Broken Crankshaft Alt Fire Cam

[Stancedlb7]

IMHO I think a company like dart needs to step in. Bigger 1st bearing. Longer throws. Longer rods. Better piston pin placement. And no need to half fill blocks.

Just out of curiosity how many builds are out there with new crank std firing cam? And what hp or rpm are cranks failing at?

 

[WolfLMM]

I'm not throwing rocks at anyone with this comment, but accurate modeling of crankshaft loads and resulting stresses / deflections / displacements with all the variables we put to it.....FAR exceeds the resources and abilities of anyone posting on these boards.

So to say definitively that alternate fire reduces stresses, at all RPMs, is still a stretch IMO. To call it "the fix" is purely opinion...and everyone is entitled to their own.

I know you weren't:hug:. I'm glad you chimed in. The members of this board are the sharpest there is..... From what I've seen. I don't even bother with other forums now. Great thread.

 

[CaptPhil]

IMHO I think a company like dart needs to step in. Bigger 1st bearing. Longer throws. Longer rods. Better piston pin placement. And no need to half fill blocks.

Just out of curiosity how many builds are out there with new crank std firing cam? And what hp or rpm are cranks failing at?

I couldnt imagine what a dart block and crank would cost for a duramax, considering what the rest of the diesel industry charges for hard parts. :spit:

 

[Dave c]

I doubt FEA was really seriously done, but I found the following, please verify the accuracy:

Hemi rod journal: 2.375" dia
Dmax rod journal: 2.476" dia

Hemi journal width: 2.060"
Dmax journal width: ~1.97" (not sure how this length is specified, quick measurement on a crank in my shop)

Hemi main journal: 2.75" or 3" dia.
Dmax main journal: 3.145" dia.

So at this point I'm at a loss to see where reducing the Dmax crank dimensions to Hemi sizes move us in a positive direction, let alone 15% more gooder.

What am I missing?

Duramax journal width is 2.260".

 

[delong_1]

IMHO I think a company like dart needs to step in. Bigger 1st bearing. Longer throws. Longer rods. Better piston pin placement. And no need to half fill blocks.

Just out of curiosity how many builds are out there with new crank std firing cam? And what hp or rpm are cranks failing at?

you front the cost for 10 and do all the engineering they'll build you whatever you want.

 

[S Phinney]

I hear rumors of some graphite blocks coming.

 

[NC-smokinlmm]

I hear rumors of some graphite blocks coming.

CGI? Or?

 

[colorado.dmax]

IMHO I think a company like dart needs to step in. Bigger 1st bearing. Longer throws. Longer rods. Better piston pin placement. And no need to half fill blocks.

Just out of curiosity how many builds are out there with new crank std firing cam? And what hp or rpm are cranks failing at?

I think Kyle's first build he had a brand new lb7 crank and standard firing cam and his crank broke at ~5000 miles. I believe he was running the setup that put up the 950+hp.

 

[Harbin_22]

I think Kyle's first build he had a brand new lb7 crank and standard firing cam and his crank broke at ~5000 miles. I believe he was running the setup that put up the 950+hp.

Correct. Went with a used LBZ crank this time with AF cam and so far have around 7,000 miles with above 900hp. Actually have a handful of track passes and dyno runs with plenary of street beating on this engine.

 

[chrisuns]

I'm sorry to ask, but what is short rod syndrome vibrations. I can't find reference on the internet to explain this :/

 

[PureHybrid]

Short rod ratio if I had to guess

 

[OregonDMAX]

I'm sorry to ask, but what is short rod syndrome vibrations. I can't find reference on the internet to explain this :/

Short rod syndrome is slang for bent rods unless I'm mistaken

 

[Fingers]

http://en.wikipedia.org/wiki/Piston_motion_equations

Has the equations for those interested. As the rod length gets closer to the stroke length, the engine will start to develop noticeable second order vibrations in a v-8 that can not be balanced out. The dmax has a ratio of 6.42 / 3.8976 or 1.65 which is on the short side, but not overly so.

 

[chrisuns]

http://en.wikipedia.org/wiki/Piston_motion_equations

Has the equations for those interested. As the rod length gets closer to the stroke length, the engine will start to develop noticeable second order vibrations in a v-8 that can not be balanced out. The dmax has a ratio of 6.42 / 3.8976 or 1.65 which is on the short side, but not overly so.

I just learned some interesting things I've never thought of - in relation to piston travel speeds between TDC and BTC. Then to top if off with the type of vibrations they create between crank/piston/cylinder configurations.

Thanks!

 

[chevyburnout1]

:happy2:

Definitely learning more about vibrations than most people would ever even care about.

 

[OregonDMAX]

http://en.wikipedia.org/wiki/Piston_motion_equations

Has the equations for those interested. As the rod length gets closer to the stroke length, the engine will start to develop noticeable second order vibrations in a v-8 that can not be balanced out. The dmax has a ratio of 6.42 / 3.8976 or 1.65 which is on the short side, but not overly so.

Wow very interesting!

 

[Stancedlb7]

To OP, out of curiosity what dampener and main size? I'm going to assume you used carillos? Who did your balancing? How did they remove material from the throw/counter weight. Could balancing be potential cause for a week crank?-not trying to bash you or your builder.

To anyone who knows more than me, are the glow plugs tuned with efi to fire with the AF cam or are they completely deleted?

 

[CaptPhil]

To OP, out of curiosity what dampener and main size? I'm going to assume you used carillos? Who did your balancing? How did they remove material from the throw/counter weight. Could balancing be potential cause for a week crank?-not trying to bash you or your builder.

To anyone who knows more than me, are the glow plugs tuned with efi to fire with the AF cam or are they completely deleted?

I dont believe that the glow plugs fire with the injectors, instead I believe that they all heat up at the same time.

 

[PureHybrid]

Dooooo WHAAAAT ??? :rofl:

Glow plugs are for cold starting purposes.

 

[S Phinney]

To OP, out of curiosity what dampener and main size? I'm going to assume you used carillos? Who did your balancing? How did they remove material from the throw/counter weight. Could balancing be potential cause for a week crank?-not trying to bash you or your builder.

To anyone who knows more than me, are the glow plugs tuned with efi to fire with the AF cam or are they completely deleted?

I use ATI and Howards rod's. Mains are standard size with H series bearings. Balance job is external done by a capable shop using the best of equipment. Engine was a smooth running engine. I use Merchant mounts so any vibrations would be felt easily.