The Stovebolt Site Forums The Shop Area Engine Shop Shaking rod bearings

Any time a part is machined, There is a possibility of incorrect tolerances. I have worked on motors my whole life, to the point of having tendonitus in my wrists from wrenching. I have seen people rely on the machinist, or the part#'s and suffer extreme consequences for it! I ALWAYS check/ measure everything my name is associated with, and have confidence in it. If you have a problem with your rods, you should have them reconditioned by an expert machinist, and then you should check all associated clearances before reassembly. If you dont, you have no room to [censored] when things go terribly wrong! So if you choose not to, know that it might go bang at any time!

I am sorry I and still stuck on 15K for an o/h. with an Oklahoma Warranty.
Hey if it blows your shirt up use plastiguage. I do have a question thow. What do you do when the procedure calls for throw away 1 time use bolts. We do have them now for rods and mains.
Lets see putin the plasitguage, tighten the bolts, loosen the bolts check the plastiguage, replace the bolts ------- uhhhh hummmm??????

Well, If it is an exotic motor, (aircraft, diesel, euro-car, etc.) 15k might make sense. I check my clearances, and I have had to adjust before. I have seen pistons stick, bearings spin, parts collide, and all sorts of other headaches from people not checking. I have a six speed in my shop right now thats blown up because the previous mechanic failed to loctite ONE bolt! this same bike had black plastic parts plugging the oil pump, and the only way for it to have gotten there was from it falling in the cylinder spigot while the top-end was being re-done! These were mistakes made because of someone not being thorough and double checking thier procedures! My customer has had to pay me 3K in repair-re-repairing, cuase of lazy inept mechanics not making sure the job was done right! I will never be that kind of mechanic, because I refuse to assume it will be OK! I want to know that my motors are exact, and if it takes me 15 minutes and 5 bucks worth of plastigage, I'm willing to make that sacrifice!


BTW, we have many procedures which require checking things with parts that need to be replaced. We typically use the old parts just for checking, then use the new stuff for final assembly. It beats guessing that everything is OK!

That figure includes a dyno pull, or several, if necessary, to show the new owner where his money has gone. The more dyno time the engine gets, the shorter life it will have in the race car, so most owners take my word for the way it's been built. My engines win races. It also includes a 38 lb. crankshaft that costs $2,800.00 (stock SBC crank weighs 55#), a set of $1,200.00 connecting rods with Honda journal size, about $100.00 apiece for pistons, and $200.00+ for a set of zero-gap rings. The rotating assembly costs over $5,000.00 before we figure the cost of a block, heads, cam, manifolds, etc. Average HP is 600+ for a 355 cubic inch engine that passes NASCAR round track specifications. It will be totally worn out in less than 1,000 miles.
Jerry

Must be nice building NASCAR stuff! My customers whine and cry over less than a third of that kinda motor budget!

Ok we are now talikng a race engine. That is a whole differant ball game.

*part1- I don't think you understood what was being asked, we were assuming you re-used the old bearings, and were wondering if you put them all back in the same rod they came out of. Now that we know you used new bearings, a couple questions come to mind. Were all the oil passages in the crank journals properly cleaned out before reassembly? Also, since you've been rotating the crank, was everything properly lubed before assembly.

*part2- Who's footing the bill for this project, the "mechanic" and your buddy or YOU? Don't worry about [censored] them off. Who's gonna be [censored] when you have to tear it down again, not them.
(just wondering what kind of torque wrench you've got that only goes to 80ft/lbs., mine goes to 250, and it's nothin' fancy)

Keith,

Many 3/8" drive torque wrenches top out at 80 ft/lbs. A 1/2" drive would have been the ticket, buy it doesn't sound like one was available.

Stuart

I have three torque wrenchs, an inch pound that goes to 250 in/lbs, a 10-75 ft/lbs, and an 80-250 ft/lbs 1/2 drive. It's best to use a torque wrench where your final value is in the middle of the wrenches range. Too close to the limit and accuracy suffers.

It does'nt matter what parts were where, new or used, you need to be sure of the clearances BEFORE you button it up! Anything else is gambling. How do you know your crank juournals are still round, or galled to the point of scuffing the new bearings? How do know if it's not worn to the point of having too much clearance with std bearings?

I can't believe this is controversial in any way. Measure it, double check it, be sure of your clearances, or pay the penalty!
Excessive clearance will cause at the minimum a loss of oil pressure, and at worst loss of oil film and a spun bearing!
Too little clearance will cause a spun bearing or siezure of the rotating assy! Either way measuring and adjusting is the only way to know that your not just lighting a fuse by starting it!
This applies to race motors, stock rebuilds and mild pref motors alike. The local lawnmower repair shop measures everything they build, and they only charge 50.00 to build 3 horse!

Blackjack can you honestly say that you have calibration certificates for all of your torque wrenches and when they are due again? If not you're a gambler too.

More like a calculated risk! I do however occasionally check mine against one of my employees, and have yet to find an appreciable difference. At one time I had two bikes develope head gasket leaks at the same time, so i sent my 3/8 torque wrench in for calibration, and they said that model was obsolete, and threw it away, giving me a $40.00 credit against the new one they sent me! I was [censored]! Now I have one of my customers who works at the airport who says he'll get me calibrated whenever I need it.

Short answer, NO! However I am aware of the need, albeit not as crucial as aircraft or sensitive torque applications, And have had to address the issue before.