Big Block vs Small Block in 74 Z/28 LT
 

Okay guys, I'm brand new to the forum and this is my first post. I'm hoping I can get some valuable input on a question I've been having. The time has come to pick the power plant for my 74 z/28 type lt. It currently has a manual 4 speed in it and everything else is bone stock as far as I know. What I want to know is

a) What is your preference on BBC vs SBC?
b) Why is that?
c) What do you think are the advantages/disadvantages?
d) If i were to swap to a big block, does it take very much to convert?

The car was originally a small block car, and I'm not worried about numbers not matching. THIS WILL NOT BE MY DAILY DRIVER. I'm probably going to slap some 456 gears in the rear and take it out maybe a couple nights a week and tear up some ****stangs. Gas mileage isn't of huge importance, but if I can squeeze out a few more mpg's I'm not gonna complain. I realize big blocks make more torque naturally than smalls, but I think I want a good balance in tq/hp numbers. I still want it to be streetable within city limits, this car probably won't see much highway if any at all.

I LOOOVE the 502, why? cause the bigger the better, more tq is always a good thing. But in your situation id go 350 or 454, 350 for a real balance amd an easy to work on cheap motor, 454 for a terrific base if you ever decide to beef it to the max. and on a 78 i doubt you have to change really anything.

I was debating either making a 383 stroker or getting a 454. Either way with a pretty heavy cam. Has anyone had any luck or input on forced induction with either of these? Also from what I've researched, 454's don't produce very impressive power ratings stock.. what would need to be done to fix this?

The power is there, it has to be unlocked, no smog stuff free flowing intake and exhaust, good tune up and you should be golden if you want a powerful stock motor. Also 454s are some of the best sounding motors ever. My family has a camper with an all stock one and it will rip that thing around on a 2speed plus overdrive(3speed) auto trannsmission
A 40 foot long one mind you, not a little camper truck

Also no offence forced just isnt the way to go with big v8s untill you want huge power. Bolt ons ftw, and with a BIG cam in there that motor will be ripping and roaring(litterally)

It depends on how much money you plan on putting into this engine. Big block parts are more expensive than small block parts. Personally, I've don't have any experience with big blocks. The car was originally equipped with a small block, so I would go with a small block 383. Thats just me, it depends on how much money you want to spend.

Money isn't a huge issue, I'm probably planning on spending a couple grand, maybe 2500 on parts and that should do a pretty well rounded job. I've never worked on a big block before, only rebuilt a couple 350's. Should I have someone spec out what parts I should use? I've never actually blueprinted a motor myself, and I know people with money have professionals build their motors, but I don't really want to go that route.

I would build the engine. Building a big block will cost more than $2,500 though. How much power do you want out of the engine?

well I think something in the 450 hp range would be about ideal, 500 if possible? I know 500 hp for a 383 is a pretty high demand of power, and like i stated earlier I am not very familiar with big blocks and their potential. How much do you think building a bbc would run me?

Like I said, I don't have any real experience with BBC's. My guess would be roughly about $5,000. I say do a lot of research on BBC parts and research builds that are proven to produce 500 horsepower.

i would say go Big block if you can afford it and yeah building it yourself will really cut down on cost. a 450-500hp big block is kind of mild. you could do that with a 454 and good heads and a cam. The torque can't be beat with a big block and if you wanna cut down on weight then you could get some nice alum heads like AFR's or Brodix and that would save like ~80lbs on the front.

I'm getting a 468 big block with around 570hp and i'm just using the 781 GM heads with CNC porting and bigger valves and a solid roller cam with 10:1cr. a 383 would be nice because its lighter but the large torque of the big blocks is just awesome and the sound is amazing too! Also a 500hp 383 is gonna be pretty radical but the extra cubes of the 454 would really help if you want it to be streetable at all. some people build some nice 406 or 408 small blocks also

I know you don't plan on driving it on the highway much but I don't think I would put 4.56's in with a torquey big block unless you plan on strictly racing it because if you ever do decide to go on a cruise, your RPMS will be way too high. you will need very good traction to get it too hook with all the torque and such low gears.

Jason,

That is very true about the gears... I apologize for some of my incompetence about motors. But I've got to figure this stuff out somewhere. I was also looking at some blown 383 applications with a weiand 144 supercharger where they have made 500hp plus on 91 octane. I honestly just can't decide. I don't want to get halfway through building a bbc, and then change my mind and think **** I should have gone blown sbc!! I could get a decent 383 kit for around 1k, and heads for not much, and 144 superchargers aren't terribly expensive... although if I bought a 454 and simply swapped the cam/pushrods/lifters/rockers and springs with a nice set of heads, you think 500hp with a heavy cam is possible? Could I just keep the stock crank connecting rods and pistons? What would you do?

Oh it's cool Rogue, I'm not an expert either but just passing on info that I have learned. yeah a blown 383 would be sweet but if you want a blower than it's best to go procharger IMO. but I also love a big 6-71 or 8-71 blower sticking out of the hood :) Blown engines are trickier to tune. Yeah there are lots of options out there and it drove me nuts trying to decide too but i eventually decided on the BB. But yeah you don't wanna change gears halfway through since it wastes time and money so think about all of the options. I think I would go N/A though since anykind of FI would require more money and time spent tuning. If you get FI you will need to upgrade to forged internals and lower cr pistions and the supercharger itself can cost around 3-5k.

keep in mind though if you go to around 450-500hp you will need to build up your trans and rear end especially if you plan on racing it. well i think you can get 500hp with a good set of heads, compression and a good sized cam especially a solid roller as those really wake up the engine. You could probably use the stock crank and rods since they can take quite a bit of power but mise well just build it once with good parts, just incase. I would personally build either a 383 or 408ci SB or 454 BB. i think you would be happy with either

The more I think about it, I'm warming up to the naturally aspirated 454. That was a very good point about FI being harder to tune, and would be much trickier to dial in. Have you ever had any luck scouting for an engine at a salvage yard? I've heard stories of guys finding 454's for about 200 bucks complete which is very very tempting. Have you installed your motor yet? Did you rebuild it or buy it crate? Also, what gears would you suggest running with a bbc? Since they wrap out much lower than small blocks, what gears are you running? Your car also looks terrific by the way, I love 2nd gens!!

well make sure that the engine you decide on is really what you want and can afford and will work with your goals for the car. I love the power big blocks have and the potential for even more power should you decide too. They sound amazing too! Love it! i haven't looked for a big block at a salvage yard but have seen a few on craigslist locally that didn't seem too bad of a deal. No i haven't installed the motor yet, I'm waiting until i can afford to swap my trans. It's built by a engine shop but i kind of wish i built it since it would be cheaper. well my car is mostly street with maybe a few strip visits so i'm planning on using 3.73 or 4.10 gears but i also am going to swap in a 4L80 OD trans. If your gonna use your 4 speed then I wouldn't go lower than 3.73 and you will probably have traction issues. I would go 3.42 if you didn't wanna race it much for a good balance of RPMS and acceleration. but if you don't wanna drive on the freeway much then you might get away with 3.73's.

Oh thanks! :) your car looks sweet too! I also love 2nd gens! I can't wait til i can get it painted though

How much did the shop charge to build yours? Do you have any knowledge on what rebuilding a 454 would run me? If I could do it for around 2500-3k I would be pleased. I really want to keep my 4 speed in it, I just like shifting gears. If it was strictly a track car I would definitely put an auto in her. What I was thinking is that I could find someone with knowledge of big blocks that could help me blue print the parts I would need, and then take some night classes at the local community college and rebuild it there that way I would be sure to do it correctly.

well they charged like 7000 but because it's turn key, all forged and with the solid roller. Well you could probably build a 454 yourself for under 3k if you used the stock heads but ported them and got a nice cam but if you go aftermarket heads that can cost 2k alone then it would cost you a little more. but you can get 450-500hp with the stock heads (ported with bigger valves), 781 or 049 heads are the best stock heads. Yeah i kind of wish mine had a 4 speed but i don't wanna convert mine so i'm just gonna do a manual valve body 4L80 trans. yeah that would work and they also have books on rebuilding engines that might be helpful too.

I also have a follow up question I forgot to ask. If I were to replace the rotating assembly of a 454, should I just stroke it with a 4.250 crank and bore it .060 over to make a 496? It wouldn't cost much more to just stroke it, and while its in the machine shop anyway I might as well bore it??? What heads seem to be popular for big blocks in aspect of bang for your buck

yeah i was going to mention that earlier too. it doesn't cost much more to stroke it and if your gonna tear it apart anyway then I would stroke it to a 496. mines bored .030 over to a 468. you could have a relatively mild 550-600hp engine. well for your power goal of 500hp you could just use the 781 or 049 GM heads but if you wanted aftermarket heads the best are AFR but Brodix's are also good

This info has helped out so much. I know about AFR's, I've heard very good things about them, but again I didn't pay much attention to big blocks and still don't know much about them. I think tomorrow I'm going to give a few salvage yards a call and see what I can dig up. I found a couple decent deals on craigslist too, but if I can get one cheaper at a salvage yard I'll probably go that route. What are you running as far as intake and carb setup? More hp/tq equals more fuel/air demands also, so I should probably upgrade to an electric high performance fuel pump. Have you beefed up your rear end? Do you think traction bars will do the job or? Sorry for all the questions!! haha I'm simply curious as to what your general setup is going to be once you've got all that power in your 81!!

yeah see if you can find any deals at the salvage yard tomorrow. well intake will be a edelbrock air gap RPM intake and demon 850cfm carb. well you don't need to use an electric fuel pump but you can if you want. I'm going to get a Moser 12 bolt rear end but you can beef up your 10 bolt for around $1000 that will hold up to over 500hp. well traction bars will be needed. I think im gonna use cal tracs. Oh no ask away lol :) well i'm going to get a Pro Touring F-body suspension kit with new shocks and subframe connectors and then will probably end up getting cal tracs to help with traction. I already have 28x12 rear tires and 235/60 front's so I'm good there. I'm also gonna upgrade radiator and get a 3000 stall and big trans cooler to go along with my 4L80 trans.

If you go with a BBC 454 you'll easily get 450 hp for under $2500, IF you're not including the initial purchase price of the engine. From what I've seen locally a solid rebuildable 454 goes around $500-$700 for a complete block, and you should try to find one in a vehicle to get all the brackets, and pullies as that will save a lot of money and time on the conversion.
I personally would not waste a lot of money boring and stroking a big block if you're looking for cheap HP. Cheap HP wont be possible when you start talking cranks, rods and pistons. Getting carried away boring a engine too far will just result in an engine that runs too hot, and has no future for further upgrades.
If you keep the stock stroke, and just bore it enough to clean it up and make it like new you'll save a lot of money that can be used towards other performance options in the build. I'd go .010" or .030" over, and then look a t a engine rebuild kit, as these kits will really give you great value for what you want to do. A complete engine rebuild kit with forged or hypertectic pistons will run under $650 for a good quality Sealed Power complete with pistons. This kit keeps your engine just under 10:1 compression, and that's a very good idea for a street driven car on today's fuel. More than that and you'll be sorry, as you'll need racing fuel or octane booster to keep it from pinging.
http://www.summitracing.com/parts/FEM-CSMHP768-311/

Add a good cam, intake, headers, carb, etc. and you'll easily have funds left over for the machine shop work. For heads I'd either have a good set of stock 116cc heads reworked, or go with a name brand aluminum like AFR's or Edelbrocks. Of course you'll break your $2500 buget to pieces when you step up to aftermarket aluminum heads, and you really don't need them to get to 450hp. I've been running cast iron heads on my .040" over 427 for nearly 40 yrs. and I'm over 450 hp.

I agree with Jason on the gearing. Don't even think about going lower than 3.73 gears for a street driven BBC. If it's mostly stoplight to stoplight the 3.73's are a great choice. If you occasionally want to cruise to the next town at 55-70 mph, then better to go with 3.42 to 3.55 gears. With the massive torque you'll have either will transfer power to the ground and still not have you overwinding it at 70 mph.

That's very good advice, and I think maybe I will keep my eye out for a good used set of aluminum heads. Although a stroker still seems really tempting... especially when there are some complete kits out there for not much dough. I'm just going to need to do some price checking see what it a realistic way to go about it. I think if I could stroke it 4.250 with a complete kit and reasonable bore, a nice used set of aluminum heads intake and carb I could probably sit around 3k or just a little more if I find the right parts for cheap enough.. What do you guys think? And Jason, that sounds like a pretty solid setup. I love the pro touring styles. I wanted to get disc breaks all around and get something like a pro touring suspension setup. The car already has some beefy tires in the back, so I think I'm set in that department =)

yeah Vall aka 1971BB427 has alot of knowledge with cars esp 2nd gens. Alum heads are nice but if you wanna stay 3k and under iron heads will do just fine. well if you just use worked stock heads plus intake, carb and stroke kit you might be able to for under 3k but like Vall said, you won't need it to make your 450-500hp goal. yeah mine's gonna be semi pro touring but i'm not gonna have it slammed or anything. I might convert my rear drums to discs when i swap in my Moser 12 bolt. what kind of tires do you have in back?

Well I just have what was on the car right now when I bought it, but I think they should hook up alright for a while. The backs are 275 60's and the fronts are 215 70's on 15 inch cragers. The tires themselves are Cyclone Radial GT's. Where are you going to pick up your axel? If I end up doing a rear end swap that might be when/if I switch to a full disc setup. And what do you think would be better, if I had to choose between stroker kit or aluminum heads? Wouldn't the stroker kit end up giving me more of an advantage over just having better flowing aluminum heads?

i'm going to get my rear end through a Moser dealer. you can also get them with disc brakes. well if you just want 450-500hp then i would spend it on alum heads but if you wanted more streetable hp like over 600hp then i would say stroke it. Better flowing heads along with a good cam is one of the best ways to gain hp.

Even stock big block cast iron heads flow very well. They're a much improved design over the early smallblock heads, so if I had to choose between a stroker or heads I'd choose the stroker. I still think it's a waste of money considering the amount of torque a BBC builds, but if you're stuck on a stroker, then go for it. BBC's have so much low end power and torque I doubt you'll every use what a stroker motor has and not end up with a glove box full of speeding tickets. (not that a stock 454 couldn't get you the same results!)

Vall,

So are you saying that you are not really a fan of stroking a bbc? If so, I would like a little more info as to why you think so. Would you just get a bone stock 454 and just do a bigger cam and intake and not even bother swapping out a rotating assembly?

One more thing, I seem to only be able to find 2 bolt main 454's. I would really prefer using a 4 bolt main. Any tricks on finding a 4 bolt, or can I find one on this forum maybe? Or do you think the 2 bolt would hold up just fine?

I have a 406 small block with a procharger d1sc on a blow thru carb and can tell you it is very expensive but its great to pick on unsuspecting souls who dare to engage with me at the race strip because it sounds mild.I've found after wasting loads of money on many other cheaper combos that its best to drive what you have until you have the money to build it the way you want it.also racing is for the track not the streets,too many people get hurt in so little time just to say "I won". good luck on your build whatever it may be and stay safe.

I'm not against stroking any engine, but from a cost point of view it adds a major step up. A 454 can easily produce 500 hp without stroking, and even with a 2 bolt main block. When you get over 500hp, or plan to rev it beyond normal accepted ranges, then you should consider a 4 bolt main block, or ading 4 bolt main caps to a 2 bolt block.
Actually the add on 4 bolt aftermarket caps are a bit stronger than factory 4 bolt main caps as they splay the outter two bolts at a angle that gives additional support. If you think you're going to be revving your big block beyond 5,000 rpm's then I'd go for the 4 bolt main block. Speaking from my personal experience I rarely take my 427 over 5k even when I drag raced it. It had plenty of useable power without going thast far into the rpm's.

It's not like I'm going to be running around town blowing stop lights and racing ever person I see. I want the power just to simply know that I have it. I also want a street machine that I can take to the track maybe a couple times a year and see what she's got. Vall, so at a cost conscious perspective, you say that stroking it is not necessary for big power numbers. Can I reach a 500 hp goal with stock heads? What if I got a somewhat heavy cam, and switched to hollow stems and had a full roller setup and maybe had some valve work done on the old heads to clean them up, would this alone get me to my goal? Can I just take the heads to my local machine shop and say have at it? And when I swap out cams, what numbers should I be looking at? I'm not very keen on knowing what parts and sizes to use that will make it run smoothly. For instance, depending on what cam size I get, what type of springs will I need, and the same for the rockers and pushrod length. I guess I'm just in the dark a bit about this, and if you could shed some light on it, maybe from experience you have had with building one I would appreciate it.

well rogue, you can make 500hp with the stock heads as long as there reworked with bigger valves. I'm using the stock 781 heads but there ported and polished with a CNC port job and with the bigger 2.18/1.88 valves put in. My car specs are a Howards solid roller cam with 285/285 dur and .660 lift with a 112LSA so it's got a wider power band and not such a rough idle. With my 10:1 cr I should be at around 570hp or so. So you could easily get to your 500hp goal with reworked stock heads and maybe a cam in the 270 range with a 9.5-10cr

That is the info I was looking for Jason, thanks. How much would a cnc port job cost? Or I should be asking, how much did it run you? Did you just get the valves yourself separately or have the shop put them in? A rough idle is okay with me, as long as it still has street manners. I don't want it to die on my all the time or take half an hour to start idling because the cam is too hot. Would it be unwise to also put a cam roughly the same spec as yours in mine? If I go to a full roller setup, I can run a bigger cam correct?

your welcome. well i'm not sure how much it costs seperatly to have the cnc port done, maybe someone else can comment on that because it was included in the price. I had the shop put the valves in when the machined the heads and when you get the heads machined the shop can put them in for you. I don't mind a rough idle either as long as it's streetable and runs good vacuum for my power brakes. No it wouldn't be unwise because with my compression and cam it should be plenty streetable but also sound good and have a good wide power band. yeah you can run a little bigger cam since it's a roller. one of the best things about roller cam's is they experience less friction, have more aggressive profiles and you can run more lift without increasing the duration so you can get more power without having a radical duration.

Does your 112 lobe separation make it so the power band is wider? Or am I totally off on this one? I think I might have come to a conclusion on what I want to do. I think I want to stroke it and bore it .060 over, and possibly get the heads on it machined and run a heavy roller cam setup with an aluminum intake and aftermarket carb. Do you know where I can figure out what specs I need on these items? I'm not sure what kind of pistons to get for a good compression ratio, and can I get a cam package somewhere that would include a cam pushrods lifters roller rockers and springs that all work together? Because if I have to find these parts separately I wouldn't know where to even start... I fear that I would get the wrong length pushrods, and say 1.7 rockers when I needed 1.8, and completely the wrong lifters. Or what if I got springs that were too heavy, would that eat up the cam?? There are just so many variables, if I could find a complete package from one of the fine sponsors of this site it would help me out so much.

Edit: I did a bit of research on summitracing and they have comp lunati and Howards cam and lifter packages some that come with a double timing chain. What makes it a retro fit kit? I've heard good things about Comp, and the three main kits I see are either with a Thumper Cam, and XXtreme cam or Magnum cam. Any suggestion on which one is best? I'm looking for performance not just something that sounds like it's fast. Prices also vary from almost 600 to over 1k. I also found comp ultra gold extruded rocker arms and they come in different styles and ratio's. If I called summit when I was ready to order a full roller setup, could they help me spec what parts would work well with each other? Could they help me pick a cam size and put it in a lifter package and also find the correct rockers pushrods and springs to go with that setup?

Rule of thumb with a BBC engine is to get the highest lift cam you can find with the shortest duration while staying under 114 degrees. I'm running a solid lifter cam (old school) with 528 lift, 114 spearation, and 284/288 duration. It has a nice somewhat lumpy sound to it, revs easily to over 5k, and has tons of low end torque and power.
My cast iron heads are factory stock valves with the small combustion chambers and oval ports. Don't get stuck on open chamber or sq. port heads! They be nothing but trouble on the street and you'll lose compresion too. I ported mine myself, and didn't do anything radical. Just smoothed and opened them up a little, then matched the intake and exhaust ports to the gaskets and polished them.
As Jason said, keep the compression down around 10:1 for best street manners. I'm running 9.5:1 TRW forged pistons with the small chamber heads and .010" milled off the heads it comes in right under 10:1 ratio. Runs great on premium pump gas with no pinging. Jason has ridden in my Camaro, and I'm sure he can attest that it's quick enough, yet extremely streetable.

When you say under 114 degrees, you mean lsa right? If you were to personally pick out a cam spec and were in my shoes, what would you get? I still want to have good overall power, while still being forced back in the seat of course!! Also, could you maybe give me a quick lesson as to what the difference in lift/duration/and lsa are in a cam spec? And how do you port your own heads? Does it require special tools? I would love it if I could save a few bucks and do it myself, while also retaining the knowledge of how to do something like that. To get my heads milled down .010 like you said, do I need to take it to a shop? When I pick up the motor, I'll be sure to keep an eye out to make sure it has oval port heads like you said. Once again I apologize for a million questions in every response I have, but you and Jason are such a plethora of information that I have to ask!

Edit: Once again, i've done a bit of research and think I am catching on to the jargon of cam specs, but am still in the dark on what choice I should make.

yeah his camaro does sound badass and is def quick enough! that's awesome you ported them yourself vall. *bows to the master* lol

and yeah rogue, you wanna get oval ports for the street since rectangular port heads will cause you to lose some bottom end power. there better for higher revving.

yeah 114 degrees is lsa. well if you do stroke it then you can run a little bigger cam since the extra cubes will help.

here's the cam im gonna run: http://www.summitracing.com/parts/HRS-121313-12/

i think a cam with 280-290 dur and .600-.630 lift would be good for you. but you would probably be at more than 500 hp. maybe this one: http://www.summitracing.com/parts/LUN-60212/

here's a top end kit by edelbrock with cam and alum heads rated at 540hp but it would break your budget: http://www.summitracing.com/parts/EDL-2095/