In light of people talking about proper quench, degreeing cams, block decking, etc. I would like to shed a little light on a subject I have yet to see brought up here, and that's the difference between having a crank ground, and having one index ground.
*this topic refers to factory cranks, but aftermarket cranks should at least be checked for accuracy*
When you have a crank reground, each rod pin is set up induvidually and ground to the next undersize. Zeroing the journal prior to grinding requires you to alter the stroke and/or pin timing (index) in order to center the journal.
Having a crank "stroke and indexed" is very often overlooked and is definately worth some power. How this is done is the crank grinder is set up for a certain stroke (3.480" for instance with a 350 crank) and then the front rod pin is zeroed so you don't change the crank sprocket timing. Prior to grinding the rod pins, you rotate the chuck (and crank) to the other 3 rod positions (a good crank grinder has detents exactly 90 degrees apart from the 4 positions) and check the journals for stroke and timing. Let me tell you, Chevy's are BAD for differences in stroke and horrible for pin timing. What that means is even if you degree your cam in perfectly for # 1 cylinder, with most factory cranks you will have a situation where the cam (and ignition) timing will be either retarded or advanced with cylinders' 3 through 8. By having your crank stroke and index ground, you ensure that all 8 cylinders are producing equal work. (naturally, this doesn't consider any other variables such as port flows, cam timing variances from front to back, manifold flow, etc.) You can expect the crank to have to go .020" or .030" under on the rods rather than .010" to allow this process to happen, and there are many factory cranks that would have to go .060 under on the rods to get them indexed properly. Those cranks go into stock engines, we save the good ones for performance engines.
If you are considering having your block "zero decked" then this is really a "must do" operation. It is not uncommon to have the crank stroke vary .015" from one pin to the next, and that will mess up your efforts for a perfect job. Imagine how disappointing it would be to measure the 4 corners, have the block decked to zero, then install the rotating assembly, only to have your center cylinder pistons hanging .010" low or worse yet .010" OUT of the bores.
Another trick we use when looking for that last horsepower is to increase the crank stroke by a little bit, called offset grinding. We are not talking a huge amount, but say .005 to .025" additional stroke. (My .030" over 400 is 408 cubes due to an additional .010" of stroke, 3.760". You bet it's indexed at 90 degrees!) Stock and super stock use this trick, I recall them being allowed +/- .015" from factory stroke. This move gets the pistons up higher and may eliminate needing to deck the block with certain combos.
So next time you need a crank ground, consider getting it blueprinted, or "stroke and index ground", it doesn't cost a lot more than a regular grind and can result in a more powerful, efficient engine. Just remember, your crank may not clean up in a reasonable undersize, so don't be suprized to see it .030 under on the rods when you get it back.

Hope this story was interesting and shed some light on a rarely discussed topic.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Rust, very interesting indeed. On the subject of offset grinding, how do you modify the big end of the rod for the smaller journal size on your engine? For example, if I was to index grind my stock 400 crank for say 3.850" from the stock 3.750", would this not require something like a small-journal 327 rod?

I'm not as up on this particular topic as I'd like, but have often wondered if its worth the while to offset grind a stock 400 crank to get say, 415ci.

What's your take?

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'Silver Bullet' 1977 Z-28 413" SB
11.73 @ 115.10 and dropping...
Old Vortec combo:
12.15 @ 110.52
1989 GTA L98
Daily driver

This thread should have been called 'Rusty's christmas performance tip'

I like the idea of offset grinding as a substitute for chopping a lot off the decks. You achieve the same thing but gain a little advantage in the process.

Now that you have mentioned the indexing thing Rust I think I might get my chinese stroker crank checked before it goes in, there's quite a possibility it wasn't built to precise tolerances...

Very astute Dirt!
Unfortunately, due to factory variances, starting with a standard rod pin you are unlikely to get more than .080" additional stroke out of .100" of rod journal. You might be able to hit 3.850 stroke at say .020" under small journal size. And you are correct in suggesting the SJ 327 rods. However, you would be much better off buying aftermarket rods to do this, the 11/32 rod bolts in those rods are mighty small.
If a guy wanted to do one of those, you could start with a TRW long rod flat top piston and after doing a mock up just top the pistons as required to hit zero deck.
Real world reality is that cost will always be a factor with these oddball combinations. Now if you had a buddy that would do the machine work for cheap or free, that is a different situation. http://www.nastyz28.com/ubb/wink.gif
Of course, with the factory crank, balancing becomes more critical as the stroke increases, requiring more counterweight to balance.
C'mon Dirt, bite the bullet and get that 3.875 stroker crank, you know you want it! http://www.nastyz28.com/ubb/wink.gif

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Thanks Matt!
To be honest, I don't recall the last time we actually checked a shiney new stroker crank for index. It's tough to charge for it, and what little profit there is selling an aftermarket crank, you would burn up checking it out. Unless the crank grinder is already set up for your particular stroke, expect to pay roughly 30 mins of shop time to have it checked out.
Best of luck and please let us know if it's good and what brand it is.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Har har. And I know how much you're itchin' to build me a 427 MoTown motah too, eh? http://www.nastyz28.com/ubb/biggrin.gif



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'Silver Bullet' 1977 Z-28 413" SB
11.73 @ 115.10 and dropping...
Old Vortec combo:
12.15 @ 110.52
1989 GTA L98
Daily driver

In the 80s lots of folks found their way to the shop I worked at not due to its performance reputation but due to the industrial equipment there. We had 6 crank griding machines. One was a small Berco automotive only grinder that was quick to set up and wicked accurate. Index grinding and offsetting was a snap. No one else around had anything like it at the time.

Factory cranks were 99% of the stuff hot rodded as cheap quality sftermarket cast cranks didn't yet exist and aftermarket steel was for rich guys. We got in lots of practice. Cheap tricks are great. I second what Rust says...It was amazing to see how far out factory cranks could be sometimes .020 was beeded for a correction. We also noted most stock cranks were "twisted" and seemed to settle that way after they'd come out of 100000 mile blocks. Indexing cured the twist and they don't seem to "twist" again after they've done it the first time.

*Prints this post, and immedeatly runs down to the machine shop*

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73RS/LT/427

What about the twist that happens when the engine is in operation? http://www.nastyz28.com/ubb/smile.gif

Wouldn't you want to index grind to account for the rear journals being twisted into a retarded timing due to the load of driving the drivetrain...

Front journal indexed, each successive journal behind it being an additional 1 degree advanced...


LOL,
How complex do we want to get?

Index grinding is a common practice on truly blueprinted motors.
It is a requirement on a motor that will be subject to teardown inspection for tolerances such as NHRA Stock Eliminator where they get down to a gnats ass.

It is a worthwhile deal to do, but there can be more to it than the 90* offset of each journal.

<font face="Arial,Verdana" size="2">Originally posted by Matt Jones:
[B]This thread should have been called 'Rusty's christmas performance tip'

\B]</font>
I agree,
My friends did an index grind for my 427 crank to cure a couple pistons that were coming out of the hole because I changed my mind on using the stock rods and bought some Eagles after the block had been decked.
I didn't know until now that it may be good for a couple extra hp. http://www.nastyz28.com/ubb/smile.gif

Tks Doug




[This message has been edited by craggar (edited December 24, 2004).]

<font face="Arial,Verdana" size="2">Originally posted by ZS10:
*Prints this post, and immedeatly runs down to the machine shop*

</font>

I can guarantee Chuck is knowledgable in this area. Perhaps he will grind you a stock 427 crank and another one that's nice and indexed and dyno both combos so you can post the results?

Seriously guys, I feel this is an often overlooked area for those building on a budget with stock components. I hope the information was clear, concise and helpful to all who read it.

Merry Christmas!

P.S. Jake, how can you be guaranteed the journals lag exactly 1 degree behind one another, maybe it's 2 or 4 degrees? Then what about the cam, a big roller with a small base circle will certainly "wind up" and release depending on it's position. You are correct, where does it stop? Without overthinking this, getting all the pistons to TDC when they are supposed to be is the idea behind the post. I feel it is a very worthwhile operation.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

I whole-heartedly agree on this BUT it won't be cheap, therefore won't be done all that much!! IMHO...

This stuff is in the realm of GOOD"blue-print" stuff so you pay for the quality of workmanship that you want..

pdq67

PS., and this is why two guy's could order identical '66 Dueces and one would run better then the other from the git-go!! Like one motor was made on a Monday morning after a holiday AND the other Wednesday afternoon sorta deal when the motor guy felt better..

I agree with you wholeheartedly Rust,

Just throwing something else in the mix that is also a real factor.

The Formula 1 guys take all this into account, and sems I remember reading they had done some studies to determine the approximate amount of flex encountered (reluctor rings between each throw..?)
but as stated, it is impossible to know, it is an ever changing measurement, as the rpm and load would affect the amount of cranckshaft distortion...
There's a reason we run harmonic balancers.

Paul,
Seems like last one I had indexed was $45 additional...

So a normal grind was ~$75, and indexing was $120.

I do wonder how close my stroker crank was...

Hmm, if it ever needs turning we'll find out.

And additionally,
as Rust stated, getting the stroke length accurate is the most beneficial part of this operation IMO...

The slight variation in timing of the crankshaft throws on a typical street/strip motor isn't as critical.

Wonder if the $12 plastic distributor cap terminals are indexed as good as the OEM cranks...

Now,
oil hole timing...
Wanna open that one Rust?

I think this string flirts with a point thats always debated here. When discussing little individual tricks, someone always reminds us that "its not needed on the street". Viewed one at a time things like indexing, decking, long rods, partial fills, balancing for lower rpms, etc are all supposedly "not needed" on a 6000 rpm street car. Many have run great without any of it. On the other hand depending on GM quality control on a mass produced engine also explains lots of mishaps and results that were less than expected.

Step back tho and look at the cumulative effects of careful attantion to lots of small details and you get reliable, repeatable horsepower. Thats how they build diesels to work at 18 to 1 compression! They "blueprint" them. As long as they aren't a big cost then lots of small attention to detail can add up and get you a small but noticable edge over the other guys "same" engine. Maybe the engine just seems to rev a little snappier or run a little smoother but it can show. I enjoy playing with the engines and wouldn't dream of leaving it all up to a bought package.

By the way, I did a bit of math and on a 3.75 stroke crank .027 out in radius equals 1 degree. The point that the indexing helps straighten out the stroke more than the timing seems fair. Still its seems to me to be easier to straighten out all GMs stock machining, nail your clearances and end up with just a little less friction in a lot of cases.

PDQ-In your P.S. you nailed that one on the head, take one new "whatever" and compare it with another of the same model and buildup and it would perform better, that's the difference between the tolerences stacking up in the favor of horsepower and the other one having poor cylinder timing, cam timing, chamber volume, etc.

We charge less than half again over a normal crank grind to stroke and index. No doubt this option is chosen by those looking for additional power, not those looking for a stock rebuild.

Jake-Your right about all the ignition intolerences. I'm sure that's why looking for the last horsepower run a crank trigger. Those who can afford run the fancy digital ignition boxes play for a day on the dyno, altering the timing for each of the 8 cylinders. Would be nice to do/have, but WAAYYYY out of my budget!
Dunno what affect oil hole timing has, they seem to be all over the place on some cranks, but as long as the oil is supplied all is well. You need a fluid engineer for that one, can't help you there.

Camertom-I'm glad you figured out what a degree represents in thousandths of an inch, I was kind of curious on that but never bothered to check it out on the crank grinder, would be easy to do though. I forget which way the 2 middle crank pins are normally oriented with a SBC crank, but most of them I have to advance the crank to grind one of the pins then redard the crank pin to grind the other, that is referring to the # 1 pin. The front and rear pin seem to be pretty close on most of the cranks I have done, 350 cranks anyways. As you have stated, it's the little details that mean the difference between a good engine and a great engine. When I did the conversion from my stock rods to the Scat rods I also milled the top of the pistons back down to zero deck, and they were all over the place, meaning the tolerences of the stock rods and having resized them twice over the years varied their lengths quite a bit. Of course, this assumes the Scat rods are all identical in length. http://www.nastyz28.com/ubb/rolleyes.gif

If you are looking for the edge and can afford to do so, take care of all the little details that are often overlooked and you may very well lay the smack on you're buddies identical car. I can't begin to name all the people who have seen my car run ask if it's a big block or how much nitrous I run.

It's fun to get people thinking about something with a fresh thread, and if someone applies this info and goes faster, good for them!

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Rust,
I was looking at a aftermarket forged (SCAT or Eagle) SBC crank a few weeks ago at my machinist place...

It had faulty oil timing on the #3 journal.
it LOOKED OK. I couldn't identify what was faulty by looking at the oiling passage, location on journals, etc.

But it had failed the rod bearing there 3 times.

Machinist said, crank had been replaced with a different one and problem went away....

The closest dealings I have had with the crank grinder is helping to move that heavy son of a $%&(&^%(&*^ off the semi and into the shop, then level it. What a pig those things are.

You are right Rust that some cranks are really screwed up and it takes a lot of time and skill to get them right. No way does my brain wire up correctly to do that type of work. All I know is when Jon is grinding a crank up it's best not to bother him lest he whap you upside the head. That stone doesn't allow too much of an error when your bringing it in toward the journal.

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70 SS 454 CI Dynoed 684 HP, 702 TQ All Aluminium Fuel Injected Small Block , plus 200 - 500 HP NX nitrous system.

Of all the machine equipment I've never run it is also the crank grinder, so I'm in the boat with you RickWI..

I've watched it many times, I understand the process, but I get confused about the setup on the actual grinder...

I think I could setup the mains and successfully grind one after a few tries on a junk crank, but setting up the rods... I dunno...

The wheel on a crank grinder is one BIG mutha though, I'd hate to have one of those suckers come apart on me.

Jake-I couldn't begin to speculate what's up with that crank. Ok, I could speculate, oil passage offset on the main journal enough to not line up with the groove in the main bearing, that would be my best guess. Other issues dealing with journal shape or condition (surface finish), tough to even guess without the part in front of you.

The most stressful part of the operation is bringing the stone into the workpiece. You can adjust the infeed speed (and I should slow ours down) and believe my my heart has stopped more than once, kind of the same feeling one would have the moment the police's lights start to flash after doing a huge smokey burnout to impress your buddy in the passenger seat. Setting up the rod journals is actually easier (once the course setting is done, say within .050" in timing, stroke is normally within .015" of stroke) than setting up the mains. With the mains I shoot for a maximum runout of .0005" on the 2 end journals, so naturally an adjustment on one end affects the other. Setting up a rod journal, first you set your stroke to factory specs, then there is a fine adjustment for the pin timing, then whatever offset your dial gauge shows for stroke, you adjust both your chucks that amount, and a final timing adjustment. Easy to talk about, easy once you've done a few cranks, but definately a ton of steps to remember for the first few cranks. Nerve racking for sure, especially on the oddball cranks. (mess up a stock 350 crank, grab another core, mess up some old diesel crank from an early 1900's tractor, you ain't gonna have that on the shelf http://www.nastyz28.com/ubb/wink.gif ) I guess you could say the stress level of the job is proportionate to the rairity of the crank or the value of the crank. The worst is probably a loud noise such as someone using a hammer while you're deep in concentration while grinding. http://www.nastyz28.com/ubb/eek.gif

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Rust,
When I saw the crank, I thought (diagnosing in my head LOL ) spun a rod bearing...

Casually talking about it to the machinist, he said yeah, and started telling the tale of woe.

This guy is SHARP. He's early 60's, does everything, lots of pretty healthy stuff. Has been doing it for years. 90% performance work.

He has NO employees... (one of the reasons I use him) Not the quickest to get something done, but second to none on quality.

He does cranks in house.

He said he suspected an oil timing issue.
So of course out of curiousity, I had to examine it closer.

I couldn't see anything out of place, centered, looked about right index wise, could see through the hole, etc..

One journal was black and scored, others fine...

Looked like a spun bearing...seen it a thousand times...

He had originally built it ( I THINK this might have been a roundy-round deal, and I also think it was a 3.48 stroke)
it had failed twice, and on the 3rd try he installed a stock GM forged crank and fixed it IIRC.

It's been a couple of months ago so I'm foggy on it.

Anyway,
I've read some articles on oil timing and looked at the SBC design.
And can't remember half that stuff, especially lifter/pushrod oil timing, but...

I asked him,
why not use fully grooved mains, wouldn't that "fix" the issue. He said no..

Then we started talking about a real motor ( my BBC http://www.nastyz28.com/ubb/smile.gif ) and forgot about the scrap metal. LOL

Actually I think that was when I was helping a board member with his 421 SBC... LOL

Perhaps noone will ever know the issue on that crank, it could have easily had an issue with a tight rod housing, incorrect bearing clearance (1 rod shell a different undersize), insufficient side clearance, out of round rod housing, etc. After turning a rod bearing the rod would have needed a resize, correcting the issue.
Just guesses

You may recall the bearing issues I had with my 408 a couple of years ago, tearing up the faces. Internally balancing the crank corrected that issue 100% (bearings looked like new) but using the Federal Mogul race series bearings for the half season in 2003 provided much better looking bearings during teardown at that time. The mains are of a 3/4 groove design and since then we have used them on all the high HP setups.

An interesting note with the mark 5 and 6 cranks, I believe GM has changed the oil timing/gallery locations to match the small block cranks.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Great thread, please continue.

I was talking about first the rods getting equalized, then the crank equalized, then taking one rod assembly, less rings, and the crank and installing both, but shifting the rod to the four corners of the motor so you could figure out the decking dimensions.

Pulling her back down and decking her on the money, then reassembling her for one final check, then tearing her down and then cleaning everything and finally assembling her the final time!!

Most of us, AND especially "shade-tree" guy's like me won't opt for the added fitment costs BUT I am sure glad that others do..

BUT I gotta say that if I was after the money and going "balls-out", I would do all this AND probably more to be competitive!!

pdq67