Knife Edgeing your crankshaft???

[timberwoof]

Has anybody ever done this to their GA. And is there an advantage to it?

I was talking with a buddy who has a purpose built 67 Camaro SS and he told me he sent his crank off to get knife edged. He told me the reduction in weight is just like getting a liter pulley and such, just more drastic.

Any opinions?

[canadian_racer]

I've never heard of people knife edging throtle bodies but the crank, thats new. I couldnt see it really making much difference, you'd be further ahead to get the light/underdrive pully it would be easier and would yeild probably more HP.

[pyro]

I've never heard of people knife edging throtle bodies but the crank, thats new. I couldnt see it really making much difference, you'd be further ahead to get the light/underdrive pully it would be easier and would yeild probably more HP.
*iagree* thats a new one in the n-body world. never heard of it either.

[timberwoof]

Aight just wanted to ask if its been done. I know they do it for alot of different frace cars for faster reving, but didn't know if its been done with the n-body.

[canadian_racer]

I've never heard of it al all, whats the point of it?

[timberwoof]

to shave weight off the crank so its easier to spin.

let me find a picture of it and show you guys.

edit: Okay I found a pic that is worth it. Its from Turbo Mag. and shows the crank after being knife edged.

http://www.turbomagazine.com/tech/0610turp_castillo_crankshaft_service/photo_02.html

[Skullrot]

Here is a tid bit I found on the net about knife edged cranks. I hope this clears things up for all.

"By knife-edging the individual throws, we both strengthen and lighten the crank. This allows the engine to rev up faster while still maintaining balance to reduce internal vibration. It also reduces windage in the oil in the bottom of the case, thereby reducing both friction on the throws and the potential for oil frothing. In combination with our other internal engine improvements, this helps the engine last much longer between teardowns."

[lastyear4gt]

It is definately a performance enhancing mod, it cuts down on resistance when the crank hits the oil as well as lighten the crank. Its actually quite a common mod among serious engine builders.

[timberwoof]

its just surprising as hell that not to many people on here with some serious mods haven't heard of it. Oh well.

[Vegeta]

I sort of knife edged the crank in the engine I am building. The stock crank is already edged compared to the old 2.8 cranks that have a flat spot on the throws. The knife edge will help cut through the oil mist, so aside from reducing weight (that will possibly have to be added to balance everything anyway), the most noticable aspect is throttle response. A crank scraper would be a good idea if you are going to knife edge the crank so that you have less oil mist for the crank to spin through.

[Sprucegagt]

I sort of knife edged the crank in the engine I am building. The stock crank is already edged compared to the old 2.8 cranks that have a flat spot on the throws. The knife edge will help cut through the oil mist, so aside from reducing weight (that will possibly have to be added to balance everything anyway), the most noticable aspect is throttle response. A crank scraper would be a good idea if you are going to knife edge the crank so that you have less oil mist for the crank to spin through.

It would be even better to have a dry sump oil system, but nobody here is that serious.

[Vegeta]

Yup, that would be ideal for oiling. I disagree that no one here is serious enough for it though....

[Sprucegagt]

Well other than you! lol

[timberwoof]

Well I can see Spy of Milzy possibly looking into something like that. Its definately a benefit.

[gectek]

great...yet another perf mod for me to consider...id pony up the money

[AaronGTR]

its just surprising as hell that not to many people on here with some serious mods haven't heard of it. Oh well.


No, we just don't look for this kind of stuff in the newbies and faq section. Should be in "all go" since that's a serious modification and thats where the serious power modds are. I've certainly heard of it... never heard of anyone doing it on a GA. If I ever build my motor I'd like to get it done. And it's far far more effective and will yeild more power than a light weight pulley, and will allow you more rpm when combined with other balanced/forged internals and proper valve train parts.

[gectek]

yah the only prob is to find a competent shop around ur area to do that. i think the only person i would trust would be the castillo's cranck shop, just send him the crank i have and tell him what i want. but that would mean taking the measurements on my own or at my machine shop, then sending him the instructions

and then a nice machine place to make the scraper...tce???;)

[Sprucegagt]

... and then a nice machine place to make the scraper...tce???;)

I take it you haven't checked out any of the sponsor pages... ;crap :nono:

http://60degreev6.com/store/index.php?act=viewProd&productId=19

[gectek]

no i did i know about the I-J crank scraper, but i mean it would have to be reshaped because the counterweights and both sides of the journals would be changed from the original pattern, so then the scraper would have to be redesigned to scrape the oil off the knife edged crank

[Vegeta]

They make a teflon scraper that you cut to shape. I bet they can make me something up with a good design to start with. I have yet to get one myself to take pics of but the cost is 120 plus shipping. You can only take so much off the crank though before you have to add lot of heavy metal, which increases the cost to something insane. It was around 300 to have my bottom end balanced.

To be honest though, if you are going that far you may as well start with the 3500 crank (or the whole 3500 block for that matter). Forged steel vs cast iron and its already bad ass in design with undercuts. Can't do that to the cast iron crank:P

[gectek]

yah, but i thought the crank on the 3500 had bigger journals and some other differences, but yah i was gonna start with that. better than stock crank and porb not much higher from gm anyway. how rigid is the teflon scraper?

[Vegeta]

You have to machine the mains and rods down and notch the block for the 3500 crank. I think you could machine the crank to clear the block though as well.

The Teflon scraper is sandwiched between 2 metal pieces. You have to bed the crank in so its "scraping" it so its not going to be flimsy.

[gectek]

o i c. ok well it just really depends on what i really wanna do. i think right now its 3500 top end and maybe the 3500 crank with knife edging, plus the scraper. if i get tired of that setup, i may just buy a 3500 bottom and swap the whole thing. but i am just experimenting to see what i like. i know the 3500 has more cr than the 3400, so boost might be not too friendly with the 3500 yet, but i like the idea of the oil squirters even though they are on 5 &6 only, unless i could get the new vvt block, i think it has all 6 cyls with the squirters...(or maybe im wrong)

[bszopi]

The 3500 crank has larger rod journals. If these are machined down to fit stock 3100/3400 rods, then you don't have to clearance the block any (unless you offset grind the crank and thus increase the stroke). The only interference to the block is where the rod end swings, and even then, its only ~3/16" that needs to be clearanced.

[gectek]

so to keep stock stroke, id look at cutting the journals down on center and just clearancing the block for the throws on each side of the block or just on the oil pan. so is that the bottom of the rod end(big end) or the bottom of the cylinder that would nee to be clearanced

would there be any advantage to stroking it if i were using stock pistons...that would only raise cr wouldnt it.

[bszopi]

To keep the stock stroke, yes, you would grind the journals evenly, keeping the "center" in the same location. If it was ground this way, there would be no clearancing of the block required because the rod ends would move in to the same locations as the 31/400.

If you offset grind the crank to increase stroke, the outer end of the crank would maintain approx the same location, and thus the rod ends (big end) would hit the block. Both the block and the oil pan would have to be clearanced. I'm trying to find a picture to show the 3500 block alterations...

Well, I can't find the pictures I have, so I'll have to go take some more. But, the baby is crying and the wife is working, so it probably won't be tonight.

[lastyear4gt]

o i c. ok well it just really depends on what i really wanna do. i think right now its 3500 top end and maybe the 3500 crank with knife edging, plus the scraper. if i get tired of that setup, i may just buy a 3500 bottom and swap the whole thing. but i am just experimenting to see what i like. i know the 3500 has more cr than the 3400, so boost might be not too friendly with the 3500 yet, but i like the idea of the oil squirters even though they are on 5 &6 only, unless i could get the new vvt block, i think it has all 6 cyls with the squirters...(or maybe im wrong)

Why bother if you really want a 3500 pull the 3400 put in a 3500. Kind of a waste of time to gain 20 HP though.

[gectek]

not with the mods that sappy is lookin at for the heads and other areas. the cams i heard are the same, so that is another area. but this post has gotten way off topic. if i had the chance i would knife edge my crank

never heard of it before this, but good info and looks like good perf/ DD mod

[AaronGTR]

I thought they also changed the internal crank position ring on the 3500 crank which made it incompatible with the 3400 sensor and pcm? Did someone find a way around that?

Anyway, I'm not sure if it would be worth all that trouble since I still haven't ever heard of anyone breaking a 3400 crank. It might not be as strong as the 3500 but it's plenty strong enough and if you had it properly worked over I think it would handle anything that anyone on these boards is going to throw at it.

[gectek]

yah they (http://60degreev6.com/store/index.php?act=viewProd&productId=42) have the reluctor ring mount that goes on the crank pulley. i guess that would be the way to make the 3500 crank work in the 3400, if you either machined the journals on the 3500 crank or made the mains bigger on the 3400 with clearancing and plugged the old 7x cps hole

[Vegeta]

ive heard of a 3400 crank breaking...on a stock engine driven by an older couple. Yeah, defect or something.

The point isn't the strength,its the design of the crank. That is pretty much what knife edging is about, the design. Undercut throws cut through the oil mist easier:)

[timberwoof]

Aight my Buddy got his crank back in but hasn't put it in the engine yet. When he dyno's it I will give you low down on what the gains were.

[Blackbombshell9]

My 3400 crank is getting a knifeedge in a week or so. But like Ben said, they will add material to help balance the crank.

[timberwoof]

I think the deal with this process is to help reduce the drag created by the crank hitting the oil. Which is pretty good. Example: take your hand and put it flat, now hit a pool of water and feel the resistance and observe the big splash. Now take your hand and turn it sideways and strike the same pool of water with the blade formation, less resistance going through the water and less splash. Awe Confutious say go to sleep with hard problem, wake up with solution in had.