[Vid]

Originally Posted by tom s

How lucky do you feel?

Haha well Tom that comment is surprisingly spot on accurate. It seems for every “Mine broke” comment the next is a “Mine’s fine”. So it really is a coin toss.

Like all things in life, “Everything is fine until it isn’t.”


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[ekancler]

Originally Posted by Dragncar

Dude, the dowels do not mean jack $&!#. Its about iron. 557s lack iron in the critical places to prevent the mains from ripping out of the block with just a 3.75 crank. Let alone the fools game of putting a 4.25 crank in there.
You seem to not want to listen and are trying to talk yourself into this being somewhat safe to do.
Its not.
The blanket statement that 557s are cr@p for performance builds is 100% correct.
Stop it with the "specific solutions" lighting money on fore nonsense.
Look at the girdle that Jay S made. He is a smart and talented member and made that nice girdle. He had a valid reason to go through all that effort to come up with a numbers matching 550 HP engine.
The OP does not have that issue.

Take the risk of your engine looking like this.



Or pay a few hundred bucks for any 400 Pontiac block other than a 557.

Cool pic. Are those solid dowels I see in there?

[Dragncar]

Originally Posted by ekancler

Cool pic. Are those solid dowels I see in there?

They are screen shots from one of the threads that you posted a link to ???

You can polish a turd, sprinkle powdered sugar all over a turd. Its still a turd.


More pics from your thread.

[25stevem]

Luck has nothing to do with longevity!
Once again it boils down to block prep, accurate balance and a tune that keeps the motor from detonating.
Lighter reciprocating parts are another plus!

[ekancler]

Originally Posted by 25stevem

Luck has nothing to do with longevity!
Once again it boils down to block prep, accurate balance and a tune that keeps the motor from detonating.
Lighter reciprocating parts are another plus!

In light of that last statement... what are your thoughts on using the stock crank?

[25stevem]

The stock Crank will out live the block in a high hp build as long as it passes a Mag test .

[Dragncar]

Super Stock 400 guys used to find mid 70s 350 cranks as they were lighter. Might be a good way to go with a 557.

[25stevem]

Your logic is wrong in regards to having block life extension take place from the use of a 350 crank.

The super stockers run the 350 cranks because the lighter weight helps them to gain rpm faster, that’s the only reason.
A crank when property balanced, weather it’s a overall heavy or lighter crank does not make for eased loads on the blocks main webs, it can just make for a overall lighter or heavier total engine weight.

I am assuming you do not want to bring bearing speed into this conversation?

Anyway let me reiterate yet again, it’s the accuracy of the the balance job that can reduce the loads on the bearings and the main webs that house them.

[ekancler]

So when we talk about lightweight rotating assembly… we’re talking pistons and rods but not crank?

[jhein]

The proper terminology probably should be the rotating and reciprocating assembly. If the crank is properly balanced then it's rotation shouldn't matter much. It's the reciprocating mass of the pistons and rods that's the issue.

[PAUL K]

When you start making big power a crankshaft flexes... Sometimes a LOT. The design of the crankshaft and material will help keep a crankshaft from flexing as much and therefore, making a factory block seem stronger.

Years ago we would split a factory block atleast once a season using a factory crankshaft on a high power engine (about 1200 hp). Once we installed a properly designed aftermarket billet crank we went close to two seasons with the same combination and the block was fine.

[ekancler]

Thanks Paul. Is crank flex gonna be an issue with stock cranks at 500hp or less? Or is it really only when you have big big power that it becomes an issue?

[PunchT37]

I don`t worry about factory cranks at those power levels. Pontiac went with large mains on their cranks compared to most others. That`s a bad thing for bearing speed/heat. It IS good for a strong crank, simply because of it`s mass.

[PAUL K]

Originally Posted by ekancler

Thanks Paul. Is crank flex gonna be an issue with stock cranks at 500hp or less? Or is it really only when you have big big power that it becomes an issue?

You're welcome. No, not at that power level. We use the factory 103 cranks in NA builds up to 800 HP.

[25stevem]

Paul, did your aftermarket crank you had to go to at the 800 hp level happen to have all 8 counter weights?

To you other folks who have been reading all of this and asking good questions, one very important question I see has yet to be asked!

This question is why does your motor have 8 rods and pistons, yet only 6 counter weights appear on the crank, it has no center counter weights.

There comes a point in the level of power production where no only is a aftermarket crank needed for its added strength, but for the needed two counter weights that stop the crank from flexing as much .

Flexing of the crank get transmitted right into the bearings and on then into the block.

This is also a very big part of why with a 6 counter weight crank a very accurate balance job is needed!

I am starting to sound like a broken record I know, here,but this point seems to need to be driven home again.

[ekancler]

I’ve actually been wondering about this. Are the stock cranks 6 or 8? Assuming 6.

I’m also assuming it’s also really important to have both a well balanced damper in front and torque converter in back.

[Dragncar]

[QUOTE=25stevem;6361562]Paul, did your aftermarket crank you had to go to at the 800 hp level happen to have all 8 counter weights?

To you other folks who have been reading all of this and asking good questions, one very important question I see has yet to be asked!

This question is why does your motor have 8 rods and pistons, yet only 6 counter weights appear on the crank, it has no center counter weights.

There comes a point in the level of power production where no only is a aftermarket crank needed for its added strength, but for the needed two counter weights that stop the crank from flexing as much .

Flexing of the crank get transmitted right into the bearings and on then into the block.

Kinsler took a Scat non fully counter weighted crank to 1400-1500 HP for years. But he was spraying it.
It seems like the big NA guys go to billet fully counter weighted cranks and billet pistons when they try for over 1000 HP NA.
Molnar BBC cranks fully counter weighted can be had for 1060$ I bet Pontiac folks would pay 1500$ for a 8 counter weight crank.
I asked Tom Molnar what it would take for us to get one. He said the commitment financially and payback time made it prohibitive.
But he did commit to this new 4" stroke forging for us so maybe there is hope.


BBC version.

https://cnc-motorsports.com/molnar-f...dc8f-6385.html