I’ve got a 73 and I’m looking to build a L46 to replace the L48 does anyone know where to find the complete engine specs I found cylinder head casting and block casting numbers and a couple numbers for intakes but that’s it any other information is gladly appreciated

 

Download the GM Heritage Center's 1970 Corvette PDF. Near the end of the doc (starting on pg 92 as well as the AMA specs further in on pg 133) it will have full engine specs for the L46. https://www.gm.com/content/dam/compa...t-Corvette.pdf

https://www.gm.com/heritage/archive/...formation-kits

 

Thank you that helps a ton

 

If you are wanting to build a true L46 they had a fair number of parts that made them unique.
Factory forged steel crank (1182 cast number)
Pink or heavy duty rods. Most of these rods with the pink paint long gone had an "O" cast into the cap.
Factory windage tray.
Forged doomed TRW pistons.
8" harmonic balancer and timing cover to match
All deep groove belt pulleys
There were 3 different block cast numbers in 1969. 3932386 3956618 and 3970010. The 3970010 carried over into all of 1970. All were unique 4 bolt nodular mid mains.(2482 cast number on the mains).
Heads were closed chamber with 2.02 intake valves and 1.60 exhaust valves. The most common cast number was "186". Early heads had pressed studs, later had screw-in with guide plates
3927184 iron intake for 1969 paired with 7029207 Quadrajet
3955667 iron intake for 1970 paired with 7040207 Quadrajet
The L46 engine to my knowledge were only paired with a manual 4 speed transmission. There are many others on this forum that can add or correct any mistakes I have made.
Good luck,
Norm

 

I appreciate the info I plan on making it as true to form as I possibly can I want to keep my car looking stock and the L48 and L82 are sub standard performance. I’ve picked up a 3970010 block and a forged steel crank and recently picked up a set of pink rods. I have full intention on finding a set of 186 heads research I’ve seen on the heads is murky I’ve found some people saying that they used492 casting on some engines both had 64 cc cambers and 2.02 1.60 valves I don’t know if that’s true. I also plan on using a cast iron intake and a Quadrajet. Pistons though I’ll probably use aftermarket as close to factory as possible I have not found anything marked LT1 yet. Any other numbers that you may have would be helpful. My car is Automatic and yes you are right all l46 cars were 4spds

 

If the engine is not original to the car....I wouldn't spend the time or the money to build a spec L46 350......which is basically a high compression L-82......Intake, Camshaft, Block, Crank, Rods, but the heads had a 64cc chamber.....either one is a bit of a turd out of the hole with an automatic.....the L-82 is about 25 horsepower shy of the L-46 with the almost the same torque and powerband.
Last year I built a 357ci small block that had 10.5 to 1....Trick Flow DH175 heads....(with the camel back humps cast into the head) which were painted orange along with the Edelbrock EPS intake.....it threw 340 to the tire and looked stock from 5 feet away.....one ride through the gears and you wouldn't think about an L46 again......we ran the L46, L82, LT-1 valve covers and the 650 Holley DP carb had a big 14 inch air cleaner over it along with the original L46 fuel line/filter setup going to it.....it is sneaky.....even the idle is sneaky......one could build this with a 2101 Performer and a nice Q-jet and it would make the same power if tuned right......
Its the heads that are the big deal......if you going to spend $2000 on a pair of GM 186 heads then why wouldn't you put something on it that is better in every aspect for the money? The newer head is lighter, flows 25% better and has a super efficient chamber that allows you to run high compression on pump gas.....win-win....
Of course, you can do what you like......it is just my spin as I am an engine builder......power and efficiency are the name of my game.....you can enhance a Gen 1 small block to make a lot more these days with no negatives.

Jebby

 

Pistons I bought were I believe SRP SKU: 206040 They are nice pieces.
I built the motor a while back but never fired it up. Sits on the stand in my shop for now. Cam in there would need to be changed, but no biggie. Has LT-1 aluminum intake on it now.

I also have extra original L46 heads ready to go if you need some.

 

Yes, I agree with regard to the confusion of other head cast numbers used however, regardless of cast number if they have the small camel humps with accessory holes, and the large valves they will be correct. I have a 1969 with the L46 and I run a 2 valve relief flat top Wiseco forged piston. They are much lighter than the original TRW and the lower compression makes them pump gas friendly. Jebby is correct with regard to being sluggish out of the hole with an automatic. He can probably help you with a cam selection that will help get the car moving better off the line. Its all subjective to expectations and opinions as for whats the best way to go. The original parts and setup from GM made a fantastic performer. It certainly does not compare with 50 years of advances in performance parts available today but not everyone has the same goal in mind. I currently run aluminum heads, intake, more modern cam design, and headers. All hidden with orange paint looking very factory. I have my original heads, intake and exhaust manifolds stored away. The next owner may have a different vision for the car and want the nostalgia of the more original L46 under the hood.

 

The L46 is 140 hp more than a L82 and my whole point is to keep it looking stock I want to keep manifolds and the Qjet

 

Any reason not to fix this issue first, or at the same time?

BTW, don't be fooled by the HP numbers quoted. There is not a huge difference between the L46 and the L82, just the manner of testing. Headers and a tune should more than make up for this difference. If you do choose to stick with manifolds, why not find a set of 2 1/2" collector manifolds? They will still look stock to the untrained eye, and should flow a bit better.

Here's one of many threads on the subject of changing reference systems.

https://www.corvetteforum.com/forums...sus-today.html

 

I get that in 72 and up the hp rating drastically changed it changed due to fuel consumption policies and slowly introducing emissions restrictions. The L46 and L82 used almost identical camshaft that’s where it ends. The L46 has different heads, pistons , intake carb. There’s Dyno sheets that show what these engines produce. You’re not gaining a 100 hp with a tune and manifolds not on a carbureted car. I’ve driven a 70 with a stock LT1 and driven plenty of 73 and newer L82 cars the L82 runs ok but it can’t hang with the early C3’s

 

It had 1.25 to 1 more compression (measured) and a chamber that was 12cc smaller.....the carb and intake were the same POS and the heads still flowed 205-210cfm.....

L-82 through headers makes 325hp on an engine dyno...L46 makes about 340 thanks to the **** intake.

There is very little difference....other than compression ratio, the two engines are almost identical......

LT-1 felt faster but barely made more than the L46 at 355hp.....this is no matter if you have the low or high compression version.....

The later L-82 might not be able to "hang"....but not like you are saying....
I've driven all of these cars too.....all that "pre-smog" is a placebo.....I have also dyno'd a lot of "spec" GM small blocks....most all of the history back then was BS.....

Most all had crap intakes and crap heads.....they all were machined very quickly and it was 50+ years ago.....

Jebby

 

If you keep the manifolds and Q-Jet don't waste your money....you will not make anymore power replicating a L46.....
the L-46 did not make 140 more horsepower....it made about 30 more on an engine dyno.....

Only way you will make any power with these engines is with bowl blending the heads....a real intake and at least the 64-65 2.5" exhaust manifolds....and that is a fact.

The last thing to consider is that a real, to the nut L46 will not run on pump gas.......so to drive it, you spend $7+ a gallon for fuel......

Jebby