Girdle in cummins?

4340 is stiff, you dont want it to flex.

Gene's machine quoted me $2300 for the girdle intstalled, line bored, cam bushings, decked, and torque honed.
 
Right, I just mean for the cost difference would it even be an advantage over plain mild steel? I mean if I hold the Cummins stiffener in my hands I can not really flex it and it is just stamped out 1/4".
 
Yes, but how many ft-lbs do your hands generate? :Cheer:

A flexible block girdle could actually compromise overall strength, due to more highly dynamic clamp loading it would allow through the main studs.
 
Please explain it to me.
If i would buy a girdle (14mm thick) which integrating the mains.
Would i need to linebore or something else on the block or is it enough to just machined the main caps and bolt it on place?
 
Ideally, you would bolt the girdle in place and torque the studs down and then have the line bore checked to determine if it needed machining or not.

Regardless, I don't see how you could get around not machining the spacers that would go between the girdle and the main caps. There would be some tolerance between each block and probably each main that would have to be accounted for.
 
For you backyard engineers out there...lets clarify a few points...

"Stiffness" is more of a geometric based property than anything for materials that have similar modulus of elasticites...

4340 is approx 10% greater of a E...soooooooooooo,

Thickness is to the third power when computing I...way bigger effect than a slight increase in E!

When considering thickness alone...1/2" material is 42% "stiffer" than 3/8".

So...7/16 A-36 is Almost 30% "stiffer" than 3/8" 4340...and ALOT cheaper and easier to tool.

Long story short before I bore anyone...buy mild...and use a fraction of your savings for 1/16" more thickness!!
 
cquestad said:
"Stiffness" is more of a geometric based property than anything for materials that have similar modulus of elasticites...

When considering thickness alone...1/2" material is 42% "stiffer" than 3/8".

So...7/16 A-36 is Almost 30% "stiffer" than 3/8" 4340...and ALOT cheaper and easier to tool.

buy mild...and use a fraction of your savings for 1/16" more thickness!!
Click to expand...

Great explanation! :Cheer:
 
cquestad said:
For you backyard engineers out there...lets clarify a few points...

"Stiffness" is more of a geometric based property than anything for materials that have similar modulus of elasticites...

4340 is approx 10% greater of a E...soooooooooooo,

Thickness is to the third power when computing I...way bigger effect than a slight increase in E!

When considering thickness alone...1/2" material is 42% "stiffer" than 3/8".

So...7/16 A-36 is Almost 30% "stiffer" than 3/8" 4340...and ALOT cheaper and easier to tool.

Long story short before I bore anyone...buy mild...and use a fraction of your savings for 1/16" more thickness!!
Click to expand...


Excellent info!

Also remember that any girdle is better than no girdle.

Add that to the fact that lots of guys spin 5k on a stock bottom end...
 
cquestad said:
For you backyard engineers out there...lets clarify a few points...

"Stiffness" is more of a geometric based property than anything for materials that have similar modulus of elasticites...

4340 is approx 10% greater of a E...soooooooooooo,

Thickness is to the third power when computing I...way bigger effect than a slight increase in E!

When considering thickness alone...1/2" material is 42% "stiffer" than 3/8".

So...7/16 A-36 is Almost 30% "stiffer" than 3/8" 4340...and ALOT cheaper and easier to tool.

Long story short before I bore anyone...buy mild...and use a fraction of your savings for 1/16" more thickness!!
Click to expand...

Thank you! That is cool info!
 
I agree with the statement that anything is better than nothing... I think I am going to go with the Dr P unit. I think that seeing as I dont go over 4000 rpm anyways this should be plenty.. in my warped mind anyways
 
Also to add...I should have said this before...stiff and strong are different things...

In this application...design is based on stiffness...so deflection is an issue far before yeild or ultimate failure is even considered...THICKER IS BETTER.
 
When are the cummins guys going to make a girdle that extends beyond the sides of the oil pan, so they can make a head girdle, and use long studs to fasten the two together?
 
I have never seen it, but I have heard on the IH pulling tractors they make some type of head girdle that uses long studs that tie into the main girdle on the exterior of the block. It clamps the head and block together, I guess they can make so much power they blow the blocks in two on those engines.
 
Go look in the jetski world. Yamaha 650/701 series are know for the cylinders cracking.
 
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