How much Horsepower and Torque can a GM Forged Crank Handle - Chevelle Tech
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post #1 of 16 (permalink) Old Nov 26th, 19, 4:21 PM Thread Starter
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Andy
 
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How much Horsepower and Torque can a GM Forged Crank Handle

Big Block GM short 427 Forged crank 3.766" Stroke.
How much can these safely handle if they are in good shape in a good well put together 4 bolt GM block?
How about if it is double keyed for low boost?


Thoughts? Looking to do a low buck low boost (5 lb's) 427" based engine. Short throw, slower piston speed, and lower internal weight?

Thank you for all your input.
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post #2 of 16 (permalink) Old Nov 26th, 19, 6:01 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

Quote:
Originally Posted by Ialone View Post
Big Block GM short 427 Forged crank 3.766" Stroke.
How much can these safely handle if they are in good shape in a good well put together 4 bolt GM block?
How about if it is double keyed for low boost?


Thoughts? Looking to do a low buck low boost (5 lb's) 427" based engine. Short throw, slower piston speed, and lower internal weight?

Thank you for all your input.
Hi Andy, that shaft will most likely do the number you're looking to get.

We've had many of them in "blown" units over the years, both the 427" and the 454" "steelies". Most had in the 700+ Hp range!

On a side note here, there were a couple "production-line" 3.766" shafts being used, the 6223's were the most common, the 7115's were the sought after pieces back then, these came in the Hi-Perf 427's with the 7/16" rod bolts!

Thanks, Gary in N.Y.

P.S. Absolutely do the extra 1/4" key-way and keep a very close eye on the "tune", this is one of the most important items with blown or turboed units. run it "lean" and you'll have big-time issues! Here's a shot of an Aluminum Keith Black 454" done here about 25/26 years ago using a BDS blower, had the stock OEM 7416 shaft and matching 7/16" rods inside!
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post #3 of 16 (permalink) Old Nov 26th, 19, 6:03 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

This will get interesting. I shall follow. In my time I have seen a lot of power put on the gm forged cranks. Some in the 7 second quarter mile fastest street car stuft. Seen some last a season in top fuel running 5 second quarter mile times. Have a hot rod magazine where a guy named scott shoroof used and ofset ground GM crank in his 7 second Camaro years ago before there were stroker cranks. Think it was called tge fun city flyer.

RH
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post #4 of 16 (permalink) Old Nov 26th, 19, 6:31 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

I had one of those 1979-80 I was running 9 lbs. single key on the crank. It was a Dyers blower with the lower pulley bolted to the stock damper.
I don't know how much power it was making ran 130 @ 3750 lbs.
I had a crank from a 366 truck engine.
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post #5 of 16 (permalink) Old Nov 26th, 19, 9:04 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

That stroke will allow for a very long rod and short pin height, lightweight piston. With the main/rod pin journal overlap that this stroke crank has, they're stronger than longer stroke cranks. Good rods and pistons and gap the rings for max boost plus a fudge factor and give 'er hell!
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post #6 of 16 (permalink) Old Nov 27th, 19, 10:51 AM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

Think people don't believe it but I was looking to put my l88 internals in this block that was for sale

Chevrolet ZL1 fuel short block

Looks like gm zl1 block and gm 427 crank in a nitro blown top fuel went 5.96 and 242 mph. Is that enough to put your mind at ease. John found this add for me.

RH
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post #7 of 16 (permalink) Old Nov 27th, 19, 11:16 AM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

Quote:
Originally Posted by Ialone View Post
Big Block GM short 427 Forged crank 3.766" Stroke.
How much can these safely handle if they are in good shape in a good well put together 4 bolt GM block?
How about if it is double keyed for low boost?


Thoughts? Looking to do a low buck low boost (5 lb's) 427" based engine. Short throw, slower piston speed, and lower internal weight?

Thank you for all your input.
Lot of marine guys use that crank in blown alky engines making 1500+ and turning 8000rpm.
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post #8 of 16 (permalink) Old Nov 27th, 19, 11:26 AM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

It looks like a new forged Scat crank it about $900.

The 427 crank it 50 plus years old and will need to be cleaned magged and possible turned. So how much is the saving of using the old crank?


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post #9 of 16 (permalink) Old Nov 27th, 19, 12:48 PM Thread Starter
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

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Originally Posted by artmalibu View Post
It looks like a new forged Scat crank it about $900.

The 427 crank it 50 plus years old and will need to be cleaned magged and possible turned. So how much is the saving of using the old crank?
Well... good points, My crank has already been done. No extra cost at the moment unless I purchase a new crank.

Thank you!
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post #10 of 16 (permalink) Old Nov 27th, 19, 12:49 PM Thread Starter
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

I appreciate the posts guys. I will get some good rods, and lightweight pistons to go along with.

Thank you all!
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post #11 of 16 (permalink) Old Nov 27th, 19, 1:26 PM Thread Starter
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

Quote:
Originally Posted by GOSFAST View Post
Hi Andy, that shaft will most likely do the number you're looking to get.

We've had many of them in "blown" units over the years, both the 427" and the 454" "steelies". Most had in the 700+ Hp range!

On a side note here, there were a couple "production-line" 3.766" shafts being used, the 6223's were the most common, the 7115's were the sought after pieces back then, these came in the Hi-Perf 427's with the 7/16" rod bolts!

Thanks, Gary in N.Y.

P.S. Absolutely do the extra 1/4" key-way and keep a very close eye on the "tune", this is one of the most important items with blown or turboed units. run it "lean" and you'll have big-time issues! Here's a shot of an Aluminum Keith Black 454" done here about 25/26 years ago using a BDS blower, had the stock OEM 7416 shaft and matching 7/16" rods inside!

Thanks Gary- Mine is a 6223 unit. Hopefully will hold up to the 700+ HP and 600+ lbs of Torque ... Will keep her fat and happy and limit timing to about 30-32 degrees with like maybe 5 Lbs of boost.
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post #12 of 16 (permalink) Old Nov 27th, 19, 1:54 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

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Originally Posted by Ialone View Post
I appreciate the posts guys. I will get some good rods, and lightweight pistons to go along with.

Thank you all!
Even with new rods, have a good machinist verify both ends in spec and straight. Balance assembly.
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post #13 of 16 (permalink) Old Nov 27th, 19, 5:28 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

This is a little off this thread but does anyone reasonable close to the west coast do nitriding on reground GM cross drilled cranks. I've found fewer and fewer who offer this anymore. Thanks for any input and have a great thanksgiving!
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post #14 of 16 (permalink) Old Nov 27th, 19, 5:55 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

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Originally Posted by Olchevparts View Post
This is a little off this thread but does anyone reasonable close to the west coast do nitriding on reground GM cross drilled cranks. I've found fewer and fewer who offer this anymore. Thanks for any input and have a great thanksgiving!
Marine Crankshafts in SoCal.

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post #15 of 16 (permalink) Old Nov 28th, 19, 1:10 PM
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Re: How much Horsepower and Torque can a GM Forged Crank Handle

I can give you 1st hand experience from back when the 1053 Chevy forged crank was about the only thing we had.

I raced APBA Circle boats all through the ‘70’s, all three classes. In K Boat, which was more or less Unlimited on engines, we either ran an injected methanol motor with about 14 to 1 compression, or a blown motor on methanol, with about 10 pounds of boost. The engines made anywhere from 800 tp 1200 HP. We revved them to an average 7000 rpm.

I preferred the injected methanol motors, which were based on 427 tall truck blocks with 1/4 inch longer rods.

It did no good to make much more power, you set the boat up to run around 110 mph on the straight always with good excelleration out of the turns.

We used the standard 427 cross drilled nitride cranks, which could be bought from Richardson Chevrolet for $150. We always had to straighten them, as they typically ran out about .007 to .009 inch. We used a radius air chisel in the throw radii.

I never saw a broke one. Even with severe connecting rod failure the cranks stayed in one piece. Granted, the power we were making seems puny by today’s standards, but when you rev a 1000 HP engine at 7000+ rpm for five laps, it is taking some punishment.

The races were typically 5 laps on a one mile course.
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