Camshaft Installation (Small-Block Chevy)
Article by Mark Trotta
The camshaft and lifters on small-block Chevy engines wear pretty fast, particularly if they're over-revved and don't get regular oil changes. Replacement isn't too hard, but a couple specialty tools are needed.
Read: Engine Disassembly/Remove Camshaft
This engine featured in this article is a 327 in a 1966 Corvette.
The original Chevrolet camshaft for this L75 motor has been long discontinued and homogenized into GM #3896929, which is similar. Several companies, such as Crane, offer this in their "Blueprint" series.
Read: Camshaft Selection Guide
After a bit of research, we chose the Melling MTC-1 cam kit, which comes with American-made Johnson lifters. The following stats show how close this cam is to the original:
- Intake Valve Lift: O.E. cam .390" vs Melling cam .422"
- Exhaust Valve Lift: O.E. cam .410" vs Melling cam .444"
- Intake Duration at .050" Lift: O.E. cam 195 vs Melling cam 204
- Exhaust Duration at .050" Lift: O.E. cam 202 vs Melling cam 204
Step-By-Step Camshaft Installation
Clean and lube the new cam before installation. Most cam and lifter kits include a small assembly lube bottle. Coat the cam lobes, distributor gear, and fuel pump lobe completely, but not excessively.
Read: Best Engine Assembly Lube
The cam bearing journals are lubed with conventional SAE 30W or 40W oil. Synthetic oil is not recommended during break-in.
Just like during engine disassembly, I re-installed the cam gear with one hand-tightened bolt to use as a "handle" to help guide the cam into the block. Care must be taken not to nick the cam bearings. After the cam is in the block, remove the cam gear.
SBC Timing Chain
On a first-gen small blocks 1965-1986, the timing chain is difficult to access. Not only do you have to remove the alternator, water pump, and other stuff, the front of the oil pan needs to be dropped about an inch.
An old chain stretches from wear and alters engine timing. If you're not sure how many miles were on the engine, it's a good idea to replace your timing chain when replacing the cam.
Read: SBC Timing Chain, Gears, and Cover
With the cam completely in the block, wrap the timing chain around the cam gear, and then under the crank gear.
The small-block Chevy engine uses a "dot over dot" alignment. On the cam gear, notice the manufacturer's pre-marked timing dot, which should be at the 6 o'clock position. Rotate the crankshaft until the same dot on the crank gear is at 12 o'clock. This sets the engine's rotating assembly at Top Dead Center (TDC). The front drivers side piston will be all the way up in the bore.
Bolt the cam sprocket to the camshaft. Make sure the sprocket is pulled up flush onto the cam.
Double and triple check that the timing marks are positioned properly and according to the engine manual. With a socket and ratchet on the crank bolt, I backed up the rotating assembly slightly and then forward lining the dots up again, to make sure I was getting the most accurate reading.
You can add a dab of non-hardening sealant on the three cam-bolt threads and torque them to the specified 30 lb/ft. This will insure the bolts remain torqued to the proper specification. A camshaft bolt locking plate could also be used.
To complete the camshaft installation, the timing chain cover was re-installed. First, it was sanded to bare metal, treated with phosphorous acid, and painted Chevy Orange (no primer required).
This is my timing cover seal "tool". It's the hub of an old SBC harmonic balancer.
Timing chain cover bolts require 7 to 9 lb/ft of torque, no more.
Lucas 10631 SAE 30 is a high-zinc break-in oil used for flat tappet camshaft break-in. No moly supplement or additional additives are needed with this oil. Not recommended for passenger cars with catalytic-equipped emissions controls.
Shop: High Zinc Break-In Oil
Classic Car Engine Oil
The 10W-30 oil your car left the factory with is not the same 10W-30 that you buy today. There are more flat-tappet hydraulic cam failures than ever before, brought about by inferior foreign lifters as well as the removal of ZDDP additives from motor oils.