I have just purchased a 1979 C3 with an L48 motor and a 4spd. I want to increase the performance but don't know where to begin. I live in AL and do not have to meet any Smog certification. What do I need and what can I take off. I would like to change the carb and exhaust but the performance pakages in JEGs for instance say that they are recommended for high compression engines. Mine is only 8.2:1. Can some one help me get this intake and exhaust worked out please? I am real excited about this and am ready to get started but don't want to start putting on the wrong things, or take them off. Also, the windows leak water when it rains right at the rear corner where the window meets the door (opposite the hinge side of the door - the rear side). Can anyone point me to where I might get help in that area as well? Thank you - John

 

Save yourself tons of time, $$$ and headaches....
Buy a crate motor & don't drive in the rain!!!

 

I would do the exh first (true duals) then depending on your budget I would do a head/cam/intake/carb change all at once. There are some decent packages avail from either Jegs or Summit. Your exh will hold back any upgrades you do to the eng but your heads will do the same for if want to get some real power out the motor.

 

Cam change is a must to get more power out on L-48. Q-Jet is a good carb and can feed 400 HP, no need to change that.

Exhaust
Cam/Intake
Head

As one poster stated, a crate motor may work better for you. A Stock L-48 has cast pistons and crank, limiting you to about 5000 (5500 max) rpm.

 

If you're only 8.2:1CR, quickest bang for the buck would be a shot of nitrous.

 

John, I also live in Alabama. My 75 has true duals, 2.5" including the manifolds, a performance cam, and about 9.8:1 compression. It also has an Edlebrock manifold and carb, but as pointed out earlier, that's sort of unnecessary. Your stock intake and Q-Jet will work fine. This combination runs real well, with performance similar to a 60's or early 70's 350. If you have the stock exhaust system, that's the first thing to get rid of. Next, I'd go to an L-82 cam or something similar, and get the compression up to at least 9:1, either with some new pistons or some better heads.

 

do you know your head casting #'s if you have the 882 castings or something similar, you can easily pull 300 horse with a good home port and polish job,match the gaskets,clean up around the short side radius of the exhaust,polish the exhaust ports etc you can easily add 35 h.p. to the dead stock heads, now headers,a good cam,put a shift kit and 2400+- stall torque convertor in the tranny, and your off to 300 h.p. and planting it nicely. if you toss the 400 turbo and install a 350 turbo(if you have the 400).not too hard a swap,you will gain another 20 or more h.p.
also get a recurve kit for a h.e.i.,toss it away less a light and medium spring, install these.
you can do this on less than a grand or close if you get a good used tranny,just check for long or short tailpiece.
you can just put a 4.11 rear end and go squealing the tires but you won't be able to highway drive it without the revving.
some are using the 700r4 with the 4.11 rear , it works well but then adds the price and time for a rear end.
the th350 is argueably better and more reliable than the 700r4.(not nessesarily my opinion)have fun.

 

my '77 L48 4-spd runs good with headers and 2.5 duel exhaust.
fast idle, Is there a written procedure for the home port and polish job you mentioned?

 

The '79s don't have the 882 heads. They have the 624 castings, which are prone to cracking. Set the heads aside and get a better set. Exhaust, heads, and cam. And recurve distributor.

Or a crate motor.

 

Exhaust http://www.corvettefaq.com/c3/ganeyexhaust.htm
Cam L-82 or Comp Cams HE268H if you drive hard which is max. for stock valve springs.
Better heads rec.

 

Get that small block breathing.
Right now it's got asthma and needs Heads, Headers and Duals to run like its supposed to.

Chris B

 

77 vettejeff, i had a web site shortcut that took you right thru the procedures, they were selling the kit but a good dremmel and or die grinder with a teardrop burr and some assorted sand rolls will do the trick.thats what i did mine with.the hotrodders.com or something site will turn it up with a search quick enough

 

Well - it looks like the order of things is 1 - a new exhaust system. then after that change the intake manifold and see how it performs. I want to go with duals all the way. What headers do I need to get that I can install without having to cut away at anything. I have read posts where people speak of bending and pinging here and there to get the headers to fit. Is there a set I can buy (coated for temp) that will just bolt right in? Then what exhaust system would I need to get to run duals all the way back? I won't use the cat conv's so the system does not need to have them. The headers I will do myself but I will take the exhaust system to a local muffler shop. Also, what does this do to all that stuff under the hood. There is a Thermatic Air cleaner (very ugly), exhaust heat stove, There is also the EFE valve in the exhaust manifold on the passenger side. From What I have read it blocks exhaust and forces it through passages in the right cylinder head. When I put headers on what happens to those passages - Do I have to plug them. I don't know what all this stuff does??? What do I do with all that stuff. What do I need, what and how do I get rid of what I don't need? Can I get to where I have just a simple crome covered air cleaner or maybe a simpler snorkel to air filter connection, and a simple exhaust?

 

We said you DON'T really need an intake manifold. Stock one is pretty darn good, actually. You can also run true duals with the stock exhaust manifolds -- they're not as bad as people think either. Save the money for cam and heads -- they are the serious weak link on this engine! If you don't like the way they look, repaint the intake and put some calyx on the exhaust manifolds. Or get 'em ceramic coated like I did...



With regards to the air cleaner, you can get an open element cleaner. Or a chrome lid if you want to keep the cold air intake system. The EFE valve can be removed and the guts taken out, but it only affects things in cold weather -- helps the choke work faster. The heat stove (and the ugly) can be removed. Just be sure to pull and plug the vacuum line going to the bottom of the aircleaner to disable the thermatic thingamajigs.

Mid-America sells a true dual exhaust kit that would work for you. Click on their link (it's somewhere on the left) and check it out.

 

I just put headers on my '77 L48. I bought block hugger style. They did bolt right in.

The engine ground strap had to be rerouted a bit. Other than that the fit right in. I bought these for $65 on ebay from "rodpartsdealer". Funny thing, they told me they wouldn't fit! Anyway, I didn't notice much of a performance gain from what I had which was the ramhorn manifold to 2.5 duel exhaust. I think the old manifolds were not much of a limiting factor on my stock motor.

 

Do you have problems changing your spark plugs? Can you get to all of them without your headers getting in the way. I put a set of Stn Stl SLP headers on my Camaro. Man they are great but there is was plug that I have never changed because of them.

 

For a street motor, the old ramshorns are hard to beat. i have 2.5" ones on my 75, but I think you are about as well off with 2" if you go straight to 2.5" pipes and some low restriction mufflers.

 

If you are not going to change the motor, dump the rear spare tire under the car, next ditch the heavy rear steel leaf spring and replace it with a fiberglass rear leaf-spring which is only 7lbs. You will be surprised what weight reduction will do to a car which only has 190hp. All for only a couple hundred bucks.

 

Had the same question when I purchased my L48 1980 last year totally stock.



Here it is now...



bored to 383
edelbrock rpm heads
xe274 cam
hooker headers
performer intake
thunder avs carb
msd digital 6

478 tq
427 hp

That's enough for me...

 

my plugs are easy to get at after installing my hugger headers