1973 k20 project. Should I buy brand new 454 bb? or rebuild my 402bb?

[connerh]

for me and my fathers 1973 k20, we are at the point where we NEED an engine.

when we bought the truck, it had a 402 big block which we ended up storing to the side and planning on selling. Im not sure myself whats wrong with it, but my dad says the engine was at the end of its life and it would cost a lot to rebuild. maybe 3k?

my questions are, is it safer and more valuable to get a brand new 454?
or would it be better to rebuild the 402 BB we have? what kind of power can i get out of the 402? better than the 454 numbers for cheaper?
just any advice or opinions would be appreciated.

Option 1. nevermind this option (edit) ignore the "350" in the poll
Option 2. we can buy a brand new 454 with 415 hp and 500 ft/lbs for $6k
Option 3. or we can rebuild the 402 for $3k+, not sure what kind of numbers we could get out of this

 

[Bextreme04]

It only cost me $2500 to fully rebuild a Gen VI 454... You could get a running one from a junk yard for about $800, clean it up, slap a comp extreme energy XR276HR cam, standard edelbrock carb intake on it, and you'll have a ripper with way more power than the small block for less money. The only downside would be the lack of a mechanical pump on the block, so you'll have to have some kind of fuel solution too. Lots of guys just get a basic electric pump on the frame rail. If you have the cheddar, best bet would be to get 87 EFI saddle tanks with the stock TBI low pressure electric pumps and run an adjustable FPR in the engine bay before it goes into the carb.

Here's a dyno run with headers, cam, and carb induction on a Gen V vs Gen VI 454 junkyard motor. You'd be WAY ahead of the small block power-wise, for less money, with either one of those.

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[connerh]

It only cost me $2500 to fully rebuild a Gen VI 454... You could get a running one from a junk yard for about $800, clean it up, slap a comp extreme energy XR276HR cam, standard edelbrock carb intake on it, and you'll have a ripper with way more power than the small block for less money. The only downside would be the lack of a mechanical pump on the block, so you'll have to have some kind of fuel solution too. Lots of guys just get a basic electric pump on the frame rail. If you have the cheddar, best bet would be to get 87 EFI saddle tanks with the stock TBI low pressure electric pumps and run an adjustable FPR in the engine bay before it goes into the carb.

Here's a dyno run with headers, cam, and carb induction on a Gen V vs Gen VI 454 junkyard motor. You'd be WAY ahead of the small block power-wise, for less money, with either one of those.

xc_hide_links_from_guests_guests_error_hide_media

you know you just reminded me of an option i completely forgot we had.
our buddy offered us a built 454 but it had tons of miles on it for $1k.
we can buy that then check everything on it, if its bad we just get it rebuilt for similar price to rebuilding the 402bb, if its good then we got a badass 454 for cheap!

 

[Big Ray]

Find a Vortec 7400. Salvage yard has plenty.
Got one in the garage I got a deal on. New top end parts, roller rockers, numerous other parts.
2500$
Look for for the gen 6 L29. Roller cam equipped from the factory, great heads.
Richard Holdener on youtube took one, used the same cam I have and made over 450 ft-lbs of torque from off idle to 4500+.rpm.
With a carb.
Do it. You know you want to...

 

[Gray Beard]

I have built both a 396 with 425hp and a 454 with 450hp. Both ran on pump gas and were very reliable gas hogs.
402 is a good engine. Should not cost you a lot to build, will have great torque and can take 400+hp with no problem.
You have the 402, if nothing is broken, you have a good start for your build.

JMO

 

[Strick]

I just rebuilt the 454 for my '79 Big 10 and it wasn't terrible about getting replacement parts. I have; however, been looking to upgrade from the 396 to a 454 in my '72 Camaro. The last time I checked there were no 454HO engines available from GM and there were incredibly pricey engines available from several different sources in several different forms. I've decided to rebuild the 396 and get some pricey aluminum heads for it instead of pony-ing up for the 454 upgrades.

Strickland

 

[Craig Nedrow]

All aftermarket blocks are based on the mark lV 454, with the round hole for the coolant. These engines are stronger then the mark V and mark Vl, but are not roller motors. They are cheap, make great power, Bextreme has a good cam choice. Need a good intake, and a HOLLY 750 4150 style carb. All the 454 are easy to work on, and have huge torque. I have flowmaster headers on mine, 1 7/8 tubes. These are low compression motors, 7.8-8.2 compression so you can run regular gas with 34 degrees of timing with no knock. Only problem with mine is that I go through tires, but that is the brain connected to the foot’s fault. My advice is based on experience with my motors, but I would encourage you to do some study, maybe buy David Visard’s big Block Chevy book, lots of tested info there. In the end, the BBC is the funnest motor I have driven, and I have had a number of the LS LQ motors, and they are great, but lack the simplicity of the fo fiddy fo.

 

[Craig Nedrow]

All big-blocks utilize the same 4.840-inches of distance between the cylinder centerlines, and have LOTS of space for stroker cranks. Best torque per dollar is stroke that 402, and bore to 4.250-4.310. Pump gas, I mean 87 octane friendly, gobs of torque, (500 ft lbs pretty easy,) 450 hp very easy. Small peanut port heads work well with this setup, do not use rec port, you would loose the torque, 1 7/8 headers, air gap or equivalent intake, Heads that flow around 280, 9:0- 9.5 compression, 265 cam. If you go roller lifters, (I like Scorpion, as they will sell you 8, 1.8 ratio, for the intake, and the 1.7 exhaust,). This assumes you will rebuild.

 

[82sbshortbed]

Facebook market place can be your friend. I was able to find a Gen V 4 bolt main 454 with cam Lt hedders and intake with 30k miles for 2k. You'll definitely love the power of the 454. Put a 3.73 gm Trutrac 8.5 10 bolt posi rear end in too. It's fun to drive. So my vote is 454. You won't be disappointed.

 

[Craig Nedrow]

My bad, posted by mistake, sorry.

 

[Shorty81]

Either one would make plenty of power. Leave modern engines for modern trucks. My old Mark IV 496 is a great ol' mill.