Forged Crank ,Cast Crank

[SpoolinGLH]

Im in the process of building a +300hp 2.2 CB. I have a forged crank that I was going to use but after really thinking about it I think i should go with a 2.2 TBI crank... Where do you guys usually get your cranks? Fwdperf?

* If the new crank is turned 10/10 what bearings do you recommend? I want this bottomend to be tight with great oil pressure so should i go even tighter then the standard 10/10 bearings??...

[turbovanman²]

For 300 hp, I would stick with the cast, its lighter so it will rob less HP.

As for bearings, they come in 10, 20 and 30 under and you can't mix and match. Now if you have a set of 10 under, you can mix and match each shell to get the tightest clearances. The clearances are also determined by the crank grinder, if he's good, you will have nice clearances.

[SpoolinGLH]

Is it common for people to run 20 under bearings on a 10 over crank just to get tighter clearances?

[turbovanman²]

Is it common for people to run 20 under bearings on a 10 over crank just to get tighter clearances?

Sure, if you want the crank not to turn.


When a crank is turned, its done with .001-.003" clearances in mind so a total of .011-.013. Now use a .020 bearing and you now are .007-.009 too tight.

[SpoolinGLH]

what is a std bearing in mm? I have a bearing here that i used for my last engine and it is .001 oversized...i had awseme oil pressure (25 at idle after being warmed up).....what im getting at is i would like to go .001 over sized again when a get a turned crank,but i doubt clevite carrys them...i had a hard enough time finding the .026 mm...

[Mario]

What about knife edging the crank and polishing it? With proper oil control, is there still HP to be picked up here?

[SpoolinGLH]

I guess my main question here is ...What size bearings are people using for there engines???.... if the crank is turned 10/10 then just use .25mm bearings?? Maybe im making this harder then is should be but i would like the bottomend to be tight...

[GLHSKEN]

Bottom line, buy the bearings for the amount the crank has been worked.

[turbovanman²]

I guess my main question here is ...What size bearings are people using for there engines???.... if the crank is turned 10/10 then just use .25mm bearings?? Maybe im making this harder then is should be but i would like the bottomend to be tight...

You use whatever size you need so if the crank is good and doesn't need machining, you use standard size. If the crank cleans up at 10 under, thats what you use. The advantage to going undersize is the bearing is thicker but the disadvantage is your taking metal off the crank.

Yes, your making this more difficult than you need. Use inches, its easier.

If you have a good oil pump, bearing clearances between .001-.004", you will have wicked oil pressure.

[Russ Jerome]

I used to be a proud advocate of the lighter cast crank.

Bending a freshly machined (.010-) crank .006" at less
than wild HP levels changed my mind. Dont get me wrong
my new crank is cast as well but only because I am running
a 2.5 this time, if you have the choice I would go steel.

[SpoolinGLH]

I have a nice forged crank here...use it??? And from what ive been reading ken wouldnt agree.....I mean really......how much would using the forged crank hold me back??

[GLHSKEN]

Its all a matter of personal preference. I mean Reeves makes 460+ torque to the wheels with a cast 2.5L crank... The rotating mass up top is the advantage of the cast crank. That's what I like. Russ made a good point. A forged is "more" bullet proof.

[turbovanman²]

And remember, Russ is a 16V Hybrid making over 400 HP I believe,

[GLHSKEN]

Reeves Makes 406 to the wheels... Just like G Donovans arp bolt letting go, there will always be anomolies that cost $$$ when you are making power.

[GLHNSLHT2]

agreed. If you've got a choice go steel. The weight is mostly around the center of the rotating assembly. An Aluminum flywheel will have a much more dramatic difference. The steel crank motors I've driven and had have always revved up much smoother and nicer than the cast crank versions. 2.2 vs. 2.2.

[Russ Jerome]

I just think for insurance purposes in a high reving 2.2 the
forged crank if available is a wise move. I found my bent
crank while tearing down the block that broke..one of them
went first and may have been related to the other? The
2.2 rev's so fast the 38 vs 44# weight may help keep
the tires from lighting up out of the hole?

As for 2.5 crank I have layed awake at night wondering how
they have outlasted Gary's thrashings. Someone should
lay a 2.2 and 2.5 crank side by side and closely examine
them as to why they outlast rods and forged slugs pushed
to extremes?