Trying to see what other C3 owner think...71 LS5 coupe with TKO600 and A/C. Motor is original to the car. Many upgrades done to this car to make it more practical. Fuel injected, tubular suspension, Hydra boost, and much more. Made 460HP to rear wheels with a mild cam, heads, headers. It can make more specially down low, but Torker II and 2" air filter are my only option with BB hood and it can't performs better. Well...people see big block in there and thinking I have 700-800 HP in there. Kinda disappointing such displacement can deliver only 460HP. Now, I know a bigger cam will make bigger number, but I'm not a high reving driver at all, rather keep drivability. I don't care about "chop" factor...This whole thing made me thinking about how can I make this car more efficient, while making more power. My thoughts:
1. Keep the motor and put a L88 hood so I can fit a dual plenum intake, bigger air filter or possibly fresh air box built into hood (which one has that?). This route requires finding someone to paint that hood and match the paint exactly.
2. Get a LSX 454 and keep it N/A. costs about 20K.
3. Get a LS3 and twin turbo it. I also made a Single S480 on a LQ4 in my 73 Camaro with great success. maybe a LS3 with 2 smaller BW. Intercooled.
I wish someone makes some FI for BBs with throttle body, not port injection that I could fit under my hood. Some probably did, but not much feed back and no idea where I'd standing after spending that much.
See what you think.

 

My 2 cents worth. The engine is the soul of the car. If it came as a big block I’d keep it a big block. Im not a fan of fuel injection (part of the soul thing) but I get it why folks change over to it. There are multiple systems that should fit the bill your asking for. Both FItech and Holley have carb lookalike fuel injection and there are probably others. I will say this. If you are making the jump to fuel injection get something that also controls your timing. Controlling just your fuel maps can leave alot on the table as far as power potential and drivability.

Personally if you want some additional ponies your whole setup needs to be looked at. Cam is such a small part of it. Heads are honestly most of the time where the biggest gains are found.

Another question that begs to be asked is what do you have as far as an exhaust goes. If your running through manifolds your choking any real performance engine.

What is your whole current combo?

 

I wouldn't be changing up the car because of what other people think. The L88 hood and air box is a decent option. I would keep the big block over the LS swap. If you are not racing, there is no need for lots more power. The 460 to the wheels is a decent number for an older car. Stock it probably did 200-300 rwhp.

 

I'm curious, do you know what your typical gas mileage is?

 

Keep the BBC in there and make it as efficient as possible. This will make your driving experience more enjoyable and when you pop the hood the “awe factor” will be unmatched.

 

I built a 99% replica of an LS6, down to the OEM Aluminum heads. 230/240 roller, & the flat Vette 569 dual plane intake. 10.5 CR. Dyno'd at 485HP and 550 ft lbs. I was a little dissapointed also, expected low/mid 500s. What I learned since is there are two things holding my motor back. Heads and heads. R-ports are just too big for the street and don't really come on the "port" until 5000+ rpm. They'll flow to 7000+ on a race car though. The flow numbers are OK, they just have too much volume and low port velocity. Oval ports are stronger below 6000. Second the the whole head design is 50 years old. The L88 heads have horrible round exhaust ports, they "stall" . Cylinder head airflow R&D improvements have been enormous in that interval, especially in the 90s. Several well respected engine builders I have spoken with said if I switched to the current design AFR heads I would gain 80HP with zero other changes!! Bringing it to 560. A taller intake could be another 20 but only past 5000rpm.

You can do a little better than that with an LS427 or so, because the LS heads are so much better. Mainly it will be more efficient. But it really won't be as much of an improvement as most people think if you want to keep the cam civilized, and if you use current BB heads. 230/235 duration is about the limit for a civilized street cam, in either engine series. You can go with a bigger cam, and a lot of people do, but it will sound and run like a race car at low rpm & cruise. Some want that, some don't.

I would keep it a matching number BB, but change the heads, etc. EFI if you really want. The throttle will be crisper, and it is so much easier to fine tune the fuel maps. But ultimately it will only be a slight improvement over a carb. If you tune the carb hard enough.

What kind of gas mileage can you get with your current OD setup? I know of one guy who can tickle low 20s with his 6 spd OD EFI 496 cruising.

Oh and you need a OEM drop down style air cleaner base so you can fit a larger 3" tall filter under that BB hood. 2" is not enough. My air cleaner base is not even an inch higher than the valve cover.

 

Which fuel injection system?
Which heads?
How much power would you be happy with?

 

Oops. Remembered your car and read thru your old threads. Great setup & results already. You have already done most of what I suggested even EFI. 460 chassis HP is already around 560HP gross. 17" of vac at idle means you could go with a little bit bigger cam, but not that much. 224? could turn into 232-236. That's about it for the driveability you want. More lift would help some tho. Mine made 15" of vac at 850 with a 230 solid roller .625 lift. Bullet cams can make any duration/lift combo you would like, no need to go with Comp Cam stock cams. I am switching mine out to 236 dur and aiming for 13" vac.

Not sure how much more you are going to get it out of it tho, since you want a street motor.

Which aluminum heads?

 

Keep the big block.
I’m not a numbers guy and I’m not a street racer.
I had a nice streetable 496 built for my 73.
The builder said it should easily make 600+, but I really don’t care.
I wanted an engine I could easily cruise in for several hours and not worry.
If you want to change cams, look more at the operating range of the cam and don’t worry so much about lift or duration.
My cam builds power between 2000 and 6000 rpm and I’m sure my engine will never see the 6k mark.
I went with Edelbrock RPM oval port heads which flow perfect for the street and are naturally port matched with my RPM air gap intake.
I could have easily built an engine with the WOW factor to impress everyone else, but I built what I wanted and will make me perfectly happy.
When people have asked me in the past what hp my engines have put out, I basically shrug and state “I’m not sure”.

 

Please look at it...It has Holley Sniper EFI already and it does control the timing. Rest of it: Studed original 2 bolt mains block, original forge steel crank 0.001 under micro polished, Wiseco dome forge pistons 0.030 over and scat rods. All ARP Fasteners. Around 10.2:1 static compression. Can't find the exact specs on heads, Unknown Aluminum oval port with large size valves. 118cc chambers. They're not high dollar heads. Cam: 224.6/ 230.6 duration, 0.567/0.578 lift 112 LSA, Hydraulic roller retrofit setup and rockers from Comp Cam. Edelbrock Torker II (unfortunately) intake. and 2" tall open filter element. Full length hooker headers and 3 (or maybe 2.5" not sure) exhaust. MSD box, distributor, and coil. Vintage air Front runner serpentine setup. Be Cool Alum. Radiator and 2 12" I think fans. HV Oil pump ( a mistake also). TKO 600 with 0.64 Overdrive ratio, 3.70 original Final drive. What else I'm missing...
I mean...it runs fine, not like there's something wrong with it. I know for a fact my intake is not good, my air cleaner is too short and I see my IAT reading climbs, especially if I turn it off for a while and proceed again. It just doesn't receive enough cool air under that hood. I'd like better performance low to mid range. Thanks a lot. I didn't know any better back then when I put this together.

 

'Smiles per gallon" I say...Highway could get 17 with current 3.70. City with some "Spiritual" driving I don't think any better than a single digit. 0.64:1 5th gear. Goes 70 MPH a bit shy of 2000RPM if that helps.

 

Man...I see good dual plenum intake there. IT WON'T FIT UNDER MY HOOD! that torker crap is killin me. Just feel bad to put the whole motor aside and figure something else. my junkyard 6.0 LS ($400 at the time) made 500 HP N/A with a cam and CNC ported heads, then 770 WHP with a single S476 at only 12 Lb. of boost. Is only a 6.0L. not a big cube BB. "Wow" factor is there, without actual "WoW" performance.

 

Wieand makes a nice intake for our big blocks that has a low carb pad.
PM forum member Resdoggie from Lincoln, Ca.
He is running one on his 496 with great results and I believe under his stock hood.

 

It sounds like you have a good base. I'd do the hood and get a better intake setup on it. I'd also consider better heads if you find they could be improved upon.