains and rods in .001 and .002 thicknesses. I always have to cut my own which is a pain in the butt!
As a rule, babbitt won't squeal. When it gets too tight, it will get hot and melt so, I don't think the bearings are your problem.
As an aside, I have seen babbitt bearings that were so tight in a Model A that it would slide the tires in third when pulling it. Once the engine started and ran for a few minutes the bearings limbered up and you could turn it with the hand crank. I don't condone setting a motor up that tight but watched some others do it. When the motor started it never made an unusual sound of any kind.
Here is another test I thought about today which will tell you if your transmission triple gear bushings are squeeling.
Jack up the rear wheels and put on stands. Then leave the parking lever forward in the high gear position. Start up the engine and run it for a while. If it still squeels, the problem is not in the transmission bushings. However, if it doesn't squeal and then you pull on the parking brake and continue to run the engine and it squeels, the problem is in the transmission.
Well, I added shims to the 1st and second main... ran good - no more squealing - however, when I went up any hills where the engine lugged, there was a knock toward the front end and a slight squeal... drained the break in oil and put in synthetic oil with a bottle of Slick 50 synthetic.. no more knock or squealing now. Hopefully it'll stay that way...