Big Block Questions! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GloryHound · 07-29-2005, 09:28 AM

I looked through the FQAs and did not find anything to cover this. So I figured I would ask a question I know has been answered on here before. To convert a Small block truck to a Big Block truck what all is needed? I am considering this for my truck. I have a swb C-10. I already have plans to install the 4 core radiator. Are any of my brackets useable on a Big Block? (ie. alternator bracket and power steering bracket. I do not have AC.)

Right now these are the things I believe I will need:
BB front springs (Needed new ones anyway)
BB engine towers
New alternator bracket
New power steering bracket
new radiator cowl (needed a new one anyway)
New motor mounts
New exaust manifolds or headers (want to go ceramic coated headers anyway)
New intake (probably step up to a 850 cfm carb also)
and since I'm running an auto tranny I will want to have the clutches upgraded.

Other than the stock 68-71 and the rare 72 engine towers are thier any other engine mounts that are direct bolt in? (such as like a 78 chevy truck tower) Do I need a tall hump or will this still work with a short hump?

Thanks all for your advice in advance!

stllookn · 07-29-2005, 12:08 PM

You might consider a 4-core radiator. I believe that the small block towers will work you just have to get creative about the headers/exhaust. If you are lowering the truck...use the small block springs.

TireSmoke420 · 07-29-2005, 12:09 PM

I believe all ya need are the bb motor mounts. also no need for a high hump.

**Desert Rat** · 07-29-2005, 12:24 PM

You will need

1. 68-71 or 72 style motor towers (there is no other direct bolt in without some sort of modification)

2. alternator brackets
3. power steering pump and brackets
4. pulleys
4. exh manifolds or headers
5. yes you will need a new intake. I would put on a 850 carb unless you have a healthy motor.
6. small block coil springs work fine, barely noticable drop.
7. no need for the high hump.

I don't know anyone who has had the clutched upgraded, I have known many people to run t350s straight from the small block truck without any problems. Unless its old and tired and you get on it hard often.
Using your small block mounts will cause the motor to sit funky. You might run into some pinion angle problems and vibrations. Id recommend the '72 style mounts they may be more expensive to purchase but when you replace the rubber mounts you will be in them less money! and they are a much better and safer design. If you have any questions shoot me a email.

Longhorn Man · 07-29-2005, 08:05 PM

to be factory correct, there is a heat shield on the passenger floor board where the firewall meets the floor, and also a spacer to raise the tail of the tranny too.

cochran63 · 07-29-2005, 09:57 PM

I have an almost new 850 speed demon for sale. It is listed in the 67-72 chewvy parts board.

BTW I put a big block in my 63 and I still used the 6cyl springs. I dont think it sets a half inch lower.

**Desert Rat** · 07-29-2005, 10:02 PM

I have never found the heat shield on anything but 72's Ive parted a few 68, 69, 70 and 72 big block trucks and burbs it's the only year that ive removed them. I have a few available if you want to look correct. I may have a big block fan shroud still?

vtblazer · 07-30-2005, 11:00 AM

Quote:

Originally Posted by Desert Rat

I have never found the heat shield on anything but 72's

My 71 has a heat shield.

**Desert Rat** · 07-30-2005, 11:13 AM

Quote:

Originally Posted by Desert Rat

Ive parted a few 68, 69, 70 and 72 big block trucks and burbs it's the only year that ive removed them.

I believe thats the only year bb truck I have never parted. It may also be one of those things that made it on some trucks and not on others I have no idea.

Cornfed- They big block and small block towers are the same in the 73 up style trucks. Also in the early trucks if you take out a big block and replace with a small block it will technically work. I love going to the bone yard finding small blocks sitting on big block towers, it gives me alot more room to remove them! I have purchased several this way over the last several years. I love it when people leave the big block ps pump. Alot of the yards around here charge more for big block parts. If I say "how much for the motor mounts and PS pump from the 72" I always get "is it a big or small block?" I honestly reply " It's a small block."

GloryHound · 07-30-2005, 09:28 PM

Quote:

Why don't you look around for a truck that someone has already spent the fortune on and buy it for a lot less. You can be driving it tomorrow instead of two or three years down the road and you can still modify it to suit you.

What would be the fun in that? That would not nearly bug my wife as much.

Then were is the pride of doing something from the ground up with your own two hands. Also it has something to do with the fact that it would be 3 to 4 years before I could save the money up to buy an expensive truck. That is if the washer didn't break or my wife got the idea that the money could be used elsewhere better. So for me it is better to make the $500 here and $200 there type purchases. The wife doesn't have enough time to think about a better way of spending my money!

Longhorn Man · 07-29-2005, 11:06 PM

interesting... I thought they were on all big blocks.

corn · 07-30-2005, 02:22 AM

I took the big block out of my son's '69 & just bolted his new 350 right in. No tower or motormount changes at all. Not sure about the other way around but on my 84 I took out the 305 & bolted the 396 right in...corn

corn · 07-30-2005, 02:24 AM

Forgot, I have a 396 radiator/fan shroud & maybe some of the brackets from a '69...corn

GloryHound · 07-30-2005, 08:38 AM

I appreciate all the parts offers but I need to get rid of some of my small block stuff so I can afford to start buying the Big block stuff. My truck is on the 10/20 plan. (I think it will take me ten years to complete so it will probably end up being more like twenty!) Since I already know I'm going to spend a fortune on the truck I might as well spend the extra money and drop a big block in since the conversion will not be hard especially considering my truck is a bare frame ready to be hauled to the sand blaster/painter.

**VetteVet** · 07-30-2005, 10:38 AM

Quote:

Originally Posted by GloryHound

I appreciate all the parts offers but I need to get rid of some of my small block stuff so I can afford to start buying the Big block stuff. My truck is on the 10/20 plan. (I think it will take me ten years to complete so it will probably end up being more like twenty!)

Since I already know I'm going to spend a fortune on the truck I might as well spend the extra money and drop a big block in since the conversion will not be hard especially considering my truck is a bare frame ready to be hauled to the sand blaster/painter.

Why don't you look around for a truck that someone has already spent the fortune on and buy it for a lot less. You can be driving it tomorrow instead of two or three years down the road and you can still modify it to suit you.

cduster · 07-30-2005, 08:51 AM

When I put my big block in my 72, I had to change the towers. The exhaust manifolds would not go on, and the header also hit the tower. The BB towers drop down off the frame to clear the exhaust manifolds or headers. I bought the 72 towers and things worked perfect. Dan

07-29-2005, 09:28 AM	#1
GloryHound Working on a Nova. Join Date: Nov 2002 Location: ## Posts: 506	Big Block Questions! I looked through the FQAs and did not find anything to cover this. So I figured I would ask a question I know has been answered on here before. To convert a Small block truck to a Big Block truck what all is needed? I am considering this for my truck. I have a swb C-10. I already have plans to install the 4 core radiator. Are any of my brackets useable on a Big Block? (ie. alternator bracket and power steering bracket. I do not have AC.) Right now these are the things I believe I will need: BB front springs (Needed new ones anyway) BB engine towers New alternator bracket New power steering bracket new radiator cowl (needed a new one anyway) New motor mounts New exaust manifolds or headers (want to go ceramic coated headers anyway) New intake (probably step up to a 850 cfm carb also) and since I'm running an auto tranny I will want to have the clutches upgraded. Other than the stock 68-71 and the rare 72 engine towers are thier any other engine mounts that are direct bolt in? (such as like a 78 chevy truck tower) Do I need a tall hump or will this still work with a short hump? Thanks all for your advice in advance!

07-29-2005, 12:08 PM	#2
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	You might consider a 4-core radiator. I believe that the small block towers will work you just have to get creative about the headers/exhaust. If you are lowering the truck...use the small block springs. __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

07-29-2005, 09:57 PM	#6
cochran63 Registered User Join Date: Jan 2004 Location: Oklahoma Posts: 1,057	I have an almost new 850 speed demon for sale. It is listed in the 67-72 chewvy parts board. BTW I put a big block in my 63 and I still used the 6cyl springs. I dont think it sets a half inch lower. __________________ Youth soon passes away, but immaturity can last a life time.

07-30-2005, 08:51 AM	#16
cduster Registered User Join Date: Oct 2002 Location: S.W. Michigan Posts: 403	When I put my big block in my 72, I had to change the towers. The exhaust manifolds would not go on, and the header also hit the tower. The BB towers drop down off the frame to clear the exhaust manifolds or headers. I bought the 72 towers and things worked perfect. Dan __________________ Good Judgment comes from experience. Most experience comes from bad judgment.

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07-29-2005, 12:09 PM	#3
TireSmoke420 One of the few GMC'ers Join Date: Jul 2005 Location: Des Moines, Iowa sometimes Butler, PA Posts: 146	I believe all ya need are the bb motor mounts. also no need for a high hump.

07-29-2005, 12:24 PM	#4
Desert Rat Senior Member Join Date: Dec 1999 Location: Darrington, Washington Posts: 3,963	You will need 1. 68-71 or 72 style motor towers (there is no other direct bolt in without some sort of modification) 2. alternator brackets 3. power steering pump and brackets 4. pulleys 4. exh manifolds or headers 5. yes you will need a new intake. I would put on a 850 carb unless you have a healthy motor. 6. small block coil springs work fine, barely noticable drop. 7. no need for the high hump. I don't know anyone who has had the clutched upgraded, I have known many people to run t350s straight from the small block truck without any problems. Unless its old and tired and you get on it hard often. Using your small block mounts will cause the motor to sit funky. You might run into some pinion angle problems and vibrations. Id recommend the '72 style mounts they may be more expensive to purchase but when you replace the rubber mounts you will be in them less money! and they are a much better and safer design. If you have any questions shoot me a email.

07-29-2005, 08:05 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	to be factory correct, there is a heat shield on the passenger floor board where the firewall meets the floor, and also a spacer to raise the tail of the tranny too.

07-29-2005, 10:02 PM	#7
Desert Rat Senior Member Join Date: Dec 1999 Location: Darrington, Washington Posts: 3,963	I have never found the heat shield on anything but 72's Ive parted a few 68, 69, 70 and 72 big block trucks and burbs it's the only year that ive removed them. I have a few available if you want to look correct. I may have a big block fan shroud still?

07-29-2005, 11:06 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	interesting... I thought they were on all big blocks.

07-30-2005, 02:22 AM	#12
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	I took the big block out of my son's '69 & just bolted his new 350 right in. No tower or motormount changes at all. Not sure about the other way around but on my 84 I took out the 305 & bolted the 396 right in...corn

07-30-2005, 02:24 AM	#13
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	Forgot, I have a 396 radiator/fan shroud & maybe some of the brackets from a '69...corn

07-30-2005, 08:38 AM	#14
GloryHound Working on a Nova. Join Date: Nov 2002 Location: ## Posts: 506	I appreciate all the parts offers but I need to get rid of some of my small block stuff so I can afford to start buying the Big block stuff. My truck is on the 10/20 plan. (I think it will take me ten years to complete so it will probably end up being more like twenty!) Since I already know I'm going to spend a fortune on the truck I might as well spend the extra money and drop a big block in since the conversion will not be hard especially considering my truck is a bare frame ready to be hauled to the sand blaster/painter.



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