481 build

[Duane Yates]

I had been doing a little research in the beginning of my build. Just got my 454 crank back from the grinder and in my research I found several post on various sites saying you need to reduce the diameter of the counter weights to fit the block, but no real info that I could find on the subject.
I drove down to my buddies Speed Shop this morning to compare the 409 crank to the 454 steel crank. To my susprise the 454 crank's counter weights were smaller. I didn’t get a exact measurement, but off a main journal it was .125 smaller than the 409 crank. I am working with a 65 409 block. Maybe this pertains to 348's only. It looks like my crank will drop right in.
This what I have going:
65 409 truck block
.068 KB/Ion 11-1 comp. No counter bore.
454 steel crank w/ BBC snout
6.135 Scat Rods
BWR Heads
Muther Thumper cam
1.8 Rockers
Looking into fabbing a 440 tunnel ram for it. Two 650 double pumpers
I am hoping to get all together by Summer time

 

[Murphdog]

The counterweights on a W crank are concentric to the main journal. The counterweights on a 454 are not. Without looking at and measuring on both I cannot tell you numbers off the top of my head. If you measure on the 454 the leading & trailing edge of the counterweight is farther radially from the main journal than the center of the counterweight 180 out from the crank pin. Before & after bottom dead center the bottom of the piston is farther from the crank center line allowing for more counterweight. I have had to cut the counterweights on 396/3.766" stroke going in a 348 & 454/4" stroke & 4.25 stroke BBC cranks to fit into and turn in 409 blocks. I left the counterweights slightly larger than the 409 crank because I had room to do so and could use the weight to help balance.
Jeff

 

[Duane Yates]

Thanks for the reply. To look at them side by side I didn't notice the difference. I measured from the main journal in the center of a counter weight. I will measure again.

 

[Murphdog]

Just snapped this pic. This is the 4.25 crank I am planning on using. You can see the shiney parts where I turned the OD of the ends of the counterweights making them concentric to the main journal and the center area 180 from the crankpin still has the original heat treat finish/color. This will probably be the same scenario for any BBC crank in a W, whether GM or aftermarket crank. Also notice the notches in the bottom of the cylinder walls for rod clearance. You will probably have to do this also.
Jeff

 

[Iowa 409 Guy]

Using that crank in your street cat Jeff?

 

[Barry Taylor]

Using that crank in your street cat Jeff?

Boy that spell check is wearing you out!!

 

[Iowa 409 Guy]

I guess so....Damn....

 

[Murphdog]

Using that crank in your street cat Jeff?

That's the plan Dave. Doing some things just to see what it takes, and to be different. Being my own guinea pig. Felt I had somewhat of a challenge from a fellow member and a 4" just kinda fell into place, so I figured what the heck. Calculator says it will work. If I had more deck I could go bigger, room in the bottom, but out of room for a piston
Jeff

 

[Iowa 409 Guy]

Challenge from Tooth or James?

 

[Murphdog]

Challenge from Tooth or James?

Neither. But someone made a comment something to the effect of "go big or go home" if I remember correctly. So here I am!
Jeff

 

[Barry Taylor]

When you get it in the car just be sure someone is there to video the first drive!

 

[region rat]

There was a builder on the forum that built his with a 4.375 stroke and 6.385 rods. 527 for his street rod.

 

[benchseat4speed]

To my susprise the 454 crank's counter weights were smaller. I didn’t get a exact measurement, but off a main journal it was .125 smaller than the 409 crank.

Either that's not a GM crank, or the weights have been cut down already. Got a casting/forging number? Photo's?

@Murphdog is on it

 

[Duane Yates]

I don't have casting numbers. Just went and looked at it today. The widest counterweight edge to edge is 7 1/8. My friend has been building engines since the late 70's, he says it's a 454 steel crank. It's been ground to 409 mains. I will look up the casting numbers when I get back down to his shop.

 

[Murphdog]

The 1 GM 454 steel crank I am familiar with is a 7416, there may be others. I am positive a GM 2 pc rear seal 454 crank with the mains turned to 409 size will not turn round & round in a 348/409 block without turning the od of the counter weights. The od of the rear thrust flange needs cut down also. The counterweights on BBC cranks are elliptical, they are not on a concentric radius to the main journal like a 409 crank. When the journal is at bottom dead center the counterweight will clear. 75/80 degrees either side of that they will not.
Jeff

 

[Duane Yates]

The number on the crank is 3967416

 

[Murphdog]

I am pretty sure there were some factory cross drilled over the counter cranks that had a different #.
Jeff

 

[benchseat4speed]

Good info Jeff. Well articulated.

Yup that's the same crank that LS6's and 7's have, 1970 and up. Not sure what the last year was for that forging. Same crank I have in my 55.

If you are at all in doubt, get that thing magged! I bought a 7416 crank at a swap meet for 300 bucks and thought I scored big.........#1 rod journal was cracked Btw, the 'ring' doesn't mean s--t. To me anyway, maybe some guys have a better ear. That crank 'rang' great and had a crack in it.

Also, if the weights are even smaller OD than a stock W crank, that things gonna take a lot of metal. My 396 crank was cut identical to a W dimension and took two 1" slugs on each end.

 

[Murphdog]

Kevin, "That crank 'rang' great and had a crack in it."
25-30 years ago I had a sprinter bring me a 350 Chevy steel crank to do for him. Magged it 1st thing, had cracks, called the customer, he drove an hour +, looked at the crank, gave it the hammer test and said it's ok, proceed. Cross drilled it, ground it, balanced it, customer picks up. Sprinters have a thing about using harmonic balancers, the old school ones just want to run a hub of sorts, weighs less and takes less time to wind up off the turns. Short time later he/it comes back, no ring left, dead as a door nail!
Kinda rhymes with the song, "It does mean a thing if it ain't got that ring"
Jeff

 

[benchseat4speed]

Wow. No kidding? Well that disproves two theories at once! I gotta give the guy some credit for bravery. It's one thing to grenade a SBC on a dirt track but,

The crank (mailbox post) I bought was destined for a 409 block so, that whole 'pinching pennies with swap meet cranks' plan was scrapped. Learned my lesson on that deal. Saving for a Callies Magnum now, gimme another 2-3 years and I'll have one lol.