Why did 4x4s never get big blocks? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

davepl · 09-16-2014, 06:03 PM

In our 67-72 series what kept GM from putting the 402 in it? Was it a fitment issue or a marketing decision (it's always the latter, but was it forced by the former?).

For that matter why was the 427 or 454 never offered, even in the big 30s?

turp mcspray · 09-16-2014, 06:39 PM

They moved the engine rearward in the 4x4, for oil pan to axle clearance. Without making a 2nd firewall stamping, and possibly creating more necessary changes, I'm guessing they just took the easy way out, by not offering a big block in a 4x4.

**'68OrangeSunshine** · 09-16-2014, 06:45 PM

Another theory might be that they didn't want to warranty the drive train, with the massive torque of the BBC on 4x4 equipment.
They also didn't offer the 292 L6 [another torque monster] in the K/5.

tcrist · 09-16-2014, 06:55 PM

Neighbor put a 396 in a 72 4X4 with no firewall clearance issues at all. Not sure what he had to do the pan though, if anything.

**'68OrangeSunshine** · 09-17-2014, 12:35 AM

Yeah, and I used to run a '67 K/10 Suburban with a 454. PO told me he got frustrated with trying to pull his boat up to the [AZ] White Mountains. When the original 283 couldn't cut it he put in a 350. When he thought the 350 was too slow he dropped in a 454.
I'd like to ressurect that truck, there were only like around 1600 1/2 ton 4x4 [K/10] Suburbans in 1967, kinda rare. But I can't afford to rebuild that BBC, when it only got 8 highway and 6 city miles. It would pass anything on the road but a gas station. And it only liked Premium.
The points distributor fit OK. When I swapped in an HEI, it got tight. Don't remember any oil pan issue.
The BBC would also beat the driveline into submission. I was replacing uni- joints every 6 months.

**Bob B.** · 09-17-2014, 04:08 AM

The story I was told is that it had to do with torque, the 396's would put too much stress on the transfer case and Dana 44 front axle. The 351 V-6 was not available in 4X4's either. The first year for the big block in a 4X4 was 1982, and then it was only available in the K-30 with the Dana 60 front axle. Ford was basically the same way, no 390's in 4X4's.

Keith Seymore · 09-17-2014, 07:11 AM

Torque multiplication through the transfer case in low range.

It doubles the torque and the axles are not up to the task.

K

09-16-2014, 06:03 PM	#1
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Why did 4x4s never get big blocks? In our 67-72 series what kept GM from putting the 402 in it? Was it a fitment issue or a marketing decision (it's always the latter, but was it forced by the former?). For that matter why was the 427 or 454 never offered, even in the big 30s? __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

09-16-2014, 06:39 PM	#2
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	Re: Why did 4x4s never get big blocks? They moved the engine rearward in the 4x4, for oil pan to axle clearance. Without making a 2nd firewall stamping, and possibly creating more necessary changes, I'm guessing they just took the easy way out, by not offering a big block in a 4x4. __________________ Turp Mcspray New life for an old 2wd, farm blazer http://67-72chevytrucks.com/vboard/s...d.php?t=505987 My Blazer build http://67-72chevytrucks.com/vboard/s...d.php?t=342299

09-16-2014, 06:45 PM	#3
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,203	Re: Why did 4x4s never get big blocks? Another theory might be that they didn't want to warranty the drive train, with the massive torque of the BBC on 4x4 equipment. They also didn't offer the 292 L6 [another torque monster] in the K/5. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

09-16-2014, 06:55 PM	#4
tcrist Registered User Join Date: May 2014 Location: Manteca, Ca. Posts: 274	Re: Why did 4x4s never get big blocks? Neighbor put a 396 in a 72 4X4 with no firewall clearance issues at all. Not sure what he had to do the pan though, if anything. __________________ Terry Soon to be retired and moving to Bristol, TN.

09-17-2014, 12:35 AM	#5
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,203	Re: Why did 4x4s never get big blocks? Yeah, and I used to run a '67 K/10 Suburban with a 454. PO told me he got frustrated with trying to pull his boat up to the [AZ] White Mountains. When the original 283 couldn't cut it he put in a 350. When he thought the 350 was too slow he dropped in a 454. I'd like to ressurect that truck, there were only like around 1600 1/2 ton 4x4 [K/10] Suburbans in 1967, kinda rare. But I can't afford to rebuild that BBC, when it only got 8 highway and 6 city miles. It would pass anything on the road but a gas station. And it only liked Premium. The points distributor fit OK. When I swapped in an HEI, it got tight. Don't remember any oil pan issue. The BBC would also beat the driveline into submission. I was replacing uni- joints every 6 months. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not. Last edited by '68OrangeSunshine; 09-17-2014 at 12:42 AM.

09-17-2014, 04:08 AM	#6
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,320	Re: Why did 4x4s never get big blocks? The story I was told is that it had to do with torque, the 396's would put too much stress on the transfer case and Dana 44 front axle. The 351 V-6 was not available in 4X4's either. The first year for the big block in a 4X4 was 1982, and then it was only available in the K-30 with the Dana 60 front axle. Ford was basically the same way, no 390's in 4X4's. __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

09-17-2014, 07:11 AM	#7
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,181	Re: Why did 4x4s never get big blocks? Torque multiplication through the transfer case in low range. It doubles the torque and the axles are not up to the task. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/



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