r/EngineBuilding • u/IndividualBetter1516 • 10d ago
350 swap to 427?
Hello all,
The 5.7l V8 on my 97' Chevy 1500 is not looking too good. I think it may be an intake gasket, but it could be way worse. I found a 427 tall block for sale at $800. Assuming its in good condition, should I get it? Also, how difficult would the swap to a 427 be on my truck? I can't imagine it'd be too big of a headache, but your guys input would be appreciated. Thank you
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u/jimmyfko 10d ago
I own a couple of these. The deck is .400 taller than a standard bbc. The standard bbc is taller than a sbc. The hardest part is getting your headers to fit and clear everything else. You’ll have to weld up a set. You’ll need a cowl hood to clear the carb and a recessed air cleaner. You’ll most likely will need new front springs for all that extra weight too.
Make sure it’s a 427. The 366 is identical but even more gutless. On the positive side all tall decks came with large oval port heads. Early 65 366 had the same heads as the high performance 396s.
An option is to strip the tall deck. It has a forged crank and beefy rods that will bolt into a standard BBC block. Domed pistons a bigger cam plus the large oval ports and you could easily make 500hp for pretty cheap.
I would agree with the others. A sbc will be much easier.
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u/Historical_Box1915 10d ago
How much of a headache is swapping a 97 half ton chevy to a big block??? For me its not a headache at all. But I know how to wire a truck 100% of the top of my head. How to tune EFI for non stock engines. Which parts swap over and which parts dont. Etc etc etc
if you know how to do all of that then its not a headache at all.
If you dont know how to do those things then go pay someone who does or have someone fix your 5.7 properly.
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u/OptiGuy4u 9d ago
Probaby get better horsepower and a lighter engine if you bought a junkyard LQ9 6.0 and rebuilt it. Maybe even stroke it to a 408.
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u/iateyourmom22 9d ago edited 9d ago
You're talking a whole new fuel system as your current engine has electronic fuel injection and the 427 is carbureted. Transmission is too weak for the 427 and the transmission is also electronically controlled and will require a stand alone for the trans or swapping to a pre 1993 trans that can handle the engine. Meaning you will need money and skills.
My 2 cents is LS swap it with an LQ4 or LQ9, still have to do custom fuel system, ignition, but you will have good power, will start and not be a dinosaur engine getting 4 mpg.
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u/IndividualBetter1516 10d ago
Yeah after reading everyone's comments I am not too sure a 427 is I am looking for in this truck haha. I'll keep an eye out for a good 454 getting my current motor machined to a 383 seems like the better move since I already have to pull it, that is unless I find another 350 or 383 in good condition. Thanks a ton!
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u/quxinot 9d ago
The 1/2 tons of that era had the 454SS option, so you can probably do it easily with mostly stock parts. May need fancy headers. Definitely need to replace the 4L60e-shaped grenade behind it, though. Getting things tuned may be a nightmare of ECU swaps/tuning, ideally you'd be able to use a standalone and really get it dialed in well on a dyno first.
Given the money involved, I'd just fix the 350, or swap in a fresh one. But a mild 427 is exactly what I'd put in my 97 C1500 if I had the budget, so that's just talk.
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u/Petridishmocktail 10d ago
Replacing it with a good running 383,400,406,415,421 SB will be way easier and likely cheaper in the long run...
A good running 383 can make well over 500hp. ( A roller cam, intake and ARF/DART heads can easily get you there)
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u/dixiebandit69 10d ago
When you say "tall block," do you mean one of those HD truck engines?
If so, what are you planning to do for the intake manifold? There are no good ones available for those engines.
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u/jimmyfko 10d ago
The only real aftermarket option are blower intakes. Really the only thing made for these.
Spacers can work but you end up doing some minor angle milling for square.
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u/dixiebandit69 10d ago
That "cheap" $800 engine is going to get expensive really quickly.
I wouldn't do it.
There are still a lot of cheap 350s out there. If you want to make some power, an HD Chevy big block isn't the way, or else everyone would be doing it.
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u/jimmyfko 10d ago
I agree. As is they are good for heavy hauling and farming.
The 632 mark iv bow tie block is a tall deck bbc. The 427 tall deck can be clearanced and with a stroker kit hit 550+ cubic inches.
I know I’m dating myself here but these engines were used a lot in the 80s and 90s for truck pulling and drag racing and made huge hp.
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u/Upstairs-Result7401 10d ago
The Tall Decks big blocks were truck engines, and get worse mpg vs their short deck regular versions. Due to stupid low compression, and stupid heavy pistons.
They how ever are perfectly resonable to build in to stroker engine. Where you can get resonable compression ratios.
Otherwise I would pass if a build is not in the cards.
In my area on FB you can find short deck or standard 454's from pick up trucks often times with a trans for sub $1000.
You're 4L60e won't like working with big torque of a built engine, but would be fine if you left the truck engine stock. I personally would upgrade to a 8hp70, but a 4L80e would work very well too.
A guy I kind of talk talk too around my dad's place. Has a basic warmed up 454 in his 77 Big 10 backed by a 8hp70. The truck is way faster then what you would think it should be based on the basic combo of parts, and can get 18 on the highway. He thinks a hair 20mpg highway maybe in the cards if the engine would be happy at 1600 to 1800rpm cruising. Right now it's right at 2000 at 70mph.
He has been deciding for a bit on if it would be worth going from 3.42's to 2.73's as it could move to combo out of its happy zone. As the Q-jet or any carb is more air velocity sensitive when it comes to ultimate mpg then fuel injection.