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C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

More HP please!

 
Old 05-19-2019, 06:25 PM
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PoprocksC4
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Default More HP please!

okay 42k on my 93 300hp lt-1 A4 trans dana 36w/ 3:73 gears. Now I'm interested in getting 450hp to be able to keep up with today's Stingrays.
Any suggestions would be helpful. Stop light drags is my thing. I don't want to blow it up. It was my dads car and I'll NEVER sell it.
Turbo vs. Hot cam?
Thanks
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Old 05-19-2019, 06:42 PM
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qwiketz
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nice car. Heads, cam and intake will get you there or very close. You'll also want headers and a free flowing intake tract. Turbo will get you there but will be custom and a lot a $$$ by the time things are done. Same with blower.
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Old 05-19-2019, 07:02 PM
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ctmccloskey
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Here in Virginia you "lose your car" if they catch you drag racing at stop lights or for that matter anywhere. With all those cameras on intersections I sure hope you live someplace like Wyoming. Here they would nab you in minutes. I have a 1968 C3 with over 550 hp at the crank and everywhere I go people want to race me in the C3. Are they so dumb that don't know I have a serious HP advantage? There must be some misconception about C3's out there, not all of them are slow. Anyway go to a race track and race, don't do it on public highways and endanger those around you.

It is great that you inherited your Dad's Corvette but modifying it to keep up with today's Corvettes is going to be very hard and expensive. Leave the 26 year old car the way it was intended and enjoy the performance of the LT1 engine. When somebody first gets a Corvette they start planning all the things they want to "Improve". My best advice is to drive the car for a couple years and then decide if you need more power. You can get a ZO6 C5 pretty cheap now days, that kind of performance comes as a "package" and works very well.

When you build your HP to a higher level Corvette parts start to break and they are harder to find and expensive. Your car will need to have several modifications to make that kind of power reliably. C4's are great handling cars, the brakes are fairly decent and the body is gorgeous and that clam shell hood makes life so much better when you have to work on it. The Corvette you have is far more advanced than my 1988 C4 Coupe with it's L98 that is only five years younger.

My C3 can turn some impressive numbers at the quarter mile track. Problem is I make so much power that the second I hit the 12 second area I would be led off the track as I have a convertible. Should I put a roll cage in a fairly stock 1968 Corvette? If I did the value would drop dramatically to a collector and I can't do that. My C3 is a early model and it is cool the way I have it set up. I just spin my tires for 1/8 mile at the quarter mile tracks, I can't get any traction. Put a set of slicks on it and I would be picking up parts all the way to the end of the track.

From a long gone song, "Love the one you are with". Keep your Dad's old Corvette, enjoy that car in every way but be able to leave it to your kids the way your Dad left it to you....

I hope that I have not seemed offensive, if I was taken that way I apologize. You see a lot of people, some new to Corvettes and some not. For some reason people like to instantly start modifying the car to make XYZ horsepower. Your Car was designed for the new LT1 and that is a nice engine. If you have to modify it remove the engine and store it, then go crazy on a engine designed to make considerably hp. I still have my spare Chevrolet 1970 LT-1 engine in my garage for when I play with my 427. Pull the 427 out and drop the small block right in and go for it. That works better on the older non-emissions cars anyway.

Corvettes are fun and every time I drive one of mine I am grateful that I am allowed to own one of these magnificent cars. Just remember to wave at other Corvettes from C1 to C8 and all will be well.

Best Regards,
Chris
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Old 05-19-2019, 11:45 PM
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Default Thanks

nope. No offense taken. Well said. I've considered a 383 crate just to keep the original, original. But that is yet another thing to store and i honestly don't think it'll ever go back in.
STOP light drags, i don't speed.... by much. Just up to the posted limit. I know it's still EXCESSIVE ACCELERATION. I live in a small mountain town so i don't screw around at home.
And YES i do plan on leaving it my kids.
Thanks for the input.
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Old 05-19-2019, 11:47 PM
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If you swap heads to Vortecs or the GM Fast Burn heads, you can either use an LT4 intake or the aftermarket Holley version, so you can match the ports on Vortec-style heads. Put in an LT4 cam and 1.6 ratio roller rocker arms, 28 lbs/hr injectors, and a 52mm throttle body, and then headers and a good exhaust (headers and true duals). That should bump hp up to around the 400HP mark (at the crank, maybe 330 at the wheels for around an 80 HP net increase) due to flowing a lot more air, and that is about what you can do on a stock-ish 350 ci small block that is very driveable. It should run you between $4K and $5K depending on how much work you do. Your '93 should be close to (but not be able to beat) a stock C7 Stingray. The engine will look like you painted the LT1 intake red (if you use the Holley), otherwise it will look and sound stock.

Last edited by obijohnkenobe; 05-19-2019 at 11:52 PM.
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Old 05-20-2019, 09:48 AM
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ctmccloskey
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PoprocksC4,

I may be a bit over the hill but I know what you are talking about.

The thrill of the 0-60 times are what I use to scare off would be wanna-racers. You have got to be careful doing it around the darn cameras. Here in the Washington D.C. area we have a TON of cameras at every intersection and they can watch your every turn if they so desired. I still like going out on the highways and running the car hard, the acceleration is amazing and one of "limiting factors" was my 3.36-1 rear. Comp Cams said that I HAD to replace the rear with at least a 3.70-1 or even a 4.11-1. I can run well past the 12 second mark and according to my calculations it should be mid-to low 11's if I could get traction but without the roll cage I can't do it. Most safety inspectors warned me about turning into the 12 second range so I spent the day making consistent runs just out of the 12's and that was a challenge. I had two people come up to me and try to buy the car from me after they saw it in action.

We bought our first Corvette the C3 in 1991 when I was 33 and I have had it since. I did think about modifying it but the performance was not bad. I learned a painful lesson back then. NOBODY liked the 1968 C3, Carlisle blew us off on our 25th anniversary and instead honored the 1978 Pace Cars with the prime parking spots. I tell people that the 1968 C3 is like Rodney Dangerfield "It gets no respect". That was then, now the 1968's have taken off and are worth some serious money if it was a big block car with a manual.

When I built the 427 it took almost a year to do it as I could afford to do it. I had a friend who owned a speed shop and sales were slow so he and I built the 427 in front of all the other customers. At the Christmas Party at the speed shop my engine was finished and on display. My buddy sold a lot of engines after people saw what we did with mine. A slow build gave me the time to determine exactly what parts I would need. What we ended up with was this High Compression 427 in the hay day of the Five-0 mustangs and boy that engine was surprising to everybody after it was tested. It would break the 3 second barrier for 0-60 quite easily.

I need to be more honest about this as I have a C4 which is very close to stock and the C3 was the one I fixed up to make a bit more horsepower. I did spend time driving the car for a while before I started by rebuilding the differential as my posi clutches were making a lot of noise. Then came rear trailing arm bearings from Van Steele. I spent a lot of money on the car but I have all the original parts for it. Currently it sports a 1968 L88 Factory hood with the wedding cake intake system. The carburetor is a custom built unit from AED in Richmond, VA and it works great. I have an electric fuel pump and electric fans on the car so I also beefed up the charging system. It has the Snow Performance Water/methanol injection system on it and the 427 loves 36* of total timing and never makes any detonation even with the Snow system disabled unless it is really HOT.

I apologize if I sounded too strict. It is your Corvette now and you can do with it as you please. I have always seen myself as the "temporary custodian" of the Corvettes. Down the road somebody else will be driving this car and I want them to enjoy it for all it is worth as well. My two kids are trying to decide who gets what after Dad is done with his Corvettes. My daughter drives a nice 2011 Camaro with a six speed and my son doesn't know how to drive a manual transmission so it won't be hard. My kids have been into Corvettes since they were even born, I used the C3 for various errands with a car seat in the passengers side. Finally after the second child the need opened up for a second Corvette for the girls. That is why I bought my C4 Coupe as it doesn't make a mess of long hair.....

Corvettes are a Lifestyle, Be sure to get to one of the larger Corvette events. We go to [email protected] as it is a 105 mile trip from home, August can be warm but the drive is worth it even without AC. They have hundreds of vendors and over 50,000 Corvette enthusiasts all at one fairground for the third weekend of every August. The C4 parts are there but not in the quantities they used to be there. Lots of GREAT deals to be had there if you know your prices.

I really hope that your Father's Corvette will enrich your life. They are so much fun to drive and own. "We are the Lucky Few"

Best Regards,
Chris
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Old 05-20-2019, 01:05 PM
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I know if you go to a larger throttle body, LT4 intake, LT4 Cam, 1.6RR, and get some head work done and then put an 8PSI intercooled supercharger on it, you can get 450hp at the crank or about 385 out to the wheels.

You are asking to up the horsepower by 50%. That is a tall order.

If you don't go blower. Heads/Cam/Intake/Fuel Injectors and custom tuning will be a minimum.
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Old 05-20-2019, 03:56 PM
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450 at the crank to match up with a stingray can be done. Bigger heads, ported/LT4 intake manifold, the right camshaft, 1.6 or 1.7 RR, then headers to get the air out of the engine. More cubes are needed under all that to keep it driveable with a big camshaft. After that, a custom PCM tune will be required.

I would probably do a 383 or 396, AFR 190 or 195 cc heads, 1.6 RR, Something around 220-230 on the int/exh side camwise, but you can go bigger with more cubes, 1 3/4" headers.

If you havent upgraded the TC to a 2400 stall or better, then that is a change you should think about too.
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Old 05-20-2019, 09:35 PM
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Originally Posted by obijohnkenobe View Post
If you swap heads to Vortecs or the GM Fast Burn heads,
These won't work on an LT1.

Last edited by STL94LT1; 05-20-2019 at 09:36 PM.
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Old 05-20-2019, 11:04 PM
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The other thing to think about is the D36. If you do up the horse power considerably you will need some sticky tires to put that horsepower to good use. Then if you do hookup well you have to worry about tearing up that D36. High horsepower should come with a swap to the D44 differential.
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Old 05-21-2019, 01:23 AM
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Originally Posted by STL94LT1 View Post
These won't work on an LT1.
You're right... reverse-flow heads. My bad. So, you're going to have to find some aftermarket LT4 heads... something like these that will be a few hundred more than the Fast Burns... https://www.jegs.com/i/AFR-Airflow-R.../1039/10002/-1

Other than that, the LT4 cam (see https://www.jegs.com/i/Chevrolet-Per...586K1/10002/-1 ), and either a '96 LT4 intake manifold or an aftermarket Edelbrock 7109 which is a Chevy LT4 clone... https://www.jegs.com/i/Edelbrock/350/7109/10002/-1

With headers and exhaust, this is effectively turning your LT1 into a hotrodded LT4, and should bring 50 or 60 HP above the factory LT4 spec due to better heads and exhaust. You might want to consider getting the heads shaved a little to match the LT4 compression. Obviously, this is a project that you should work on with a qualified engine shop, and it will be around $6K. Still, the cheapest approach to getting C7 base HP without radical engine work or a new stroker engine, which will about double the price.

Disclaimer: I have no connection with Jegs… just easy to search their website once you know the part #s.

Last edited by obijohnkenobe; 05-21-2019 at 01:25 AM.
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Old 05-21-2019, 09:32 AM
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Thanks for the part numbers and links! I imagine a larger throttle body will be on the parts list as well. The full on Corsa exhuast pkg. is awful spendy as well. But it's still cheaper than a C7. I'd like to be able to surprise a C6-C7 off the line.
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Old 05-21-2019, 09:46 AM
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Default Need more oxygen!

I live at 9000ft elevation so I suffer a 20% or more HP loss same as everyone else up here. But the view is worth it.
AND no EPA regs in Teller county CO

Keepin' cool in Cripple Creek.

Last edited by PoprocksC4; 05-21-2019 at 10:07 AM.
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Old 05-21-2019, 09:54 AM
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I need to be more honest about this as I have a C4 which is very close to stock and the C3 was the one I fixed up to make a bit more horsepower.
Easier to start out with, you don't have the factory computer controls to have to take into account. I am currently helping my friend plan out a 1969 restoration and engine/trans build. Much easier to pick components when you don't have to work around them.

An apples to oranges scenerio.

I know if you go to a larger throttle body, LT4 intake,
you can either use an LT4 intake or the aftermarket Holley version
LT4 intake on LT1 heads ? It has been proven many times that the LT4 intake and the other aftermarket intakes don't flow any better than the stock LT1 does. The only difference between the OEM LT1 and LT4 intakes are how the ports fit the heads.

The LT1 intake can be port matched just fine. LLoyd Elliot offers that service, along with porting the heads.

There have been lots of technical articles over the years evaluating the flow of the LT1 intake vs the others and the benefits just don't justify the cost. The only real time you need an LT4 configured intake is for the heads with raised ports.

Summit Racing also offers a complete package that will get you all but where you want to get to

https://www.summitracing.com/oh/part...make/chevrolet

This kit, a set of headers and most importantly, finding someone who can tune the car for you.

Then don't forget the transmission, they weren't built for this level of power and will go sooner or later, you will also need to make sure the rest of the suspension of is up to snuff, and in good repair.

Figure $5000 to $6000 in parts (easily) if you are going to do all the work yourself, more if not, quite more. A set of headers for these cars will lift your eyebrows, unless you buy Chinese knockoffs.

Stainless Steel Works and American Racing Headers are north of $1500.00.

You don't say where you live. Do you have to take into account EPA regs ? That can affect the cost.

Last edited by drcook; 05-21-2019 at 09:58 AM.
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Old 05-21-2019, 10:09 AM
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No EPA regs. So goodbye cat crap! BUT only if i do the work myself. There are no inspections but no shop is legally allowed to alter the factory emissions standards. And they get a hefty fine if caught.

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Old 05-21-2019, 11:18 AM
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modern day cats don't degrade the flow like old technology ones did
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Old 05-21-2019, 02:36 PM
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How much money do you have to spend? That limits what happens. 450 is achievable but you might have to drop some serious coin. A $200 camshaft alone won't cut it.
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Old 05-21-2019, 04:47 PM
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Originally Posted by PoprocksC4 View Post
I imagine a larger throttle body will be on the parts list as well. The full on Corsa exhuast pkg. is awful spendy as well.
Those two parts will do basically 0 as far as HP to the wheels. The stock throttle body and exhaust is plenty. Now if you go with heads/cam/headers and tuning they will help.

The Corsa exhaust is more about looks and sound (without drone... seriously zero drone).
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Old 05-21-2019, 04:51 PM
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Originally Posted by KyleF View Post
Those two parts will do basically 0 as far as HP to the wheels. The stock throttle body and exhaust is plenty. Now if you go with heads/cam/headers and tuning they will help.

The Corsa exhaust is more about looks and sound (without drone... seriously zero drone).
I would take that $1500 for the Corsa system and buy some LT headers and tie it into the stock and free-flowing exhaust....I bet the headers and labor will be less than the Corsa system, it apparently sounds pretty good!
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Old 05-21-2019, 04:55 PM
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Originally Posted by vette196 View Post
I would take that $1500 for the Corsa system and buy some LT headers and tie it into the stock and free-flowing exhaust....I bet the headers and labor will be less than the Corsa system, it apparently sounds pretty good!
I would unless you drive it in winter where they dump salt
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