L76�>LT-1 Cam Swap

[Dennis K.]

[Duke W.]

Looking into the LT-1 cam swap that Duke and others have discussed in prior forums. Anyone do this and happy? A few questions:

1. Do I need to remove the engine for the swap or can it be done with (removing radiator, etc)?

2. Advice on degree’ing and setup?

3. Any change to the valve train (springs, rockers, tappers, push rods), etc?

4. Valve lash settings?

5. Just getting educated - it appears that there are several “LT-1” camshafts from GM (am I wrong here?)… which one should I be looking at? GM (Chevy Performance) sourced?

My L76 is blue-printed/stock (30-30 cam) except cylinder bores are .030 over, and I have a roller tip set of rockers. I run an octane additive and tight lash (.029 - .028) to “keep it happy” today.

Thx,
L76 (Dennis)

1. I've never done it, but I believe you can swap the cam by removing the radiator without removing the engine.

2. Install it at the as ground OE indexing. Inlet POML is 110 deg ATC and exhaust POML is 122 BTC for a LSA of 116 deg.

3. Negative. The LT-1 cam works fine with sixties vintage valve train components. It used the second design SB valve spring 3911068 (Sealed Power VS677), same as your grandmother's '67 283 2bbl. Powerglide

4. Web search: hinckley williams valve adjustment. Make sure you get the Sept 2008 edition

5. There is ONLY ONE LT-1 cam. The finished camshaft part number/drawing number is 3972182 and "2182" should be embedded in the casting of an original LT-1 cam; 3972178 is the camshaft/pin ASSEMBLY, which is what was sold over the counter by GMPD.

6. Get rid of the Mickey Mouse roller tip rockers and replace them with sixties vintage non self aligning rockers/balls. DO NOT use guide plates with 60's vintage heads.

Elgin and Howard's cams can grind an LT-1 cam. Basic specs are 242/254 deg .050" lifter rise duration (which includes the clearance ramps....050" lifter rise duration net of the clearance ramps is 231/239 deg.) with .306/323" gross lobe lift, which includes the clearance ramps of .012/.017"; POMLs and LSA as previously mentioned.

The inlet lobe is from the BB SHP cam (L-72/71/LS6) on a smaller base circle, and the exhaust lobe is from the 30-30 indexed four degrees earlier.

Duke

[Tim S.]

[Joe L.]

1. I've never done it, but I believe you can swap the cam by removing the radiator without removing the engine.

2. Install it at the as ground OE indexing. Inlet POML is 110 deg ATC and exhaust POML is 122 BTC for a LSA of 116 deg.

3. Negative. The LT-1 cam works fine with sixties vintage valve train components. It used the second design SB valve spring 3911068 (Sealed Power VS677), same as your grandmother's '67 283 2bbl. Powerglide

4. Web search: hinckley williams valve adjustment. Make sure you get the Sept 2008 edition

5. There is ONLY ONE LT-1 cam. The finished camshaft part number/drawing number is 3972182 and "2182" should be embedded in the casting of an original LT-1 cam; 3972178 is the camshaft/pin ASSEMBLY, which is what was sold over the counter by GMPD.

6. Get rid of the Mickey Mouse roller tip rockers and replace them with sixties vintage non self aligning rockers/balls. DO NOT use guide plates with 60's vintage heads.

Elgin and Howard's cams can grind an LT-1 cam. Basic specs are 242/254 deg .050" lifter rise duration (which includes the clearance ramps....050" lifter rise duration net of the clearance ramps is 231/239 deg.) with .306/323" gross lobe lift, which includes the clearance ramps of .012/.017"; POMLs and LSA as previously mentioned.

The inlet lobe is from the BB SHP cam (L-72/71/LS6) on a smaller base circle, and the exhaust lobe is from the 30-30 indexed four degrees earlier.

Duke

Duke------


Not all GM LT-1 (or any other) camshafts have the raised casting number on the camshaft core. When the camshafts were being used in PRODUCTION, GM used specific cores for each camshaft grind to minimize machining. These camshafts were used in PRODUCTION and available in SERVICE during the PRODUCTION era. After the camshafts were no longer used in PRODUCTION, GM often used generic cores with no casting numbers. However, these camshafts usually have the camshaft ID number or part number die stamped on one end. So, the location and type of identifying number on a SERVICE camshaft depends upon when the camshaft was manufactured.

[Dennis K.]

[Duke W.]