Center main

[DeathBySnuSnu]

Well I got a set of silverline mains, supposedly metal backed.
But they are external oil grooves.
Where do I find inside groove Center mains?
Or do I chuck these up and put a groove on the ID?

What about putting a #2 Center bearing on #3 by the gear stack?
What is involved in this?

86mm stroker in an older cb super case. All std.

[Brian_e]

I add the groove to the ID. I usually do about .040 deep and about .080 wide.

The split #3 just needs another set of bearings and another dowel pin drilled into the other case half.

Brian.

[DeathBySnuSnu]

Hmmm.
This case has an unused pin hole in the other side.
Maybe it came set up for that possibility.
I bought this case new.

I can handle cutting a groove, just dont want to ruin a bearing if it is the wrong thing to do.

[esde]

[raymon covey]

I always do it on every build. On race only motors I do it on all 3 large mains.

[DeathBySnuSnu]

It used to be that you always ran the internal groove Center main on stroker cranks. The last time I put bearings on the old crank I could not readily find them and put outside groove in it. Could not tell a difference on my bearings.
This time i have a new 86 crank. It has very little cheek or side thrust face on the outer edge of the throw. It is gonna loose a lot of oil there. I am thinking i really need the flow, maybe on all 3.

[neil68]

You will be fine with the Silverlines, as is. I now only use externally grooved main bearings, as they have always lasted longer...probably because they spread the oil out over the bearing via the two scoops.

My current set of main bearings has 34,000 miles and over 650 drag races and they are still in perfect shape. This is with 84 mm stroke and 8000 rpm rev limiter.

In talking to my V8 buddies, they recommend only a 180-degree groove, if you feel that you still want this.
_________________
Neil.

Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo

[esde]

[modok]

For us that would be two 90-100 degree grooves. The groove is put in the less loaded area of the bearing.

I extend the oil grooves freehand with a carbide burr, but everybody is too chicken to try it.

[neil68]

The theory is that you want the crank to ride on the oil like hydroplaning, for maximum bearing load like the plain bearing with external groove.

However, in some rare cases you might want to supply extra oil to the rods (probably only in an extreme racing engine). The research apparently shows that full-circle groove bearings damage the crank more than 140-180 degree or plain bearings with the two scoops. It's a balance.
_________________
Neil.

Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo

[esde]

Interesting. Any thoughts on why Scat machines a full 360º groove on the center crank journal? Did they do the groove on the crankshaft way back when internal groove bearings were readily available?
_________________
modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.

[DeathBySnuSnu]

Much of anything I called myself knowing is very outdated.
But as I used to understand it....
Because of the drilling in the stroker cranks the center two rod throws get their oil from the center main. That oil is only available when the crank oil hole in inline with the wedge shaped scoop. Considered enough oil.for a single rod but not for two. So the internal.groove for the center main increased oil Supply to the two Center rods.
I dont really know if this holds true....
I have run outer grooved with an 82 stroke without issue.

But this new 86 crank don't have much rod side thrust face and also the chamfer on the oil holes is smaller.

[modok]

Outdated but mostly right.
Traditionally you use a single drilled "1500" crank to build into a stroker, and so having only one oil hole, go for the full groove bearing.

Although, you can stroke a x-drilled 1600 crank as far as 78, and some have stroked them farther by welding over the additional oil hole, and all kinds of different ways and combinations.

-single drilled use internal groove
-x-drilled with the HUGE scoops use external groove
That much is simple, but there are other kinds

The aftermarket cranks have a different oiling arrangements, and I don't really know they works better or worse.

[vwracerdave]

[nsracing]

I am not fond of molesting the bearing surface by gouging it. If you want ID groove on #2, get you some German bearings.

The ID type groove has best oil rod feeding -constant oil feeding. Compared to the 180 degree grooved OD which only feeds to rods every 180 degree.

If you wonder why more rods get cooked, check out the center main bearings type installed -almost always the mostly used groove-on-the-back type.

For high performance builds, I use exclusively German KS bearings w/ groove on the inside.

A split bearing can be installed in #3 -just add another dowel across.

[DeathBySnuSnu]

Thanks Nick.
This is Rex.....and you know I aint skeered to whittle on sumthin.
I might just do it too, I am hiring a real hard time finding anyone with any of the ID grooved bearings.

[nsracing]

Are the Kolbenschmidts out of business too? Check w/ John at AirCooled.

German bearings the only way to go, imo

[vwracerdave]

Kolbenschmidt no longer makes bearings in Germany. They are now all made in Brazil and are all externally grooved aluminum main bearings.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK