Is the only difference between an L82 and an L48 the engine? Is the suspension, transmission, fuel capacity, etc, etc, etc the same?

 

same-same

 

So, if I just change the engine to a crate engine w/300hp, then it's now an L82????? Just curious......

 

No, it's still an L48 with a NOM crate engine................

 

There are internal differences to the engines,the L 82 is the high performance engine of its day,a four bolt main engine block, performance cam,larger valves for the heads as compared to the two bolt main engine block,milder cam,smaller valves of the L 48. As mentioned by Mike as far as installation it is all the same.

 

The L82 itself changed over the years and was rated different hp nearly each year. The earler (70s) L82's made more hp due to more compression and better heads than the later (70s) L82's - detuning for smog didn' help power either. But they all used the same camshaft - called the 962. I recall chevy started using that 962 cam in 69 making like 350hp in thier smaller 327. This is a healthy hydralic camshaft that is still used today in the GM HO 350 motor but combined with vortec heads making 330hp. It shows that just increasing compression and better breathing heads will work great with that camshaft - no reason to replace the 962 cam unless its worn out (> 135k mi).
Your 300hp crate engine may well have this cam but i don't know which heads unless u provide the casting number. I suspect the early HO 350 engine used this L82 962 cam but had the L98 iron heads as found on '85 corvette.
Regardless your 300hp crate engine is very similar to the L82 engine, uses the came 962 cam and probly faster than most L82s too. The later L82's had the worst heads with open chamber thin castings - u could only improve them by replacing them with nearly any other chevy sb head.
Nice knowing that chevy cylinder head casting numbers are under the vavle covers and the only markings are cast on front of the cylinder head. Soo not many will know wether u have the smog head or some real performace heads.
I gues what i'm trying to say here is GM sold alot of similar 350 engines to L82 but they all had the 962 cam. Major difference is the cylinder heads.
Hope this helps more than it hurts,
cardo0

 

The L-82 was only produced by GM from 73-80, there is no L-82 engine prior to 1973. The 1971/1972 engines were either called the base engine or the optional LT-1. As has been discussed before, the HP ratings of all these engines changed in 1972 from a gross HP rating to Net HP rating so the comparison of HP ratings prior to 1972 to the 73-80 HP ratings of the L-82 are not accurate by just looking at the numbers. For example a 71 LT-1 was rated at 330 Gross HP with a 9:1 compression and the exact same motor in 1972 was Net rated at 255 at the exact same RPM (5,600 RPM). These 2 engines are pretty much the same motors.


As stated above, the engine internals of the L-82 are fairly different for the L-82 versus the base engine L-48 which was just a run of the mill GM passenger car engine.
The 73-80 L-82 are almost the exact same motors internally, heads, valves, aluminum intake, cranks, pistons, etc-The BIG difference and the major reason for the HP changes from year to year are the exhaust system configurations, the mufflers, and the smog gear which got progressively worse as the decade progressed. A 1974 L-82 with true duals rated at 250 Net HP is the same motor as my 78 L-82 rated at 220 HP with the horrible 2 into 1 into 2 exhaust with very restrictive mufflers and a VERY restrictive cat. The only change in 1979 to the L-82's was less restrictive mufflers and the rating changed to 225 HP. In 1980, the roughly 5,000 L-82's that were made that year (auto only) added tubular exhaust manifolds and a slightly different exhaust configuration-presto 230 HP!

Change the intake and the general air induction as well as headers of some sort, a 2.5 true dual exhaust, and free flowing mufflers of some type on the later L-82's, get rid of all the smog equipment and these engines are really no different than the early 70's low compression (not the 11:1) LT-1's. The differences are blown way out of proportion between these engines. The minor performance difference in cars so equipped if they have the same transmissions and gearing is the weight-the early 70's cars can be a couple of hundred pounds lighter.

2 examples-I Drove a friends 79 with a GM crate 300 HP engine but with an automatic and it was definitely slower than my 78 L-82 4 speed with 3.70 gears and setup as described above. Another example is a friends 71 LT-1 (330 Gross HP rating) with a 4 speed but not sure of the gears and his car feels VERY similiar to my 78 L-82 4 speed again setup as described above.

If you really want performance beyond an L-82 or even the low compression LT-1's, my recommendation would be the GM ZZ-4 crate engine rated at 355 HP which is Net HP versus the old LT-1's gross rating of 330/350/370 HP. The L-82's though are really a terrific engine for that time! They just need help breathing a little on the intake and definitely on the exhaust side.

Lastly, only the L-82 in 1978/1979 could come equipped with the 3.70 gears and only the L-82 in 78/79 came with the close ratio 4 speed. Even the wide ratio transmissions were different between the L-82 and the L-48 with the L-48 having a 2.85 first gear in the wide ratio versus a 2.65 first gear in the wide ratio box for the L-82's.

The suspension options and brakes are the same for both engines!

Hope that helps!

 

No, if your car came equipped with an L-48 it will NEVER be an L-82 car, as stated above it will simply be a L-48 car w/ non matching motor.

L-48 and L-82 are production option codes for the engine, they do not have any direct effect on anything else except to determine what optional gears or transmissions may be available.

 

If you own an L-48 car/engine forget about cloning parts for a L-82 engine.

With today's aftermarket heads, roller hardware, and stroker cranks, one could easily make 100-150 more HP vs. the L-82.

 

Ok i fixed the part number in my post #6 - in case u noticed the wrong cam number.:o BTW even the tiny 929 cam made 300hp in only 327 cubes to show what a difference heads and compression make in matching the camshaft. I have to emphasize here that the later smog heads were terrible - the combustion chambers dropped a lot of power and that is reflected in the hp ratings even though rating method changed. Yes that was "gross hp" but most of us install headers and performance intakes so older gross hp rating should be very similar to what we would produce. And u can see the hp drop significantly by '74 even though dual exhuast was still availible as stock.

The entry performance level engines are easy to make into fun builds without much $$$$ spent and are a great place to learn the skills we all need to go to higher po engines. Even a 300hp C3 should be fun to drive and can be made from any stock 350" with just junkyard used parts.

U can check your block casting number on many w/s to see what year it may or may match - #3970014 would be a good one for ya. BTW stamped numbers can always be restamped and there are plenty of '75 blocks still availible so u could take this as far as u want to go with it.

Good luck,
cardo0

 

Here are the specs for the 962 cam per an old Hot Rod mag article.
3896962 is or was the full number. I believe it was also used in the '69-'72 L45, the 350/350 engine
Duration at lash point
Intake 312°
Exhaust 312°

Duration at 0.050"
Intake 222°
Exhaust 222°

Max lift with 1.5:1 ratio rockers (inches)
Intake .450
Exhaust .460

Lobe center-line degrees
114°


Pete

 

Not really= '73 and up has the original engine type encoded into the VIN, so this car is forever identified as an L48. Nothing wrong with that.

 

that really depends. if you get technical, there were other options (like the different manual transmissions and rear gearing that was only available on the L82, etc), so technically, not really "same-same". admittedly and based upon the tone of the OP, i would say they probably don't come into play, but technically they aren't the same.

 

 

Yes,

You're right, I was think of earlier cars where there were fewer or no restrictions.

 

Also the aluminum intake disappeared from the lineup on the 350 in '73 and didn't return until 1978 on the L82. Some retrofitted them to the earlier engines, but the choke also changed in the mid 70's so the choke might have needed to be changed to work with the new manifold.

GUSTO