Hey all,

What is the general consensus as to what level the stock crank and case bearings will take?

This question is probably the biggest thing holding me back from deciding on what I want to do build wise. Ive looked at everything from just a cam swap to dropping in an SE120R

What Id most like to do is just do a set of jugs/pistons and a cam swap, there's a couple combos that will put me at 110 square or better going this route , which was my original goal, BUT I'm concerned that the crank or bearing wont handle that level.

So, if anyone has some input here I'd appreciate some guidance on power levels at which to not be worried and at what level bearing swaps and crank work really SHOULD be done

thanks in advance

 

Plenty of 120R crate motors running with OEM cranks which are not welded. Any crank can be tweaked, even if the pin has been welded. If you don't abuse the build you are planning, i.e., wheelies, burnouts and dumping the clutch/drag racing, you should be OK. No need to borrow trouble; build it, run it and if you tweak the crank, address the issue then.

 

The 120R has a: "4-5/8" stroke SE Pro Stroker Flywheel and rod Assembly", which may well be pressed and not welded, but does sound rather special!

 

That bearing is waaaaaaaay tougher than folks give credit.
We step those up to that power level all the time, and as djl has said, as long as your not fanning the clutch lever, you should be fine.
Scott

 

I wasnt wondering about the 120R's crank, I know it'll take a pounding, but going that route is wayyy overkill for what I want to do and wayyy more $$$

I was concerned about the 96 inchers stock crank, rods and bearing, if I do a top end job to get 110-120 square

thanks all and thanks Scott, Ill go with my original plan and do a top end job, ride sanely and enjoy myself.

 

Undestood. Just using the 120R crank as an example of a non welded crank that will hold up to subtantially more power than you will be making.

I get it and, like I and Scott told you, don't be abusive and the stock 96" crank will probably hold up but if you tweak it, you can address it then.

 

Lots of different answers for this question,it depends on who you ask.The verdict is not out on the 120's yet,they are too new.If its so bullet proof then why no warranty?? Anything you take the time to build should be as bullet proof as you can make it.It's an investment,so invest in making it sound.Why build a bigger motor, & not be able to get on it sometime knowing it can handle it!!! Even if i was to buy a 120R i would tear it apart ,& do the crank!! It has to ,& needs to be done.1 downshift with to much rpm & the crank is toast,tearing up the entire motor.That's not worth it to me!!!To each his own,but there is no way I would build a motor without building a solid base!! A good Indy will recommend you do the crank & probably wouldn't build the motor without doing the crank!!!

 

There is not warranty because it is "For Race Application Only". Welded cranks aren't bullet proof either. Sure, the little bit of weld on one side of the crank pin is some additional insurance but no guarantee that the crank will hold up. Hoban Brothers, aka Darkhorse pro plugs their cranks and won't weld them unless the customer requests the crank be welded. Of course it is an individual call but I would not tear a 120R down just to weld the crank.

 

The general consensus opinion is that the stock crank and bearings should be good to about 120 ft lbs. Some guys will say that's too much power, and others will say you can build beyond that, but as a general statement, keep it under 120 ft lbs and you're relatively safe.


It's doable to hit 100 hp with stock heads and throttle body, but to get beyond that takes a little more work and planning. 90 hp is easy, 100 hp is harder, 110 hp is a bunch harder. It's almost an exponential curve once you start nearing the practical limits of stock equipment.

 

There are no unanswered questions on the 120R that I have seen. We haven't had any reports of failures on them, only wide grins at the performance they give.

There is no warranty on those engines because the factory cannot sell an engine that does not comply with all the noise and exhaust emissions regulations. You should buy one now, before they are discontinued!