Big Block Swap

VorTecxas · December 9, 2011

I have a '96 Sierra 1500 with the 350 and am wanting to swap in a Vortec big block (I don't want throttle body or carb, it's my daily). Obviously I'll need the whole harness and computer, and I'd like to do the 454 since it's the most common to find but would also entertain a 396/402/427. I just found and purchased the L21/L29 intake after trying to find one for months, for some reason these are impossible to find in North TX. I don't have anything else yet, as I was waiting to find the intake first since its the hardest thing to come by. Basically my question is, can I find and use just any ~'67-'98 big block and heads with the Vortec intake as long as it all bolts up correctly or do I have to have the later block and heads? If I don't have to have the later block and heads, can I use any size block without programming or computer issues? I haven't had them side by side but from doing some research I see no difference besides the lifter hold-down spider. Thanks for the help

GMstrong · December 10, 2011

Youll need the 454 computer ecm,harness,vortec heads,vortec intake you can use a older block 454 block.Would be a good swap.

VorTecxas · December 14, 2011

Do I have to use the Vortec heads? I know you have to for the small block, but from what I've found I can use any oval port head for the BB. I have the old intake gaskets from the intake I bought and compared them to an earlier model gasket and they matched up as far as the intake ports, cooling ports, and bolt holes. The newer ones had a slightly different outside shape due to the intake style, but looked like they would bolt to any oval ports.

Another question - I know that the 7400 came with a roller cam, and as much as I'd like to have one in there, could I just use a hydraulic flat tappet? (Can't exactly afford a roller on my budget)

tyhuck · December 14, 2011

Would you have to modify the motor mounts? I know that swapping smalblocks, i.e. 305 to 350, is a direct bolt in, but does the BB have the same mounts?

VorTecxas · December 16, 2011

Yes they are the same. We figured that out when we dropped a 454 in my buddies '79 Camaro

GMstrong · December 16, 2011

You dont have to used vortec heads on a vortec block since its the same as the older block.You can use any 454 head on a 454 block but if you use vortec heads you must use vortec intake,you should be able to find 454 vortec heads for a good price now since everyone is swapping to LSx's.And the vortec 454 carb intake isnt that much either make sure you get the right gaskets though.

VorTecxas · December 21, 2011

I really appreciate the help GMStrong, but like I said in my first post, I want to do the SFI, not throttle body or carb. And I know that with the SB you have to use a Vortec intake w/ Vortec heads, however I have figured out that you can bolt the BB Vortec intake to any oval port head. Does anyone have an answer to my cam question? Like I said, this is going to be my daily, I'm keeping the 3.08 rear and I want to put just enough cam to give me some more off-the-line torque and a little better efficiency, nothing crazy that I'll have to mess with the computer with. I just want to know if I have to use a roller cam like the factory or can I use a hydraulic flat tappet? With correct pushrods, of course. I don't need any cam suggestions, I've got which one I need figured out if I can use the flat tappet one. I picked up an 85 longblock for $100, I havent measured the cam but he said its a "torque cam", if it's what I want after I measure it I just want to make sure I can use it. Thanks

spankrz · December 21, 2011

i think if you want to run the vortec fuel injection, ect. than you have to use the vortec heads. if you want to run a carb, you can run any heads you want and just match a manifold to it. this is the case with smallblocks. i am not sure with big blocks.

VorTecxas · December 23, 2011

I've already figured out that I can run any Oval Port with the Vortec intake, I just need to know if I have to use a roller cam or can I just use a hydraulic flat tappet without screwing with the computer.

I got two sets of heads with this engine, 14092360 and 14081045. I cant find much on either one except that they're small valve open chambered. Which ones would be the better pair?

GMstrong · December 23, 2011

i thought you just wanted to stay the vortec route but i havent tested oval port heads to a vortec intake.You can switch to a flat tappet cam the roller cam are expensive.But considering how big of a duration and lift the cam is you might or might not have to mess with the computer.If you have a cam card of the cam your looking at ill tell if you need a tune or not.iirc the 14081045 78-87 Oval Port Open chamber ,14092360 was 85?-90 mostly used on trucks they had the peanut round ports 2.06/1.77 .The 14092360 wont have much after 4k.Better for low end torque.

VorTecxas · February 13, 2012

Been awhile since I've been on, been gathering parts and getting divorced. Funny how that goes hand in hand. Anyways, GMStrong, since this will be a mild mannered daily that wont hardly ever see 4000 RPM except for passing and the occasional just-for-fun race, do you think those 360s will be just fine or should I look for something else? I've kept my eyes peeled but noone posting on CL around here seems to know what the hell a casting number is, it's always "I have BBC heads for $100, come get them". Also been looking at Marine cams since they have a nice steady power band. I'm liking the Howards 122521-15

I have also acquired a full harness with ECM and a 4L80E. One step closer. Getting machine work done this week

VorTecxas · February 13, 2012

And it's small and hard to tell, but being a Pontiac guy I'd have to say that's a Poncho in your pic is it not?

GMstrong · February 13, 2012

They would be fine for a DD,What year block do you have?And if you swap cams get it tuned.Get some pics up,Its a 400sbc out of a 69gto.

VorTecxas · February 15, 2012

Originally told it was an '85 block, after finally looking at the date code myself its a '77.

Even though that cam is not a big one (just longer duration), would I still need to get it tuned? Trying to avoid anything other than drop n' go.

The 400 in a GTO is a Pontiac big block. The pic is small but I could tell from the shape of the valve cover, the placement of the alternator, and how the intake sits over the valley instead of on it. Pontiacs are my first love, If I could make the factory computer and injection work on a Poncho 400 that would be going in this thing instead. I'll take that over a Chevy any day. But I'm working on making that work too haha. Vortec Pontiac anyone?

GMstrong · February 15, 2012

It really depends on the LSA,lsa will determine how choppy the idle will be.with slightly bigger cam and stock tune driveabilty wont be too good the truck will still run but not 100%.