I am rebuilding the correct engine for my '65 365 HP. I bought the car with the wrong engine; 350 CI 370 HP LT1. The previous owner gave me a new cam along with the correct block and crank. I want to verify the markings. Can you help me ? It has GM12. 9347 and D10. I assume the D10 is the month and day.
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Re: GM Cam markings
9347 are the last four digits of 3849347 that is the finished part number of what we call the 30-30 cam that was used on the 365/375 HP 327s and the 302/290 HP Z-28 engine. What GM sold over the counter was 3849346, which was an ASSEMBLY of the 30-30 camshaft and indexing pin.
This is a very poor camshaft for a road engine due to a paucity of low end torque, which is the reason it was replaced with the LT-1 cam both in production and as service for the OE 30-30 cam engines.
The LT-1 cam inlet lobe is the same as the big block SHP cam, which is about 8 degrees shorter than 30-30 lobe (same one on both sides) other than having a smaller base circle. The exhaust lobe is the 30-30 lobe indexed earlier. The combination of a shorter inlet lobe and earlier phased exhaust lobe cut overlap to a more reasonable level, which provides more low end torque with about the same top end power as the 30-30 cam.
Using any SHP/FI 327 as a basis the "327 LT-1" configuration with massaged heads, high strength aftermarket connecting rods, and the LT-1 cam makes close to 300 SAE corrected RWHP at 6500 with a useable power bandwidth extending to 7200 with the second design SB valve springs that were used on everything from 2-bbl. 283s to the 350 CID LT-1 engines, while making 80 percent of peak torque at 2000 versus about 3000 with the 30-30 cam.
Duike -
Re: GM Cam markings
Thanks Duike for this knowledgeComment
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