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Question about Little M main cap material.

General engine tech -- Drag Racing to Circle Track

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Bwh998
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Question about Little M main cap material.

Post by Bwh998 »

At what point does someone need to choose the steel mains over the ductile iron? Can the ductile iron mains handle roughly 1000hp reliably?
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Kazoom
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Re: Question about Little M main cap material.

Post by Kazoom »

Bwh998 wrote: Fri Jul 24, 2020 9:17 am Can the ductile iron mains handle roughly 1000hp reliably?
NO ... FACT, block HP ratings are directly related to the main cap they have...

this is WHY some dart blocks have a 600hp rating is because they have/use inferior cast iron caps...

("Designed for high-performance and heavy-duty applications producing up to 600 horsepower")
> https://www.jegs.com/p/Dart/Dart-Specia ... reId=10001 <

"There is way too much BS posted by some dummies on forums about block HP rating #'s using inferior cast iron main caps...

for those wanting FACTS about main caps, seen a good vid clip with info/tech repeating what i have been told by all builders i spoke with when i was shopping for new blocks about cast iron main caps fretting/flexing/moving/walking/galling, again confirming that 4 bolt CAST IRON main caps should be upgraded to BILLET STEEL if your doing over 700+hp builds and this is coming direct from a block manufacturer."

important iron/steel main cap hp rating info at 1:55 on this manufacturers vid...

https://youtu.be/lX9OPEuEyBs?t=110

also be-aware that dart blocks have had issues with cracking... > viewtopic.php?p=867687#p867687 <
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Re: Question about Little M main cap material.

Post by modok »

steel is maybe 15% stiffer than iron, which is not a big deal, but if you are aiming for the moon it's that much closer.
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Re: Question about Little M main cap material.

Post by Kazoom »

"stroker cranks & short rod ratios also put MORE stress on inferior cast iron main caps... Billet Steel is Best

when most all weaker cast iron caps Fail, they fail (crack/break) in saddle area inbetween the main bolts Because of the weaker inferior iron main caps flexing (made worse by stroker cranks & short rod ratios) contributing to the weaker inferior iron cap fretting/walking/galling/moving
This is where the greatest cap stress is and where the superior Billet Steel Main Cap wont flex/crack/break. theres hundreds of threads on forums showing this problem with inferior Cast Iron main caps with even tight interference AND even doweled cast iron caps STILL end up flexing/cracking/breaking"...

https://www.460ford.com/threads/main-ca ... ost-922004

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Re: Question about Little M main cap material.

Post by Momus »

'Billet Steel' is a buzz word.

Grown ups talk about the grade of the steel material so the components properties can be evaluated.
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Re: Question about Little M main cap material.

Post by Kazoom »

> https://www.powernationtv.com/two-minut ... bolt-mains <

Image
bit more general info on using billet main caps
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Re: Question about Little M main cap material.

Post by Bwh998 »

Man thanks for all the replies folks. Lots of good info to digest here but looks like you've all answered my question.

Thanks again.
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Re: Question about Little M main cap material.

Post by BCjohnny »

Momus wrote:Grown ups talk about the grade of the steel material so the components properties can be evaluated.
Agreed ...... and they also talk about the grade of 'cast iron' used for similar evaluation purposes

Even with 'ductile iron' there are so many grades the tensile and yield strengths can vary by as much a 100%

With the strongest 'cast iron' grade available, ADI, I couldn't see anyone having problems directly related to the material itself, but the fact of the matter is that 'billet steel' might often be cheaper to produce

On a purely theoretical level I've always wondered if steel caps, due to their relative lack of internal resonant dampening, didn't introduce other problems themselves, particularly under detonation conditions
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Bwh998
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Re: Question about Little M main cap material.

Post by Bwh998 »

Problem is that manufacturers rarely go into any detail about which grade of metal is used, its almost always some vague terms like billet steel, cast iron or my favorite, "military grade aluminum".
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Re: Question about Little M main cap material.

Post by 1972ho »

I’ll bet most the companies that make these products don’t really have a clue about what the limits are on there stuff because they have never tested the limits on any of it because if they had it would be plastered all over there sight and other internet sights bragging about.I remember when nascar tried steel main caps they abandoned it but never really gave a reason why.As the end user you just have to take chance and hope for the best.
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Re: Question about Little M main cap material.

Post by Krooser »

Will a Rockwell hardness test tell me much about the composition of the iron main caps on my SBM project?

Aftermarket four bolt caps are available but many in the Mopar world dont think they are needed at my target 650hp power level. Most argue good 1/2" main studs are all that are needed.

If I am going to consider this one last block mod now is the time to do it.
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Re: Question about Little M main cap material.

Post by mag2555 »

1000 hp out of how many cylinders are we talking and what stroke,main journal size and rpm?

It's the G force loads that matter more then the hp since they go up with the square of the rpm seen.
Last edited by mag2555 on Thu Nov 19, 2020 12:25 pm, edited 1 time in total.
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Re: Question about Little M main cap material.

Post by af2 »

Good read.

viewtopic.php?t=1853

Another.

https://www.makeitfrom.com/material-pro ... r-Mo-Steel


Lots of variations to all metals.
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