[vicgto]

I figured I should start a new thread instead of hijacking Jlmounces recent post regarding cast vs steel crank post. I have an Eagle 4.25 stroke cast crank with 3.25 mains and BBC size 2.220 rod journals. Eagle makes a general statement, big block cranks can handle 700 hp and small block can handle 500 hp. My question is where does the Pontiac crank fall here? The Pontiac V8 is considered a small block but the journal sizes and stroke on this crank are bigger than most other big block cranks. Is Eagles horsepower rating difference due to the small block cranks being made with a different material than the cast big block cranks or is it more to do with general size/architecture of the crank? I'm interested in hearing what you guys have seen in terms of power handling capability with the Eagle cast cranks.

[mgarblik]

Pontiac V-8's are often referred to as "middle blocks" 383 Chrysler engines are also referred to in that way. 287-455 cubic inches covers allot of ground. Eagle stating some HP numbers for their crankshafts is literally just a guess, unless they have done some destructive testing, which I doubt. Small block 500 HP? Big Block 700 HP? Middle block Pontiac 600 HP?. How does that sound? It's all just a guess and speculation. If buying an Eagle crankshaft, very important to have it carefully measured and checked for surface finish. Especially the thrust surface on #4 and the areas around the gigantic oil feed holes in the journals. There are certainly much better crankshafts to work with in the aftermarket than Eagle. IMO, stock Pontiac Arma Steel or cast "N" crankshafts are superior to anything Eagle sells in the cast crankshaft line. Forgings are much better for performance builds of course.

[steve25]

There was a long post about this running last month and to sum up what was covered it came down to run a factory cast crank or bust out the added green for a aftermarket steel crank.

Not many trusted the aftermarket cast crank.

[PunchT37]

Originally Posted by mgarblik

Pontiac V-8's are often referred to as "middle blocks" 383 Chrysler engines are also referred to in that way. 287-455 cubic inches covers allot of ground. Eagle stating some HP numbers for their crankshafts is literally just a guess, unless they have done some destructive testing, which I doubt. Small block 500 HP? Big Block 700 HP? Middle block Pontiac 600 HP?. How does that sound? It's all just a guess and speculation. If buying an Eagle crankshaft, very important to have it carefully measured and checked for surface finish. Especially the thrust surface on #4 and the areas around the gigantic oil feed holes in the journals. There are certainly much better crankshafts to work with in the aftermarket than Eagle. IMO, stock Pontiac Arma Steel or cast "N" crankshafts are superior to anything Eagle sells in the cast crankshaft line. Forgings are much better for performance builds of course.

Yeah. I don`t get off to any absolute hp or rpm numbers. 700hp? 5500rpm`s?

[grivera]

Maybe a little off topic for your question but what engine combination are you using it in and what is the intended purpose? There are thousands of these crankshafts in circulation and one rarely hears of one breaking. I’m not suggesting you go with the cast crank as I have a forged in my Firebird. But my 64 Lemans has one (engine already assembled when I bought it) and I’m not disassembling the engine to take out the crankshaft. Maybe contact Butler Performance and ask them for an opinion on hp rating since they sell many ala carte and in stroker kits. You could also call the other Pontiac shops and ask the same. Hell you could even call some Chevy shops.

[b-man]

Are you thinking of building 500 hp or perhaps more ?

If so the let’s stop right here and say you’re much better off selling this cast aftermarket crank and buying an aftermarket forged crank, even if you’re taking a loss on the sale.

Personally I wouldn’t want to use that Eagle crank for much over 400 hp.

[Steve C.]

I've never read where he substantiated the fact but I've heard Jim Butler was involved with input for the development of the the Eagle 4.250 stroke Pontiac crank.

This said, from the Butler website regarding the Eagle crank.....

"Cast crankshafts are an excellent alternative to O.E. Cranks. These crankshafts are new cast pieces made with modern material and casting processes to be a great alternative to 30 year old factory cranks.
Recommended for use in street engines without power adders. Many factory cranks we check have stress cracks, so even though your crank has not broken yet, you may have a problem developing that could destroy your engine."


( Information provided in this post does not represent any endorsement. And unless specified it is not based on personal experience and is offered for general interest only )

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[Steve C.]

Also somewhat related to Jim Butler, the use of the 6.8 length rod became popular when spearheaded to an extent by Jim with the advent of the longer 4.250 stroke Eagle crank deal.
He liked the better rod angle, the rod-to-stroke ratio of 1.6:1, and combined with the raised pin location on his custom pistons which helped relieve the sidewall stress on the block.


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[i82much]

do you already have 6.8 rods?

[vicgto]

Regarding mgarblik, grivera, b-man and i82much's comments/questions, the motor is already built (2008). It's in the car shown in my signature. 468 motor has 4.25 cast Eagle crank with studded 2 bolt mains with 6.8 rods and JE/SRP forged pistons. I polished the crank journals and thrust surface in a lathe prior to assembly. It is mainly a street car but will see the strip once or twice a year to test performance improvements. My guess for HP is about 550 based on 1/4 mile time and MPH.
One of my bucket list items is to run the quarter in the 10's, although I'm still working on the package and fine tuning, I am considering a 100 shot of NOS to get me there, that's when I start to wonder how much can the crank take. Butler is selling 550 hp crate engines with Eagle cast cranks so it appears that they have some confidence in them. I was hoping to hear from someone that is running in the 10's or better with an Eagle cast crank. Has anyone broken an Eagle cast crank, if so at what power level?

[grivera]

I’m impressed that 8.2 hasn’t let go yet! That car is running great - gives me hope to get my Firebird into the 11s. I have the smaller SP cam. I’m certainly curious to hear other’s and Butler’s opinion on that but personally would not be pumping another 100-125 hp power shot into that engine.