I need help from you 4+4 guys! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Gordo · 04-24-2002, 04:53 PM

I'm helping a friend that has a 72 C20 step 4+4 standard shift. Are intentions are to pull the small block and install a big block. What I need to know is what problems will we run into such as frame mounts and which set of frame holes do we use and anything else you guys can think of. Thanks!

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

71Chev · 04-24-2002, 05:12 PM

Not positive, but I think the xmember stays in the same place and just use different engine to xmember motor mounts.

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71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

71402BB · 04-24-2002, 05:15 PM

Hey Gordo, not sure as where the engine mounts go cause I've never put a BB in a 4x but I do know that you are either going to need to do a body lift on the truck or bang on the firewall with a hammare because the distributer will hit the firewall other wise. and you won't be able to get it in!

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71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's

72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!)

68 BURB 50TH LOOKALIKE with built 350 4-speed 4.11's and posi

'72 Cheyenne Super · 04-24-2002, 05:29 PM

No, you shouldn't have firewall clearance problems with the distributor, but you will with the driver's side valve cover. That's if you're planning to use a TH350 with a big block.

71402BB · 04-24-2002, 05:39 PM

ok never mind what I said, my bad.

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71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's

72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!)

68 BURB 50TH LOOKALIKE with built 350 4-speed 4.11's and posi

rabbittdawg · 04-24-2002, 07:29 PM

well frommy experience with chevys it dosn't matter u can take out a straight six and bolt in a bb they r all interchangable exept exaust work good luck

keenee · 04-24-2002, 08:24 PM

Yo Gordo! You will use the same engine mounts. If you use the X member in the stock location, you may have clearance problems at the firewall, as was stated above, at the valvecovers. In the past we have used a combo of 3" lift and firewall mods. Now we have switched to moving the x-member forward to avoid both the lift and cutting and welding the firewall. New holes will have to be drilled AND the X-member will HAVE to be narrowed to fit in its new location. Also, both driveshafts will have to be worked, front shortened, rear lengthened, the tranny X-member will have to be moved forward, Both shifters will be not so centered in their floor cut-out, and the clutch linkage will have to be reworked(we have done 4 automatic trucks). Good luck! As I made the list I realized that the lift/firewallmod is a lot cheaper! And quicker!

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72 3/4 lwb fleet 427 t350 4x4 under construction

71BBK10 · 04-24-2002, 09:30 PM

my truck is a 4x4 with 402 and turbo 350, from what i can tell the engine x-member has been moved forward, no firewall "massaging"

imdarren · 04-24-2002, 10:49 PM

Keenee and 71 are correct. Just move the motor forward to the front holes (on the drivers side of frame). On the passenger side of the frame you will need to drill holes, because there are NO forward holes. I belive this is the "Correct way" to install a big block.
This Pic. is of the drivers side frame in the forward holes. The motor is a 502.

Good luck!! Darren

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Darren
Washougal, Washington
darrengale67@hotmail.com

1972 GMC C1500 (Bone Stock)

Looking for a 72 SWB 4X4 Or 2WD Automatic with little or no rust.

Gordo · 04-25-2002, 06:10 PM

Thanks guys,,,your the best! I'll keep you posted.

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1971 C10 swb stepside 350/700R4/3.73posi
Killingworth, Connecticut

04-24-2002, 04:53 PM	#1
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	I need help from you 4+4 guys! I'm helping a friend that has a 72 C20 step 4+4 standard shift. Are intentions are to pull the small block and install a big block. What I need to know is what problems will we run into such as frame mounts and which set of frame holes do we use and anything else you guys can think of. Thanks! ------------------ 1971 C10 swb stepside 350/700R4/3.73posi Killingworth, Connecticut __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

04-24-2002, 05:12 PM	#2
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	Not positive, but I think the xmember stays in the same place and just use different engine to xmember motor mounts. ------------------ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear. __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

04-24-2002, 05:15 PM	#3
71402BB now thats a true COON DOG Join Date: Nov 2000 Location: Franconia, NH Posts: 1,977	Hey Gordo, not sure as where the engine mounts go cause I've never put a BB in a 4x but I do know that you are either going to need to do a body lift on the truck or bang on the firewall with a hammare because the distributer will hit the firewall other wise. and you won't be able to get it in! ------------------ 71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's 72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!) 68 BURB 50TH LOOKALIKE with built 350 4-speed 4.11's and posi __________________ current project 67 402BB stout th350 3.08's with a locker. Plan on tubs 18.5's out back! (thanks Burnsman!) 71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's ( was crushed by a tree, bed sold, motor pulled) was my first truck!... oh well... 72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!) 68 BURB 50TH LOOKALIKE work in progress, soon to have 250-I6 with a 3-speed on the tree 4.11's and posi ( currently sitting in back yard tarped awaiting time, $$$, and lots of love!) 67 1 TON- work truck 396 sm 420 4-speed, flat bed 4.57 gears "big red" (my first landscape truck, very rusty and crusty! but still gets the job done when needed!)

04-24-2002, 05:29 PM	#4
'72 Cheyenne Super Registered User Join Date: Feb 2002 Location: Puyallup, WA USA!! Posts: 85	No, you shouldn't have firewall clearance problems with the distributor, but you will with the driver's side valve cover. That's if you're planning to use a TH350 with a big block. __________________ '72 Cheyenne Super 4x4, 468ci, 700R4, Import Stomper. A couple pics at http://www.picturetrail.com/gallery/view?p=6&uid=529895&

04-24-2002, 05:39 PM	#5
71402BB now thats a true COON DOG Join Date: Nov 2000 Location: Franconia, NH Posts: 1,977	ok never mind what I said, my bad. ------------------ 71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's 72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!) 68 BURB 50TH LOOKALIKE with built 350 4-speed 4.11's and posi __________________ current project 67 402BB stout th350 3.08's with a locker. Plan on tubs 18.5's out back! (thanks Burnsman!) 71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's ( was crushed by a tree, bed sold, motor pulled) was my first truck!... oh well... 72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!) 68 BURB 50TH LOOKALIKE work in progress, soon to have 250-I6 with a 3-speed on the tree 4.11's and posi ( currently sitting in back yard tarped awaiting time, $$$, and lots of love!) 67 1 TON- work truck 396 sm 420 4-speed, flat bed 4.57 gears "big red" (my first landscape truck, very rusty and crusty! but still gets the job done when needed!)

04-24-2002, 07:29 PM	#6
rabbittdawg Registered User Join Date: Mar 2002 Location: harrison, mi. u.s.a. Posts: 13	well frommy experience with chevys it dosn't matter u can take out a straight six and bolt in a bb they r all interchangable exept exaust work good luck

04-24-2002, 08:24 PM	#7
keenee Registered User Join Date: Mar 2002 Location: Houston, Pennsylvania Posts: 231	Yo Gordo! You will use the same engine mounts. If you use the X member in the stock location, you may have clearance problems at the firewall, as was stated above, at the valvecovers. In the past we have used a combo of 3" lift and firewall mods. Now we have switched to moving the x-member forward to avoid both the lift and cutting and welding the firewall. New holes will have to be drilled AND the X-member will HAVE to be narrowed to fit in its new location. Also, both driveshafts will have to be worked, front shortened, rear lengthened, the tranny X-member will have to be moved forward, Both shifters will be not so centered in their floor cut-out, and the clutch linkage will have to be reworked(we have done 4 automatic trucks). Good luck! As I made the list I realized that the lift/firewallmod is a lot cheaper! And quicker! ------------------ 72 3/4 lwb fleet 427 t350 4x4 under construction __________________ '96 GMC Suburban 6.5t '99 F**d Windstar '07 SON '09 DAUGHTER XOXOXO Wife

04-24-2002, 09:30 PM	#8
71BBK10 Teufelhunden Join Date: Oct 2001 Location: Camp Pendelton Ca Posts: 572	my truck is a 4x4 with 402 and turbo 350, from what i can tell the engine x-member has been moved forward, no firewall "massaging" __________________ 1971 K10 lwb fleetside 402 T350 205

04-24-2002, 10:49 PM	#9
imdarren Registered User Join Date: Oct 2001 Location: SW Washington Posts: 1,006	Keenee and 71 are correct. Just move the motor forward to the front holes (on the drivers side of frame). On the passenger side of the frame you will need to drill holes, because there are NO forward holes. I belive this is the "Correct way" to install a big block. This Pic. is of the drivers side frame in the forward holes. The motor is a 502. Good luck!! Darren ------------------ Darren Washougal, Washington darrengale67@hotmail.com 1972 GMC C1500 (Bone Stock) Looking for a 72 SWB 4X4 Or 2WD Automatic with little or no rust. __________________ Washington State 1967 Chevy C10 LWB Rodstoration In Progress. 1972 K20 Cheyenne Super

04-25-2002, 06:10 PM	#10
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Thanks guys,,,your the best! I'll keep you posted. ------------------ 1971 C10 swb stepside 350/700R4/3.73posi Killingworth, Connecticut __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

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