72 4wd getting a big block - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Agent · 11-19-2013, 10:58 AM

Hello, I am new to this site and was wondering if anyone had any advice for installing a 402 BB in my 72 4wd Cheyenne? I have set a dummy block in place with the small block motor mounts and it seems to bolt up ok. I have heard that if you use the small block engine "perches" that I may have exhaust issues. I plan on using headers but don't have any at the moment to try.

Any thoughts or advice would be appreciated. Thanks

PanelDeland · 11-19-2013, 01:03 PM

If it's a factory 4X4 there is usually some interference with the firewall.It's not a lot but enough to need relieved.A body lift or other mods may make it work without.There should be some examples of what others did If you do a search.

**jocko** · 11-19-2013, 02:23 PM

Welcome agent! Am curious as to whether or not you're removing the original small block from the truck? Big block was not an option from the factory for a K model, so the swap will stand out as a custom owner mod if/when you sell it. If you just want a big block, then, all good and enjoy, but thought it worth mentioning. What are your long term plans with it? We love pictures.... Again, welcome to the site.

Agent · 11-19-2013, 03:19 PM

Unfortunately, I do not have the original 350, the owner traded it in for a rebuilt motor back in the late 80's when it was a daily driver. Yea, I know it wasn't an option and I thought real hard about making the change, but I had a 72 402 from a Monte that is long gone and thought that I might like it in the truck. I had to do something as the 350 I have is real tired. I just drive it locally around home when the weather is nice.

**kwmech** · 11-19-2013, 04:53 PM

You will have issues with the cyl heads hitting the firewall along with the dist., if you step up to an HEI. While everything is apart I would move the x-member forward. Of course the trans will have to come forward also

turp mcspray · 11-19-2013, 05:21 PM

On my Blazer build, I am going bb. I also switched to a th400. I moved the transfer case back 1 inch, so the transfer case stick still comes out in the original location. The extra length of the trans, moved the engine forward 2 1/2". I used a short water pump setup. The fan ends up being 1/2 way into the bb, 2wd shroud. It looks like a factory install. Without moving the engine, you will have to cut up the firewall.

Agent · 11-19-2013, 05:26 PM

Thanks for the info and pics, what are those headres originally made for?

turp mcspray · 11-19-2013, 09:44 PM

They came from a 73 up truck. I think they are headmans. I hung them on the engine, since I had them in my junk stash. I actually am using a set of Dougs tri y headers.

c20pickup · 11-19-2013, 11:00 PM

Quote:

Originally Posted by turp mcspray

They came from a 73 up truck. I think they are headmans. I hung them on the engine, since I had them in my junk stash. I actually am using a set of Dougs tri y headers.

how do you take the valve covers off? looks to close to the firewall?

turp mcspray · 11-20-2013, 11:28 AM

There is plenty of room for the covers to go on and off. If they were tall, it would be an issue.

11-19-2013, 10:58 AM	#1
Agent Registered User Join Date: Nov 2013 Location: Watkins, ia Posts: 8	72 4wd getting a big block Hello, I am new to this site and was wondering if anyone had any advice for installing a 402 BB in my 72 4wd Cheyenne? I have set a dummy block in place with the small block motor mounts and it seems to bolt up ok. I have heard that if you use the small block engine "perches" that I may have exhaust issues. I plan on using headers but don't have any at the moment to try. Any thoughts or advice would be appreciated. Thanks

11-19-2013, 01:03 PM	#2
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: 72 4wd getting a big block If it's a factory 4X4 there is usually some interference with the firewall.It's not a lot but enough to need relieved.A body lift or other mods may make it work without.There should be some examples of what others did If you do a search. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

11-19-2013, 02:23 PM	#3
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,940	Re: 72 4wd getting a big block Welcome agent! Am curious as to whether or not you're removing the original small block from the truck? Big block was not an option from the factory for a K model, so the swap will stand out as a custom owner mod if/when you sell it. If you just want a big block, then, all good and enjoy, but thought it worth mentioning. What are your long term plans with it? We love pictures.... Again, welcome to the site.

11-19-2013, 03:19 PM	#4
Agent Registered User Join Date: Nov 2013 Location: Watkins, ia Posts: 8	Re: 72 4wd getting a big block Unfortunately, I do not have the original 350, the owner traded it in for a rebuilt motor back in the late 80's when it was a daily driver. Yea, I know it wasn't an option and I thought real hard about making the change, but I had a 72 402 from a Monte that is long gone and thought that I might like it in the truck. I had to do something as the 350 I have is real tired. I just drive it locally around home when the weather is nice.

11-19-2013, 04:53 PM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,469	Re: 72 4wd getting a big block You will have issues with the cyl heads hitting the firewall along with the dist., if you step up to an HEI. While everything is apart I would move the x-member forward. Of course the trans will have to come forward also

11-19-2013, 05:21 PM	#6
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	Re: 72 4wd getting a big block On my Blazer build, I am going bb. I also switched to a th400. I moved the transfer case back 1 inch, so the transfer case stick still comes out in the original location. The extra length of the trans, moved the engine forward 2 1/2". I used a short water pump setup. The fan ends up being 1/2 way into the bb, 2wd shroud. It looks like a factory install. Without moving the engine, you will have to cut up the firewall. Attached Images __________________ 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

11-19-2013, 05:26 PM	#7
Agent Registered User Join Date: Nov 2013 Location: Watkins, ia Posts: 8	Re: 72 4wd getting a big block Thanks for the info and pics, what are those headres originally made for?

11-19-2013, 09:44 PM	#8
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	Re: 72 4wd getting a big block They came from a 73 up truck. I think they are headmans. I hung them on the engine, since I had them in my junk stash. I actually am using a set of Dougs tri y headers. __________________ 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

11-20-2013, 11:28 AM	#10
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	Re: 72 4wd getting a big block There is plenty of room for the covers to go on and off. If they were tall, it would be an issue. __________________ 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



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