Re: Guess the SB Crank.
[Re: rtcoronet440]
#1313785
10/01/12 05:04 PM
10/01/12 05:04 PM
|
Joined: Jan 2003
Posts: 5,895 Florida
Locomotion
master
|
master
Joined: Jan 2003
Posts: 5,895
Florida
|
The wide parting line would indicate a forged crank as compared to the thin lines on the other cast cranks. I'm wondering if it could be a 318 truck crank which didn't have lightening holes in the journals. Don't know about the numbers, but process of elimination would point towards the truck crank.
Last edited by Locomotion; 10/01/12 05:08 PM.
|
|
|
Re: Guess the SB Crank.
[Re: dogdays]
#1313791
10/01/12 07:31 PM
10/01/12 07:31 PM
|
Joined: Jan 2003
Posts: 5,895 Florida
Locomotion
master
|
master
Joined: Jan 2003
Posts: 5,895
Florida
|
Quote:
The 340 crank because it has less rotating inertia. R.
I know cast cranks are actually lighter than a forged crank for the same application. But aside from the extra expense of rebalancing the rotating assembly, won't most or all of that advantage be offest by the extra weight he has to put back in, especially if it's external with the counterweighted balancer and flexplate/converter?
(I'm assuming that the plan is to keep the existing pistons & rods as opposed to lighter versions.)
|
|
|
Re: Guess the SB Crank.
[Re: Locomotion]
#1313792
10/01/12 07:50 PM
10/01/12 07:50 PM
|
Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 16,376
|
NONONO! The middle and right are forgings. That should be obvious. Look at the parting line on the crank on the left, it's sharp. Typical casting look. Both the center and right cranks have wide, ground off parting lines customarily seen on forgings. Also, check the shape of the counterweights. Forged counterweights have a more organic shape, they look like kidneys. Cast cranks have square, sharp corners.
Now on to reciprocating and rotating inertia. When MOPAR hung those monster 340 pistons on the ends of the rods on basically a 318 crank, they drilled the crankpin in order to be able to use the crank without external balancing. So any weight removed from the crankpin side, either by weight reduction of the rods, or weight reduction of the crankpin, or weight reduction of the reciprocating weight, allows the counterweight to be SMALLER.
Thus, the drilled crankpin allows for even less rotating inertia becase it doesn't take such a big counterweight to balance it.
R.
|
|
|
Re: Guess the SB Crank.
[Re: dogdays]
#1313793
10/01/12 08:29 PM
10/01/12 08:29 PM
|
Joined: Dec 2006
Posts: 3,396 Pa
Hot 340
master
|
master
Joined: Dec 2006
Posts: 3,396
Pa
|
Quote:
NONONO! The middle and right are forgings.
I thought that at first...look at the middle crank closer towards the thrust, particularly the second crankpin.. Its a casting. Not to mention the little "clock" cast into the first crankpin.
|
|
|
Re: Guess the SB Crank.
[Re: rtcoronet440]
#1313796
10/01/12 09:24 PM
10/01/12 09:24 PM
|
Joined: Dec 2006
Posts: 3,396 Pa
Hot 340
master
|
master
Joined: Dec 2006
Posts: 3,396
Pa
|
Quote:
The middle and left crank are cast. I agree the one on the right should be forged but the number on it says it is cast. (which I do not believe.) the rods on it claim to be for a cast crank also. But, They are bushed floating pins.
Right one is definetly a forging. No doubt about it.
|
|
|
Re: Guess the SB Crank.
[Re: rtcoronet440]
#1313799
10/02/12 12:41 AM
10/02/12 12:41 AM
|
Joined: Jan 2003
Posts: 5,895 Florida
Locomotion
master
|
master
Joined: Jan 2003
Posts: 5,895
Florida
|
Considering that the 318 steel crank list is exactly the same as the 340 steel crank list, it would appear that the list shows which like-material cranks will physically interchange without regard to original application or balance. 340 cast crank isn't mentioned probably because of it's rather short term of use. It should be late '72 and '73.
|
|
|
Re: Guess the SB Crank.
[Re: rtcoronet440]
#1313801
10/02/12 01:45 PM
10/02/12 01:45 PM
|
Joined: Aug 2003
Posts: 43,307 Bend,OR USA
Cab_Burge
I Win
|
I Win
Joined: Aug 2003
Posts: 43,307
Bend,OR USA
|
Back in the day when NHRA was still racingmodified production cars john Diana told me to try and find a forged steel crank out of a Dodge truck 318-3 motor, it was a lot better than the stock 340 where according to him and the Mopar drag engineers No way I would use a cast steel crank when I had a forged steel crank to use OP, take it to your machine shop and have them magnaflux it to make sure it is still good, no cracks, and have them check the balalnce, if it needs fixing on the balance have them do it I no several NHRA stock class racers that took the 340 rods out and switch to 318 rods along with lightweight pistons, they sat several NHRA class records Light weight(rotating) is better than some heavy weight parts in our motors, as long as they will do the job without failing
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
|
|
|
|
|