I thought the L-46 cam specs were: 222/222 .444/.444
Can someone verify...?

Anyway, I had an L-46 in my 69 vert until it exploded. It certainly was no dog combined with 3.70's gears and an M-21 close ratio trans. I've never driven an Lt-1 so can't comment on the differences.

 

factory spec'd at 346/340. measured at .008 lift- 284/278. Either way the lift is 0.45/0.46

I checked mine at .050 when I rebuilt.I'd have up dig out the info , but your 222 seems about right.

 

HDIRONMAN,i agree the L-46 is no slouch.My 69 vert was fast as hell and very responsive.

 

I have always respected the early 70's LT-1

Anyone know of a web link with all the info? part numbers , specs, etc...

Thanks

 

L46-350cid\350hp Specifications (still in draft)

RPO L46 = 350cid\350hp (Hi Per V8)

Brake horsepower: * 350 hp (261 kW) @ 5600 RPM (See note 1)

Torque: * 380 lb-ft @ 3800 RPM

Bottom end: + Good for 6500K RPM

Block: ** 4-bolt main, +++ #3970010 (+ possibly high Nickel/Tin content
Iron 010/020 numbers under timing cover and other locations)

Camshaft: * Hydraulic Flat Tappet (See note 2)

Valve lifters: * Flat Tappet - Hydraulic

Compression ratio: * 11.0:1

Heads: ** 2.02\1.6 Valves (See note 3)

Crankshaft: ** Forged steel (See note 4)

Rods: ** Hardened "pink" rods (See note 5)

Pistons: ** TRW domed, forged, and pressed pins (See note 6)

Oil pan: + Windage tray

Harmonic Balancer: +++ 8” non-finned, 6 ¼” Hub, 8” diameter, 1 ¾” thick

Intake Manifold: * Cast Iron Spread bore (See note 7)

Carburetor: * Quadrajet, 4-bbl (See note 8)

Exhaust: ** 2" Exhaust pipe with Walker mufflers

Exhaust Manifolds: ** RH - #3932465
++ ** LH - #3846559

Tachometer: * 6000-RPM Redline

Air Filter: ** Open element air filter (Early), Dual Snorkel (Late)

Water Pump: ** #3782608



Ignition: + Distributor w\points & HP curve
** #1111491
** #1111493
** #1112021

Alternator: ** #1100900

Transmission: ** Main case #3925661, Extension Housing #3857584, Side
#3952648 (Right side of maincase, just in front of extension
housing)

Rear End: **** CAM=3.36:1
**** CAT=3.08:1

Radiator: **+ Copper with plastic fan shroud and no overflow tank.

Console Data Plate: * 350cid, 350hp, 380 lb-ft Torque (L46)

Valve Covers: ** Aluminum, 7-finned, with twist on cap and each side vents

Notes:

1. + A 1966 L79 (327/350hp) with a fresh stock rebuild run on a chassis dyno, and his best was 238 hp at the rear wheels.

2. * Part Number 3896962, Hydraulic, 69-81 L-46 and L-82 Corvette cam, moderate torque, excellent power, casting #3896964. The casting symbol is a vertical diamond.

* Duration at lash point: (I:312\E:312)
* Duration at .050” Tappet Lift: (I:222\E:222)
* Maximum Lift with 1.5:1 Rocker Ratio: (I:.450”\E:460”)
* Valve Lash: Zero\Zero
* Lobe Centerlines: 114

3. Heads – ** 300hp engines did not get screw in studs or guide plates, 350 hp did.

** Casting #3927186, 63.305cc combustion chamber. 2.02 Heads got screw in studs, and guide plates. Casting #3991492 may appear on this part after 4/5/71. Casting #3947041 head was possibly used interchangeable with this head through 1969 and 1970 production. Small camel humps casting symbol.

** Casting #3927187, 63.305cc combustion chamber. Casting #3927186 may appear on this part until 10/9/70. After this date #3991492 may appear. Casting #3947041 head was possibly used interchangeable with this head through 1969 and 1970 production. All #3927187 heads have 2.02\1.60 valves. Casting symbol is small camel humps.

** Casting #3947041, 63.995 or 63.305 combustion chamber. 1970 had 2.02/1.60 valves, used as interchange on some models with #3927186 and 3927187 heads. Casting symbol is a slanted triangle.

+ The 69 L46's had pressed in rocker studs while the 1970 and later L46's and LT1's got the better screw in variety. 1970 did not get push rod guide plates. Uses steel shim head gasket.

+ Heads have machined combustion chamber relief (un-shrouded) for flow and 2.02/1.6 valves, pressed in rocker studs.

+ There were no screw-in studs on anything before 1970 so they were not a requirement for the 69 L-46 in the original configuration. Might have been used in '70 and up though as they are included with L-82 for sure. It just makes sense that they would be included during L-46 production for '70 and up. Not a big deal as they are easy to add.

+ The factory 64cc heads such as the "186" that have the big valves (from the factory) will definitely have the chamber un-shrouding where the small valve versions of the same head casting will not. The later smog open chamber heads do not have un-shrouded chambers.

4. ***** Large journal (2.10"\2.450"), stroke 3.484, casting number 3941182 or **3941188.

5. ** Rods are forged, shot-peened, magnafluxed, and heat treated to 500 degrees for ten or more hours Introduced in 1970 as a pressed-pin design with large rod diameter journal and high-rpm rod bolts used in the 302cid.

6. + Part numbers are stamped into the top. Standard piston is 3942541, the +.001 was GM #3942542, and the +.030 was GM #3942543.

7. ** Large raised letter S on underside, and oil splash shield, casting #3965577

8. ** 1969, Model 4MV, 7029207, ST
** 1970, Model 4MV, 7040207, ST non-CA
** 1970, Model 4MV, 7040507, ST-CA

* Source = GMC
** Source = Corvettes by the numbers
*** Source = Corvette Black Book
**** Source = 1970 Corvette Registry
***** Source = Mortec.com

+ Quote from Corvette Forum member
++ Source = NastyZ28.com
+++ Source = Chevrolet Small-block V8 Guide
++++ Unverified

 

Sorry if this is a stupid question, but what is the main limiting factor with redline for L-46 @ 6,000prms vs. LT-1 @ 6,500rpms? Is there extra safety margin in the L-46 redline being set at the lower redline? I have a 69 L-46 that I recently purchased with a non-documented totally rebuilt 10,000 miles ago L-46 except for the fact it was supposed rebuilt with the best of parts available and compression lowered to 9.5:1. Can I safely run above 6,000rpms? All I know is the car moves really fast.

 

Camshaft and stiffer valve springs.

 

Not sure but valve float (with hydraulic lifters) may have been a factor on the L-46 and not the LT-1.

 

Good info. 70 didn't have screw in rocker studs though

 

The difference in top RPM is just a combination of the different parts used, i.e., better flowing intake, solid lifters, and larger cam, stiffer springs, guide plates... The LT-1 was designed to rev higher...

Audie

 

When I bought my '69, it had a '70 LT-1 in it with angle plug heads. Were these not the correct heads for the engine?

 

I'm confused I have a 69 350/350 Hi Performance L-46 Everything power and my tach says 7000 rpm's?? My heads are stock 63CC 202 4bolt main. Also they are 3927186 L28 heads with pressed in studs (stock). So someone's info is wrong? Car was manf. in late Dec. of 69

 

Wow!!! I love this thread. Lets see... your heads should be 64cc.(type-o)? Whats the red line on your tach?look like this one?




Guessing on your 186 heads that L28 is the date code.(Dec.2 1968). I think I'll still go with that head not having screw in studs. Added? Or I could be completely wrong.

 

I believe the angle plug heads were only available over the counter.

Rich

 

Yes thats it

 

Ok your tach is correct.

Now that build date you stated is a year later than that head date. Whats the vin number?

 

Vin Number is 194379S738501

 

69 vin numbers started with700001 and ended with 738762. I would say that puts your coupe toward the end of the production run. So your correct there.

Whats the date code on the other head?

 

Regarding the screw in studs:

I had a first day production '70 L46 roadster (#131). I was 2nd owner. It was an original, unmolested engine except for the Moroso valve covers and air cleaner and the alternator had been replaced. This engine even had the VIN stamp by the oil filter, rather than on the pad, as was done in the first few days of '70 production.

When Steve LuVisi of Automotive Expertise had the car, he asked if I had replaced the heads. I asked why and he replied that it had push in studs and that GM was extremely proud of the screw-in studs used in the 2.02 heads. I replied that all numbers checked out (he knew that) and there was no reason to belive that the lady who owned the car before me would have changed them. I even met and talked with the lady and she had very little work ever done on the car.

BTW, the engine also had the '69 balancer.

 

[QUOTE=toddalin]Regarding the screw in studs:

I had a first day production '70 L46 roadster (#131). I was 2nd owner. It was an original, unmolested engine except for the Moroso valve covers and air cleaner and the alternator had been replaced. This engine even had the VIN stamp by the oil filter, rather than on the pad, as was done in the first few days of '70 production.
QUOTE]

Todd,

Think we can agree on the press in studs. As for that vin location, thats a new one on me. Where was the engine code located? Your car,( donnybrook conv), was a top flight no?