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Discussion Starter · #1 ·
hey all!

Just thinking out loud here...

I have a L-48 '76, and was wondering what kind of a project it would be to put in a bigger cam.

I don't have much mechanical knowledge, and am wondering...should I take it to my mechanic to do? would a L-82 cam work? Is it labor intensive...engine hoist, etc...

I'm just looking for a bit more power, and I've been told upgrading the cam would help.

Any suggestions?
 

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The L48 does not have enough compression to support a hot cam, if you overcam the engine you'll have no low end power.... car will 'feel' slower than before....

You'll have to remove the radiator to gain enough room to pull the cam out. You'll have to drop the oil pan to get the timing chain cover off and most likely you'll end up with a leaking front if you don't use the 1 piece FelPro gasket...

The L48 cam is not all that great (low duration and low lift numbers)... keep in mind that the valve springs are designed to work with this cam. If you increase the cam/valve lift you'll need better valve springs.

It's a lot of work and you won't gain a lot from the cam if you keep the stock heads and exhaust.
 

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Discussion Starter · #3 ·
Good info to know! gheeez, I'm glad I didn't make that mistake! :surprised Back to the drawring board!!

What's a good way to get more hp? Headers/catless/hi-flo cats/exhaust? I've already put a drop-in K&N in, and had a mechanic work on the timing.
 

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What's a good way to get more hp? Headers/catless/hi-flo cats/exhaust? I've already put a drop-in K&N in, and had a mechanic work on the timing.

If the carb and timing is all set don't mess with it, leave the engine alone until you can do the heads, intake and cam at the same time ... including new lifters, pushrods, timing chain set, gaskets and a few tools (you can rent most tools from AutoZone or AdvancedAuto at no charge) it is going to cost a few bux but it's best to do it once instead of all over again...

Start with headers and a true dual exhaust, that will make a difference without touching the engine....

One more thing worth mentioning is that your stock heads have pressed in studs for the rocker arms. With higher lift or higher duration camshafts these studs can come out of their bore.... aftermarket aluminum heads have screwed in studs
 

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Start with headers and a true dual exhaust, that will make a difference without touching the engine....
:agree: most bang for the buck with the least mechanical work. No smog inspection laws to worry about here in NE so you've got lots of leeway with exhaust. Step 1 is letting her breath!

also, FWIW, I'm a fan of doing everything yourself. Shops charge an arm and a leg and half the time they don't do a worthwhile job. Spending more time on it yourself you can often do a better job than someone with lots of tools.
 

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Discussion Starter · #6 ·
Okay all!

Made an appt. to go straight duals to flowmaster (probably super 40's) mufflers next tues. Hopefully w/0 the cats, it'll have a little more pep!!:partyon:

Question: what size pipe should I have them use?

David
 

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The stock cast iron manifolds are very restrictive, Summit has some long tube headers for under $100 (painted black).... yes, they'll rust but so do your stock manifolds.... ceramic coated headers are $350 and up...

Pipesize: 2.5" and tell them to use the good stuff, not the thin 24g "tubing" :laughing:

Many have complained about the Flowmaster low rpm drone... it can get annoying after a while. My Camaro seemed to be louder inside the car than outside.... that was a 80s Flowmaster.

Unless you like it really loud I'd get two Dynomax Ultra Flows (not the SuperTurbos)...
 

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Discussion Starter · #8 ·
I've got Flowmaster Original 40's on my 05 GTO, and Flowmaster SUV on my Durango...to be honest that's all I've ever used. Would Dynomax make it sound louder, quieter?

I'm still not sure what sound to go for....definitely not obnoxious. I'd order the LT headers, but I doubt they'd get here by Tuesday's install. darn it. Are they easy to find on Summitt?
 

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Something to think about...

#1. headers work best when they are WIDE OPEN. The horsepower/performance increase is gonna be minimal when you hook up an exhaust system to it.

#2. For many folks "loud noise from exhaust = increased performance". The car may "sound faster", but actual performance increase will be less than what it sounds like ;)

#3 Small valves (like you have) and huge exhaust are not a good combination for power. With that engine you are handicapped from the start on how much power you can make and how much abuse the engine can take. What you basically have, and this tends to piss people off when I say it, is a Chevy Caprice engine with a 4 bbl carb bolted on.

#4 For the really best FELT as well as ACTUAL performance increase, I always recommend a stiffer rear end gear. But because of the limitations of your engine, I don't think it's such a wise idea. You are almost stuck with installing a crate engine if you really want to go fast and want a good foundation to build on. Installing the standard carb/cam/headers on the L-48 is not really going to make you a Mustang GT killer :D

Dep
 

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Small valves (like you have) and huge exhaust are not a good combination for power. With that engine you are handicapped from the start on how much power you can make and how much abuse the engine can take. What you basically have, and this tends to piss people off when I say it, is a Chevy Caprice engine with a 4 bbl carb bolted on.
Ah. Caprice powered rubber baby bumper disco buggy. The stuff legends are made of. :laughing: I have one. Be proud. No chrome bumpers to rust. Power windows and power seats with A/C. Don't let their jealousy fool you.:laughing: :laughing:
 

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Just some food for thoughts:

- the long tube headers are under $100, same price as shorty headers.

- the stock manifolds are restrictive.

- the exhaust shop will charge more for connecting the exhaust pipes to shorty headers or stock manifolds (more pipe and two more bends)

bottom line: i don't see a disadvantage, maybe a little reduced ground clearance but that's it.


It won't be a Mustang killer but the exhaust alone should increase performance noticeable.

When you install good heads, cam and intake you'll already have the exhaust to support the better breathing top end....

My L48 was pretty fast with 64cc heads, flat tops and 'mild' cam... :cheers:
 

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More food for thought (you are gonna get fat off this thread)...

Stock manifolds are restrictive, but that's not where the restriction STARTS. It starts with the heads and the "nail valves" (an old Buick term) installed in them. Any cam, headers or exhaust system are going to be inefficient because you aren't sending enough exhaust through them with the tiny valves you have.

Example: Open your mouth as wide as you can and fill your lungs with air and then keep your mouth open all the way and blow the air out. WHOOSH! All out in less than a second.
Now suck in a mouthful of air through a tiny hole in your lips like when you whistle and squeeze it out through that same sized hole.

First time illustrated an engine with big intake and big exhaust valves. Lots of air in and lots of air out in very little time. Second time was your engine with tiny intake and exhaust valves. A small amount of air in and a small amount of air out. So installing 2 1/2 inch pipes and 1 3/4 or even 1 1/2 inch headers is going to have minimal effect on performance. Understanding that an engine is nothing more than a big air pump means you have 1/2 the battle won :D

BTW...the easiest, cheapest, most reliable way to make your car go faster is to LOSE WEIGHT. Not you, the ground weight of your car. :thumbsup:
That is what car makers are doing now with performance cars. Lots of plastic/carbon fiber parts mean less weight and faster cars.

Dep
 

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Discussion Starter · #13 ·
Dually noted. Thanks for all the input. Here's my take:

It's an L-48. Not much I can do for speed. That's ok, I have my "go-fast" car already.

I'm just trying to get as much pep w/o doing major surgery. :)

Now, its between doing the headers...which one, black or coated! :cheers:

And what mufflers to go with.
 

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Dep,
I'm not disagreeing with you on how an engine works but look at what the original poster asked:

"I'm just looking for a bit more power, and I've been told upgrading the cam would help.
Any suggestions?"


The cam is definately the wrong place to start, at least the cam by itself...

removing the catalyc converter and running two pipes out the back is likely improving performance more than the headers but would you leave the stock cast iron manifolds in there only so that later you have to change the exhaust again when you're installing heads/cam and headers ??

If you have the cash do it all at once: heads (incl bigger valves, better springs), cam, lifters (retro roller), pushrods, flat tops, intake ..... many have to take it one step at a time and the exhaust is the best area to start IMO....

You could just throw a 383 or bigger SB in there, add a 5spd and a new diffy with better gears but that cost a little more than the cam he originally wanted to do....:cheers:
 

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Dep,
I'm not disagreeing with you on how an engine works but look at what the original poster asked:

"I'm just looking for a bit more power, and I've been told upgrading the cam would help.
Any suggestions?"


The cam is definately the wrong place to start, at least the cam by itself...

removing the catalyc converter and running two pipes out the back is likely improving performance more than the headers but would you leave the stock cast iron manifolds in there only so that later you have to change the exhaust again when you're installing heads/cam and headers ??

If you have the cash do it all at once: heads (incl bigger valves, better springs), cam, lifters (retro roller), pushrods, flat tops, intake ..... many have to take it one step at a time and the exhaust is the best area to start IMO....

You could just throw a 383 or bigger SB in there, add a 5spd and a new diffy with better gears but that cost a little more than the cam he originally wanted to do....:cheers:
LOL...I'm the wrong person to ask that question. First of all I would understand that the L-48 is NOT a good foundation to start hopping up. It's a nice car motor, but NOT a performance engine. Spending money to make it go faster is simply a waste of money. I know not everyone is a multizillionaire like me (HA!), but you have to be realistic too. Too many guys buy a Vette with that motor thinking only "WOW...I got a great deal, and it's a Vette so it's GOT to be fast, or a least have the potential to be fast". Unfortunately, the L-48 is best left alone and just drive the car the way it is. You can put on noisy mufflers and chrome goodies and nice wheels and tires. But that's about it. It's kinda sad that Chevy installed that engine in the Vette. :(
 

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hey all!

Just thinking out loud here...

I have a L-48 '76, and was wondering what kind of a project it would be to put in a bigger cam.

I don't have much mechanical knowledge, and am wondering...should I take it to my mechanic to do? would a L-82 cam work? Is it labor intensive...engine hoist, etc...

I'm just looking for a bit more power, and I've been told upgrading the cam would help.

Any suggestions?
Okay, here is my experience for what it is worth. I had a similar car/engine. Installed a performer rpm intake, 750 holley, headers, and hurst 4 speed. It was a lot more fun to drive. I drove it for a year like that and decided to install a big block.

Summit and Jegs sell reasonable priced kits with alum heads, cam, intake, etc. You might want to look at those.

As far as headers with a full exhaust, my 427 really came to life by installing the headers. The Corvette factory exhaust manifolds were pretty poor. The improvement with headers wasn't as noticable with the small block L48, but still was an improvement.
 

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The dual exhaust and the headers are still useable (or re-useable) when the engine is upgraded some time down the road. Even if you install a 383, the exhaust with 1 5/8" primaries will be fine... for 396ci and bigger you might want to upsize to 1 7/8" primary tubes, maybe even bigger than that ....

If the bottom end of that L48 is in good shape I'd leave that alone and just install heads/cam/intake - why would heads for a L48 be a waste of money ? If you choose the right parts (AFR 195 for example) you can use these heads again on a hot 350 or a 383 or whatever you want to replace that L48 with... unless you want a BB

Again, a L48 with a little higher CR (heads), cam, intake and a better exhaust is not slow.... and the cast crank and 2bolt mains are good enough for that level of HP....
 

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rtj: Two things...
#1 A 427 has MUCH bigger intake and exhaust valves than an L48, as well as better cam specs. So it would make sense that headers would offer a noticeable gain.

#2 Define "came to life". Did you put either the 427 and/or the L48 on the dyno before and after installation of the headers? Too many times we get seat-of-the-pants evaluations based on noise levels and optimistic estimations based on the $$$ spent and the results of others who did the same mod. Can anyone remember a post where a guy installed headers and DIDN'T notice a "performance gain"? LOL...I didn't think so. :D

I'm not trying to be an asshole or wiseass. I'm just saying we should be realistic with our expectations and base our feedback on actual proof from either dyno testing or drag strip runs. And even the strip runs would have to be suspect unless they are done under very closely monitored conditions. You can run at 9Am when the track is cold and get awesome times. Then run at 1PM and the times will suck. Temperature is normally the culprit.
 

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The dual exhaust and the headers are still useable (or re-useable) when the engine is upgraded some time down the road. Even if you install a 383, the exhaust with 1 5/8" primaries will be fine... for 396ci and bigger you might want to upsize to 1 7/8" primary tubes, maybe even bigger than that ....

If the bottom end of that L48 is in good shape I'd leave that alone and just install heads/cam/intake - why would heads for a L48 be a waste of money ? If you choose the right parts (AFR 195 for example) you can use these heads again on a hot 350 or a 383 or whatever you want to replace that L48 with... unless you want a BB

Again, a L48 with a little higher CR (heads), cam, intake and a better exhaust is not slow.... and the cast crank and 2bolt mains are good enough for that level of HP....
Yes to your first point. The exhaust system can be used for other engines. But now you are talking about other engines...which was my point in my post. :D

"Why would heads for a L48 be a waste of money?"
Why waste the effort of BUILDING UP an L-48 when you can get a crate engine with all the good stuff already installed that will be more reliable and in the long run probably cost less? What you are talking about veers considerably from the original post of "just looking for a bit more power".
If this was an L-82 engine with the 4-bolt mains and good heads, I'd say go for it. Consider what the L-82 has compared to an L-48... the L-82 has large port cylinder heads, pushrod guideplates, a longer duration camshaft, a forged-steel crankshaft, forged aluminum pistons, moly rings, finned aluminum valve covers, a higher capacity starter and a four-bolt main block. Plus 2.02-inch intake/1.60-inch exhaust valves. That is at least the basis for a good high performance build. All you really need are 10-1 pistons if the engine itself is in good shape.

L-48 has 1.94-inch intake/1.50-inch exhaust valves and a camshft with the profile of a broomstick. Plus all cast engine parts.
"An L-48 is not slow"...it's not the engine that is slow...it's the CAR that it's installed in combined with the engine and drivetrain that makes them slow. A 1976 is a heavy car to start with. Stock 1/4 miles times were around 16.5 for a 1976 L-48 Vette. The stock 2005 Mustang GT is in the mid-13s. Even with carb, cam, heads, manifold, etc etc you STILL won't beat a 2005 Mustang. And WHY waste all that time and effort building an engine that is basically NOT a performance motor?? You'd almost be better off finding a good L-82 in a boneyard and working from there.

Dep
 

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I guess it comes down to "what power level do I want and what am I willing to spend?"

I'm still saying it's not a waste to throw some good heads on a L48... with heads,cam, intake and exhaust you'll have a nice engine.

The L82 isn't all that much better, the heads are still cast iron boat anchors... prone to cracking, have weak valve springs and pressed in rocker studs ... reworking these heads would indeed be a waste of money .... and the cam: although it's way better than the L48 broomstick it's still not all that great...

If you do the heads and cam first you can always buy a short block some time down the road.... re-use the parts so there's no money wasted....

And btw, when you reach a power level where you really "must have" the forged internals you better upgrade the trans, driveshaft, diffy and half shafts as well....
 
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