Anyone know the specs on the L-68 427 engine? I'm really looking for the cam specs, mains (2or4 bolt?) Just general info. I havent found anything on internet searches.

 

400hp427vette,

Let's start with the cylinder case (engine block), three different castings were used. 3935439, this is an early 427 casting used after January 1968, comes in 2 & 4 bolt main configuration. Listed as 2 bolt for 390 hp, I would suspect it also to be for 400 hp application. 3955270 is second casting used from August 1968 thru Oct 1968, also comes in 2 & 4 bolt main configuration. Listed as 2 bolt for 390 hp, I would suspect this to apply to 400 hp application. 3963512 casting used from Oct 1968 thru end of production in Dec 1969 for your model year. Listed as 2 & 4 bolt main configuration. Listed as 2 bolt for 390 hp, I would again believe this to be true for 400 hp application.

Cylinder head, possibly two different castings used, most common one is 3931063, valve size 2.06 intake diameter, 1.72 exhaust diameter. Combustion chamber is 100.96 cc's, a closed chamber design with oval intake port shape, and larger spark plug seat. Second possible casting is 3964290, this casting is identical to the above, but uses a smaller tapered spark plug seat.

Crankshafts, the 427 is basically the same as 396/402, however it is heavier due to a different counterweight design to balance heavier pistons. All 1966/1967 cranshafts were forged, however for 1968 and 1969 only special high performance engines used forged crankshafts, all other high performance engines were equipped with a cast iron unit. HP engines were 385hp, 390hp & 400hp. SHP were 425hp, 430hp & 435hp. Stroke was 3.76 inches, rod journal was 2.20 inches.

Connecting Rods, four different designs used during production from 1965 thru 1974. 390hp, 400hp 427cid use a forged steel piece with 3/8ths knurled-shank rod bolt with pressed pin design. SHP 427's used a stronger second design rod, identified with a single bump on each side of the rod beam with a stronger design at the crankshaft end of the rod, it also uses a 3/8ths rod bolt, with a higher P.S.I. rating.

Camshafts, there are two different casting & part numbers for the 390hp/400hp camshaft, both have identical specifications, but the 1968 cam has a different part # than the 1969. 1968 part no. is 3904359, and casting # is 3904364. 1969 part # is 3883986 and casting # is 3883944. Both camshafts are a hydraulic design, with intake lift @ .461 inch, exhaust lift @ .480 inch, intake duration 350 degrees, exhaust duration 352 degrees. I don't have the overlap or lobe separation specifications at this time.

Crankshaft harmonic balancers, 427 engines used 3 different ones. 390hp/400hp engines used a 7 inch unit. 425hp/435hp use an 8 inch unit and 430hp L-88, ZL-1 use a special 8 inch design.

Pistons are usually of two varieties, low performance 427 engines, ie: 385hp, 390hp, 400hp are a cast aluminum design, while 425hp, 430hp & 435hp are an impact extruded design of aluminum forging.

Hope this helps answer some of your concerns.

 

great info earlyshark

From the GMPP catalog, the cam specs are
.461/.480 lift
214/218 dur
115 LSA

same cam also used in the 70-72 454 LS5

 

Thanks a million that is the exact info I was looking for

 

Is it a fact, that the L-68 (427/400) has a 2-bolt-block - or just your meaning?

There are statements, that the L-68 ist a 4-bolt.

I would like to know, what's definitely the true fact.

Could anyone help?

Sir-Tripower

 

For future reference.

http://www.gmheritagecenter.com/gm-h...tion-kits.html

 

Thanks for thelink - but I couln't find any answer to my question

Gerrit

 

The 390 and 400 HP motors both have 2 bolt mains. The difference between the two is the intake manifold/carb set up.

 

my 69 has a 512 2 bolt main block