Stroker thrust bearings
07-04-2007, 01:58 AM
#3
Former Sponsor
Marc:
Discussion of theory/notes only. No ego. No arguement. Cool?
I groove both halves with no apparent bad results. The stock bearings (on #1, #2, #4 and #5) are actually grooved over 180 degrees, so I've always been afraid that grooving only 180 degrees would not be adequate....especially with cranks that do not have the oil holes exactly opposite each other. What's your theory? All the other main bearing I can find (Chevy, etc.) are grooved 180 degrees, plus the "eyebrows" on the non grooved bearings.....like the Porsche bearings.
greg brown
Discussion of theory/notes only. No ego. No arguement. Cool?
I groove both halves with no apparent bad results. The stock bearings (on #1, #2, #4 and #5) are actually grooved over 180 degrees, so I've always been afraid that grooving only 180 degrees would not be adequate....especially with cranks that do not have the oil holes exactly opposite each other. What's your theory? All the other main bearing I can find (Chevy, etc.) are grooved 180 degrees, plus the "eyebrows" on the non grooved bearings.....like the Porsche bearings.
greg brown
07-06-2007, 01:22 PM
#4
Rennlist Member
Go to this SAEpub 2000-01-1341 good reading, neat data on half vs full.
Chevy/clevitteoffershalf, 3/4 and full chevy bearings avail. I would consider using the geometry of those bearings grooves as reference...they have a lot more R&D funds than many.
I use the normal lower with a grooved upper #3 and would consider full grooving on all if i was designing a racing engine. I took apart a stroker built in 1996 with 130K miles on it and the mains were still usable. Not a race engine, but it is hard to change without testing, and unfortunately, that is not on the list of activities in the near future.
Chevy/clevitteoffershalf, 3/4 and full chevy bearings avail. I would consider using the geometry of those bearings grooves as reference...they have a lot more R&D funds than many.
I use the normal lower with a grooved upper #3 and would consider full grooving on all if i was designing a racing engine. I took apart a stroker built in 1996 with 130K miles on it and the mains were still usable. Not a race engine, but it is hard to change without testing, and unfortunately, that is not on the list of activities in the near future.
07-06-2007, 02:13 PM
#5
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Another thrust bearing-related question, if you don't mind...
Do you guys think the oil feed notches for the bearing outer face are OK as is? We just took apart a 17K mile GT shortblock and both faces of the thrust bearing were worn through to copper.
Do you guys think the oil feed notches for the bearing outer face are OK as is? We just took apart a 17K mile GT shortblock and both faces of the thrust bearing were worn through to copper.
Last edited by Bill Ball; 07-06-2007 at 02:41 PM.
07-06-2007, 02:36 PM
#6
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If full 360 grooved work without any ill effect I can't see any reason not to do it. Certainly price can't be limiting factor since it costs $$$$ to do basic nothing special rebuild.
07-07-2007, 02:02 AM
#7
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Thanks for the reference, Marc. I'll give it a read.
gb
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07-07-2007, 02:54 AM
#8
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For anyone who wants to read the article Marc suggested, here is a link to buy a copy...
http://www.sae.org/technical/papers/2000-01-1341
http://www.sae.org/technical/papers/2000-01-1341
07-07-2007, 10:36 PM
#9
Rennlist Member
Either wear caused by lack of oil supply or it is not "really" a 17,000 mile short block...sorry.
I have rebuild quite a few engines in the 60,000 - 200K range and in the lower range the mains are almost still usable with minimal wear..sometimes will show a streak of copper, but mostly just fine.
The wear in single disc clutch engines is greater than in dual disc. Porsche had originally had a very small thrust surface in the 4.5/4.7 engines and increased, radially, the thrust surface in the later dual disc, S3, single disc engines and single disc engines. The early twin discs had lower pressure plate force than the later twin discs, and much less than the single disc. Prosche matched the clutch force with thrust surface area.
That is why I warn against using high force racing pressure plates for street use.....
At 17K miles, the mains could be reusable!
Greg..if you want me to ship you two grroved bearing halves...let me know...pm me and we can discuss.
For longivity, I am sticking with grooved on the top and plain on the bottom for greater wear surface to fight the combustion forces. Race engines might consider 3/4 or full...read the sae paper.
Cheers,
marc
I have rebuild quite a few engines in the 60,000 - 200K range and in the lower range the mains are almost still usable with minimal wear..sometimes will show a streak of copper, but mostly just fine.
The wear in single disc clutch engines is greater than in dual disc. Porsche had originally had a very small thrust surface in the 4.5/4.7 engines and increased, radially, the thrust surface in the later dual disc, S3, single disc engines and single disc engines. The early twin discs had lower pressure plate force than the later twin discs, and much less than the single disc. Prosche matched the clutch force with thrust surface area.
That is why I warn against using high force racing pressure plates for street use.....
At 17K miles, the mains could be reusable!
Greg..if you want me to ship you two grroved bearing halves...let me know...pm me and we can discuss.
For longivity, I am sticking with grooved on the top and plain on the bottom for greater wear surface to fight the combustion forces. Race engines might consider 3/4 or full...read the sae paper.
Cheers,
marc
07-08-2007, 01:06 AM
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Marc, the rest of the bearings and journals looked very nice. The thrust bearing face was not fully worn through to copper, but some was showing, I would say more than just a few small streaks. Appreciate the bearing groove discussion and information.
07-08-2007, 09:59 PM
#11
Former Sponsor
Nice thread.
Porsche originally started with full grooved bearings in the 928 engine and then superceeded these to 3/4 grooved bearings. They always seem to have a reason when they change something. I guess I'd be more confortable if the center thrust bearing could be grooved to a 3/4 bearing, but the half only makes me nervous, especially on an engine with an aftermarket crank that has the rod bearing fed only by this bearing. It is nice to hear that Marc has had great success with this combination, so it might not be neccessary to have oil pressure to the rod throughout the rotation. It would seem like the starting and stopping of the oil flow might be detrimental, but many engines do it this way and run forever. I guess it all depends on where the rod is and what load there is when the oil pressure is lost.
gb
gb
Porsche originally started with full grooved bearings in the 928 engine and then superceeded these to 3/4 grooved bearings. They always seem to have a reason when they change something. I guess I'd be more confortable if the center thrust bearing could be grooved to a 3/4 bearing, but the half only makes me nervous, especially on an engine with an aftermarket crank that has the rod bearing fed only by this bearing. It is nice to hear that Marc has had great success with this combination, so it might not be neccessary to have oil pressure to the rod throughout the rotation. It would seem like the starting and stopping of the oil flow might be detrimental, but many engines do it this way and run forever. I guess it all depends on where the rod is and what load there is when the oil pressure is lost.
gb
gb
07-09-2007, 09:37 AM
#12
Race Car
Originally Posted by GregBBRD
Nice thread.
07-09-2007, 01:43 PM
#14
Three Wheelin'
I might be able to help with machining bearings. I'm setting up to groove mine using a CNC mill. I plan on giving mine a full groove, leaning towards a narrow width, the way I'm machining them lends itself to making a 3/4 groove with ramps if desired. PM me if interested, I'll be grooving bearings later this week.
