L82 Cam good enough
Burning Brakes
Joined: Nov 2012
Posts: 788
Likes: 100
From: Indianapolis IN
Damn good looking garage my friend! Nice collection too. Are we playing 'one of these things, doesn't belong here' from Sesame Street? lolol.
Currently I have a regular 2c garage in a subdivision outside Indy so ...I'd be scared the weight of the engine would pull the house down!! lol
Rest assure though...I will figure it out...
Currently I have a regular 2c garage in a subdivision outside Indy so ...I'd be scared the weight of the engine would pull the house down!! lol
Rest assure though...I will figure it out...
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,094
Likes: 4,449
From: Marlton NJ
I know those percentages because GM measured them both ways in 1971, as posted.
I am basing this on those four known good data points, that I trust.
I analyze data for a living.
This is actually simple.
But you have to keep in mind the boundaries. That I set for myself, that I may not have mentioned.
The internet quotes all sorts of numbers, but I do not pay any attention to them, unless the source is very good, like GM.
So it is your choice whether you want to believe GM or not.
But I would caution anyone not stretch that 80% (+/-5) net to gross HP conversion any further than typical 70s V8 stuff, and near stock at that.
No 4 cylinders, no 90+ LS stuff, no $1000 exhaust systems, It just won't be right. Too many other parameters change.
I am basing this on those four known good data points, that I trust.
I analyze data for a living.
This is actually simple.
But you have to keep in mind the boundaries. That I set for myself, that I may not have mentioned.
The internet quotes all sorts of numbers, but I do not pay any attention to them, unless the source is very good, like GM.
So it is your choice whether you want to believe GM or not.
But I would caution anyone not stretch that 80% (+/-5) net to gross HP conversion any further than typical 70s V8 stuff, and near stock at that.
No 4 cylinders, no 90+ LS stuff, no $1000 exhaust systems, It just won't be right. Too many other parameters change.
Drifting
Joined: Jun 2025
Posts: 1,723
Likes: 599
As both a QE & QMgr in Tier 1 and Tier 2 manufacturing, I too analyzed data & measurements for a living. That's one means by which I've learned to determine & KNOW what's valid and what's not. The above are, at best, guesstimates; nothing more. If that floats your engine-building boat, fine. But not for me, sir.
Drifting
Joined: Jun 2025
Posts: 1,723
Likes: 599
Oh, I trust implicitly the oft-quoted and credible MY1971 Gross + Net power ratings. Those are Not guesstimates; Not At All.
OTOH, it is Yours & others' guessimates, somehow or another extrapolated from that credible data, that I have taken issue with; and will continue to do so.
OTOH, it is Yours & others' guessimates, somehow or another extrapolated from that credible data, that I have taken issue with; and will continue to do so.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
I'm shakin' up a fresh Martini and moving on.
OP: If you need assistance or info, just send me an e-mail.
Lars
Drifting
Joined: Jun 2025
Posts: 1,723
Likes: 599
And I prefer a more modern design than a 962. I'd ask Jones for his recommendation. Did you ever repair your distributor machine ?
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
The cam is a great street cam. Providing it does not have a flat lobe.
The #1 thing I would do first is put real dual exhaust on it, headers, and magnaflows. Worth 50+HP. BTDT on my 75. Ran like a different car. Those early cats were awful for HP. But it depends on inspections in your area....
#2nd thing I would do is change the heads. New ones offer MUCH better airflow, and a CR increase besides.
You get what you pay for here. AFRs are the best, many others are pretty good. You can get 50+HP out of a set of good heads vs stock.
That'll put you around 400HP.
The new heads are that much better than 70s ones, and if you get close to 10.5CR you basically have a 350HP L46 with much better heads on it!
An L82 is a really good strong base for a great strong street SBC. The "Bones" are great. It is just crying out for the above two mods!
The #1 thing I would do first is put real dual exhaust on it, headers, and magnaflows. Worth 50+HP. BTDT on my 75. Ran like a different car. Those early cats were awful for HP. But it depends on inspections in your area....
#2nd thing I would do is change the heads. New ones offer MUCH better airflow, and a CR increase besides.
You get what you pay for here. AFRs are the best, many others are pretty good. You can get 50+HP out of a set of good heads vs stock.
That'll put you around 400HP.
The new heads are that much better than 70s ones, and if you get close to 10.5CR you basically have a 350HP L46 with much better heads on it!
An L82 is a really good strong base for a great strong street SBC. The "Bones" are great. It is just crying out for the above two mods!
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Le Mans Master
Joined: Oct 2010
Posts: 6,937
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
If you are adding headers and a good set of heads the factory.intakr.is an obstruction and should be changed to optimize the combination. Either a quadrajet or properly sized Holley carb would work well.. the only real drawback to as quadrajet is do you have a solid dependable core or are you going to have to search for one. I have a Holley and wouldn't change it
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Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,094
Likes: 4,449
From: Marlton NJ
And yes I would keep the q-jet.
The free-flow exhaust may mean it needs a jet change, but they will easily have better street manners and mpg than a Holley. Just not "anyone" knows how to tune it tho.
As mentioned, if you can sneak a better intake under your hood, that would help too, but it's tight.
If you just want to change the cam, you could, but anything with similar street manners is not going to add much HP.
Less duration may even give you more TQ under 3000, ideal for street.
But basically, yeah, a L82 cam is more than "good enough".
Your low hanging HP fruit is elsewhere.
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Pretty close!
And yes I would keep the q-jet.
The free-flow exhaust may mean it needs a jet change, but they will easily have better street manners and mpg than a Holley. Just not "anyone" knows how to tune it tho.
As mentioned, if you can sneak a better intake under your hood, that would help too, but it's tight.
If you just want to change the cam, you could, but anything with similar street manners is not going to add much HP.
Less duration may even give you more TQ under 3000, ideal for street.
But basically, yeah, a L82 cam is more than "good enough".
Your low hanging HP fruit is elsewhere.
And yes I would keep the q-jet.
The free-flow exhaust may mean it needs a jet change, but they will easily have better street manners and mpg than a Holley. Just not "anyone" knows how to tune it tho.
As mentioned, if you can sneak a better intake under your hood, that would help too, but it's tight.
If you just want to change the cam, you could, but anything with similar street manners is not going to add much HP.
Less duration may even give you more TQ under 3000, ideal for street.
But basically, yeah, a L82 cam is more than "good enough".
Your low hanging HP fruit is elsewhere.
Melting Slicks
Joined: Apr 2021
Posts: 2,716
Likes: 2,163
From: Minnesota
Le Mans Master
Joined: Oct 2010
Posts: 6,937
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
I have used 1.6 roller rocker with that cam and it worked very well. Roller rockers are a good addition as the factory stamped steel rockers almost never measure out to 1.5
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Would those fit under my stock valve covers? I hate going with the taller ones. They sometimes interfere with AC compressors and Alternator brackets.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,094
Likes: 4,449
From: Marlton NJ
You could use Stainless Rockers.They are much smaller than the aluminum ones. The ones from Liberty Performance are good enough for racers and not all that expensive. They fit under my own bb covers.
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Burning Brakes
Joined: Oct 2001
Posts: 842
Likes: 3
From: Woodruff SC
St. Jude Donor '10
Sick L48
I've been reading thru this post and wondering if there's any hope for doing something to my L48 in my 77? It's mostly stock except for aluminum intake, rebuilt Q-Jet, headers, true dual chambered exhaust, and Lars' distributor weights and springs, 3:70 rear gear, Rebuilt Turbo 350 trans. Yes that helped but, we all want more! I'm thinking different cam and maybe heads but, the L48 is more of a base engine than the L82 so I'm not sure if there's any hope! I just don't want to drain the bank. Any suggestions are appreciated! Dan
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Comp cams 270H and Sportsman II heads got me over 300HP. The flat tappet cam is /was the biggest cam you could use with everything else stock. Then add an AirGap dual intake and a Classic 4779 Holley and it will make considerably more HP. Now you are digging into the engine and using flat top pistons with a steel shim gasket to get the compression up to 10:1+cr.
HP costs money, no way around it
HP costs money, no way around it