Dumb question... +/- .015 on crankshaft
 

Ok dumb question, how much power is there in having the crank machined +.015 on a sbc. Is it actually worth the expense? Is there another purpose for this other than added stroke?

Thanks,
John Beasaw

Re: Dumb question... +/- .015 on crankshaft
 

Yes.

Re: Dumb question... +/- .015 on crankshaft
 

If you are making 1.5 HP per cubic inch, in theory you add 1.5 HP for every cubic inch you add.

A correctly stroked crankshaft will also correct a poorly indexed crankshaft.

Re: Dumb question... +/- .015 on crankshaft
 

I personally have found cubic inch to be worth nothing with induction, comp, and cam being the same in a modest bracket race situation.

Re: Dumb question... +/- .015 on crankshaft
 

It depends, if you want to run with the BIG DOGS, ...you can’t leave ANYTHING on the table.....

Re: Dumb question... +/- .015 on crankshaft
 

It's the thing you do when you want that "LAST" little bit......

Re: Dumb question... +/- .015 on crankshaft
 

On a Stock or SS we always run .013 stroked crank.
Has to be indexed anyway at least with all our Mopars
I have seen 10 stockers in class within less than a Tenth
of a second

One year in Class in Denver Natl's = we had a race decided
by .0001

Plenty of Class racing with an hundred or two!

Re: Dumb question... +/- .015 on crankshaft
 

Dean is correct, you're effectively killing two birds with a single stone!

Re: Dumb question... +/- .015 on crankshaft
 

Adjusting stroke will not correct index. To fix index try to find a grinder, machine, with new or rebuilt chucks that has index stops at 90*. After its index always check TDC and zero on damper. Rolling the crank to get it to "clean up" @ .020" under while stroking it .014" will some time change the relationship between the two. To check quick index #1 and #6 should arrive at TDC at the same time using two dial indicators.

We use to grind cranks for Kuntz & Craft years ago. In fact we have lost to a 428 heads up with a crank we stoked and indexed for Jim and Keith.

Re: Dumb question... +/- .015 on crankshaft
 

Thanks for the insight. I knew the rules allowed indexing/stroking, i just wasn't sure if there was a large enough advantage vs expense.

As for my combination i don't have a budget to run with the big dogs. Game plan is .40-.50 under in the heat just to play.

Thanks
John Beasaw

Re: Dumb question... +/- .015 on crankshaft
 

Stock or super stock? A lot of builders are grinding the rods journals to a smaller size say 2.100 down to a honda rod 1.88, less bearing speed and lighter. Tom

Re: Dumb question... +/- .015 on crankshaft
 

I put that in the category of 20 things that add up to make a difference.

If your goal is 5 to 6 under, at this time, it's not worth the effort or cost.

Re: Dumb question... +/- .015 on crankshaft
 

As my friend George would say “ if it can’t hurt it helps”

Re: Dumb question... +/- .015 on crankshaft
 

Tom stock has an undersized limit on how far under a crank pin or main can be turned. I think it’s.070”, unless it’s a FE Ford crank pin of 2.438” it can go to 2.200”. “If can’t hurt it helps”. That is almost 10% reduction in surface area. And so it goes

Re: Dumb question... +/- .015 on crankshaft
 

When I built my last engine, I had the crank work done by Bullet. They stroked, indexed, added a large radius in the corners, and treated the crank for around $300 if I remember correctly. I'm not sure if they do this any more or their current cost if they do. I think they will even balance in you have the bobweight.

I do know that my local machine shop charges over $100 to turn a crank. I don't see how having a local shop turn your used piece or buying a ready to go out of the box stock crank is saving that much money.

Add to that, I've used some ready to go cranks by companies like Crankshaft supply in my day job. To pull an already prepared crankshaft out of the box to find it's had the journals welded up and then turned....well it's a sickening feeling.

Re: Dumb question... +/- .015 on crankshaft
 

I remember when I was doing my first "Stocker Crank" in 82 or 83 that I had to bring in 3 or 4 Cranks (std size) to the machine shop before we found one they could use to get it both indexed and stroked for me at .010 and .020,I dont remember what max undersize was back then but you didn't wanna go to .030 and dont have another shot at grinding it, if someone already had turned a crank .010 at the rod for some reason it most certainly was waste for a serious Stocker engine,since those days they allowed more and more undersize and also aftermarket parts that was nowhere on anyones horizon.

p.s. I personally think it was a good move for the FE Fords to get the Chevy Rod,they messed up the tracks pretty bad before that :D

Re: Dumb question... +/- .015 on crankshaft
 

I don't understand how turning a cast crank pin down .238'' to 2.200 would make the engines self destruct less.

Re: Dumb question... +/- .015 on crankshaft
 

No...ofcourse they should have gotten a Rod that fit the engines as they where approved instead of what they submitted..I said it before, it must have been some real Ford lovers in power there at NHRA for a while:rolleyes:
But they needed a better rod for sure to able to be in the mix at the time.
I remember talking to Aldon Miller some 20 years ago or more when he was one of the top dogs, he said when they got to 500+ hp they started becoming hard to keep inside the block.

Re: Dumb question... +/- .015 on crankshaft
 

I worked in an engine/machine shop back in the 1980-1990 era

That's about when the .015" added crank stroke spec came along.

We used a real popular crank shop about an hour away and the guy who did the cranks was very well known and had a ton of experience going all the way to famous shops in California.

We did a ton of work for a real well known shop in NJ.....we also picked up cranks from them and they went to the same crank grinder.
We were just passing them along....

A 454 crank was done for a SS car and it got DQ'ed at Indy for being over the .015" limit after a class win.....

The engine builder never caught it.....he was not happy....the car owner was really not happy.....

I remember the flack after that one......

Stuff happens.....

Re: Dumb question... +/- .015 on crankshaft
 

Larry what about the guys that put those big old big block cranks in a lathe and take a bunch of weight off? Mostly chevys. Tom

Re: Dumb question... +/- .015 on crankshaft
 

The Lemans capscrew rods are a fine piece and are good for well over 500hp so I don't know what you guys are talking about.

Re: Dumb question... +/- .015 on crankshaft
 

The LeMans cap screw connecting rods, were a good rod in its time. Connecting rod technology, materials and fastener technology has changed.

Re: Dumb question... +/- .015 on crankshaft
 

I don't know Ford's, only what I get told.
If they where ava. for all and approved at the time I guess there shouldn't have been a problem then!

Aftermarket Rods is the least problem in what parts NHRA has approved for Stock,in fact the best move so far imho.

Re: Dumb question... +/- .015 on crankshaft
 

As far the BBC crank stroke go they can vary quite a bit, lets take a 454 cast 039 crank for instances, the factory grind had a high of 4.010 and a low of 4.002, we indexed it and ground it to 4.010. We just did a steel 454 7416 that came in at a low of 3.990, it was indexed and ground to 3.990. Just because its suppose to have a 4.00 stroke and be equal on all four pins, its NOT. So it makes since any crank prepped for a stocker would be indexed and ground .013 over factory specifications.

Re: Dumb question... +/- .015 on crankshaft
 

We had a crank in the shop that was .011” long from the factory but the index was off a few degrees. It still made a good stroked stocker crank at .010 .010. Informed the customer we had to roll the crank to get it to index and the timing marks would be off at TDC on the damper.

Re: Dumb question... +/- .015 on crankshaft
 

I go with the every little bit helps theory.. 1 here 2 there 5 there all ads up into a bigger number....
the+.013 stroke is the probably least amount of gain in the crankshaft mods.. I believe the equalizing of the stroke and the indexing of the throws are the more important...
getting all the cylinders equal on stroke and same timing...having all the cylinders equal, producing same power..you could ride a bicycle with two different length cranks for the pedals and have them 120* apart, but it sure wouldn't be smooth or very efficient
when you are grinding a stocker crank you better have a stroke gauge.. crank grinders are set for stroke but it doesn't always come out exactly what it is set to .... we go +.013 and if you miss by a couple thou on the stroke wont check legal... I check stroke as I go and some times have to adjust +/- a few thou on stroke...
best I can tell around .040' on index=about 1*

Re: Dumb question... +/- .015 on crankshaft
 

Every crankshaft grind starts with a straiten and then this.