396 Crank, forged or cast? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Big69C20 Toy · 06-23-2002, 05:26 PM

Anyone know if the crank in my truck is a forged or cast piece, the block has high pass or high perf stamped on it but i dont know. anyone know shy of taking off the pan?

*Randy70C-10* · 06-23-2002, 05:29 PM

The only way you'll probably know is to take off the pan. If it's cast, you can see the mold seams in it.

Big69C20 Toy · 06-23-2002, 05:30 PM

grr i kinda figured Randy, but i had hope. what HP could a cast crank take?

Super Chevy · 06-23-2002, 06:04 PM

All BBC had high perf or HP stamped into the block,i never actually seen a cast or forged crank "break, ,i know a few racers that run cast cranks, i think the cast is mabe alittle easier to scuff and scare though....

SC

*Randy70C-10* · 06-23-2002, 06:11 PM

I broke a cast crank on the Model A, but you should never see it happen on a street motor unless you run a blower.

Big69C20 Toy · 06-23-2002, 06:29 PM

well it'll be a street motor but with what i'm planning it should be about 700hp and not spinning above 6500rpm. i know cast can have more flex which can be good/bad but i'm curious if i've gotta find a forged crank for what im thinking, the motor wont be worked hard really, as it's my daily driver but it will be turbo/twin turbo setup.

junkyardjohn · 06-23-2002, 06:30 PM

YOU WON'T HAVE TO PULL THE PAN TO FIND OUT. JUST TAKE OFF THE TORQUE CONVERTER COVER, & WITH A FLASHLIGHT,LOOK UP AT THE FLANGE WHERE YOUR CRANK CONNECTS TO YOUR FLEX PLATE. IF IT HAS A THIN PARTING LINE-ABOUT 3/16" IT'S CAST -- OR THICK PARTING LINE - ABOUT 1/2" IT'S FORGED

Big69C20 Toy · 06-23-2002, 06:33 PM

ohh that wont be tough junkyard eheh, thanks man

mikep · 06-23-2002, 09:15 PM

I had a 325 horse 396 in my 68 when I bought it. It was the original numbers matching engine. I thought it must have had a steel crank because it was in a heavy 3/4 ton with the 4 speed tranny. I was wrong. When I pulled the engine I dropped the pan to satisfy my curiosity. It was a 2 bolt , cast crank engine. I was shocked to say the least. It was also stamped hi perf pass and had the oil cooler ports on the block.

*Randy70C-10* · 06-23-2002, 10:06 PM

You shouldn't have any problems with a twin turbo setup either. The problem with blowers is that the crank works so hard to turn them. Also, once they heat to operating temp, the alunimun expands and actually tightens the belt. I twisted the front of my cast crank clean off! That's when I learned you must run a forged crank and balancer with a blower.

06-23-2002, 05:26 PM	#1
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	396 Crank, forged or cast? Anyone know if the crank in my truck is a forged or cast piece, the block has high pass or high perf stamped on it but i dont know. anyone know shy of taking off the pan? __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

06-23-2002, 05:30 PM	#3
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	grr i kinda figured Randy, but i had hope. what HP could a cast crank take? __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

06-23-2002, 06:29 PM	#6
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	well it'll be a street motor but with what i'm planning it should be about 700hp and not spinning above 6500rpm. i know cast can have more flex which can be good/bad but i'm curious if i've gotta find a forged crank for what im thinking, the motor wont be worked hard really, as it's my daily driver but it will be turbo/twin turbo setup. __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

06-23-2002, 06:30 PM	#7
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	YOU WON'T HAVE TO PULL THE PAN TO FIND OUT. JUST TAKE OFF THE TORQUE CONVERTER COVER, & WITH A FLASHLIGHT,LOOK UP AT THE FLANGE WHERE YOUR CRANK CONNECTS TO YOUR FLEX PLATE. IF IT HAS A THIN PARTING LINE-ABOUT 3/16" IT'S CAST -- OR THICK PARTING LINE - ABOUT 1/2" IT'S FORGED __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

06-23-2002, 06:33 PM	#8
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	ohh that wont be tough junkyard eheh, thanks man __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

06-23-2002, 05:29 PM	#2
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	The only way you'll probably know is to take off the pan. If it's cast, you can see the mold seams in it.

06-23-2002, 06:04 PM	#4
Super Chevy Registered User Join Date: Feb 2001 Location: Ohio Posts: 1,025	All BBC had high perf or HP stamped into the block,i never actually seen a cast or forged crank "break, ,i know a few racers that run cast cranks, i think the cast is mabe alittle easier to scuff and scare though.... SC

06-23-2002, 06:11 PM	#5
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	I broke a cast crank on the Model A, but you should never see it happen on a street motor unless you run a blower.

06-23-2002, 09:15 PM	#9
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	I had a 325 horse 396 in my 68 when I bought it. It was the original numbers matching engine. I thought it must have had a steel crank because it was in a heavy 3/4 ton with the 4 speed tranny. I was wrong. When I pulled the engine I dropped the pan to satisfy my curiosity. It was a 2 bolt , cast crank engine. I was shocked to say the least. It was also stamped hi perf pass and had the oil cooler ports on the block. __________________ No truck :-(

06-23-2002, 10:06 PM	#10
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	You shouldn't have any problems with a twin turbo setup either. The problem with blowers is that the crank works so hard to turn them. Also, once they heat to operating temp, the alunimun expands and actually tightens the belt. I twisted the front of my cast crank clean off! That's when I learned you must run a forged crank and balancer with a blower.



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