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I have a 1977 L48 auto with stock heads (recently machined), headers and sidepipes, Edelbrock2101 Performer intake, and I will be installing a Holley 600CFM carb this winter. I am also going to be installing a new torque converter because mine is leaking (I will decide which one after I buy a cam). I am wanting to install an aftermarket camshaft, to 1, get a little more power, and 2, get a little chop. I am not looking for some extreme choppy cam with a ton of lift. I am looking at about .430-.460 for lift on one. I believe that will wake her up a bit and give me a little chop, while still being drivable. I do not want to get new heads, but I do know I will have to do new springs, rockers, lifters, timing chain, etc. I am looking at getting this cam kit: https://www.compcams.com/xtreme-ener...all-block.html
I have a few questions before purchase:
Will the link I listed work with my engine setup? With regards to in lift duration etc. Also can I install a hydraulic roller cam? I believe these engines had a flat tappet cam. I am under the impression that if I swap all of the springs, rockers, rods, and lifters, I can do a hydraulic roller. Has anyone installed a similarly sized cam before? If so, how did you like it?
Anyways, as a 20 year old kid with a love for this car, I am wise enough to know that I do not know enough to build it on my own, so any help is appreciated!
P.S. in case you were wondering, here's what she looks like:
Nice looking car. not sure how much chop you will get with that cam. it is a mild grind. you could probably add about 10* more intake duration and that would still drive nice and proabaly have a little chop to the idle.
If I summon him, perhaps @Jebbysan will post his budget top-end rebuild recipe. I certainly wouldn't waste time with the L48 heads when you can find Vortec heads for peanuts on Facebook Marketplace. He can also post the correct Holley to use, if you don't want the Q-jet for some reason.
Beautiful car! White on red C3s with sidepipes are the very best Corvettes.
The specs on that cam would actually go well with the low compression on a stock L-48.
Most folks try to over cam an engine. Will it be choppy, maybe a little, not much. Going roller is similar to adding a good 15* to the duration vs flat tappet. So it may have a bit of chop.
The biggest problem with the L-48 is the absolute garbage heads and garbage dish low compression pistons. Your advertised 8.5:1 compression is actually more like 7.8:1 compression. So if you don't want a real dog of an engine below 2500 rpm you are stuck with lower duration cams.
That cam is a reasonable choice. it has 41 degrees of overlap which I think will work good with the stock compression. As good as can be had with just a cam change in any case.
If you want to continue in the future, consider re-curving the timing, Look for Lars' papers, ditching the restrictive exhaust for a true dual system, replacing the stock intake with an Edelbrock performer intake. Then get to the carburator. Send it to Lars or learn to do it yourself by reading Cliff Ruggles' book. 20 somethings don't generally read books much, but given you're working on a 40 something year old corvette, you may.
Biggest problem here is as others said the low static compression. Not sure what your budget is but getting a set of 64 cc heads on there will open up your possibilities camshaft wise. That will take your static compression to roughly 9:1. The 76 cc chambers plus dished pistons is killing your compression. The chop you’re after is an effect of the high overlap of the intake and exhaust cycles.
There is something called dynamic compression you also need to get educated on. Cliff notes are the dynamic compression is a correlation of the static compression in conjunction with your camshaft duration and timing events. General rule of thumb is you want around 8:1 on dynamic compression. Higher static compression gives you more leeway to move around lobe timing and durations. You can also raise the dynamic compression by advancing the valve events. Conversely you can lower your static compression by retarding your camshaft timing events.
It’s not super hard, but there is alot to consider. Personally if you have the budget I would do a top end kit from a catalog. Reason I say that is they are proven combinations that generally are pretty safe and conservative. Are most top end kit camshafts pretty soft on specs? Yep….. But it won’t throw you way out in left field either.
That's a smaller cam than the stock GM cams for the Vette engine. And it's gound on a 110 LSA, which will give you a "big cam sound" while giving you small-cam performance. You'd be much better off installing the factory L48/L82 hydraulic flat tappet cam than that POS...
Stock cam specs were/are: .390/.410 lift, 196/202 duration @ .050. and a wider LSA, 112 I believe. And a flat tappet.
Stock factory L48/L82 cam specs @ .050" were 222/222 duration and .450"/.460" lift on a 114 LSA. He's looking at installing a cam with 206/212 duration with .480 lift on a 110 LSA. No off-seat time with a narrow LSA to give it poor idle, poor idle vacuum, and bad tunability, but it will sound good when driving through the drive-in... Not what I would do, but to each his own....
Lars
Not to mention it's a POS Comp Cam that will go flat during break in these days. Comp.has a terrible rap right now. Use an Isky or Howards setup and as Lars said, something more along the lines of a L82 cam spec with 64cc heads.
The cam that was designed for this application is the Comp 268H. Low compression, basic bolt ons and no head swap, no special pushrods, no special valve springs. Lope in the idle. Easy on the valvetrain.
Saves $1000 you would need to add for the retrofit roller that will require all new springs, pushrods, roller cam, roller lifters, button spacers etc. It's your money so maybe you are OK with that?
Stock factory L48/L82 cam specs @ .050" were 222/222 duration and .450"/.460" lift on a 114 LSA. He's looking at installing a cam with 206/212 duration with .480 lift on a 110 LSA. No off-seat time with a narrow LSA to give it poor idle, poor idle vacuum, and bad tunability, but it will sound good when driving through the drive-in... Not what I would do, but to each his own....
Lars
He has an L-48. 3.08 rear diff.
It will run like crap with an L-82 cam in it.
L-48 cam specs were significantly different to accommodate the lower CR and the high gear ratio.
L-48 specs can't be put into same category as the L-82.
The cam that was designed for this application is the Comp 268H. Low compression, basic bolt ons and no head swap, no special pushrods, no special valve springs. Lope in the idle. Easy on the valvetrain.
Saves $1000 you would need to add for the retrofit roller that will require all new springs, pushrods, roller cam, roller lifters, button spacers etc. It's your money so maybe you are OK with that?
$600+ to convert to a roller cam. I did it a couple years ago for about $500.
Not to mention it's a POS Comp Cam that will go flat during break in these days. Comp.has a terrible rap right now. Use an Isky or Howards setup and as Lars said, something more along the lines of a L82 cam spec with 64cc heads.
Ive read many of the comp cams are made by Howards these days as the flat tappet cams are more of a novelty.. They are all just different brands from the same company.. https://www.dragzine.com/news/howard...media-network/ they own Lunati as well... They continue to buy up market under all these well known brands of the former individual companies because they know a lot of people are brand loyal regardless of who is making the product now days and how.
Last edited by augiedoggy; 08-05-2023 at 11:01 AM.
I wouldn't even look at a flat tappet these days. Unless you like doing it twice and paying twice...or more.
Roller will give you the ability to run any oil and the comfort in knowing that you won't be wiping a lobe. Will a flat tappet work and last? Sure, maybe. But with all the problems even professionals are having with flat tappet failures in the last several years, there is no way I would risk it. I like to do things only once.
There are considerations with roller cams of course.
The cam button, fuel pump pushrod material and HEI drive gear. However these can all be addressed. Contact the manufacturer and ensure you're using the proper interface materials so as to not destroy your new roller cam.
If the quality is suspect then you could try a different manufacturer. But once you enter the world of aftermarket parts the quality usually is suspect.
I'm using a lunati roller cam and now the fuel pump lobe is going flat after 12,000 miles, despite using the reccomended and expensive pushrod. So you take your chances.
So I found most retro roller cam shafts will work fine with the steel distributor gear material the aftermarket distributor all come with but its something you want to check. and you will want a composite fuel pushrod vs the brass tipped one which many claim will mushroom I chose a nylon cam button which I was able to easily clearance for my application
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I'm using a lunati roller cam and now the fuel pump lobe is going flat after 12,000 miles, despite using the reccomended and expensive pushrod. So you take your chances.
I dont like seeing this especially since I believe im using the fuel push rod I believe you recommended.
So I found most retro roller cam shafts will work fine with the steel distributor gear material the aftermarket distributor all come with but its something you want to check. and you will want a composite fuel pushrod vs the brass tipped one which many claim will mushroom I chose a nylon cam button which I was able to easily clearance for my application
What did you use for the button and timing cover? Links or part numbers?
I'll convert to an electric pump while I'm at it...
I dont like seeing this especially since I believe i'm using the fuel push rod I believe you recommended.
Yes, I believe you are. There is no way this should have happened on my cam. I blame Lunati on this one. Someone didn't anneal or case harden the lobe. It must be dead soft steel to wear down as it has. It gives me pause on the rest of the cam as well. Only time will tell. For the time being I'm going to go low psi electric pump. Easiest and quickest solution. Fingers crossed that the rest of the cam was properly treated.
He has an L-48. 3.08 rear diff.
It will run like crap with an L-82 cam in it.
L-48 cam specs were significantly different to accommodate the lower CR and the high gear ratio.
L-48 specs can't be put into same category as the L-82.
I have to agree with this comment. Many years ago I put an L82 cam in an auto 75 Camaro with an L48. The engine was lazy/soggy at low rpm’s. Letdown really. So annoying that after a few weeks I swapped it out to a better matched Sig Erson TQ20. That cam is similar to like a CC HE260 maybe a little
bigger. Can’t remember. But night and day. Car performed well. A lesson was learned the hard way that you need to match your cam to your motor, tranny and rear gear ratio. As mentioned, different heads will open up options.
08-04-2023, 04:35 PM
Aftermarket Camshafts
