Help Needed to Replace Burned Rod Bearing

Earlier I posted a request for some info about my 1986 Chevy Silverado C30 1 ton dually with a Big Block 454 with about 100K miles on it that was overheating like a son of a bitch when I towed my 13000lb 5th wheel trailer. From Bad to Worse I got a Knock in my number 7 cylinder, (3erd back drivers side) pulled the plug wire and of cause the knock went away. I then pulled the oil pan and the number 7 and number 3 rod caps and of cause the number 7 insert bearings showed signs of heat cracks an quite possibly were spinning or at least had the tabs that lock them in place worn off. The number 3 insert bearings looked good but showed signs of wear at their sides. I would suspect that the other 6 sets are probably worn too, but not knocking yet. The journal that I exposed that held the 7 & 3 rods looks pretty dam good. It has some slight signs of wear such as minor lines but nothing that appears to have been abused to long.

MY SITUTATION IS… I am not in a position to pull the motor and have the crank turned or replace the motor, so I have decided to replace the rod bearing inserts and try to get the truck home to Arizona from California as soon as my business trip is over. (a 700 mile ride done in to short days) NO MORE TOWING THE 5th WHEEL OF CAUSE.


MY QUESTION IS…. 1) Do you think that replacing the bad insert bearings might buy me some time, if not fix it for a few more thousand miles. (My wife Loves this Truck) 2) Do you think I should go 10 thousandths or so over size in the bad cylinder to compensate for ware or leave it stock. 3) And last do you think I should go ahead and change them All while its open to at least bring the bearing thickness back up to stock and to be sure another one doesn’t crap out on me next week.



I also measured 2” + 170 thousands across the journal. Would any one know if that’s close to normal Spec. I’ve never done a rod job before and don’t know if I need to measure the rod as well and if some of the numbers like 0022 or 0025 are referring to actual bearing thickness. And how would i go about sizing up the Wright set of Bearing Inserts.


Any help would be appreciated. I can also send some photos. Or your can e-mail me at [email protected]
Thanks………..

The .0022 and .0025 numbers are the factory specified clearance between the bearing and journal. Which should be maintained when the crank is turned to remove score marks with an oversize bearing set.

If your crank is not going to be turned, your best bet is to replace the bearings with the same size set. You can't use a .010 under set with a stock crank.

I think you can run for home if you change all your rod bearings, providing that the rod and rod caps are not excessively scored up. (At least drop the other caps for a visual inspection). Rework of the rods & caps requires major engine disassembly to remove the rods. Do check the journals in question using plastigage. See the link below.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2DPG1&N=700+4294760493+115&autoview=sku

I would get some crocus cloth and polish up the scored journals, use something like Marvel Mystery Oil for lube. The cloth should come in a 2" roll or come in a sheet about the size of a sheet of paper. Tear strips slightly narrower than the journal. The cloth is looped over the journal and use a "shoe shine" motion and keep moving it around so the whole journal gets polished evenly. Then you have to clean out the oil holes thoroughly, carb cleaner is ok, also get some pipe cleaners.

Once everything is surgically clean, press the new bearings into the rod caps and rods dry. They should "click" right in, make sure the oiling holes line up in the rod and caps, very important!

Then oil up the bearing surfaces, the crank journal and install the rod cars and start tightening them up. Use pieces of fuel line hose on the rod bolts so you don't nick the crank when you pull them down.

Tighten them all evenly until snug, then start torquing them per specs. If you don't torque them, the enitre effort will be useless.

This is important and should be followed to make sure the bearings have oil on them when it first fires up. You need to pressurize the engine oil, which is done with the engine off. A dummy distributor shaft is required, I made one out of an old distributor. Pull the distributor, insert the shaft and make sure it engages the oil pump. I use a 1/2" electric drill and spin the oil pump until the oil light goes out of the gage shows around 20-3- psi. You can "get away" without doing it but I give you a 50-50% chance of success.

Toss in a new oil pump while you're at it. Change the oil filter too. If the weather is hot, use something like 20w-50 oil and let it warm up for a few minutes before driving off everytime you start it. Keep the speed down and make sure the thing runs cool.

Bob

It seems that the knock is a symptom and is bound to repeat if the overheat problem isn't fixed first.

OR try to figure out what the knock is or what made the bearing spin first. Replacing bearings might be a waste of money/time.

The problem seemed to be a result of towing a 13000 lb trailer with a truck with an engine with 100k on it. Which could easily do it.

The suggested repair is a "last ditch" effort and may or may not work, but could possible get the truck home. I've done it before (on your back bearing jobs) and sometimes thay work, usually if the crank is not that scarred up.

Bob

Thank you All for your replies.

I am going to go ahead and change them all back to factory size and hope for the best.

The main problem that I think caused the bearing to go was overheating due to towing that 5th wheel up a steep pass.

The Temp. went up to 260F. before I reached a spot where I could pull over. In fact some oil that dripped on the exhaust manifold due to a leaky valve cover gasket actually caught fire. A lot of RVers towing 5th wheels with 454’s have complained about similar problems, and old coaches running 454’s have been known to have manifolds that would glow red hot on climbs.

My truck like many other 454’s I’ve heard of runs about 210F. on a hot day. It doesn’t take long for one of those suckers to hit 230 or better, vapor lock and all kinds of other bad stuff on a climb while towing. I’ve heard less horror stories about 460 fords when put to similar tasks. But the 454 and 350’s are all-time favorites of mine.

To be honest I purchased a 7.3 Liter ford power stroke diesel just to pull the bitch. The price was right!

Thanks for your advice fellows, and if any one knows how to go about selecting the correct thickness of the bearings please let me know. The numbers I have are “Clevite 77, 11 89 CB743 P E1”. Also to bob, do you think I could get away with coating the journals with white lithium grease to avoid pulling the distributor to manually pump oil in to the journals.

And most of all Does anyone know the factory numbers for properly torquing a 454 rod cap.

Thanks again……..Hauler308

Your bearings I think are already .001" undersize.

If the crankpin really does look nice and you could get a mic in there to check diameter you may want to go with standards, 001 or even 002 unders. Checking rod end would be good too, but is very difficult in the engine/chassis.

rod bolt tork for 3/8 is 50 ft/pounds
rod bolt tork for 7/16 bolts is 70 ft/pounds

Oops I forgot to mention to pull the main cap if possible that feeds the #7 rod bearing because it may have turned slightly starving the rod bearing of oil. It may need replaced to deliver oil to the new rod bearing. You mentioned the 3rd cylinder back , but it is not #7. In any case the oil is fed from the adjascent main bearing (bearing right beside the rod bearing that spun)

do you think I could get away with coating the journals with white lithium grease to avoid pulling the distributor to manually pump oil in to the journals.

Do you mean for lubrication for the initial start-up? If so, then the stuff to get is Permatex Ultra Slick Engine Assembly Lube. i have a bottle, it's great stuff. cheap too, but very good. some engine builder friends of mine swear by the stuff, as do i.

I agree on the assembly lube on the bearings. Any dealer should have that on the shelf, not sure if the chain stores carry it. We used to use the good old STP in the old days. I added a good link for all your torques.

http://boxwrench.net/specs/chevy_bb.htm

Be careful with your bearing selection. I believe you measured up a journal already, normally they should be checked in 4 places in case it is out of round. Check what the stock size should be, I'm sure you can find it online or ask at the auto parts store. Sometimes replacement bearings have the size on the back of the shell, in case yours were previously changed, it might give you an idea on what the crank size is.

At the factory they are usually nominal in size or .001 over. Standard reground cranks take .010 or .020 over shells. I've seen them up to .040 over. But then you start getting into undesirable surface-speed conditions with a drastically small journal size.

Bob

Good afternoon Sir's.

I re-measured the journal diameter last night and found it to be close to the same diameter I got the first time 2.175. Pretty much the same all the way around and not falling into any oil holes.

The chart I used gives specs close to 2.200-2.199 for 1982 thru 1987 454's thats a .024 difference. I don’t know if the crank was ever turned but I doubt it, since they used stock Clevite CB743p bearings.

I enclosed a link to a web site that sells them and it does not appear to be undersized.

I think I’m going to get a set of original CB743P’s and use a Plastigauge measuring strip to check the clearance and take it from there.

Would any one happed to know What the Maximum Clearance between the Bearing and journal should be.

One more thing. I just got a call from the guy who sold me the truck he said he changed the motor to a low mileage 454 that was a 1978, 454 and he thinks the stampings on the case were 1973 or 1974. Does any one have a crankshaft Spec. chart that goes back that far? I may have been looking in the wrong place. My chart is 1982-1987.



Thanks again……Hauler308



http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?storeId=10001&catalogId=10002&langId=-1&N=2500523&Ne=2500000&Ntt=695&Ntk=brand&Nty=1&D=695&Ntx=mode+matchall&Dx=mode+matchall

That is bad news if the bearing really is a .001 then the crankpin is ruined and will need reground for .030 under or smaller. Your crank specs are correct , just have to keep subtracting .010" for each undersize.

They may be available in .001.002.010.020.030.040.060 undersizes.