I think I have a pretty normal setup... Notice chainfall for pulling engines - no cherry picker. Prior to the chainfall, I used a come-along. No need for fancy equiment to pull an engine out of a Vette, but you have to have some beer on tap:




Just a come-along and a chain is all that's needed:


Installing a cam correctly means you need to check it and correct it. Here I'm degreeing a cam for an L79 327. I wouldn't consider doing this with the engine in the car - that would be a truly horrible experience:

 

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...

 

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!

 

With only 60k on the engine I wouldnt even be messing with the l82 cam personally. The low hanging fruit here would be higher compression modern heads and a better flowing exhaust and intake.. sure you can get more from a bigger cam or advancing the existing cam but its not going to make as much difference here than if you had an l 48 cam. in fact depending on what gears and transmission setup you have more cam might not give you the results you want with your combo. I swapped to 3.55 gears and an overdrive trans with a stronger first gear because it restores the low end torque the bigger cams give up..

 

I agree 100% from someone who has owned an originally bone stock 78 L-82 4 speed for over 43 years. I did all of what was discussed over the years in this thread to the OEM L-82 from removing the pan cake cat, first using a "test" pipe in 1983, eventually deleting all the emissions garbage that choked the engine, free flowing OEM turbo style mufflers, true dual 2.5 inch dual pipes, Monza Turbo mufflers, shorty headers, performance timing, etc etc. The best the motor achieved with 65,000 miles on it on the dyno was 233 RWHP (guessing around 275 Net HP versus the factory 225 Net HP) as a stock motor with the 887 cast iron heads and the OEM L-82 cam. Was it a BIG improvement over how the car ran when totally stock from the factory? Absolutely!

Is there any comparison to the rebuilt L-82 355 described earlier? NONE! The AFR 180 64 CC heads, Howards Roller Cam .(525 lift/219/225 duration/LSA 110 ) and 10.2 compression, completely wrecks the power of the OEM L-82. Different league than the factory L-46/L-79, or L-82. Depends on what you are looking to achieve, stock GM gross HP or a factory look with seriously BIG HP/TQ.

 

I did this over the summer, in the car, my hammies were sore for a couple days. But glad I did, I had to retard a new cam 2 degrees to get it to match the cam card.

 

Interesting - I degreed mine on an engine stand and had to retard 2 degrees as well. Always need to check.

 

I might have done the same if I had a beam across my garage. The 2x4s that make up the trusses would not have supported a chainfall. The gantry crane certainly does, though, and it can be moved with the load suspended (useful if the car is on jackstands). However it works! Get the engine out, and on a stand.

 

Keep in mind most cam grinders often grind 4 degrees of
Advance in there cams. GM on thier performance grinds grind in 0 degrees advance. That is why it will likely be of benefit to advance your stock cam.

 

JBL82 is 100% on target!
His free flowing L82 explains the difference between RWHP (233), Net Crank HP (~275), and old school Gross dyno crank HP (~335HP). That configuration is basically an old-school 350HP L46 with slightly lower compression, not 11:1. Then the top-of the line AFR 180 heads added another 50-70 HP and the HR cam some more also, so now he has near ~425+HP Gross HP. Anyone with an L82 could easily follow his recipe. That L82 engine is a very strong foundation. It is just dying to breathe!

 

This is a great thread and got me thinking about the 78 Indy Corvette that paced the Indy 500 in 1978. Several modifications were made to the workhorse of the four upgraded for track performance. Flat-top pistons were used with the L82 cam (GM# 3896962 was selected over the 3863151) for the higher RPM power with intake and exhaust restrictions removed. Angle-plug heads were substituted in place of the stock L-82 heads but retained the L-82 valves. Along with some slight milling of the heads, added 15 hp.

But the biggest gains, as reported by many above, was opening up the exhaust, removing the cat and installing 2 1/2 dual pipes...added 20 -hp increase. Using low-restriction mufflers and tailpipes added another 25 hp. The changes increased the 78 L82 from its stock 220 hp to 300 hp. The engine designers wanted the Pace Car to come off turn four at 125 mph so it would be out of the way when the racers accelerated toward the start line. The modifications were reported by Hot Rod magazine in May 1978.

 

Great feedback!
300net HP in that configuration would be around ~355 gross HP , with stock heads.

Add the excellent AFR heads and you add somewhere between 50 & 70 HP. So ~410 gross HP
Add JBL82s HR cam and gain a few more, ~430 gross HP.

Quite a bit different than the original motors ~225 net / ~265 gross HP !

Here is the original GM LT-1 HP, rated both ways in 1971. 275 net/ 330 gross HP
You can see how much better an L82 can be, even than this well regarded, but stock engine.
The L82 starts only around ~10 HP shy of the LT-1, given equal exhaust.

 

You guys are absolutely great! Thank you for all of your insight and knowledge! I will be back with a lot more questions but I think I see my path to 400hp very clearly.
Thanks again

 

That's super interesting because my 1st Corvette was a Brandshatch Green LT-1.

 

Hey I got a forum question. Why can't I see the graph that you have in the original posting? I can see it when I reply though.

 

Be advised:
Unfortunately, there is No Linear relationship between SAE Gross and SAE Net power ratings; there never has been. Any such relationship cannot be calculated.
At Best; Only educated guesstimates.

MOST Engine Dynos operated by local shops and by boy racer TV shows, do report power ratings in terms of SAE Gross.
Both Measurement and Reporting in terms of SAE Net is Far more complicated.

Moreover. the differences between example A Gross v. Net, are Not directly applicable to example B.

FWIW: MOST power ratings for Performance Crate Motors that're advertised in catalogs and on-line ad copy are presented in terms of SAE Gross.

FYI: If IF you download the vehicle info kits from GM History Archives (free download) there are usually power graphs shown as well as in tabular format.
Some graphs were archived w/ more crisp resolution than others.

 

So true.
Conversions are only an approximate. ( ~ )
Gross HP is repeatable on a dyno.
That is why most use it.
Net HP is as installed in the car, with all accessories, water pump, ps, ac, air cleaner and factory exhaust system in place.
Accessories can vary between car 1 and car 2,. In particular High Performance engines are hit hard by factory exhaust and mufflers. The bigger the cam overlap, the more exhaust restriction hurts.
Duntov said the factory "quiet" mufflers alone cost 50 HP on a 70 BB.
Very few test engines both ways.
HP conversions can run anywhere from 75% to 85%.
Even in the GM data above, the conversion varies by engine.
L48 = 78% Net to Gross
LT-1 = 83%
LS5 = 78%
LS6 = 76%
Any conversion % you pick is just going to be a reasonable estimate.
The biggest issue I see in the data above is how well matched the exhaust system is to the engine.
The LT-1 does relatively well with the BB 2-1/2" exhaust system.
The same system, with a LS5 or LS6 chokes it relatively more on net HP.
All the little things we do, like headers, air cleaner, exhaust dia and mufflers, help the net HP up and bring it closer to the gross HP.

 

My description of the lack of equivalences and linearity between Gross and Net; try as you might, it cannot be explained away. It simply IS and it exists.
Oh, my goodness, I've run countless comparisons over many years ad nauseam, looking for some magic insight; the hole only gets deeper.

 

Gross HP is measured at the crank, on an engine dyno, headers, no air cleaner, carb & distributor at optimum settings
Net HP is measured at the crank, on an engine dyno, but with stock manifolds, air cleaner, full factory exhaust system, all accessories and factory carb & ignition timing settings. Exactly as installed in the car.

Almost everything listed under net HP can easily change from car 1 to car 2, because so much of it is external to the engine.
And factory carb & distributor timing settings are not set for maximum power. They are normally too lean and too retarded, both for emissions and just being conservative for warranty.

Using 80% for a net to gross HP conversion will almost always get you within +/- 5% of the real number.
That's pretty decent for a ball park.
That would be within +/- 20HP on a 400HP engine.

But it'll never be perfect.
Trying to decide when you should use 76% and when you should use 83% is pretty fruitless.

I know of no one who runs dyno tests in Net HP terms, except the factory. And that is all they do now. They switched from Gross in 1972.
The aftermarket always dynos in Gross HP. As well they should. Everything outside the engine itself is car dependent.
Gross HP is like "Ultimate Potential" HP, if you don't lose any by putting it in the car. And if you could re-create dyno room conditions in the car. Good luck with that!

So we need a way to compare those two rating systems, a way to bounce back and forth from net to gross. And a way to compare early 70 engines with late 70s.
Whether it is 100% accurate or not, it doesn't matter.
It's close.
Within 5%.
According to GM tests.
At least for musclecar era V8s.

 

Oh yes, accuracy does matter to me; perhaps others as well.
Again, how do you KNOW those percentage / reliability assertions ?

So long as everyone understand these sorts of figures are nothing more than guesstimates; fine.
But to consider them as more reliable than a guesstimate, borders on the disingenuous, sir.
How do you KNOW those assertions are reliable ? Can you assign a confidence level to same ? Neither can I; because this is an exercise in guesswork --- And in futility.