Replacing a 400 small block for a 454 long block

[meatbag]

Hey yall. So my 1976 1/2 serria grande 4x4 currently has a sb 400 with 350 transmission. Engines original, but getting tired, my dad has a 1983 30ft pace arrow, 454 with 50k miles on it. I want to swap, so I'm guessing i might need a flex plate conversion and possibly a bigger radiator or auxiliary cooling fans to keep it cool. Is there anything else I should consider for it. Yall have more experience on here.??? Thanks

 

[AuroraGirl]

Hey yall. So my 1976 1/2 serria grande 4x4 currently has a sb 400 with 350 transmission. Engines original, but getting tired, my dad has a 1983 30ft pace arrow, 454 with 50k miles on it. I want to swap, so I'm guessing i might need a flex plate conversion and possibly a bigger radiator or auxiliary cooling fans to keep it cool. Is there anything else I should consider for it. Yall have more experience on here.??? Thanks

your 400 radiator may already be a large one, whats it look like

 

[fast 99]

Actually, that is a bolt in. Flex plate from 454 should fit in the PU. Unless the PU rad has been replaced with a smaller one it should be adequate. Just be sure it is clean and fan shroud is installed. If it has a fan clutch be sure it is good. I wouldn't spend money new parts yet. Aux fans shouldn't be necessary.

 

[Shorty81]

My 496 has a 3 core radiator, direct drive fan, full shroud and runs cool as a cucumber.

 

[Radiohead]

Is it a carburated unit or is it tbi?

 

[meatbag]

Carburetor 4 barrel edelbrock

 

[meatbag]

Okay good, it's a big ass radiator and new as of 2 years back

 

[meatbag]

It's my all around truck. I plow snow and haul firewood, I do plan on replacing the transmission eventually but good to know it will hold up. I love how these trucks were built, very interchange parts

 

[Radiohead]

Got any pictures for the fellas? They can't read the text sometimes.

 

[meatbag]

I'll deliver pics, it's late right now and I live in grizzly country

 

[AuroraGirl]

Okay good, it's a big ass radiator and new as of 2 years back

if its the equivalent size of a 3 or 4 core OEM and you replaced it with aluminum it probably is enough. if it comes all the way flush to the top of the core support instead of using a 2 inch step down plate to hold it and if the shroud is one piece(Most likely..) then it should be good

hrre is my dads 75 gmc radiator and that plate I mentioned. the 4 cores. I believe the 454s maybe came with a wider radiator possibly or depending on RPOs but if its aluminum then it transfers heat more anyway, making up for size. Thats why I ffigure you may be good

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[Big Ray]

If it were me, I'd throw a retrofit roller cam and and a decent set of heads with 64 cc combustion chambers. I think you'll be surprised.
64cc heads will bump your compression ratio to 9.1.

Here's a chart I found when I bought my rig with a 400 in it. BBC parts are expensive.

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[Grit dog]

It's my all around truck. I plow snow and haul firewood, I do plan on replacing the transmission eventually but good to know it will hold up. I love how these trucks were built, very interchange parts

Would be a great swap for more torque (assuming it runs well) and bragging rights. Not so great on the wallet for an “all around” truck at the gas pumps.
But to be fair I’m sure the 400 with an Edelbroke doesn’t exactly sip fuel daintily either, lol.
More importantly, that Moho should have a TH475 trans in it. That’s definitely worth keeping, for obvious reasons, even if it needs rebuilt.

I love the Kettle Falls area only been up there once but it’s wonderful. If all it takes to bring in a Grizz or wolf is walking out to your truck at night, I’d do it every night….twice….with a .300WM and a spotlight! (And a shovel)