Crankshaft lightening

[Gene Fiore]

I spoke with what I consider a reputable machine shop here about lightening my crankshaft. He told me that the problem you can run into is that you might not be able to balance the crankshaft if you attempt to lighten it. Does this sound right?

 

[Does10s]

Gene,
If you run lighter pistons and rods, then they should be able to take a bit off of the crank.

At the least you could "knife edge" the counterweights. They should be able to balance after that.

That being said I haven't done this to much extent yet. Just some minor cleanup and weight removal to match the rods/pistons.

Will

 

[Gene Fiore]

I also asked them about knife edging the crank and he told me that procedure is very labor intensive...almost seemed like he was trying to discourage that procedure. He mentioned how one of their employees spent 8 hours knife edging his own personal crank.

 

[CNC-Dude]

In an inline engine, the crankshaft itself is balanced independent from the rods and pistons, as you know im sure. So any material that is removed from the counterweights, an equal amount has to be removed from the rod throw or cheek area to rebalance it. You can have a set of aluminum rods and some JE ultra-light pistons, or a set of Carrillo steel rods and heavy pistons as long as they themselves are balanced, doesn't affect the balance of the crankshaft as it does in a V-style engine that requires bobweights to be attached to the crank journals to simulate the rotating weights. I've prepped many dozens of Cheby inline crankshafts by both knife-edging and removing a large amount of counterweight, and have been able to remove 8-10 lbs. off the total weight by doing so. As the one shop you spoke to pointed out, it can be fairly labor intensive. You will or are finding out, that even today, inlines do not have the respect that they deserve, and many shops will turn you away, simply because they don't consider them a worthy engine to fool with. They actually are much easier when it come to balancing to deal with than a V-style engine, simply because they do not require the extra time involved to keep putting on and taking off of the bobweights....sounds like they just don't have the desire to help you out or take your money. It is well worth the effort to do this, so i'd keep looking for another shop that will be willing to help you.

 

[Thad]

Some where in the archives are posting of one member racing with NO counterweights on his 300 crank. Have also watched as a flathead Ford (Merc) Bonnie lakester enginbe was dyno'd, NO counterweights.
Can't get much lighter than that.

The straight six is a wonderous beast, The design can be balanced both dynamic and static without any harmonic imbalance except the actual firing impulse. The crank design lay-out is such that the impulses are cancelling rather than amplifying.

 

[rbohm]

8) any crank can be lightened up a fair amount, and knife edging isnt that difficult, but the more counter weights that need edging, the more labor that goes into the job. as for balancing a lightened crank, that isnt hard at all. slugs of mallory metal are added to the crank as needed to rebalance the crank. one thing though, if you lighten the crank too much you run the risk of breaking it, but most cranks you can take out about 10lbs with no problems.

 

[eeyore]

Many shops don't seem real interested in working on anything other than a V8. With that said does anyone know of a shop that wants to work on a six in south-eastern Wisconsin?

By the way Gene, did I see a quick glimpse of your car at the Arizona Pinks All-Out?

 

[Gene Fiore]

By the way Gene, did I see a quick glimpse of your car at the Arizona Pinks All-Out?

Not at a Pinks All-Out, but if it was at the 1320x, which was put on my Nate and Adam Prichitt from the Pinks crew last year in Arizona, then yes.

 

[82F100]

Gene, let me ask a couple of people here in town that I know also do a search for Ron Coon, IIRC they are the ones that do the 240/300 cranks for the circle track guys.

 

[Gene Fiore]

Gene, let me ask a couple of people here in town that I know

Thanks Rich! I really want to get going on this...I don't want to be putting the motor back in when it's 110 deg in my garage. The machinest that I will be using for most everything has been too backlogged for me to take my stuff down to him. Probably won't be until early to mid next week. One trick on the crankshaft that he suggested was to just polish up the throws so it will glide thru the oil easier and not pick up as much. Not sure how much that would help.

 

[CNC-Dude]

Gene, let me ask a couple of people here in town that I know

One trick on the crankshaft that he suggested was to just polish up the throws so it will glide thru the oil easier and not pick up as much. Not sure how much that would help.

Many people have the misconception that the crankshaft actually makes contact with the oil standing in the sump. In fact, it will cause catastrophic engine failure almost immediately if it does. Take your oil pan with it off the engine and fill it with the required amount of fluid, either parts solvent or water, and you will see that the full mark is well below where any rotating parts can make contact with it. The main reason for knife-edging the counterweights is for aerodynamic drag. Much like when you stick your hand out a car window going 50 MPH. Turn the palm of your hand facing forward, and you easily feel the drag pushing against your whole arm, but then turn your palm facing down and you have virtually no resistance on your arm at all. I had a customer decide one time he would just add two more quarts of oil to his stock 5 quart oil pan instead of buying a deeper oil pan for the added capacity. Just idling it around in his shop, the constant slapping of the counterweights into the oil in the sump pulled the entire main webbing out of the block before he even could get the engine to the track....

 

[Gene Fiore]

Thanks for clearing that up!

 

[Lazy JW]

I remember reading in Smokey Yunick's book how he put a plastic window in an oil pan, then observed it while running on a dyno. He described a continual mass of oil "spray" cloud in sort of a ball surrounding the crank shaft. This oil cloud was constantly moving and squirming around, and this was on a stationary dyno. Put it in a moving vehicle and the dynamics will most certainly change; this led him to question the usefulness of balancing an engine to the Nth degree.

As mentioned above, the biggest gain at steady rpm is from aerodynamic drag; reducing rotating mass certainly helps acceleration.
Joe

 

[StrangeRanger]

And a windage tray reduces the oil cloud

 

[rbohm]

And a windage tray reduces the oil cloud

8) as will a crank scraper.

 

[Thad]

And there are plans/ drawings for both in the archives.

 

[drag-200stang]

Gene,

I'm not exactly sure how high you plan on reving this engine but I get the feeling you just want to have fun and not rebuild it frequently.

I would forget about doing anything at all to the crankshaft. The 250 has enough vibration problems. Don't try to out engineer Ford.

Go with the scraper, windage tray and drop the sump as low as you can for your ride height. May need a couple gates in the bottom of the sump to control oil slosh. Of course don't forget to lower your oil pick up.

There's more power in the cylinder head than there is in the crank for what we're doing.

This is my opinion only. Good luck.

 

[Does10s]

There's more power in the cylinder head than there is in the crank for what we're doing.

AMEN Brudda!

BTW...Drag 200...where the hell have you been?

Will

 

[Stubby]

Another point, Wil ishaving trouble with timing chains. This can get worse with lighter cranks.

 

[Gene Fiore]

I'm not exactly sure how high you plan on reving this engine but I get the feeling you just want to have fun and not rebuild it frequently.

This is true...good advice and well received. Thanks!