Hello everyone,

As the title reads, I'm interested in eventually getting around to putting some more power down in my C4. I have a 1984 I picked up for $2,600 and 70K miles a few years back, and I've been slowly fixing the things it's had wrong with it. Currently it's receiving an entire suspension and bushing refresh. I've already had the trans built by a shop, and it's warrantied to 500 WHP, but not really meant to go any higher than that. I've been weighing my options, and reached out to a shop I've used previously. He is a little old school, and while I do respect and value his opinion, I figured I'd also reach out here and gain this communities feedback.

Originally I floated the idea of getting my factory block splayed into a 4 bolt and making it a 383 stroker while also pairing it with a set of Vortec heads and a Holley EFI system. I had nothing specific set out yet parts wise, but when I spoke to him, he said splaying was overkill for that power goal, and it'd be expensive to get that machine work done. He suggested looking for a good condition factory 4 bolt with the one piece rear main seal. He also stated that he wouldn't necessarily pick up the vortec heads. Really, I don't care how I get there. I just care about getting around 500 WHP reliably, while being semi budget oriented. I also had considered just buying a 383 stroker crate motor or something along those lines, but was interested in seeing the price difference after machine work and what not. Which is why I would be hesitant to buy a used block. At the point, why not just buy the crate motor? The only benefit to replacing the whole engine is, I could potentially sell my crossfire if someone would actually be willing to buy it. I'm open to general insights and opinions. I do want to stay on EFI though, and really would like to stay under $10K all in if possible. Another quick question while on this topic. I've seen/heard mixed things about Aces. Is it a decent alternative option, or is Holly the best for a reason? I've heard some people have great success with Aces, while others have nothing but problems.

Thanks everyone.

 

Hello good luck, not too sure about the computer. The 383 would be good. Personally, I would buy a crate motor and keep the numbers matching Crossfire for any future owner. I would buy a stoker kit for the stock block and put it down until needed. With inflation the parts would be cheaper than 5 or more years or more. BTW 450 true Hp in an 84' Vette would be amazing! This would be cost effective compared to reaching up for the 500hp range. Remember you would be adding double the horsepower! Just my 2 cents, Cheers J.

 

Sounds like a nice project, just make sure you're OK with $10-20K+ engine in a $2700 car. 500WHP NA (~600 engine dyno) will need some RPM for a 383 which is expensive in terms of valve train and forged components and not too streetable, more like a street and strip screamer. It will also need to move quite a bit of air, so typical SBC Corvette induction systems are not adequate (probably need to choose well for 400WHP even) fuel system is not adequate, exhaust of course, heads of course. Aftermarket 4.125+ block and 400-427 will get you in the ballpark with the right heads and intake without having to be past 7,000rpm to get there. I'd be careful about focusing only on the engine because 500 WHP is a whole-vehicle goal, not just an engine goal, and can your trans really take the RPM and/or the torque?

As for EFI, Holley is the mid-budget standard. It's not necessarily the cheapest option, but tuner support, documentation, and aftermarket integration for an SBC are second to none. Perhaps people have great results with Aces, but if I'm building a 500 WHP combination and investing $10-20K in the engine, I'd rather have the EFI system with the support network and proven track record for a little more investment perhaps.

I think a 400WHP corvette is a lot more enjoyable than a 500WHP corvette on the street, especially for a 383... the 500WHP is more of a serious roadrace or dragstrip sort of thing, temperamental and how many times will they replace that automatic transmission under warranty?

I have a 400ci with aftermarket 4.125 block dry sump motor plate forged 11.2:1 engine (actually zero OEM Corvette engine components) and it's well north of $20K with me doing all of the work. For me it's total power under the widest usable RPM rather than peak, but this is in the ballpark for what you're looking to do. For more perspective, the AFR 195 CNC Comp heads can't reasonably support 500WHP and 450 would be a stretch... they are perfect for a 383 though... the larger AFR 210/220 heads, they are not designed for an OEM 4.000" bore but aftermarket blocks or the 400SBC bore (4.125). They also need a larger intake as the OEM types are not even close to bolting up. Still needs a Jesel valvetrain to reliably rev past 6500.

 

500rwhp for 10K? That's dreamin! Boost is the best way to get there and still be a decent driver.

 

Supposedly there are crate 383s rated for 450-475 whp for 7-8K. Wouldn't think the extra 25-50 HP would be a problem for an extra 2-3K.

 

Overall, the car is in great shape. It's just with age, most of the seals have worn out. That's why we dropped the trans and had it rebuilt, because it wouldn't stop leaking. I also have a connection at a paint shop, and they are going to paint the whole car for just the cost of supplies. It'll turn out to be a nice car once I'm done. I'm well aware it's not really valuable, and I bought it with a general idea of what I wanted to do to it when I got it. I'm not hard set on exactly 500 WHP, but the ballpark is good enough. I will say it won't be a daily driver though. I have 3 cars as it is, so if she rips, she rips.

 

modern aluminum heads are way better than vortec heads. Do you care about hood clearance. People put centrifical superchargers on c4's that clear hood..

 

Do I care if it's close to the hood? No, not really. We were discussing cutting the ducting for the crossfire injection system once we swap it. Do I want a hole in the hood? No. I don't have a garage, and don't feel like messing with a car cover or what not when I want to drive it. lol

 

Yeah, I had $20K+ indicated then I didn't want to argue with anyone who comes on here and says they could do it for less than half that much per google or some sort of a Youtube engine dyno session. This topic comes up it seems like every 2-3 months it seems, waiting for the LS guys to jump in there (pretty much the same formula though NA).

Here's a $15K crate engine for 500WHP, but you still need $5-10K worth of stuff to finish the install.

https://www.shafiroff.com/chevy-pump...ltrastreet.php

Here's Speedway's formula for 600HP (500WHP)... the parts alone are $15K.

https://www.speedwaymotors.com/the-t...-600-hp/134192

 

I think that's close to the limit for a 27 degree SBC and not sure if you can make it streetable close to that NA... that would be BBC territory. Nascar squeezed out about 760hp from the basic SBC (400 block with 355cu in) but that's a $100K effort... then they went to the SBC2 for more.

 

500 whp can be done, but don't forget the rest of the car isn't set up to handle that HP and TQ so you need to factor that money in as well, which could cost more than the engine. A 500 whp C4 could be a real handful for a street car, I would personally go less and it can also help reliability.

Smeding Performance is another option for replacement engines with a good reputation. https://smedingperformance.com/colle...-block-engines

Hood clearance is a real issue as mentioned above, if you don't want to cut the hood your induction options decrease greatly and the price goes up as well.

 

Short of a blower, 500rwhp in a 383 or 396 is going to be a peaky, awful engine to drive on the street at all. You'll need probably 7500rpm to make that power, and it will feel broken below 5000rpm. So you'll be looking at something like 4.33 or 4.56 rear gears to make that drivable. It would pull hard in its range if set up like that, but it would not have a wide power band. I don't know if any of the heads commonly used on street cars would do this, even AFRs. Vortec heads are probably good for about 325rwhp at most (without an insane cam, at least). Needless to say, you'd be looking at a pretty exotic valve train to handle that RPM, along with custom light piston and rods, internally balanced crank, etc. You'll need some kind of plan for an intake and ECU or carb to control it, but a decent single-plane carb intake (Victor Jr, etc) won't fit under the stock hood.

Like others have said, I seriously doubt this is really what you want. The vast, vast majority of people who talk about power numbers like this have never ridden in a car with that much power...especially one that weighs 3000lbs like an early C4. That's a stupid-fast car (when it's in its range). Honestly, most people that think their car makes 500whp really have like 300whp. My neighbor has a 70 Mustang like that. He doesn't know the difference, and he doesn't need to know, because he's never going to drive it like a 500rwhp car.

I've written about my (no longer mine) 96 C4 before, but it's a good example of what is realistic. It was a 396 with very special ported stock heads that flowed a little better than AFR195 Competition heads (especially at low lift). It had custom pistons, H-beam rods, internal balance, a very nice valve train, etc. It had been built for a fairly radical cam, and it made 460rwhp on that cam at around 7000rpm. My best friend did all this, and he ultimately decided it was too much cam for the street or autocross use, and would have needed more gear than the stock 3.45 to keep it. He switched to a small-but radical cam (very short 0.050 duration but lots of lift and steep ramps with LSA of 110 degrees). That cam peaked the power at something like 6200rpm. It had a very midrange-focused torque curve. It was totally drivable on the street, and you could lug it down to 1500rpm in 6th on the highway and it wouldn't chug, and it would still knock down 26mpg. It was great for autocross use, and it was easy to drive on track because it didn't have to be kept in a narrow powerband. It peaked at 420rwph, but more importantly it pulled hard from 2500rpm. It would run about 130mph trap speeds, and those who road in it guessed it had 600rwhp. It was incredibly fun, and it was quite fast.

I think something like that would make you really happy. I don't know if 400s are still available, but I'd consider finding one and installing a stroker crank to build a 425. AFR 195 Comp heads and a small cam with whatever good single-plane intake and carb you can fit under the hood. If you have to stock with a 350 block, then at least push it to a 396 stroker and do the same heads and cam. 400rwph with a sane power band is possible this way. I don't know enough about the stock 84 intake/TB/ECU to know what happens if you scrap all of it, but that's what you're gonna have to do: the stock intake and TB are hopeless for making real power.

PS - I like that 434 Shafiroff engine that AZ linked. Keep in mind, as spec'd, that's still going to need to be shifted at about 6800rpm to get the most power under the curve. I'd be curious to know their cam specs. Also, no way that intake fits under a stock C4 hood. I'd be interested to see what happens with the same engine using a shorter intake and a slightly smaller cam, aiming for more like 450whp. Anyway, that's the idea, but as you can see, it costs real money. I think the Speedway build is going to be a peaky bastard with the cam they spec'd and 220cc heads. The one good thing about it is that they gave it a tight 107-deg LSA, which will push the torque more toward the midrange. Maybe that plus the two-plane intake saves it from being undriveable. I don't know. Those heads have raised ports that may also make header fitment and other stuff more difficult. For either of these, I'd want to see a dyno sheet; but they also give you a good idea what you're asking for.

 

I've never done it, there are people that have put super charger on C4 corvettes. engine needs to be built with that in mind. improper ring gap can destroy engine. stuff like that.

 

That 600hp speedway unit would probably make the same or more power using a more modern cam grind IMO. Agree it'll be peaky but That cam choice could be optimized to be not quite as bad.

The 500 hp mill is the upper end for what I would consider "streetable" and even that is a stretch.

 

I guess I'll have to look into in more. I just figured it'd be a little more do-able since it was a Corvette. I know it isn't an LS, but I squeezed just under 500 HP out of a Subaru Legacy GT with a motor I built with my father, and that's with AWD losses. It was something around 700 HP at the crank. All in all with the engine, trans blast plates, clutch, turbo, intercooler, and anything else you could possibly think of including the car itself was less than 20K and that was a 2008. With that said, I'm not opposed to forced induction, but I really wanted an all motor car. As I mentioned previously, I'm not worried if it's not really a good daily driver. Maybe I'll just shoot for 450 or so and take a closer look at those crate motors I had been looking at.

Thanks for your input everyone, looks like I've got more researching and deciding to do.

 

I recently posted about driving my brother's C6 Grand Sport, on the topic of handling and feel. On the subject of power and engines, it again provides a damned impressive and tempting example. His car, with its LS3 with just tri-y headers and full Corsa exhaust and a tune, puts down 435 hp at the wheels. That's with the stock cam and stock everything else under the hood. This suggests to me that 500 is likely within striking distance of an aggressive cam swap.

If you started with a used L92 6.2 and swapped in a stroker crank and a healthy cam, you'd have to exert effort to make LESS than 500 rwhp, I imagine. But I think we all understand that an LS swap is way more expensive than just the engine itself so of course the puissance of the LS is a double edged sword.

 

I've see a lot of ~500whp AWD boost buggies. They are ubiquitous in the autocross world where I compete. They don't hold up and they also aren't that fun to drive, with tons of lag and a power curve that comes on like a light switch. Nobody ever tracks those cars because they blow up. I have a local friend with an Eclipse that can easily put down that much power. He misses about half the autocross events each year because it's always breaking in one way or another.
It's not just that a 500whp 396 is unlikely to be a good daily driver - it's that it's unlikely to be fun to drive on the street at all. I suggest that instead of shooting for some arbitrary peak power number, think about how you want the car to perform, how you really plan to use it, and a budget. With those goals set, it becomes easier to explain how to achieve that on pure motor. When people chase a peak power number, it doesn't really help them get the car they want. For example, when I still owned my C4, a friend had a C5 with an LS1 cammed to make ~480rwhp: about 60hp more than my car made. We drove each other's cars on track, street, and autocross at different times. Compared to mine, his car was miserable to drive: it felt broken, and in most of the RPM range it was a lot slower than mine. Then it would suddenly "come onto the cam" at ~4500rpm and pull hard, but it was hard to keep in that narrow power band. It made an impressive peak power number, but we both vastly preferred my car.

It will be expensive, but more importantly it will also take a lot of time and knowledge in how to mechanically and electronically integrate systems. It's not a project for the uninitiated or faint of heart. [/color]

 

For those 50% of track days, a DSM is amazing however

 

Autocrosses aren't track days. Those are low-speed time trial events where you get 3- runs per day, 60 seconds each (max), and speeds are generally 70mph and under. AWD boost buggies can be really good at these. Nobody takes them to track days. They can't be kept cool on the intake side and they tend to blow up. My friend won't take his to a track for that very reason. I've been doing lots of track days the past few years, and these cars are never there.

 

I was just saying dsm's are cool I have owned a few of them. I forgot for a minute the C4 section of this website is the no fun zone will never happen again boss man.
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