I have read alot of early post on cams LT1 vs 30 30 and what was better with a straight up comparison, but never saw a post stating the better choice, did we ever come up with a champion. not trying to beat this poor horse any more, just curious .
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JR -
Re: Cams
The LT-1 cam makes more low end torque than the 30-30, and they both make about the same top end power with the 30-30 not rolling off quite as fast beyond the peak, but the top end characteristics for a specific engine are more a function of head flow than which cam is installed.
Bottom line is the LT-1 cam is better for a road engine because of the higher low end torque, which is a lot more useful in normal driving than a few horsepower at the extreme top end
Idle behavior between the Duntov, LT-1, and 30-30 is pretty must indistinguishable, but if you put a vacuum gage on them the Duntov and LT-1 cams pull about 12" Hg manifold vacuum at 900 with about 30 degrees to total idle spark advance and the 30-30 is about 10". The lower manifold vacuum is due to the greater overlap.
For a vintage racing engine where the rules require flat tappets and OE rockers the 30-30 cam is a good choice because it's easy on the valve train, and it will make useable power to about 7500 with well massaged OE heads and a properly designed racing exhaust system. For vintage racing, low end torque below 3000-3500 is not an issue if the car is geared properly for the track such that revs exiting the slowest corner don't get below this range.
This is an emotional issue for many, which is totally irrational. There are a lot of "LT-1 cam haters" out there. But what's interesting is that there is really not that much difference between them. The 30-30 lobe (which is the same on both sides) is used on the exhaust side of the LT-1 cam, but is phased four degrees earlier. The LT-1 cam inlet lobe is from the L-72 cam (also a "single pattern" cam), but with a slightly smaller base circle.
The net result of the earlier phased exhaust lobe and slightly shorter inlet lobe with the same POML indexing is less overlap, which is why the LT-1 cam makes more low end torque. Overlap is a low end torque killer, but can be very effective in increasing mid range to top end power when combined with a good racing exhaust system - properly sized headers, tail pipes, and no mufflers. The 30-30 cam has too much overlap for manifolds and mufflers, which is why it's so soggy down low.
Finally, if the 30-30 is so wonderful, why did Chevrolet cut it down for the LT-1 engine even though a longer stoke engine can tolerate more overlap? Answer: They realized that it was "too big" for a good high performance road engine where a basic criterion is that the engine makes at least 80 percent of peak torque no higher than 2000 revs.
Duke
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