angelz28

Hey guys!!! ok this its the deal
i have a friend a he just build a 400 ci for drag racing, and he told me that he is using the original crankshaft.
He told me that he is going up 7000rpms? ???
is it possible???
cause i knew that you can only go 5500 rpms with that stock crankshaft
am i wrong???

Sonix

iTrader: (1)

valve train limits your redline, as in, how high it "will" rev. How long it'll last at that RPM is defined by the stability of the bottom end.

It won't last very long.

angelz28

mmmm and what about 6000???

Irockz

iTrader: (1)

He's right.The stock cast crank in my 406 only has about 200 passes down the strip on it,mostly with a 200hp shot of juice.It'll never live.I know mine's only been to 8500RPM.

angelz28

so if i go 6000 and less it is going to be ok???

Sonix

iTrader: (1)

mm, yea, what was I thinking? Clearly a stock 20 year old crank should be good to 600+ HP and 8500RPM, duh! I wonder why the aftermarket even makes crankshafts for that motor, seeing as how the stock ones are obviously perfect.

I guess i'll stop shovelling my in this thread then.

Rogue86

As long as everything is balanced well, and he's got some lighter slugs on there, it might be ok. What kind of balancer? A good one will help a lot.

ME Leigh

Do you have your tach on the 6 cylinder setting. Let me get this right, your saying you can turn your stock crank 400 to 8500 rpm with no problems?

sofakingdom

iTrader: (1)

I'm not going to touch this one with somebody else's 10' pole (my own sure isn't that long...)

I once learned a valuable lesson:

"Never argue with an idiot. They will drag you down to their level, and then beat you with their greater experience."

Seems like there's lots of people on these boards nowadays that make up this stuff, all about how they get results totally outside the realm of ordinary mortal experience. Maybe that's why alot of the old regulars with lots of BTDT quit coming here; they got tired of being in the middle of some kind of ****-length match? I don't know that, just a guess.

angelz28

no man it is not like that. i got a 214 224 good for 4500 rpms. But my friend told me what you allready know. I dont want to broke nothing in my engine, but i want to find out if i can get a better cam.
And how the hell does that

Dialed_In

iTrader: (3)

A stable valvetrain and good harmonic dampening are going to let you rev higher, not the material of the crankshaft. If he used a stock crank in a "race" motor then chances are that he cheaped out on the valvetrain too and he's probably got a stock 400 damper. So don't expect that thing to hold together for long if he's twisting it higher than it was made for.

I'm willing to bet that his motor quits making power waaaay before 7000 rpm anyway, so shift your car where the motor makes power and drive around his dumb a$$ while his car falls on it's face. If he used a stock crank in a "race" motor then chances are that he cheaped out on the valvetrain too.

sofakingdom

iTrader: (1)

Angel, I wasn't talking about you....

I don't hold you responsible for what your friend claimed. Which I don't believe, any more than I believe the post I was actually referring to. So, to answer your question:

A stock 400 crank won't withstand many times past 6500. I think the last one I broke from doing that, the front piece of it is still sitting on a table in my brother's house.

That one broke (as they most often do) right where the #1 & #2 rod journal meets the throw. That particular one broke in such a way that the engine actually continued to run, and I was able to drive it into the garage, pull the motor, and put a crank kit in it.

The deal with RPMs isn't something like, it'll go to 6613 RPMs, but it'll dissolve to shrapnel at 6614 RPM. Rather, the effect is cumulative; a crank might live forever if it never passes 5000 RPMs, or live out a normal service life of 100,000 miles or more if it hits 5500 RPM once a day, or 25,000 miles if it hits 6000 once a day, or 2000 miles if it hits 6500 once a day, or 20 miles if it hits 7000 once a day. Now, what's an acceptable RPM limit under those conditions? Right... it's up to the owner; and it's determined by the use the motor is being put to.

You can ALOt of cams that are A WHOLE LOT BETTER than that one, as far as just being a better cam goes. Whether some cam or other is better FOR YOUR COMBO is a whole other question though. That would depend on what heads you have, what exhaust, gears, converter, transmission, car weight, use you put the car to, money you can spend, and a whole long list of otehr factors. It's not like you can go I've got a 406, so X cam is the "best" for me. There's more to it than that.

Irockz

iTrader: (1)

YES.It's not frequent,but it has been to 8500 more than once.Anyone that doubts me is more than welcome to come to Ozark Dragway in Rogersville,Mo. and put their money where there mouth is.

Oh,and sofa,your name fits better than I thought.Does my crank have a fuse or something?I was just curious,as you seem to know more about my engine than I do.Maybe that Chunk of crank you have says something about the quality of the balance job you have.

angelz28

thanks man
ok this is my combo

400ci, 5.7 rods, 0.20 pistons, stock vorteck heads, vorteck manifold, 650 cfm edelbrock, and the 214-224, long heathers, 3.43 gears, 400tranny, sotock converter(for now),

ljnowell

You are a stooge. I dont believe you, nor does anyone else. The funny part is, you make yourself look stupid, so we dont have to call you names or help you along.

sofakingdom

iTrader: (1)

I like it that way!!

Read my signature.

I'll enter you in my next write-up for the Journal of Irreproducible Results.

Oh, and be careful what you ask for, in case you get it. I still have a piece of property after all these years near Shirley Ark. Maybe I'll come down and check out this one-of-a-kind wonder with a 6-cyl tach you've got there.

Irockz

iTrader: (1)

You or LJ are welcome to come witness it any time you'd like.If I'm a stooge,it would amaze you "experts" how many Grand American Late Model stock cars in this area are running these crankshafts that I obviously don't realize are junk.Lord knows,stock cars don't abuse crankshafts.

If you guys are so confident that my engine cannot live at 8500 for brief bursts,EXPLAIN.Because Super Chevy say's it can't?!

ljnowell

I dont base my knowledge on magazines, like some of the members here. I go by what i see firsthand. I have seen lots of stock 400 cranks going the rounds at racetracks. I see them go to 8000RPMs too. Then after a while, I see them blow. Stock 400 crank isnt that strong. If you have 200+ 8500RPM runs, you have the only one made that will do it.

Those guys you mention are probably running an aftermarket crank. Unless in your part of the states the air contains special compounds that gives cast iron cranks the properties of an aftermarket forged unit. Perhaps you found this laying in a barn somewhere? lol.

Irockz

iTrader: (1)

OK,let's get something straight,then hopefully let this die.I'm only carrying this on because I can't stand to be called a liar.Goes back to an old lecture from Grandpa when I was 6.
I never said I had 200 passes at 8500RPM.I said I had 200 passes on a stock 400 crank,mostly with nitrous,and it has been to 8500.Going through my logbook tonight,I find that I lied a bit.I have 179 passes on this engine,143 of them on juice.I have not recorded RPMs,but it has been to 8500 a FEW times.This is not a shift point,it is just something that has happened on accident a time or three.No,I don't think for a second that it would last 200 passes at 8500 RPM.But yes,I will stand behind my statement that properly balanced and lightened stock cast crank is capable of more than anyone gives it credit for.I use a very light rod/piston combo.

I am in the midst of dropping a 468 into my car because of a recurring head gasket problem.But if anyone comes here to see a stock 400 crank do 8500 RPM,give me a week's notice,and yes,I'll swap it back in with fresh head gaskets to prove it's been there before.

Now,someone please lock this thread,I've obviously sent it so far off subject that this question will never be answered accurately,and I apologize.

One last thing,PLEASE don't classify me with the Duntov cam TBI 305 guy and the COPO 427 guy,I LIKE it here!

angelz28

cool thank you all guys

shaggy56

Take an engineering course and you can understand how any component is rated. The teacher will hand out a box of paperclips and pass them around the classroom. Everyone is instructed to bend their paper clip and to record how many tries it takes to break the paper clip. Now the results will usually average the same. While some paper clips will break with more bends some will break with less and then you average it out. The general rule of thumb is to stay below the average. So if you apply this reasoning to a crankshaft you will find that some will break sooner some later but there will be an average. If a crankshaft is rated for a certain rpm or horsepower you can bet these tests were performed to attain that data. So in conclusion just because someones crankshaft has been able to handle more abuse than average doesnt mean the one you get wont break with less abuse.

IHI

iTrader: (1)

Angel, check the sig and you can see what I ran. Stock short block with stock OEM parts that were just reconditioned.

This particular crank lasted just over 1800 1/4 mil passes, 75 1/8mi passes and 5-6K street miles over 2 yrs. Shifted consistantly at 6000rpm, once in awhile I'd shift it at 6500 to play the bracket racing game to get ahead of my dial, and I have at least 20 passes at 7000rpm shift points only gaining .04 over shifting at 6000rpm. So unless your buddy has a huge monster cam, big compression to support the big duration cam his pwr band will definatly be under the 7000rpm mark. It boils down to how well the block was put together IMO since by everybodies thoughts my motor shoulda fragged the first few months I ran it LOL!!

Used a stock damper too which I believe was the ultimate casue for failure since the crank snapped off just behind lower cam gear and reacked havoc

ljnowell

I dont what you say at all. I have a 350 w/ stock crank that regularly sees 6500 and has seen 7K. Niether of these stories come anywhere close to 8.5K though. Not at all.

IHI

iTrader: (1)

I did'nt want any part of that discussion, been around too many people when we all get the cars out that have done incrediable feats with everything, yet dont have a car or participate in anything...they just "one up ya" LOL!! I find it hard to believe, but stranger things have happened I guess. Lotta weight being thrown around at that rpm and while I'm sure the crank could probably handle it breifly on accident been in a chevelle with a stick the guy missed a gear pwr shifting and it buried his 9K tach , I would think pistons would rip out at the pin or rod bolts would fail-especially with a 200 shot to boot

angelz28

ok thanx