Found this in my oil pan

[blykins]

It is. Obviously, a bigger/better head would make more horsepower, but the MR head isn't really an extreme bottleneck.....no more so than an Edelbrock head with no work done to it.

[D-CEL]

My bad, I was thinking 460 power, not FE power.
A cast crank will be plenty........
However....
Given the total cost of a rebuild, the personal labor and effort involved. the loss of use of the car for what may be an entire driving season depending on where you live. The added cost vs. the piece of mind the forging brings..
Because of my business I come with a different perspective. I see daily that Castings do not compete with Forgings.......ever.
For me, A few extra hundred dollar bills is money well spent if the car is driven like the race car it is.


Jason

[dcdoug]

Originally Posted by D-CEL

My bad, I was thinking 460 power, not FE power.
A cast crank will be plenty........
However....
Given the total cost of a rebuild, the personal labor and effort involved. the loss of use of the car for what may be an entire driving season depending on where you live. The added cost vs. the piece of mind the forging brings..
Because of my business I come with a different perspective. I see daily that Castings do not compete with Forgings.......ever.
For me, A few extra hundred dollar bills is money well spent if the car is driven like the race car it is.


Jason

I sort of feel the same way (even if it's not justified).

[D-CEL]

Duplicate post
My bad...

[FWB]

the forged crank is a heavy mass not necessary for a street engine.
the cast crank is a better choice all around for the street,
i see all to many people thinking they are building a motor to compete at lemans.

[olddog]

I suspect most people think cast iron, when they hear cast. I do believe Scat cranks are cast steel, which is quite a bit stronger than cast iron and less brittle.

That said they are a step up from cast iron and the OEMs made some pretty big power with cast iron cranks.

Sure forged is better yet, but it does nothing for you to have more strength than you need.

As for stroking an engine and not changing the cam, heads, bore, or compression, at least theoretically (well there were university studies on flat head engines, so it is pretty true), the engine will have the exact same Hp, but at less rpm and more torque. To make the math simple let's use a 3" stroke verses a 4" stroke.

Here is the rpm, torque, and Hp chart for a 3" stroke.
RPM Torque Hp
2000 - 100 - 38
3000 - 150 - 86
4000 - 150 - 114
5000 - 125 - 119
6000 - 100 - 114

Here is the rpm, torque, and Hp chart for a 4"stroke in the otherwise same engine.
RPM Torque Hp
1500 - 133 - 38
2250 - 200 - 86
3000 - 200 - 114
3750 - 167 - 119
4500 - 133 - 114

The reason or theory is that the maximum air flow into the engine is limited by heads, valves and the rest of the induction side, as well as the exhaust side. So at any given CFM the Hp will be exactly the same. With a longer stroke that given CFM will occur at a RPM that corresponds to the ratio of the stroke change. Thus the torque will increase by the inverse ratio of the stroke change.

I pulled those numbers out of my ass, but chose them to make the math easy to follow.

3/4 of 2000 rpm is 1500 rpm - the same cfm of air is flowing thus the Hp is constant.
4/3 or 100 ft-lb of torque is 133.
38 Hp = 2000 * 100 / 5252
and
38 Hp = 1500 * 133 / 5252

So the engine will make more torque at lower rpm. However if you improve the air flow into the engine you can have your cake and eat it too. You will have more torque, more cfm, and thus more Hp.

[blykins]

A steel crank is truly a waste of money in anything under 700 hp on an FE. But we make more money on steel cranks, so I'm sure your builder will be happy to sell you one though.

A new cast crank is $625. Steel is $1199. Big difference for no benefit.

[D-CEL]

Olddog,
"Cast crankshafts" are typically made of cast, Ductile (Nodular) iron with a Carbon content of 3.0-4.0%. (“ Cast Steel” by comparison is typically .1-.6%) These materials are characterized by a spheroidal graphite morphology as can be seen in the photomicrograph below

.
It is the sphereoidal shaped particles that mitigates stress concentrations and allows for the higher strength and fatigue resistance, allowing its use in this application.

Brent,
Why is the margin higher on the forging? I would think the markup would be the same
There is no question that a properly prepared cast crank is capable of supporting the majority of builds. They just lack the fatigue strength and resistance to crack propagation that is found in a forging. I always think about what happened to Eljaro back in 2011
Eagle 4.250 Cast Crank Broken
That was enough for me. $500 isn’t going to break me on a $15-$20k motor. I’ll buy rotating parts at the top of my budget, not the bottom…..
Here is an excellent study that was done in 2007
http://www.autosteel.org/~/media/Fil...ve_summary.pdf

[blykins]

Pretty easy answers.

Eagle is junk. Period. You can't compare castings between two different manufacturers and call them equal just because they're both castings. I wouldn't use an Eagle product in my lawnmower. There are more than several threads about Eagle FE cranks failing. The ones that you find on Scat are very few and far between, and even then, I personally haven't seen one that wasn't caused by lack of oil.

You will not find an Eagle part of any kind in my shop.

Why is the margin higher? It's not. The profit margin is the same, but the profit is higher because it's a more expensive part.

[dcdoug]

I assume I'm going to need to re-jet my Holley 3255-1 as well?

[blykins]

Carb is gonna be small for a 482, so yes, you will have to work on it a bit.

[dcdoug]

Originally Posted by blykins

Carb is gonna be small for a 482, so yes, you will have to work on it a bit.

Will I need to just upsize the jets or more than that? It's currently at primary jets - 73, secondary jets - 85. The 3255 is rated at 780 cfm and has vacuum secondaries.

Thoughts on where to start?

[patrickt]

Originally Posted by dcdoug

Will I need to just upsize the jets or more than that? It's currently at primary jets - 73, secondary jets - 85. The 3255 is rated at 780 cfm and has vacuum secondaries.

Thoughts on where to start?

If you use the ol' 3456 rule, you're going to need to move up to a 850 to 1000 CFM.

[dcdoug]

Originally Posted by patrickt

If you use the ol' 3456 rule, you're going to need to move up to a 850 to 1000 CFM.

You're still running a 750.

[patrickt]

Originally Posted by dcdoug

You're still running a 750.

But I only have 447 cubes and drive like an ol' fart.

[dcdoug]

Originally Posted by patrickt

If you use the ol' 3456 rule, you're going to need to move up to a 850 to 1000 CFM.

Yeah, that would put me at around 900 CFM. Hmmm. Sort of hate to get rid of the 3255, but selling it would easily buy a new carb and probably go a good way toward paying the extra for that forged crank that Brent is laughing at me for.

[FWB]

thats where i have my 468 jetted.......but i have 2 carbs

[dcdoug]

Originally Posted by fwb

thats where i have my 468 jetted.......but i have 2 carbs

:lol:

[LG57]

Brent sure is being patient with you guys. Go ahead and call him and order the damn rotating assembly and matching cam and get on with getting on the road to the next thing you're gonna break. Sheesh!

[dcdoug]

Originally Posted by LG57

Brent sure is being patient with you guys. Go ahead and call him and order the damn rotating assembly and matching cam and get on with getting on the road to the next thing you're gonna break. Sheesh!

Brent's patience will be rewarded. He spends more time helping me than most, that's for sure.