Any input on this idea for reducing spun rod bearings is welcome.
Any input on this idea for reducing spun rod bearings is welcome.
(OP)
I am going to be destroking a quad cam V6 soon and I am concerned about this engines history of spun rod bearings. The bearing speed will be lower due to the offset grinding to destroke it. I would assume that itself would help some. I was considering having additional notches cut in the rods and caps at the separation line and modifying the bearings so they have 4 tangs total per rod rather than 2. I noticed this on some of the alluminum top fuel rods I have seen. I would think that would have to help, but I would like the oppinion of some others with more knowledge about this. Any info or ideas is appreciated.





RE: Any input on this idea for reducing spun rod bearings is welcome.
Check crush. Check clearance. Check ovality, taper and finish of the journal. Check the bearings have sufficient extra clearance across the parting line so not as to wipe the journal clean of oil as the cap distorts at high rpm. Check side clearance.
Check oil pressure for at absolute minimum of 10 psi per 1000 rpm hot.
Use premium grade synthetic oil.
Make sure the pick up is always under good air free oil under all operating conditions.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
If the pump is any good at all, it will only need a slight smear of grease on the gears and internal surfaces swept by the gear to prime instantly. The best way to ensure oil pressure on start up is to have a good pump and spin it up with a drill and an old distributor bottom half and shaft with no gear.
As SMOKEY says. cleanliness is next to godliness when it comes to engine assembly.
Mineral oil will help the rings bed into the bores, but synthetic from the start with new bearings, but rings and bores that are already bedded in as you do not need to bed in bearings.
Are you sure the crank is being linished correctly. The grain raised against the direction of rotation can cause bearings to spin at times.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Any input on this idea for reducing spun rod bearings is welcome.
Pat & Smokey are on the money, is it a problem associated with a particular journal or is it random??
Cross drilling the crank will improve the oil to the rod journals & should be the end of your troubles!
If it is a particular journal all the time further inspection of the oil ways may be in order!
How much oil is going to the top end instead of where it belongs, it may need restricting??
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
I guess I am not surprised by the answers above. I did think adding an additional tang may help and seeing it on some of the top fuel rods in my mind supported it. With the additional details I gave, do you all still feel the same? Do you think there is any other way to help prevent this? It is a bad enough problem that most of the 3S owners opt for a new shortblock from the factory as opposed to a rebuild since nobody can seem to overcome this with any consistancy.
RE: Any input on this idea for reducing spun rod bearings is welcome.
An extra tang should not be necessary, there is an oil related problem. Are the blocks being line-bored when rebuilding???
What main & big end clearances are you running??
What brand of bearings are you using, are they having problems with the factory bearings or just aftermarket types!
Are the oil holes in the main bearings as large as the oil holes in the main bearing saddles??
Have you tried to feed the mains with seperate oil lines direct from the pump!!
RE: Any input on this idea for reducing spun rod bearings is welcome.
A couple of things i asked you already stated--DUH!!
The bearings you are using, are they tri-metal bearings or sintered alloy??
RE: Any input on this idea for reducing spun rod bearings is welcome.
Have you inspected and measured new parts. Do you have specs for new parts, especially bearing shell dimensions and materials.
The bearings do not know if they are in a Chev, a Mitsubishi, A F1, a KB or a Gogomobile. They know what temperatures, oil supply, clearances, loads, dynamic changes to clearances etc they see.
People like Cleveite make a number of different bearings for the one engine, to suit different applications. They do this because it is necessary to optimise different properties for different applications, eg aluminium for long wear at moderate loads, or white metal coated for the ability to wear rather than grab in very high load applications where parts flex so much that clearances are more than used up for an instant.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
If the bearings knew they were in a Gogomobile they'd want out of there!!
Wooden blocks would be fine for them!!
RE: Any input on this idea for reducing spun rod bearings is welcome.
Come to think of it, I think a Gogomobile is a 2 stroke.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Any input on this idea for reducing spun rod bearings is welcome.
Any verified failures using an oil accumulator? They are a great band-aid/insurance policy for momentary oil loss.
RE: Any input on this idea for reducing spun rod bearings is welcome.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Any input on this idea for reducing spun rod bearings is welcome.
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i know that's probably not your problem ?...but like Pat stated , i would "never" assemble a Race Engine with a "LUBE" i couldn't fillup the pan with and run the engine for 100 miles. You can't fillup your oil pan with white grease and go run it for 100 miles or so, ..so why would you assemble an engine with white grease (Lithium) ??
How about your Rod Bolt Torque ??
which method are you using to Torque the rod bolts ?
Stretch or Torque ??
i just had an engine builder come to my Shop 2 nites ago with a LS-6 engine in pieces...he used the "Stretch Method"
2 Rods wanted 80 Torque , and all the others wanted around 60 to 63 Torque for same "Stretch"
the 2 that were at 80 TQ didn't fail, and bearings looked like the day you took them out of the box !
all the others at 60 to 63 spun, blackened big ends, and some rods came apart and destroyed the engine
i took one of the rods and it wanted 78 to 80 TQ by "Feel"
pulling with my Torque wrenches, instead of his 60 to 63 by Stretch
make dead-sure your rod halves "don't" have a chamfer on the parting halves....as the bearing tangs can get rounded-off in that chamfer ! The chamfer is death to the bearing tangs...it lets the bearing halves and their tangs move in and out into that area...if the bearing is moving around , it will "blacken" the oil film on back sides and the backs of the bearings will have a faint Skunk or Rear Gear oil smell
never grind a chamfer on rod caps parting lines
the bearing tangs need a dead stop to be against, not a wedge !
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
http://www.maxracesoftware.com/
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
1. The oil groove in the main bearings, as they feed the rods.
2. The design of the rod oil holes in the crank, I'm not familiar with this engine but they may not be well suited to racing engines. Check to see that the main journal opening of the rod oil holes is right on the oil groove in the bearing.
Some people carve scoops into the main journal opening of the rod oil holes with sucess.
Jonathan T. Schmidt
http://www.schmidtmotorworks.com
RE: Any input on this idea for reducing spun rod bearings is welcome.
Also look into how that rod journal is getting its oil. I build performance Sunbeam Alpine motors, and they have a history of spinning #2 and 3 rod bearings. Turns out that 2 and 3 get their oil from main journal #3 which is also feeding the center journal on the cam as well as the entire upper end of the motor. Additionally the oil hole on the crank is providing the rod bearing with oil way too early, leaving the oil film too thin when combustion occurs at hight RPM's. These are the kinds of things that can make or break your motor.
Good luck
RE: Any input on this idea for reducing spun rod bearings is welcome.
Do you have any bearing loading figures?
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
Can you tell us more about these spun rod bearings? Is it always the same rod journal that spins? Do you have an oiling diagram of this engine? and if so can you post it some where?
Do you still have the damaged bearings and/or rods? I read an article a long time ago which showed how by examing a ruined plain bearing you could tell why it failed (i.e. oil too hot, not enough oil, foreign object damage)
Bye for now
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
In regard to the Mitsubishi engine, I wonder if there are some popular modifications that might often accompany the first rebuild and might be inferior to some of the factory parts. Looser clearances, Hot Rod oil pickups, changing rod bolts without re-sizing the rods, etc.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
The "optimum" position of the oil holes on the rod journal is not necessarily a fixed number of degrees before or after TDC. The angle of maximum force on the bearing is a function of camshaft, timing, fuel, ... etc and is obviously motor specific. However as a general rule we use a Chevy small block crank as our model for re-drilling cranks. The key is to make sure oiling is not happening too late.
I look forward to hearing your report on what you find in this motor coming to you soon.
RE: Any input on this idea for reducing spun rod bearings is welcome.
I was told (by a Japanese Mitsubishi mechanic in my old rally days) to keep the bearings super clean and dry (after cleaning with solvent) so that the bearings "gripped" properly and transfered heat well.
RE: Any input on this idea for reducing spun rod bearings is welcome.
Tigretr makes the point about oiling angle, this should not really be an issue because you should have 360deg oiling to the rod journals, if not your not racing & if not you better fix it!
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
I will have the factory specs buried somewhere in the library if you really need them
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
RE: Any input on this idea for reducing spun rod bearings is welcome.
And besides most top fuel engines are pretty much running in a full detonation range.
Hmmm I wonder why those diesel engines don't just kill bearings in a week or so. With that detonation like cetane knock?