What is the deal with flanged cranks ?

[jeff lovell]

 I've never owned a flanged crank and thought i would buy one for my next engine. But i keep hearing about problems with the  main bearing getting ate up. Is this on drag engines or street stuff or both ? Also is it more on the type 4 then the type 1 bearing style ? I have read of some diffrent mods to help this issue out. In the past , i never herd about too many problems.  Whats the story ? It's time for me to buy a crank, any help is geatly appreciated

[turboed64]

the problem is that the rear bearing has no shims in it.  As a result, after engaging and disengaging the clutch, it begins to wear out the  rear bearing.  Jack at JayCee has created a steel back bearing that prevents this premature wear on the bearing.  So now you can run the flange crank on the street.  But IMO, you don't need something stronger on the street than a wedgemate.  Good Luck

[jeff lovell]

This crank is going to be used in a all out drag/turbo engine. no street use.

[Roman]

Be careful with two things and it willl work fine on the street.
1: Never crank the starter with the clutch down. Before it starts you have no oil film between the crank and the bearing. Be careful with this on a racecar as well.
2: When waiting at a red light, put the gear into neutral and lift the clutch. To have the clutch down creates heat and wear.

[Mike Lawless]

I personally believe the thrust issue to be a myth. Every other automobile powerplant on earth gets by just fine without thrust washers and a similar arrangement to the flange crank set-up.

I believe type 4 mains are important for a high output motor, with long stroke, small rod journals.

[Tom H.]

What Mike said^^^^^^^

[1960 ragtop]

What Roman said. I run one on the sreet. I never start with the clutch in and try to stay of it at lights too. So far so good.

[Tom Simon]

Every other automobile powerplant on earth gets by just fine without thrust washers and a similar arrangement to the flange crank set-up.

Hey Mike,
I'm not so sure lack of 3 shims in a aftermarket vw flanged set up isn't at least part of the problem. Or, the three shims are a cleaver way to fix a not-so-perfect design. Here's why I say that; Look at the small total square inch area of a VW crankstock thrust surface. I can't speak for every other engine, but a few V8's I have looked over have a lot more square inches of thrust bearing surface area in which to spread the same load over. The smaller the area, the higher unit load, the more likey it will gall at some point.

In addition, I've mentioned "sanding the wrong side of the bearing" (to adjust thrust clearence) several times before, but no one ever comments. Either I have been making something out of nothing, or no one else sees this as a likely source of a rear main galling problem. The coating isn't very thick on main bearings, most of it gets sanded off when setting up a split bearing for an aftermarket flanged crank rear main. I can't imagine an uncoated aluminum thrust bearing would live very long with a 2100lb pressure plate.

what do you think?

[John Redding]

Rimco's now putting the thrust against the center bearing cradle, they are doing mine now. New process that Jack helped them work out...

[Terry Hoogstins]

I have never had a problem with the flange crank in the race car . I do set the end play loose 8 -10 thou to keep the oil flowing , but you should not sand bearings for clearance use a bearing knife and scrape the bearings .

[Type 5 Joe]

 I have run several Flange Cranks since about '79.

 I have never had problems like the thrust being eaten.... I always make my own split bearing from POTL bearings (close thrust thickness). This is a time consuming process which can take the better part of a day. You have to "finish" the thrust installed in the case... set up in the mill.

 The only problems I have seen people have are with the bearings supplied... which have always been a big joke.

 Lately...(last 20 years or so) I drill a very small direct-shot oil hole thru the thrust bearing (angled) into the main oil feed. I also do a larger volume drain-back towards the bottom of the main seal (angled to clear the stud) driver's side. 

[1946vw]

I have run a flanged cranks in all my motors. And never had a thrust problem. The crank runs on oil not aluminum.