Questions about 454 swap

[mrk5]

Been doing a lot of searching and reading about 454 swaps and I have a few general questions I'm curious about.

Do I need to plan on putting a different radiator in my truck. The radiator I have now does an adequate job of cooling the TBI 350, but I've never felt it was great. I've chalked this up to the motor running hotter because it's old and wore out. But I'm also wondering if this is an indication my cooling system won't be adequate for a 454. I am planning on an aluminum hi-flow water pump. I have Windstar fans now and plan to use them with the 454.

The other questions I have is in regards to exhaust. The factory manifolds on the 454 now are pretty crusy looking, especially the exhaust pipe and flange where it meets the manifold. No matter what I decide, all the exhaust pipe is going to need replaced. I'm leaning pretty heavily towards a set of ceramic coated Flowtech headers, full length. My trans is a 700r4 coupled (when the bolts are tight) to a half-clocked NP241. Questions:

1. Am I going to have header clearance issues at the frame or transmission? Frame I ask about because this was a 2wd truck and and the flange of the frame is wider than a 4wd frame. The headers I'm looking at are listed for 2wd trucks but they're listed for a whole bunch of vehicles so it makes me skeptical. In regards to 454 headers, do they usually fit okay in the square body trucks?
2. Should I bend over backwards to run 2.5" dual exhaust? Or can I do like the factory 350TBI setup and merge the exhaust into 1 pipe? Thinking 2.5" off headers into single 3.5". Curious what others have done for exhaust off 454 with headers.

For additional info, I'm also planning to swap in an aluminum intake. Hoping the headers, alum intake, and alum water pump will help reduce the weight gain. Cam swap isn't off the table tho I know there's not a ton of power to gain with peanut heads but I kinda want to draw the line at pulling the heads - don't want to chase the horsepower rabbit too far down the hole. Planning on custom chipped factory TBI or FiTech setup for induction. Currently the motor has an Edelbrock carb.

Kinda thinking I may initially run the truck with the Edelbrock on it to spread out the work required and cost of the swap. Catch is I'll need to run a regulator to dial back fuel pressure from the TBI fuel pumps in the tanks.

I know this isn't as exciting or glamorous as an LS/Vortec/Cummins swap, but this will be my first BBC so I'm excited about it. Thoughts?

 

[Bent77]

BBC AC radiator. They just don't cost that much

Thinking a return line like a TBI an 8 PSI on a carb should run

 

[skunked]

Radiator
Why not use the radiator from the donor truck? You need every bit of radiator you can get to cool the BBC, I run a 4 core from a mid 80's squarebody with windstars.

Exhaust
Most of the earlier BBC exhaust manifolds crack so don't be surprised if those are. I ran some headman long tubes and they fit OK but I didn't like how they hung down. I picked up some tubular OE manifolds recently that are pretty rare but they tuck up nicely and I don't expect them to leak. I'll be running a Y pipe under the bellhousing with 2.5" pipe merging to a single 3" with a 3" muffler. Dual all the way out back isn't an option for me otherwise I would probably do that.

 

[nvrenuf]

I agree, the OE 4 row is the way to go. I'm using a radiator from a 6.2, it's about 6" wider than a gas radiator. I think I'd spend the money here instead of a fancy water pump. What are you doing for a fan?

2.5" Y into 3" single here, works great. I have run Hedman and Flowtech headers in the past, both fit adequately but had the typical low hanging collectors. Fwiw, the painted Flowtechs I had rusted out fasted than the Hedmans.

This may be irrelevant but... if you're going with ceramic headers, buy them coated (if you have color choices be clear about what you're getting - glossy, dull, etc). I bought bare headers an had them coated (Jet Hot), I ended up spending more and had to get them done twice to get the color correct.

 

[mrk5]

Radiator
Why not use the radiator from the donor truck? You need every bit of radiator you can get to cool the BBC, I run a 4 core from a mid 80's squarebody with windstars.

Exhaust
Most of the earlier BBC exhaust manifolds crack so don't be surprised if those are. I ran some headman long tubes and they fit OK but I didn't like how they hung down. I picked up some tubular OE manifolds recently that are pretty rare but they tuck up nicely and I don't expect them to leak. I'll be running a Y pipe under the bellhousing with 2.5" pipe merging to a single 3" with a 3" muffler. Dual all the way out back isn't an option for me otherwise I would probably do that.

I plan to use Windstar fans, that's what I have now. The donor radiator is not factory; it looks like a decent aluminum radiator except for one thing. The inlet and outlet ports are tiny.1.25" inlet, 1.5" outlet. The previous owner just stretched the small hoses that fit the radiator over the water pump and t-stat housing on the motor. I feel reluctant to use the radiator with small ports. Feel like it'll restrict coolant flow and it'll make getting hoses a bitch.

 

[Bent77]

If you can't run duals, step it up in size as soon as possible, preferably to at least 3.5" into the muffler

 

[mrk5]

I agree, the OE 4 row is the way to go. I'm using a radiator from a 6.2, it's about 6" wider than a gas radiator. I think I'd spend the money here instead of a fancy water pump. What are you doing for a fan?

2.5" Y into 3" single here, works great. I have run Hedman and Flowtech headers in the past, both fit adequately but had the typical low hanging collectors. Fwiw, the painted Flowtechs I had rusted out fasted than the Hedmans.

This may be irrelevant but... if you're going with ceramic headers, buy them coated (if you have color choices be clear about what you're getting - glossy, dull, etc). I bought bare headers an had them coated (Jet Hot), I ended up spending more and had to get them done twice to get the color correct.

Funny you mention the 6.2L radiator, that's what I used in my K5. I had to think about blocking the radiator off in the winter because it cooled so well. I should probably look at going that route again. Too bad I got rid of the extra I used to have.

I did forget to mention in the first post. I have Windstar fans now and I plan to use them with the 454.

 

[skunked]

If you can't run duals, step it up in size as soon as possible, preferably to at least 3.5" into the muffler

3.5" huh?

 

[mrk5]

3.5" huh?

If you geek out on math the area of (2) 2.5" diameter pipes is real close to (1) 3.5" diameter. 4" is way more than the (2) 2.5" - relatively speaking that is.

 

[skunked]

This is true but if you really want to geek out you can look into friction loss on those two 2.5" pipes versus a single 3 or 3.5" pipe. Also, are you talking 2.5" mandrel bends or crush bends?

Magnaflow doesn't even make a dual 2.5 to single 3.5 merge pipe that I can find.

 

[Kay86K5]

Funny you mention the 6.2L radiator, that's what I used in my K5. I had to think about blocking the radiator off in the winter because it cooled so well. I should probably look at going that route again. Too bad I got rid of the extra I used to have.

I did forget to mention in the first post. I have Windstar fans now and I plan to use them with the 454.

I used the 6.2 diesel radiator and shroud on my crew cab for the 8.1 too. I was even able use the factory TBI350 radiator mounts (the ones that bolt to the core support) on the radiator. I say you go this route...way easier and you know it will cool just fine. I bought a brand new radiator off Rock Auto for a pretty good price and bought the shroud off Ebay for pretty cheap

 

[Kay86K5]

And you should never apologize for swapping a big block. I say you swap that sucker in there with a carb on it for right now, and save some pennies for a couple months and get the FiTech on that thing. Just keep it a simple old school big block with a little modern fuel injection for reliability....that is cool no matter what.

Some of us are dumb and just put a high tech big block in their crew cabs and have to deal with electrical issues , haha. Just kidding, my 8.1 will kick a$$ when its done, haha

 

[1-ton]

My 1985 K30 Dually has a 454 BB Chevy, and it came with a 4-core radiator stock. It also came with an oil cooler stock. A previous owner put a set of Doug Thorley, Try-Y, full length headers in it as well, and those headers are so close to the front spring shackles that when I hit a big enough bump it smacked the spring shackles. A previous owner also put a dual exhaust system in it. The right side pipe is so close to the 205 transfer case that it transfers a lot of heat into it.

 

[Bent77]

Can we nerd out on pipe wall frictional air turbulence and CFM loss?

 

[skunked]

Can we nerd out on pipe wall frictional air turbulence and CFM loss?

No

 

[Bent77]

 

[mrk5]

This is true but if you really want to geek out you can look into friction loss on those two 2.5" pipes versus a single 3 or 3.5" pipe. Also, are you talking 2.5" mandrel bends or crush bends?

Magnaflow doesn't even make a dual 2.5 to single 3.5 merge pipe that I can find.

Mandrel bends and Frankenstein exhaust assembly. That's what I call buying individual bends and cutting them apart and welding together as needed.

Not Magnaflow but....

2.5" into 3.5" https://www.summitracing.com/parts/flo-y250350

And you should never apologize for swapping a big block. I say you swap that sucker in there with a carb on it for right now, and save some pennies for a couple months and get the FiTech on that thing. Just keep it a simple old school big block with a little modern fuel injection for reliability....that is cool no matter what.

Some of us are dumb and just put a high tech big block in their crew cabs and have to deal with electrical issues , haha. Just kidding, my 8.1 will kick a$$ when its done, haha

Yeah, I was going to say... You're only feeling that way now while it's not starting. Once it starts it'll be an entirely different story.

My 1985 K30 Dually has a 454 BB Chevy, and it came with a 4-core radiator stock. It also came with an oil cooler stock. A previous owner put a set of Doug Thorley, Try-Y, full length headers in it as well, and those headers are so close to the front spring shackles that when I hit a big enough bump it smacked the spring shackles. A previous owner also put a dual exhaust system in it. The right side pipe is so close to the 205 transfer case that it transfers a lot of heat into it.

Yeah, I'm thinking duals will be nearly impossible with clocked tcase. I remember the Thorley headers on my K5 also hit the shackle come to think of it.

 

[mrk5]

Here's 2 radiators I was looking at:

6.2L radiator for an '84. 17.25"x34". $146 https://www.summitracing.com/parts/sgt-cu624

Hadn't heard of Howe radiators. 17"x32" core. $190 https://www.summitracing.com/parts/hre-342j

Kinda leaning towards the Howe because quality seems better and it will fit the Windstar fans a little better.

It's still 8" wider core than the radiator I have now but not quite as tall.

 

[skunked]

Mandrel bends and Frankenstein exhaust assembly. That's what I call buying individual bends and cutting them apart and welding together as needed.

I just find it odd a company like mafnaflow doesn't offer it, as if it's not necessary? I dunno, maybe I'm overthinking it.

2.5" into 3.5" https://www.summitracing.com/parts/flo-y250350

Vibrant makes one with the inlets parallel, easier to work with.

 

[Kay86K5]

That spectra 6.2 radiator is exactly what I got...but I thought it was a little cheaper from Rock Auto...can't remember off hand though