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

[Race Clean]

Originally Posted by Larry Hill

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

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
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.

[Rich Biebel]

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.....

[Tom Meyer]

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

[bykr]

Originally Posted by Race Clean

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.

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.

[SSDiv6]

Originally Posted by bykr

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.

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

[Race Clean]

Originally Posted by bykr

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.

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.

[HP HUNTER]

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.

[Larry Hill]

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.

[Mike Taylor 3601]

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*

[HP HUNTER]

Every crankshaft grind starts with a straiten and then this.