Scat or Eagle?

[Ishiftem]

I have to say it is mostly a matter of economics. The factory held a L88 @ 7,000 rpm for 24 hrs in testing with a 1053 crank and no problems so a forged Chevy crank is just fine strength wise for all street builds and most race builds. The problem is by the time you buy a core, magnaflux it, turn down the mains, turn down the counter weights (for a 454 crank anyway), turn down the snout (if you are keeping the sbc size damper), and add heavy metal to balance it, the 4340 chinese forgings become an attractive option for any stroker 409. As for a cast crank, why would anyone dump all that money into a cast crank? Unless someone makes a cast stroker crankshaft for the 409 that is a drop in. Then for a 500 hp or less engine, the cast crank would be just peachy.

 

[Iowa 409 Guy]

GM BB cranks should be on the preferred list.

I think 64 Super Stocker is gearing up to sell just that.

 

[Don Jacks]

I hope so,I'd like a reasonably priced 3.76 stroke crank for a 348 plus .o40 [409 cu.in.].

 

[61 Bubble]

YES very true. Cost of machining would usually put the cost of a FREE OEM crank more than what an Eagle would probably be?
Honestly, we have ran cast cranks to stupid performance area in BBc and Cleveland Fords. Places where most engine builders wouldn't feel comfortable with. We made 787Hp with a 356" Cleveland that LAUNCHED at 9100 in a B/D. Actually set the B/D record with that car. Lasted 3 years till we broke the block (sucked in a cylinder at 9600) . WATER doesn't seem to compress as well as air for some reason. I would have no issue running the cast to about 550Hp range, and an OEM steel to about 150Hp more? The only reason I would be this conservative is the piston weight and side load that I see with these engine designs.
I have a motor sitting waiting to be assembled that will make somewhere between 850-900Hp and it looks like I will be using my GM LS-7 (old 1970's version of BB LS-7, not the LS late model version) crank with it. It's a steel block version of my ZL-1, but looking at different heads and possibly a tunnelram.

 

[buildit]

Of course, after you turn the 2.75 main journals of a BBC crank down to the the 2.50 409 size, you have lost a considerable amount of strength. I have seen several broken BBC forged cranks (from either boats or drag racing engines), and enough broken 454 cast cranks (almost always in the 7-8 rod journal) to load a truck. This experience from 7 years working in a race engine shop. With internal balance and shorter stroke, the 427s did seem better.

 

[La Hot Rods]

So why not just run a 409 crank and be happy?

 

[buildit]

Displacement is what most people want, I guess. 4" stroke. Heck, I have one with a 4.380 bore and a 4.375 stroke. Forged 4340 crank of course. Still 2.75 mains.

 

[BOSSMAN]

I deal with Molnar Technologies, a step up from Eagle and Scat as far as quality is concerned. Sizing has been spot on everything I've checked that has rolled through my shop.

 

[models916]

No reason that a cut crank can't be STRONGER than the original with the right machinist.

 

[Ronnie Russell]

I have a GM CAST 454 crankshaft. At some point many years ago someone had the mains reduced to 409 size( along with the other needed mods.) When I first received it I took it to the crankshaft shop to have it checked out. It had been sitting around for years and didn't look so good. The shop, to my surprise, said not only was it good, but, it polished to std./std........ I thought maybe someday I would make a stroker truck motor for towing. I finished the job up by reducing the counterweights to clear block. I guess the previous owner gave up on the project before reducing the counterweight. Anyway, I finished it and it is ready to go. Would I use it?? No. I enjoy using parts that other people would not or have given up before finishing but reducing main journals .250 of a cast crank is too much of a gamble, even for me. The cost of blocks and machine work makes it even more of a bad gamble. It is an interesting piece but I just can't use it. Just in case there is someone out there who wants to gamble on it, any member is welcome to it at no cost if you want to use it. Maybe a 348 block project? You would have to pick it up here cause I aint shipping.

 

[61 Bubble]

No reason that a cut crank can't be STRONGER than the original with the right machinist.

Yep exactly. Funny how people get all caught up in the perceptions in this industry? That is why I have some of the friends I do. They KNOW what works and what doesn't, and IF something is needed, recommended or just a fancy piece to have! Since I'm not up to all the "numbers" on sizing and such, I will use Ronnie's numbers above. To cut .250 off the dia. of the mains I think is almost a moot point in an N/A or even a medium Nitrous engine. I wouldn't think twice about using that crank. in she goes upto about 550Hp IF you know how to assemble an engine CORRECTLY.

Now how can people, like myself and many many others, take a BBc crank, and have the ROD journals cut to Honda 1.880" from the standard 2.200" (down 3.200") on a part of a crank that is/should be more prone to flexing due to inertia and centrifugal forces? Yet this is the hot ticket in a lot of BIG Hp N/A BBc engines. As my engine 498 N/A BBc makes 1274Hp @ 8500 and hangs on to 1267Hp @ 9500. With a 1.880" rod journal? And my buddies 440" SB Ford make 1200+ N/A with the same 1.880. Both with single 4500 carbs.

 

[La Hot Rods]

When you cut the rod pins down that much you are going to have less weight pulling on the journals and have less bearing speed witch I think helps with the stress.

 

[61 Bubble]

Were still spinning the same size rod/piston at 9000+ RPM. My point is that the mains are more stable being captured in a block and just rotating, whereas the rods are moving through the arc as well as movement of the rods, plus the centrifugal forces and inertia as well as the fact of compression resisting these forces.

I'm just showing that we fell that in an N/A engine, turning the mains shouldn't be as much of and issue as the rods.

 

[Ronnie Russell]

Great news, 61 Bubble......... I don't agree with it but , hey, maybe your opinion will convince someone to drive by and let me load this crank up for them..I hate to see anything wasted so I hope someone will use it.

 

[Skip FIx]

They can come by and get this welded 409 stroker at my place next Ronnie.

 

[La Hot Rods]

I think I would like to see that crank.

 

[buildit]

Hell, I have a couple of forged 396 cranks I'd give away. but I'm not going to ship either.

 

[61 Bubble]

Great news, 61 Bubble......... I don't agree with it but , hey, maybe your opinion will convince someone to drive by and let me load this crank up for them..I hate to see anything wasted so I hope someone will use it.

Ronnie, not trying to be a d!ck or anything. Just giving our experiences with what we have or had in our pasts. 85% of the people here won't need any more of a crank that what you have there. Just something to hang the piston/rods on and move around in the block!

I know of a guy in my town. NEEDED bigger heads for more power on his 396/325Hp car. He put in a GM 350/360Hp cam BUT needed bigger heads AND MSD dist. to control the power. THEN went and got a TKO 600 for it because the M21 might not hold it, and it saves gas on the highway???? It has 3.08 gears and 6" wide 14" tires and I have NEVER heard or seen the car rev to 3200????? But local guys sold him on this as what he NEEDS!!! I laughed my ass off on him spending what he did (were in Canada with 35% exchange as of today). I said "how many L-78's or even some L-72's came with M21's? And the once a year trip a couple hours down the highway with the TKO??" He's in for about 5,000 because local guys told him he NEEDS these pieces.

I full agree, that depending on machining cost and other things, I too would go the Eagle/Scat route just for shear $$$ saved. BUT your crank is pretty much ready to go. There should be a ton of 348 guys DRIVING to your house right no and grabbing that. Or you could ship at new owner's expense!!!

Buildit, If you shipped, I would take the lot!!!!!

 

[61 Bubble]

FYI guys, here's a short block I was looking at back in 2014. This is from a TOP FUEL Funnycar. Now look at the parts these guys use in TOP FUEL Nitro motor:

"427 ZL1 Chevrolet Block, GM 3.76 Crank, Venolia rods, Arias Pistons,BME pins, Howards cam, RCD crank hub, Keith Black gear drive, Olsen oil pan, Titan oil pump.
Has run 5.96 and 242
$ 8500."

Emails from owner:
"We have made many runs with that motor the slowest it has ever ran on a full pass was 6.08 and that was on the very first run, it has run many 6.0's and a 5.96 and has gone 242 at the NHRA hot rod reunion at Bowling Green this year. The block has never been hurt, 6.5 to 1 compression ratio, we used the AJPE heads, the blower was a Littlefield mini retro 671 over driven at 14.9. AJPE Big block fuel heads"

So anyone wondering about OEM stuff might want to check their hats at the door. YES there is better, YES it might be better to use aftermarket solely for the cost to get the machining done. Remember back when Fastest Streetcar stuff first showed up. Guys Like Lukovich, Fulton, Giannino, Schafaroff ALL used OEM cranks for some of their BIG nitrous 548 builds as THE crank, offset ground and welded, but still a GM part.

So to the OP. If you're just doing a driver style or mild build, go get Ronnie's crank, it will be fine. IF you get the quote to machine a GM crank, might as well buy a Scat. It's the better usually of the 2. Either Scat or Eagle rate there cranks to 1500Hp. That's I wouldn't do myself, but that's what they "claim", so who knows.

FYI I have an 4.00" Eagle in my ZL-1 that's should be on the dyno next week!

 

[Don Jacks]

Well I can report that he went with the Scat/I con kit from Show Cars.I don't think their price is bad considering what's included,and it's all new stuff.