Shortening LS7 Crank?
06-02-2015, 09:32 AM
#1
Shortening LS7 Crank? Hi All,
I'm using the LS7 factory crank for my 418" stroker. TPS says they're "not equipped to shorten the crank" and suggests using the Scoggins-Dickey spacer over the front of the snout to keep the pulleys lined up. That looks like another $70 for the spacer and ARP LS7 crank bolt. I'm thinking about using my Portaband saw to remove all but a 1/16" or so of the needed amount (1.00" ?), chucking it in my lathe, and smoothing off/chamfering the cut end. Of course, I'll measure everything against a standard LS crank first. Anyone foresee a problem with this?
I'm using the LS7 factory crank for my 418" stroker. TPS says they're "not equipped to shorten the crank" and suggests using the Scoggins-Dickey spacer over the front of the snout to keep the pulleys lined up. That looks like another $70 for the spacer and ARP LS7 crank bolt. I'm thinking about using my Portaband saw to remove all but a 1/16" or so of the needed amount (1.00" ?), chucking it in my lathe, and smoothing off/chamfering the cut end. Of course, I'll measure everything against a standard LS crank first. Anyone foresee a problem with this?
06-03-2015, 09:21 PM
#4
Are there any other concerns, like thread depth, etc? If I can "Portaband" off excess on the snout, I could do the finishing in my old Atlas lathe. Hell, I could prolly do the whole cut with a parting tool but it would be slow going...
06-05-2015, 10:20 AM
#7
Recently I saw someone selling a shortblock at his machine shop with compstar LS7 or Eagle std LS crank; I thought take the LS7 crank all day long. Gives you more options for resale.
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06-05-2015, 09:55 PM
#8
My only concern with any thing band saw like, the blade will be deflecting like a ****. If that's not an issue it should be ok.
Recently I saw someone selling a shortblock at his machine shop with compstar LS7 or Eagle std LS crank; I thought take the LS7 crank all day long. Gives you more options for resale.
Recently I saw someone selling a shortblock at his machine shop with compstar LS7 or Eagle std LS crank; I thought take the LS7 crank all day long. Gives you more options for resale.
07-13-2015, 08:29 PM
#10
Did the chop job this afternoon, came out great. Gotta say, it was rather harrowing to have a $1k, 55# chunk of metal spinning in an 80 year old lathe that was, in all respects, a tad too small. Had visions of it jumping out and landing on the concrete floor. I hacked off 0.875" with my Portaband saw, then stuck the crank in the lathe. I don't have a steady-rest, but do have a good quality live center for the tailstock. Tried partially screwing an old (center-drilled) bolt in the crank snout, but there was enough play that it was wobbly. Had to make a bushing "shim" for the bolt neck from 0.030" aluminum stock, that cured the wobble. Then I had to neck down about 3/4" of the bolt under the head to around 1/2" diameter so there would be room for my carbide bit to get access to all of the face. Faced it so it ended up a total cut of 0.900", then an outer chamfer. Had to do the inner chamfer with a 1" drill bit in a hand drill.
HTH,
HTH,
09-13-2016, 09:59 PM
#16
09-14-2016, 08:27 AM
#17
Just pay the 70$ for the spacer. The outer diameter is for a factory ballancer so i had to have a local machine shop take a little off the outer diameter for my ati pulley but i found it a much better option then trying to chop off the snout and in the future i can always go dry sump
09-25-2016, 11:09 AM
#18
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LS-7 = Lite Rod Crankshaft WARNING : The LS-7 crankshaft is a fine piece, great for LS-7 oil pump, front cover, and oil pan.
This item IS balanced for Titanium rods, lite rods.
The cost of a balance job with Heavy Metal for use with steel rods may be over $600.00.
Many suppliers offer a 4.00"/4.10" Forged Crankshaft, standard LS crank snout, 1850 Bob weight for a small increase in cost over the balance cost of a LS-7 using steel rods.
Another feature, if rods and piston weights are matched, is a crank balance may not even be required.
Most here know Bob Weight may be greater just not less than the requirement. (Overbalance)
Lance
This item IS balanced for Titanium rods, lite rods.
The cost of a balance job with Heavy Metal for use with steel rods may be over $600.00.
Many suppliers offer a 4.00"/4.10" Forged Crankshaft, standard LS crank snout, 1850 Bob weight for a small increase in cost over the balance cost of a LS-7 using steel rods.
Another feature, if rods and piston weights are matched, is a crank balance may not even be required.
Most here know Bob Weight may be greater just not less than the requirement. (Overbalance)
Lance
Last edited by pantera_efi; 09-25-2016 at 03:28 PM. Reason: Solicitation
09-25-2016, 09:50 PM
#19
WARNING : The LS-7 crankshaft is a fine piece, great for LS-7 oil pump, front cover, and oil pan.
This item IS balanced for Titanium rods, lite rods.
The cost of a balance job with Heavy Metal for use with steel rods may be over $600.00.
Many suppliers offer a 4.00"/4.10" Forged Crankshaft, standard LS crank snout, 1850 Bob weight for a small increase in cost over the balance cost of a LS-7 using steel rods.
Another feature, if rods and piston weights are matched, is a crank balance may not even be required.
Most here know Bob Weight may be greater just not less than the requirement. (Overbalance)
Lance
This item IS balanced for Titanium rods, lite rods.
The cost of a balance job with Heavy Metal for use with steel rods may be over $600.00.
Many suppliers offer a 4.00"/4.10" Forged Crankshaft, standard LS crank snout, 1850 Bob weight for a small increase in cost over the balance cost of a LS-7 using steel rods.
Another feature, if rods and piston weights are matched, is a crank balance may not even be required.
Most here know Bob Weight may be greater just not less than the requirement. (Overbalance)
Lance
09-26-2016, 12:26 AM
#20
I ran Lunati ProMod rods with an LS7 crank and the mallory needed to balance it was around $500-600 balance job like you said. Those Lunati rods were rated at 1500hp or so and waaaaay beyond the limits of my block. It did work though 
Of note- if you want the snout cut it is about equivalent cost to using the spacer..... and you better find a quality machine shop. I had it done on an LS7 and LS9. A shop in SoCal cut them and it worked out great.
Of note- if you want the snout cut it is about equivalent cost to using the spacer..... and you better find a quality machine shop. I had it done on an LS7 and LS9. A shop in SoCal cut them and it worked out great.
Last edited by gnx7; 09-26-2016 at 12:37 AM.