C3 - 1976 Cam/Engine Question

[Steve B.]

I own a 1976 Corvette L48, original engine. I currently have the engine removed and torn down to block only. I would like to install/upgrade the cam to a little more than stock (nothing crazy just a step up). Can anyone recommend a particular brand of cam that they've had success with? Also, as a general question as I put this engine back together does anyone have advice that might alert me to any issues? The engine had 87K miles on it and was generally in good shape. In speaking with a local machine shop they suggest that since I've gone this far I might as well have it bored, what do you think? Also, can anyone recommend a parts supplier they feel confident with? Lots of questions, I know, but as always, thanks for any advice/help supplied.

Steve Boyd
76 Coupe

[Duke W.]

Re: C3 - 1976 Cam/Engine Question

The 3996962 cam as used on the contemporaneous L-82 would be a good "upgrade", but go with the OEM cam if you plan on ever doing a PV as the idle quality of the 962 cam is noticeably different and will be automatic cause for failure. I generally recommend against aftermarket cams as they will kill a lot of low end torque due to their excess overlap. The Chevrolet OEM cams are best according to my engine simulation work, even though the designs are over 30 years old. They are also bulletproof with all the OEM or equivalent valvetrain components, which are readliy available and inexpensive.

The 962 cam will improve torque above 3000-3500 at some cost in low end torque. The 3863151 cam as used on the earlier SHP 327s is a bit milder and might be a better choice if you want to minimize loss of low end torque.

If you have an automatic transmission and 2.73 axle, I would recommend that you stick with the 929 cam. Whatever you do, pocket porting and port matching the heads with a careful three angle valve job will improve mid range and top end power in the range of five to ten percent with no loss of low end torque

The requirement for boring is a function of cylinder wall condition. You should carefully measure the cylinders for wear and taper and use this information to determine if a rebore is required. Whatever you do, DO NOT let a machine shock "deck" the block. If their boring equipement indexes of the deck, the deck can be measured for parallelism. A good way to do this is to measure piston crown to deck clearance prior to disassembly. If they are consistent down the line, the deck is likely parallel to the crankshaft centerline. Better shops have boring equipment that indexes off the crankshaft centerline, so deck parallelism is not an issue.

I would recommend you use OEM or equivalent parts such as those available from Federal Mogul. They can provide all the OEM equivalent parts you need for a rebuild including the above mentioned camshafts.

82K is really not much mileage for a SB. If you have not disassembled the block I would suggest measuring bore wear and making a decision as to whether a rebore is required. If not, leave it alone. The bearings will last easily three times the mileage on the engine.

Regarding the heads you want to research available methods to restore the valve guides. Valve guide wear and sealing is the usual cause of excess engine oil consumption.

Duke

[Dave Suesz]

My personal favorite...

is the 327/350hp cam, gives excellent all-around performance and should be a bolt-on replacement, requiring no other modifications.

I would avoid boring if the cylinders are in spec, boring will reduce the efficiency of your cooling, already a problem with Corvettes. Not to mention the machining and parts cost.

[Kenneth G.]

Re: C3 - 1976 Cam/Engine Question

i put the 327/350 cam in my 69 L46 rather than the L46 cam. I have the 3:55 axle with M20 4 speed. Can anyone advise me what the performance difference will be between the two. How will each perform theoretically if i had each one installed? stop light to stoplight acceleration vs 1/4 mile etc. I know this is a bit of "benchracing" but I hope I didnt make the wrong choice with the 327/350 cam. I would be more interested in low end torque rather than revving the motor up to 6 grand. T I A

Kenny #31871

[Duke W.]

Re: C3 - 1976 Cam/Engine Question

The 327/350 (L-79) cam will make a bit more low end torque than the L-46 cam at the expense of top end power so you made the correct choice based on your requirements.

The L-46 cam was a development of the L-79 cam. Longer stroke engines need a bit more duration to maintain the same torque peak, which is what the L-46 cam does in a 350.

Both cams have the same lobe center angle - 114 degrees, but the L-79 cam has centers of 110/118 versus 114/114. Seems like a bit of retrograde as the SB generally responds well to an early phased exhaust event. The later phased inlet event is why the L-46 cam will make more peak power at the expense of some low end torque relative to the L-79 cam.

BTW the L-46 cam continued in production in L-82 engines until 1980.

Duke