72 4wd getting a big block

[Agent]

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]

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]

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]

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]

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]

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]

Thanks for the info and pics, what are those headres originally made for?

[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.

[c20pickup]

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]

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