TravMsns

I have a 78 with the L48. I want my vette to fly. Not that I drive like a maniac, I just want to know I have something under the hood. What would it take to get me about 300 or 350 hp from the L48? Is it even worth trying, or would I be better off swapping in a crate engine? I go to college at RIT($25000/year), so I need the most cost effective way to get some horsepower. Also, will my stock tranny hold up to that kind of torque/horsepower? I'd really like to keep my engine and build it up, but if it would be cheaper to get a crate engine, then I'd do that. What is the easiest way to get some horsepower out of my stock L-48? Tell me some options I have fellas, please. I just got this vette, and I have no idea what to do to give her some umph. How much power would headers and a new intake and carb give me? stuff like that. Thank you very much. please bear with me, because I've been a Jeep man for a long time, and somehow last week on a whim, I traded my Jeep for a vette.


[Modified by TravMsns, 4:56 PM 10/12/2001]

john's '81 mouse

Not sure if you have the L48 or L82, since you refer to both in your post.

If your engine is in good condition, then best bang for buck is as follows:
1) Good tune up, plugs, wires, filters, rotor&Cap $150
2) Good distributor curve kit for the HEI dist.(ask lars on this forum) $30
3) Good set of headers, with 2 1/2" dual exhaust, with high flow mufflers. $500.
4) Well tuned and adjusted Q-Jet Carburator (again suggest you ask lars) $150.
5) Better split duration camshaft, lifter, timing gear & chain kit from Crane/Comp Cams etc. Best choice depends on transmission, rear gears, and your intended useage of the vette. Probably should look at something like Comp Cam's XE 262. $300
6) If money permits, a better set of new heads would really help increase HP and performance. Chevy Vortec or World Products iron heads, or many aftermarket aluminum heads. Total cost of head package could run from $700 to $1,200.

Do all of above and believe you will achieve you desired HP / Performance goals.

TravMsns

sorry, it is the L-48...I editted my original post

MotorHead

You can get 350 HP out of an L48 quite easy, just take it to a good engine builder and he should be able to get that HP for under $2000 plus a few bolt
ons like intake manifold, carb and headers.

flood

Good choice to trade the Jeep for the Vette. I think you said that you have an L-48? But then you said L-82? Well either way Im in the same boat as you are. I have an L-48, and I can't decide which to do. From what I hear you can do some mods to the stock motor and it will shine. If you go the crate motor route its going to cost some $$$. But it will do alot more than Shine, It will ROCK !!! The inital cost for a zz4 is a little over 3,000. Not bad right? Well , you will have to look at replacing all the accessories. You will also want to do the Radiator work and new clutch get the tranny looked at. How about the rear diff? might want to make sure everything is safe and sound on the car before you pull the motor. Have you considered a rebuild of the motor you have? The extras will cost alot.

I am currently replacing all important parts. Brakes :yesnod: Rear diff with ratio change 3.70 (noticeable increase) :yesnod: Strut rods for better alignment / handling :yesnod: .

After 30 years these potental problem items are just the tip of the iceburg. But while I have been doing these things I have been driving and enjoying the car. Just think when you pull the motor, it won't be driveable for who knows how long???? These other projects are not as expensive and some may make a big difference in the overall enjoyment of the car. I had a brake failure and I was lucky it was in my driveway.

What about emissions? There are alot of things that you have to look at before you start changing the motor. Nothing like swapping in a crate motor and not being able to get plates for the car because it wont' pass emissons testing.

The motor of choice seems to be a ZZ4 swap. I have heard that the engine accessories will bolt right up to it. Hope this helps. Enjoy the car as it is and get everything you will need upfront. It will save in the "down" time and thats what will drive you cazy, not driving the car.

TravMsns

Would vortec heads bolt right on? Would I need new pistons or anything else... Ebay has some deals on vortec heads, but what else would I need to make it work, or would the heads bolt on and that's it? I'm not a huge engine buff, but I know a little bit.

john's '81 mouse

Vortecs will bolt right up OK, but note the following:
With Vortecs(a good performance, and inexpensive head) you also need the following:
1) Self aligning rocker arms
2) Special Vortec intake manifold (Edelbrock sells one for about $175)
3) Center bolt valve covers

Plus the Vortec heads have NO exhaust crossover passage and therefore prevent useage of OEM EGR valve/system, which may be a big issue/no, no, if emissions requirements are important to you and your state.

Gator81

When I did the math on that question (rebuild or crate) for my '81, the crate won easily. I got a 330hp crate from Summit Racing for less than $2500, including shipping. Now, that was a pretty good deal and it's not available anymore. But I still think a crate is probably the better deal. A lot of it depends on the condition of your stocker and how much power you want, since power = money. 300 hp is pretty easy, and your stock engine will carry it with no problem. 350 hp is a little harder. Also, you need to give some thought to the torque curve you want. My 330 hp engine makes a ton of torque (well, actually, it pulled 390 lbs/ft at 3500 rpm on the dyno), and has a really nice flat torque curve from about 1500 rpm up to around 4500. I could change the cam and have 350 or maybe 375 hp easily, but the torque below 3000 rpm would go away and it wouldn't be as much fun to drive.

You also have to calculate the cost of a rebuild as it relates to your skills, tools, facilities, and time. My skills were moderate, but I have never done a complete engine buildup from scratch, so I felt more confident in Summit. My tool set was not quite up to the job, either, so I would have had to buy or rent a few things like a degree wheel, micrometer, etc. My facilities were good (heated garage), but I saved a lot of time by having the crate engine sitting there on the engine stand ready to drop in when the old one came out and the bay was cleaned up.

When you do the math, don't forget to throw in all the costs for machine shop work, new fasteners, and peripheral parts that you won't want to skimp on (new belts, hoses, fuel pump, clutch, and all the little parts that really add up, like thermostat, filters, etc.).

Good luck with your L48/L82 whateveritis.... ;)

:seeya

Vetterodder

It'll depend on how much money you can spend and how much of the work you can do yourself. Keep in mind that a crate engine will have many of the same compenents that you already have and it's increase in power will come from only those components that you don't already have. If you aren't able to change those components yourself, the labor costs involved make the crate engine a better value. If you're comfortable doing the work yourself, you can get as much or more power for less money. The single biggest power improvement to an L48 is a better cam but it's full benefit won't be realized without improving the exhaust system.

It sounds like you're new to "rodding" your car. Instead of going for the max, do it in stages and enjoy (and learn) as you go. If more power is your goal, it'll probably remain your goal.

Smokehouse69

Best deal by far is a crate if you are limited in your engine building skills or are uncertain about local rebuilders. A good crate can be had for $2000 (330 hp Vortec head GM new Crate) plan on another $500-$1000 for ancillary parts(fly-wheel or flexi-plate, water-pump, belts, hoses, tin ware, brackets etc.)
Good luck!

Dave68

My Corvette mechanic gave me this simple bit of advise (and he's been in the business for many years.):

Install ZZ engine = go fast. You will be absolutely AMAZED at the difference in power. I went from a 327-350HP to a ZZ3 and believe me, there is NO comparison. The ZZ feels like it had 75HP more than the 327. If I was able to be that impressed, you'll be absolutely SHOCKED when you stomp on the gas for the first time.

Ganey

This is a good order for many.
1 Ex. is first. See Why Exhaust is problem for HP on 75-81 http://www.corvetteforum.cc/ubb/Foru...ML/008082.html
Duals w/ crossover & high flow mufflers.
2 Cam. Many replace intake at same time for a little more.
3 Headers.
4 Heads.

The first 2 can put you over 300 HP. What's trans.?

KenSny

my $.02 here - If keeping the L48 engine then I would do all the above mentioned things to boost performance - plus I would get rid of the domed stock pistons and install some flat notched pistons to raise compression.

Johnhueby

I have the same car and engine, and am looking to do the same thing as the guy in this thread what cam would you recommend?

Thanks,
johnhueby

hpxt

Welcome to the forum, wow, a thread resurrected form 2001!

What is your desired outcome? The cam choice depends on the heads, transmission, rear gears and what you want. I have a 78 with auto trans and wanted low-end torque and to do burn outs. This dictated the cam choice; paired with heads, matching stall speed for the torque converter and rear gears.

If you provide more details, lots of experts here to guide you.

Johnhueby

I just got back to thinking about what to do with my 78 l48 with auto trans. I'm looking to get more low end out of the car. So what would be the best add-ons to achieve this as inexpensively as possible? Thanks in advance

mobird

I would reccomend starting your own thread, since this one is about 17 years old. Not that the info isn't relevant, but it would help the friendly folks on this site make a more accurate reccomendation for you!

When you say "more low end" are you meaning just more responsive throttle? That can be done fairly easily with a recurve of the distributor and a tune up, possibly some carb tuning.

What are your power goals (roughly)? Is your car completely stock?

NewbVetteGuy

This is a great list and possibly even in the right order.
Only thing I would change would be to change the Comp XE 262 sewing machine cam to a Lunati Voodoo 262/268 http://www.lunatipower.com/Product.aspx?id=1983&gid=287


Only thing I would add is to check the flatness of the deck after removing the old heads and go with the felpro 0.015" thick gasket and copper coat if your block is nice and flat. -It will give you a 0.5 static compression ratio boost which will help out.

Clarification on headers: Get full-length headers to keep up the low-end torque which will also help your fuel economy.



The next thing to make the car more fun would be a higher stall torque converter, but it'll drop your fuel economy slightly and you'll need to install a dedicated transmission cooler.



Then if you don't yet hate the thing and land a job after school you can throw a Holley Sniper Fuel Injection unit on it and have a self-tuning EFI and a dual-sync distributor so you can control everything via touch-screen LCD for another $1,500. -Really easy starts all the time everywhere and a boost in fuel economy.

On the heads front, modified Vortecs are a good option but so are the Chinese Promaxx heads if they're worked over by a professional shop. You can also get a set of Jeg's rebranded Profiler 180cc heads for $899 including shipping and taxes on sale (depending upon what state you live in). -Although the Jegs heads and a Lunati Voodoo 262/268 might give you more than 350hp, that's a good problem to have.



Adam

NewbVetteGuy

When you pull the stock manifolds off and move to headers is also when you want to get rid of the SMOG pump and definitely the stock catalytic converter, if somehow it's still on the car. The swap to headers, getting rid of the smog crap, and getting new ignition timing will make a good jump by itself.


If you can't afford the heads, definitely still do #1 - #5 and don't forget the timing chain set- it's not just a "safety" issue, the stock cam timing is retarded by 3 degrees and the chains stretch out and can be retarded by as much as 6 degrees. Just setting the cam timing to "straight up" will give you more torque off the line and any new cam will get you more airflow AND more bottom-end and fuel economy by keeping the cylinder pressure ("dynamic compression ratio") up because the lobes will have a faster "ramp" to them AND most of these cams come with a 3 degree advance ground into them so you can move from 6 degrees retarded cam timing to 3 degrees advanced and you should notice that.


The same general concept goes for the ignition timing -it's set dramatically lazy from the factory and results in less low-end and more fuel sent out the exhaust (to lower emissions).


The cam swap is a huge jump in labor, just so you're aware. You have to take the radiator out and if you're replacing the cam you get the infamously "fun" process of replacing the cam bearings with the engine in. If you're replacing the cam, you should probably have your heads' springs checked out which means you are probably pulling the heads, in which case you want to investigate that Felpro thin 0.015" gasket...

Advance Auto Part's occasionally sends out seasonal 10% and even 20% coupons and then you can grab a set of coated FlowTech long-tube headers for under $300. Make sure you get your ignition timing dialed in if you go with them or you'll cook off the Chinese ceramic coating, and they'll rust anyway, though.

John 81's #1-#4 and changing the timing chain should be considered "must dos" because the return you get for the $$ and labor is very well worth it.


Adam

NewbVetteGuy

No, the best deal is John81's #1-4 and he'll need most of those things done anyway, if he decides that #1-4 isn't enough power and he still wants a crate engine.

A cheap crate engine slapped onto the stock exhaust system on a 78 is still going to be a bit of a dog. He's going to need the exhaust system either way, might as well do that first and see if he's happy with the $800 solution before forking out the $3000 for a crate motor.


Adam